X-ray propagation through a quasi-ordered multilayered structure

We investigate the propagation of short wavelength transverse electric x-rays through a quasiordered  (Fibonacci) atomically commensurate multilayered structure using a transfer matrix model which treats each atomic plane as a diffraction unit. The reflectance spectrum has a rich structure being dominated by peaks associated with certain critical points of the system. Peaks around these special points exhibit self-similarity with a scaling factor approximately equal to the cube of the golden mean. At a critical point itself, the  electromagnetic energy distribution is neither localised nor extended. The Landauer resistance at the reflection  peaks exhibits a power law behaviour at low Fibonacci generation numbers but eventually increases exponentially; in the presence of absorption, the Landauer resistance reaches a plateau after its initial power law behaviour. The persistence, in the presence of absorption, of some reflectivity peaks at small angles of incidence is in line with current interest in the use of quasi-ordered multilayered structures as short wavelength near-normal incidence x-ray mirrors.Keywords : X-rays, Fibonacci multilayered structure

An analysis of the excess mortality profile during the 2006 Chikungunya Fever epidemic in Mauritius

The Island of Mauritius was affected by a large scale epidemic outbreak ofChikungunya Fever (CHIKF) from February to April 2006. It was observed that this epidemic was associated with an excess mortality during the months of March to May 2006 in Mauritius. This study was aimed to analyze the gender and age group distribution of the excess mortality. Population and mortality data were obtained from the Mauritius Central Statistics Office for the years 2000 to 2006. The excess monthly mortality was computed for 2006 and the distribution of excess mortality according to gender and age groups was analyzed. For both genders combined, the excess mortality was 91.5% in the age group ≥ 50 years. For the ≥ 50-year age group, the total male excess death rate (EDR) exceeded the total female EDR by 66%. Our results indicate that CHIKF is associated withan increased mortality particularly in the ≥ 50-year age group with males being more vulnerable than females to mortality. Although there have been reports of CHIKF related deaths in other studies, the profile of the excess mortality during a CHIKF outbreak has not been previously described.KEY WORDS: Chikungunya Fever; Distribution of excess mortality; Gender; Age group

Clinical complications of Chikungunya fever in Mauritius

Chikungunya fever, an emerging mosquito-borne viral disease,has affected Mauritius with two recent outbreaks in 2005 and 2006respectively. A study was carried out in 2007 to describe the clinicalcomplications post-Chikungunya infection. Ethical clearance was obtained for this study. Data collection was carried out in February and March 2007 on a sample of people who had suffered from Chikungunya fever by means of a comprehensive questionnaire. Participants comprised 77 people; there were 41 males and 36 females. Participants ranged from 6 to 69 years. 70 participants experienced persisting joint pains for at least 6 months following the acute phase. Of these, 35 had residual joint complaints after 6 months. 44 participants suffered from psychological sequelae. 10 participants had dermatological sequelae, 6 had iatrogenic complications due to non-steroidal anti-inflammatory drug (NSAID)-induced gastritis, and 3 participants with serologically confirmed Chikungunya fever had neurological manifestations and changes on CT/MRI which could correspond to demyelination. Statistical analysis demonstrated that there was a weak linear relationship between thenumber of complications and increasing age; there was a significant difference in the number of complications according to gender, females being more affected than males; participants with co-morbidities had more complications and psychological sequelae than previously healthy participants. This study highlights that Chikungunya fever, which causes a significant impact on health in the acute phase, can have significant sequelae months afterwards and this includes psychological sequela

Modeling the Dynamic Transmission of Dengue Fever: Investigating Disease Persistence

Dengue is the most rapidly spreading mosquito-borne viral disease in the world and approximately 2.5 billion people live in dengue endemic countries. In Brazil it is mainly transmitted by Aedes aegypti mosquitoes. The wide clinical spectrum ranges from asymptomatic infections or mild illness, to the more severe forms of infection such as dengue hemorrhagic fever or dengue shock syndrome. The spread and dramatic increase in the occurrence of dengue cases in tropical and subtropical countries has been blamed on uncontrolled urbanization, population growth and international traveling. Vaccines are under development and the only current disease control strategy is trying to keep the vector quantity at the lowest possible levels. Mathematical models have been developed to help understand the disease's epidemiology. These models aim not only to predict epidemics but also to expand the capacity of phenomena explanation. We developed a spatially explicit model to simulate the dengue transmission in a densely populated area. The model involves the dynamic interactions between humans and mosquitoes and takes into account human mobility as an important factor of disease spread. We investigated the importance of human population size, human renewal rate, household infestation and ratio of vectors per person in the maintenance of sustained viral circulation

Bloch's Theorem And Quasiperiodicity In The Theory Of Optical Propagation Through An Ordered Multilayered Structure

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Maternal and neonatal outcomes after caesarean delivery in the African Surgical Outcomes Study: a 7-day prospective observational cohort study.

BACKGROUND: Maternal and neonatal mortality is high in Africa, but few large, prospective studies have been done to investigate the risk factors associated with these poor maternal and neonatal outcomes. METHODS: A 7-day, international, prospective, observational cohort study was done in patients having caesarean delivery in 183 hospitals across 22 countries in Africa. The inclusion criteria were all consecutive patients (aged ≥18 years) admitted to participating centres having elective and non-elective caesarean delivery during the 7-day study cohort period. To ensure a representative sample, each hospital had to provide data for 90% of the eligible patients during the recruitment week. The primary outcome was in-hospital maternal mortality and complications, which were assessed by local investigators. The study was registered on the South African National Health Research Database, number KZ_2015RP7_22, and on ClinicalTrials.gov, number NCT03044899. FINDINGS: Between February, 2016, and May, 2016, 3792 patients were recruited from hospitals across Africa. 3685 were included in the postoperative complications analysis (107 missing data) and 3684 were included in the maternal mortality analysis (108 missing data). These hospitals had a combined number of specialist surgeons, obstetricians, and anaesthetists totalling 0·7 per 100 000 population (IQR 0·2-2·0). Maternal mortality was 20 (0·5%) of 3684 patients (95% CI 0·3-0·8). Complications occurred in 633 (17·4%) of 3636 mothers (16·2-18·6), which were predominantly severe intraoperative and postoperative bleeding (136 [3·8%] of 3612 mothers). Maternal mortality was independently associated with a preoperative presentation of placenta praevia, placental abruption, ruptured uterus, antepartum haemorrhage (odds ratio 4·47 [95% CI 1·46-13·65]), and perioperative severe obstetric haemorrhage (5·87 [1·99-17·34]) or anaesthesia complications (11·47 (1·20-109·20]). Neonatal mortality was 153 (4·4%) of 3506 infants (95% CI 3·7-5·0). INTERPRETATION: Maternal mortality after caesarean delivery in Africa is 50 times higher than that of high-income countries and is driven by peripartum haemorrhage and anaesthesia complications. Neonatal mortality is double the global average. Early identification and appropriate management of mothers at risk of peripartum haemorrhage might improve maternal and neonatal outcomes in Africa. FUNDING: Medical Research Council of South Africa.Medical Research Council of South Africa