High-resolution structure of viruses from random diffraction snapshots.

The advent of the X-ray free-electron laser (XFEL) has made it possible to record diffraction snapshots of biological entities injected into the X-ray beam before the onset of radiation damage. Algorithmic means must then be used to determine the snapshot orientations and thence the three-dimensional structure of the object. Existing Bayesian approaches are limited in reconstruction resolution typically to 1/10 of the object diameter, with the computational expense increasing as the eighth power of the ratio of diameter to resolution. We present an approach capable of exploiting object symmetries to recover three-dimensional structure to high resolution, and thus reconstruct the structure of the satellite tobacco necrosis virus to atomic level. Our approach offers the highest reconstruction resolution for XFEL snapshots to date and provides a potentially powerful alternative route for analysis of data from crystalline and nano-crystalline objects.

Bohman-Frieze-Wormald model on the lattice, yielding a discontinuous percolation transition.

The BFW model introduced by Bohman, Frieze, and Wormald [Random Struct. Algorithms, 25, 432 (2004)], and recently investigated in the framework of discontinuous percolation by Chen and D'Souza [Phys. Rev. Lett. 106, 115701 (2011)], is studied on the square and simple-cubic lattices. In two and three dimensions, we find numerical evidence for a strongly discontinuous transition. In two dimensions, the clusters at the threshold are compact with a fractal surface of fractal dimension d(f)=1.49±0.02. On the simple-cubic lattice, distinct jumps in the size of the largest cluster are observed. We proceed to analyze the tree-like version of the model, where only merging bonds are sampled, for dimension two to seven. The transition is again discontinuous in any considered dimension. Finally, the dependence of the cluster-size distribution at the threshold on the spatial dimension is also investigated.

Climatic factors associated with hospitalizations for rotavirus diarrhoea in children under 5 years of age.

This study compares the seasonality of rotavirus diarrhoeal hospital admissions and its relationship to climatic factors across three Australian cities. Weekly admission of rotavirus diarrhoea (1993-2003) in children aged <5 years and weekly average temperature and relative humidity for each city were modelled using a log-linear model with a cubic trend and season. Interactions were included to test for differences in the effect of temperature and humidity between seasons and between cities. Admissions of rotavirus diarrhoea peaked in winter and spring and were lowest in summer. Higher temperature and humidity in the previous week were associated with a decrease in rotavirus diarrhoeal admissions in three cities. The effects of both temperature and humidity on rotavirus admissions in Brisbane differed across seasons. Strategies to combat outbreaks of rotavirus diarrhoea should take climatic factors and seasonal effects into consideration to plan for the excess seasonal hospital admissions.

WITHDRAWN: Antibiotics for preventing pneumonia in children with measles.

BACKGROUND: Measles causes more than a million deaths a year, of which most are children under five years of age who die from pneumonia. OBJECTIVES: The objective of this review was to assess the effects of antibiotics given to children with measles on reducing pneumonia or mortality, and to assess whether antibiotics should be given to all children with measles in communities with a high fatality rate. SEARCH STRATEGY: We searched MEDLINE (1966 - 1999), EMBASE (1980-1999) and the specialized trials register of the Acute Respiratory Infections Group in August 1999, and all relevant journals in the University of Melbourne medical library for the years 1935-46. SELECTION CRITERIA: Randomised or controlled trials of antibiotics for children with measles. DATA COLLECTION AND ANALYSIS: Two reviewers independently extracted data and assessed trial quality. MAIN RESULTS: Six trials with 1304 children were included. All but one of the trials were unblinded, and randomisation was either not described or was by alternate allocation. In four studies, the incidence of pneumonia in the control group was similar to that in the antibiotic prophylaxis group; in the other two studies, the incidence of pneumonia was unusually high in the control group so these children had a higher complication rate than the antibiotic group. Four of the 764 children given antibiotics died compared with one of the 637 controls. AUTHORS' CONCLUSIONS: The quality of the trials reviewed was poor, and they provide very weak evidence for giving antibiotics to all children with measles. Available evidence suggests that antibiotics should be given only if a child has clinical signs of pneumonia or other evidence of sepsis.

Work and health in a contemporary society: demands, control, and insecurity.

OBJECTIVE: To examine independent associations of job strain (high demands and low control) and job insecurity with mental and physical health outcomes. DESIGN: Cross sectional general population study conducted in 2000 using a self completed questionnaire. SETTING: Two adjoining cities in south east Australia. SUBJECTS: 1188 employed professionals, aged 40-44 years, 55% (n = 655) male. MAIN OUTCOME MEASURES: Depression, anxiety, physical, and self rated health (SRH). RESULTS: Adverse job conditions were relatively prevalent as 23% of the sample reported high job strain, while 7.3% and 23% reported high and moderate job insecurity respectively. Associations between job conditions and health persisted after adjustment for gender, education, marital status, employment status, major life events, and negative affectivity (personality). When adjusted for job strain, high job insecurity was independently associated with a greater than threefold increase in odds for poor SRH, depression and anxiety (OR (95% confidence intervals) poor SRH: 3.72 (1.97 to 7.04) depression: 3.49 (1.90 to 6.41), anxiety: 3.29 (1.71 to 6.33)), and a twofold increase for physical health 2.19 (1.21 to 3.95). High job strain also showed significant independent associations with depression: 2.54 (1.34 to.4.75) and anxiety: 3.15 (1.48 to 6.70). CONCLUSION: In this relatively privileged socioeconomic group, insecure employment and high job strain showed independent, consistent, and strong associations with physical and mental health. These adverse job conditions are on the increase, particularly insecure employment, and the influence of these two work conditions are an important focus for future public health research and their prevalence and impact should be examined in other occupations.

Acute flaccid paralysis in Australian children.

OBJECTIVES: To describe the epidemiology and causes of acute flaccid paralysis (AFP) in Australian children, and the clinical features of the two most common causes of AFP, Guillain-Barré syndrome and transverse myelitis. METHODS: Monthly active surveillance for AFP was carried out through the Australian Paediatric Surveillance Unit, with AFP defined as 'acute onset of flaccid paralysis in one or more limbs or of bulbar paralysis in any child less than 15 years of age'. RESULTS: Between March 1995 and December 1999, 143 cases of AFP were reported (approximately 0.8 per 100000 children < 15 years of age per annum). The age range was 2 months-14 years and 59% were boys. Out of these children, 137 (96%) were hospitalized and 47 required intensive care. No case of wild or vaccine-associated poliomyelitis was identified. The most common causes of AFP were Guillain-Barré syndrome in 67 (47%) and transverse myelitis in 27 (19%). Other diagnoses included acute disseminated encephalomyelitis, trauma, tick-bite paralysis and infantile botulism. CONCLUSION: The participation of paediatricians in AFP surveillance contributed to the accreditation of Australia (along with the other 36 countries of the western Pacific region) as 'polio free' by the World Health Organization in October 2000. The surveillance also provided data on the frequency of AFP and identified Guillain-Barré syndrome and transverse myelitis as the most common diagnoses. In this large national series, many other conditions that may present as non-polio AFP were identified.

Retrospective hospital-based searches for cases of acute flaccid paralysis.

OBJECTIVE: Australia had to demonstrate adequate acute flaccid paralysis (AFP) surveillance by achieving a rate of one per 100,000 in children under the age of 15 to fulfil one of the requirements of the Regional Commission for the Certification of Poliomyelitis Eradication to be declared polio free. To increase the ascertainment rate of AFP cases, a hospital search was conducted to identify cases not reported to the active AFP surveillance. METHODS: A computerised search of hospital admissions in New South Wales (NSW) and Western Australia (WA) on ICD-9 codes of Guillain Barré Syndrome (GBS), unspecified encephalitis, poliomyelitis, vaccine-associated paralytic polio (VAPP) and flaccid paralysis was conducted for the period 1995-98. Medical records of cases that were not reported to the active surveillance were reviewed in three hospitals of NSW and two hospitals in WA. RESULTS: Twenty additional cases recorded as GBS and five as transverse myelitis (TM) were identified through the searches, which increased the average four-year AFP rate from 1.0 to 1.4 per 100,000 in children under the age of 15 years in these two states and the overall AFP rate in Australia increased from 0.78 to 1.14. There were no cases of polio or VAPP found. Nine cases of GBS and five of TM reported to the active AFP surveillance were not found in the hospital searches. CONCLUSION: A combination of active surveillance and hospital-based searches increased the investigated AFP rate, which fulfilled one of the certification requirements for Australia to be certified polio free. IMPLICATIONS: Until global certification is achieved, AFP surveillance needs to be improved to identify cases of importation of wild poliovirus.

Vitamin A for treating measles in children.

BACKGROUND: Measles is a leading cause of childhood morbidity and mortality. Vitamin A deficiency is a recognised risk factor for severe measles. The World Health Organization (WHO) recommends administration of an oral dose of 200,000 IU (or 100,000 IU in infants) of vitamin A per day for two days to children with measles in areas where vitamin A deficiency may be present. OBJECTIVES: The purpose of this review is to determine whether vitamin A when commenced after measles has been diagnosed, is beneficial in preventing mortality, pneumonia and other complications in children. SEARCH STRATEGY: MEDLINE and the Cochrane Library, Issue 4, 1999 were searched. SELECTION CRITERIA: Only randomized controlled trials in which children with measles were given vitamin A or placebo along with standard treatment were considered. DATA COLLECTION AND ANALYSIS: Studies were assessed independently by two reviewers. The analysis of dichotomous outcomes was done using the StatXact software package. Sub-group analyses were done for dose, formulation, age, hospitalisation and pneumonia specific mortality. Weighted mean difference with 95% CI were calculated for continuous outcomes. MAIN RESULTS: The relative risks (RR) and 95% Confidence Intervals (CI) are based on the estimates from the StatXact software package. There was no significant reduction in mortality in the vitamin A group when all the studies were pooled together (RR 0.60; 95% CI 0.32 to 1.12)(StatXact estimate). There was a 64% reduction in the risk of mortality in children who were given two doses of 200,000 IU of vitamin A (RR=0.36; 95% CI 0.14 to 0.82) as compared to placebo. Two doses of water based vitamin A were associated with a 81% reduction in risk of mortality (RR=0.19; 95% CI 0.02 to 0.85) as compared to 48% seen in two doses of oil based preparation (RR=0.52; 95% CI 0.16 to 1.40). Two doses of oil and water based vitamin A were associated with a 82% reduction in the risk of mortality in children under the age of 2 years (RR=0.18; 95% CI 0.03 to 0.61) and a 67% reduction in the risk of pneumonia specific mortality (RR=0.33; 95% CI 0.08 to 0.92). There was no evidence that vitamin A in a single dose of 200,000 IU was associated with a reduced risk of mortality among children with measles (RR=0.77; 95% CI 0.34 to 1.78). Sub-groups like age, dose, formulation, hospitalisation and case fatality in the study area were highly correlated and there were not enough studies to separate out the individual effects of these factors. There was a 47% reduction in the incidence of croup (RR=0.53; 95% CI 0.29 to 0.89), while there was no significant reduction in the incidence of pneumonia (RR=0.92; 95% CI 0.69 to 1.22) or of diarrhoea (RR=0.80; 95% CI 0.27 to 2.34). Duration of diarrhoea was measured in days and there was a reduction in its duration of almost two days WMD -1.92, 95% CI -3.40 to -0.44. Only one study evaluated otitis media and found a 74% reduction in its incidence (RR=0.26, 95% CI, 0.05 to 0.92). We did not find evidence that a single dose of 200,000 IU of vitamin A per day, given in oil-based formulation in areas with low case fatality, was associated with reduced mortality among children with measles. However, there was evidence that the same dose given for two days was associated with a reduced risk of overall mortality and pneumonia specific mortality. REVIEWER'S CONCLUSIONS: Although we did not find evidence that a single dose of 200,000 IU of vitamin A per day was associated with reduced mortality among children with measles, there was evidence that the same dose given for two days was associated with a reduced risk of overall mortality and pneumonia specific mortality. The effect was greater in children under the age of two years. There were no trials that compared a single dose with two doses, although the precision of the estimates of trials that used a single dose were similar to the trials that used two doses.

Vitamin A for treating measles in children.

BACKGROUND: Measles is a leading cause of childhood morbidity and mortality. Vitamin A deficiency is a recognised risk factor for severe measles. The World Health Organization (WHO) recommends administration of an oral dose of 200,000 IU (or 100,000 IU in infants) of vitamin A per day for two days to children with measles in areas where vitamin A deficiency may be present. OBJECTIVES: The purpose of this review is to determine whether vitamin A when commenced after measles has been diagnosed, is beneficial in preventing mortality, pneumonia and other complications in children. SEARCH STRATEGY: MEDLINE and the Cochrane Library, Issue 4, 1999 were searched. SELECTION CRITERIA: Only randomized controlled trials in which children with measles were given vitamin A or placebo along with standard treatment were considered. DATA COLLECTION AND ANALYSIS: Studies were assessed independently by two reviewers. The analysis of dichotomous outcomes was done using the StatExact software package. Sub-group analyses were done for dose, formulation, age, hospitalisation and pneumonia specific mortality. Weighted mean difference with 95% CI were calculated for continuous outcomes. MAIN RESULTS: The relative risks (RR) and 95% Confidence Intervals (CI) are based on the estimates from the StatExact software package. There was no significant reduction in mortality in the vitamin A group when all the studies were pooled together (RR 0.60; 95% CI 0.32 to 1.12)(Statexact estimate). There was a 64% reduction in the risk of mortality in children who were given two doses of 200,000 IU of vitamin A (RR=0.36; 95% CI 0.14 to 0.82) as compared to placebo. Two doses of water based vitamin A were associated with a 81% reduction in risk of mortality (RR=0.19; 95% CI 0.02 to 0.85) as compared to 48% seen in two doses of oil based preparation (RR=0.52; 95% CI 0.16 to 1.40). Two doses of oil and water based vitamin A were associated with a 82% reduction in the risk of mortality in children under the age of 2 years (RR=0.18; 95% CI 0.03 to 0.61) and a 67% reduction in the risk of pneumonia specific mortality (RR=0.33; 95% CI 0.08 to 0.92). There was no evidence that vitamin A in a single dose of 200,000 IU was associated with a reduced risk of mortality among children with measles (RR=0.77; 95% CI 0.34 to 1.78). Sub-groups like age, dose, formulation, hospitalisation and case fatality in the study area were highly correlated and there were not enough studies to separate out the individual effects of these factors. There was a 47% reduction in the incidence of croup (RR=0.53; 95% CI 0.29 to 0.89), while there was no significant reduction in the incidence of pneumonia (RR=0.92; 95% CI 0.69 to 1.22) or of diarrhoea (RR=0.80; 95% CI 0.27 to 2.34). Duration of diarrhoea was measured in days and there was a reduction in its duration of almost two days WMD -1.92, 95% CI -3.40 to -0.44. Only one study evaluated otitis media and found a 74% reduction in its incidence (RR=0.26, 95% CI, 0.05 to 0.92). We did not find evidence that a single dose of 200,000 IU of vitamin A per day, given in oil-based formulation in areas with low case fatality, was associated with reduced mortality among children with measles. However, there was evidence that the same dose given for two days was associated with a reduced risk of overall mortality and pneumonia specific mortality. REVIEWER'S CONCLUSIONS: Although we did not find evidence that a single dose of 200,000 IU of vitamin A per day was associated with reduced mortality among children with measles, there was evidence that the same dose given for two days was associated with a reduced risk of overall mortality and pneumonia specific mortality. The effect was greater in children under the age of two years. There were no trials that compared a single dose with two doses, although the precision of the estimates of trials that used a single dose were similar to the trials that used two doses.

Antibiotics for preventing pneumonia in children with measles.

BACKGROUND: Measles causes more than a million deaths a year, of which most are children under five years of age who die from pneumonia. OBJECTIVES: The objective of this review was to assess the effects of antibiotics given to children with measles on reducing pneumonia or mortality, and to assess whether antibiotics should be given to all children with measles in communities with a high fatality rate. SEARCH STRATEGY: We searched MEDLINE (1966 - 1999), EMBASE (1980-1999) and the specialized trials register of the Acute Respiratory Infections Group in August 1999, and all relevant journals in the University of Melbourne medical library for the years 1935-46. SELECTION CRITERIA: Randomised or controlled trials of antibiotics for children with measles. DATA COLLECTION AND ANALYSIS: Two reviewers independently extracted data and assessed trial quality. MAIN RESULTS: Six trials with 1304 children were included. All but one of the trials were unblinded, and randomisation was either not described or was by alternate allocation. In four studies, the incidence of pneumonia in the control group was similar to that in the antibiotic prophylaxis group; in the other two studies, the incidence of pneumonia was unusually high in the control group so these children had a higher complication rate than the antibiotic group. Four of the 764 children given antibiotics died compared with one of the 637 controls. REVIEWER'S CONCLUSIONS: The quality of the trials reviewed was poor, and they provide very weak evidence for giving antibiotics to all children with measles. Available evidence suggests that antibiotics should be given only if a child has clinical signs of pneumonia or other evidence of sepsis.

Antibiotics for preventing pneumonia in children with measles.

BACKGROUND: Measles causes more than a million deaths a year, of which most are children under five years of age who die from pneumonia. OBJECTIVES: The objective of this review was to assess the effects of antibiotics given to children with measles on reducing pneumonia or mortality, and to assess whether antibiotics should be given to all children with measles in communities with a high fatality rate. SEARCH STRATEGY: We searched MEDLINE (1966 - 1999), EMBASE (1980-1999) and the specialized trials register of the Acute Respiratory Infections Group in August 1999, and all relevant journals in the University of Melbourne medical library for the years 1935-46. SELECTION CRITERIA: Randomised or controlled trials of antibiotics for children with measles. DATA COLLECTION AND ANALYSIS: Two reviewers independently extracted data and assessed trial quality. MAIN RESULTS: Six trials with 1304 children were included. All but one of the trials were unblinded, and randomisation was either not described or was by alternate allocation. In four studies, the incidence of pneumonia in the control group was similar to that in the antibiotic prophylaxis group; in the other two studies, the incidence of pneumonia was unusually high in the control group so these children had a higher complication rate than the antibiotic group. Four of the 764 children given antibiotics died compared with one of the 637 controls. REVIEWER'S CONCLUSIONS: The quality of the trials reviewed was poor, and they provide very weak evidence for giving antibiotics to all children with measles. Available evidence suggests that antibiotics should be given only if a child has clinical signs of pneumonia or other evidence of sepsis.

Antibiotics for preventing pneumonia in children with measles.

BACKGROUND: Measles causes more than a million deaths a year, of which most are children under five years of age who die from pneumonia. OBJECTIVES: The objective of this review was to assess the effects of antibiotics given to children with measles on reducing pneumonia or mortality, and to assess whether antibiotics should be given to all children with measles in communities with a high fatality rate. SEARCH STRATEGY: We searched MEDLINE (1966 - 1999), EMBASE (1980-1999) and the specialized trials register of the Acute Respiratory Infections Group in August 1999, and all relevant journals in the University of Melbourne medical library for the years 1935-46. SELECTION CRITERIA: Randomised or controlled trials of antibiotics for children with measles. DATA COLLECTION AND ANALYSIS: Two reviewers independently extracted data and assessed trial quality. MAIN RESULTS: Six trials with 1304 children were included. All but one of the trials were unblinded, and randomisation was either not described or was by alternate allocation. In four studies, the incidence of pneumonia in the control group was similar to that in the antibiotic prophylaxis group; in the other two studies, the incidence of pneumonia was unusually high in the control group so these children had a higher complication rate than the antibiotic group. Four of the 764 children given antibiotics died compared with one of the 637 controls. REVIEWER'S CONCLUSIONS: The quality of the trials reviewed was poor, and they provide very weak evidence for giving antibiotics to all children with measles. Available evidence suggests that antibiotics should be given only if a child has clinical signs of pneumonia or other evidence of sepsis.

Adverse events following immunisation associated with the 1998 Australian Measles Control Campaign.

The Measles Control Campaign (MCC) conducted in Australia from August to November 1998 resulted in a total of 1.7 million school children being vaccinated. This article reports on the Adverse Events Following Immunisation (AEFI) associated with measles-mumps-rubella vaccine (MMR) administered as part of the MCC. Reports of adverse events that occurred within 30 days of administration of the MMR vaccine were assessed by an expert panel that assigned a causality rating to each AEFI. Reports with missing onset dates or uncertain causality were excluded. Eighty-nine AEFI were classified as associated with MMR vaccine and the overall rate of adverse events was 5.24 per 100,000 doses of vaccine administered. Of these 46 were thought to be certainly caused by MMR vaccine, 23 were probably and 20 were possibly associated with the vaccine. Although 46 reactions were categorised to be certainly caused by the MMR vaccine, the majority of these were syncopal fits, syncope, local reactions, and allergic reactions that were short-lived, and all of these children recovered. The most commonly occurring adverse reaction was syncopal fit with a rate of 1.24 per 100,000. There was only one anaphylactic reaction, giving a rate of 0.06 per 100,000. The combined rate for anaphylaxis, anaphylactoid and allergic reactions was 1.06 per 100,000 administered doses. The rate of seizures (febrile and afebrile) was 0.30 and encephalopathy was 0.06 per 100,000 doses administered. Of the 89 children who had an AEFI, 43 did not require hospitalisation or medical attention while 13 were seen in an emergency room, 14 were hospitalised and 19 were seen by a doctor. There were no deaths reported resulting from the administration of the MMR vaccine during the period of the campaign. All children who had an AEFI have recovered although 9 children could not be followed up for reasons of confidentiality. The overall rate of adverse events was lower than that observed in the 1994 measles campaign conducted in the United Kingdom. On comparing the risks and benefits of MMR vaccine, the benefits of this MCC far outweigh the incidence of serious adverse events associated with immunisation.

Australia's contribution to global polio eradication initiatives.

OBJECTIVE: To provide evidence according to the requirements of the Global Commission for Certification of Poliomyelitis Eradication that poliomyelitis has been eliminated in Australia. METHODS: Documentation of the surveillance of poliomyelitis, the presence of a comprehensive national immunisation program, and a network of laboratories for viral diagnosis. Active surveillance of acute flaccid paralysis (AFP) cases was initiated in 1995 to prove that poliovirus does not cause such paralysis. Australia is also evaluating the surveillance of AFP through a retrospective hospital based study. RESULTS: The last case in Australia of polio due to wild poliovirus was seen in 1978 and the last case of vaccine-associated paralytic poliomyelitis detected by serology was in 1994. The latest immunisation coverage figures for OPV3 for children under one year of age is 85.6%. The Australian National Polio Reference Laboratory has tested 821 enteroviruses since 1994 and have not identified any wild poliovirus. The average rate of non-polio AFP based on 111 cases investigated for the period 1995-98 is 0.71 per 100,000 under the age of 15 years. Stool samples were collected from only 21% of cases. CONCLUSION: The process of certification of the eradication of poliomyelitis in Australia is almost complete. Although immunisation coverage is high, improvement in AFP surveillance and stool collection is vital for the certification process. The next challenge is the containment of polioviruses. IMPLICATIONS: Although Australia and other Western Pacific countries are likely to be certified as wild-polio free in 2000, a comprehensive immunisation program and surveillance must continue for three years after global certification (expected 2003-04).

Surveillance of acute flaccid paralysis in Australia, 1995-97. Australian Paediatric Surveillance Unit.

OBJECTIVE: Acute flaccid paralysis (AFP) surveillance in Australia as part of the World Health Organization (WHO) certification process for polio eradication in the Western Pacific region. METHODS: Active monthly AFP surveillance through the Australian Paediatric Surveillance Unit, from March 1995 to December 1997. RESULTS: Based on 80 cases, the reported overall rate of AFP was 0.73 per 10(5) children < 15 years (below the expected 1 per 10(5)). The major causes of AFP were Guillain-Barré syndrome (51%) and transverse myelitis (19%). According to the WHO virological classification, there was no case of poliomyelitis, 37.5% were 'non-polio' and 62.5% cases were 'polio compatible' due to inadequate stool testing and follow-up. However, case review by an expert panel enabled 95% to be classified as 'non-polio'. CONCLUSION: Australia must improve AFP surveillance to confirm absence of wild poliovirus. Paediatricians can help Australia meet its certification requirements and contribute to the global eradication effort by reporting and investigating all cases of AFP.

Thermodynamically reversible generalization of diffusion limited aggregation.

We introduce a lattice gas model of cluster growth via the diffusive aggregation of particles in a closed system obeying a local, deterministic, microscopically reversible dynamics. This model roughly corresponds to placing the irreversible diffusion limited aggregation model (DLA) in contact with a heat bath. Particles release latent heat when aggregating, while singly connected cluster members can absorb heat and evaporate. The heat bath is initially empty, hence we observe the flow of entropy from the aggregating gas of particles into the heat bath, which is being populated by diffusing heat tokens. Before the population of the heat bath stabilizes, the cluster morphology (quantified by the fractal dimension) is similar to a standard DLA cluster. The cluster then gradually anneals, becoming more tenuous, until reaching configurational equilibrium when the cluster morphology resembles a quenched branched random polymer. As the microscopic dynamics is invertible, we can reverse the evolution, observe the inverse flow of heat and entropy, and recover the initial condition. This simple system provides an explicit example of how macroscopic dissipation and self-organization can result from an underlying microscopically reversible dynamics. We present a detailed description of the dynamics for the model, discuss the macroscopic limit, and give predictions for the equilibrium particle densities obtained in the mean field limit. Empirical results for the growth are then presented, including the observed equilibrium particle densities, the temperature of the system, the fractal dimension of the growth clusters, scaling behavior, finite size effects, and the approach to equilibrium. We pay particular attention to the temporal behavior of the growth process and show that the relaxation to the maximum entropy state is initially a rapid nonequilibrium process, then subsequently it is a quasistatic process with a well defined temperature.

Determinants of childhood mortality in slums of Karachi, Pakistan.

PIP: Pakistan has an infant mortality rate (IMR) of 90.5/1000 live births, and the country's child mortality level of 117.5 is worse than in other South Asian countries. Rapid population growth combined with rural-to-urban migration has led to the creation of urban slums in which morbidity levels are usually higher than in rural populations. A study was conducted in January 1993 in 6 slums of Karachi where the Aga Khan University has operated primary health care programs since 1985. Researchers recorded the deaths of 347 children under age 5 years old due to diarrhea and acute respiratory infections (ARI) during 1989-93. 235 mothers of these children were interviewed. The following are discussed as risk factors for under-5 child mortality: the use of traditional healers, poor nutritional status, incomplete or no immunization, the quick change of healers, inappropriate child care arrangements, mother's literacy, who decides about outside treatment, short birth interval, bottle feeding, and nuclear family structure. Maternal autonomy, appropriate health-seeking behavior, and child-rearing processes identified in the study point to the need for intervention strategies which go beyond the usual primary health care initiatives and involve communities in developing social support systems for mothers.^ieng

Housing and environmental factors and their effects on the health of children in the slums of Karachi, Pakistan.

To examine the association of environmental factors (including housing) with respiratory infections and diarrhoea in children under 5 years of age, a cross-sectional study of 403 families was conducted in a squatter settlement of Karachi. In the 2-week period before the survey prevalence of diarrhoea and respiratory infections was 14.4% and 15.0% respectively. The factors significantly associated (p < 0.05) with diarrhoea in households in the multivariate analysis were: number of children under 5, regular cleaning of sewers, storage of water in small utensils and cooking inside a one room house. Five households risk factors were identified for respiratory infections: the number of children under 5, poor housing structure, increased household density, humidity inside the house less than the humidity outside house, and frequent cooking inside the house. These results suggest that children under 5 years of age in lower income areas are at additional risk to health because of poor environmental conditions.

PIP: This article examines the impact of sociodemographic, housing, and environmental conditions on diarrheal and respiratory infections in children under 5 years of age in a Karachi slum in Pakistan. Data were obtained from interviews conducted during October-November 1990 in Essa Nagri slum among 403 families with children under 5 years (698 children). Most adults worked as cleaners in the city. Over 75% of houses had access to communal water taps and indoor toilet facilities. Symptoms were recorded as reported by the mother, and severity and duration of illness was not assessed. 14.4% of children suffered from diarrhea during the 2 weeks prior to the survey. Diarrhea was significantly associated with number of children under 5 years, regular cleaning of sewers, storage of water in small utensils, and cooking in one-room dwellings. 15% of children suffered from respiratory infections. Household risk factors for respiratory infection were poor housing structure, frequent indoor cooking, lower indoor than outdoor humidity, increased household density, and number of children under 5 years. The most prevalent risk was having more than one child aged under 5 years. The least prevalent risk factor was housing structure. Malnutrition was not a risk factor. Income of the household head was not a risk factor, but other housing facilities that were related to income were risk factors. Maternal education was not a risk factor. It is argued, however, that the very contaminated living environments undermine the effect of education. Families should be educated about public health measures such as improved ventilation in houses, hygienic practices, sanitary disposal of wastes after cleaning of the sewers, storage and boiling of water, and home management of diarrhea.