Fracture Propagation Driven by Fluid Outflow from a Low-permeability Aquifer

Deep saline aquifers are promising geological reservoirs for CO2 sequestration if they do not leak. The absence of leakage is provided by the caprock integrity. However, CO2 injection operations may change the geomechanical stresses and cause fracturing of the caprock. We present a model for the propagation of a fracture in the caprock driven by the outflow of fluid from a low-permeability aquifer. We show that to describe the fracture propagation, it is necessary to solve the pressure diffusion problem in the aquifer. We solve the problem numerically for the two-dimensional domain and show that, after a relatively short time, the solution is close to that of one-dimensional problem, which can be solved analytically. We use the relations derived in the hydraulic fracture literature to relate the the width of the fracture to its length and the flux into it, which allows us to obtain an analytical expression for the fracture length as a function of time. Using these results we predict the propagation of a hypothetical fracture at the In Salah CO2 injection site to be as fast as a typical hydraulic fracture. We also show that the hydrostatic and geostatic effects cause the increase of the driving force for the fracture propagation and, therefore, our solution serves as an estimate from below. Numerical estimates show that if a fracture appears, it is likely that it will become a pathway for CO2 leakage.Comment: 21 page

Epidemiology of Malaria in an Area Prepared for Clinical Trials in Korogwe, North-eastern Tanzania.

Site preparation is a pre-requesite in conducting malaria vaccines trials. This study was conducted in 12 villages to determine malariometric indices and associated risk factors, during long and short rainy seasons, in an area with varying malaria transmission intensities in Korogwe district, Tanzania. Four villages had passive case detection (PCD) of fever system using village health workers. Four malariometric cross-sectional surveys were conducted between November 2005 and May 2007 among individuals aged 0-19 years, living in lowland urban, lowland rural and highland strata. A total of 10,766 blood samples were collected for malaria parasite diagnosis and anaemia estimation. Blood smears were stained with Giemsa while haemoglobin level was measured by HaemoCue. Socio-economic data were collected between Jan-Apr 2006. Adjusting for the effect of age, the risk of Plasmodium falciparum parasitaemia was significantly lower in both lowland urban, (OR = 0.26; 95%CI: 0.23-0.29, p < 0.001) and highlands, (OR = 0.21; 95%CI: 0.17-0.25, p < 0.001) compared to lowland rural. Individuals aged 6-9 years in the lowland rural and 4-19 years in both lowland urban and highlands had the highest parasite prevalence, whilst children below five years in all strata had the highest parasite density. Prevalence of splenomegaly and gametocyte were also lower in both lowland urban and highlands than in lowland rural. Anaemia (Hb <11 g/dl) prevalence was lowest in the lowland urban. Availability of PCD and higher socio-economic status (SES) were associated with reduced malaria and anaemia prevalence. Higher SES and use of bed nets in the lowland urban could be the important factors for low malaria infections in this stratum. Results obtained here were used together with those from PCD and DSS in selecting a village for Phase 1b MSP3 vaccine trial, which was conducted in the study area in year 2008

The decline in paediatric malaria admissions on the coast of Kenya

<p>Abstract</p> <p>Background</p> <p>There is only limited information on the health impact of expanded coverage of malaria control and preventative strategies in Africa.</p> <p>Methods</p> <p>Paediatric admission data were assembled over 8.25 years from three District Hospitals; Kilifi, Msambweni and Malindi, situated along the Kenyan Coast. Trends in monthly malaria admissions between January 1999 and March 2007 were analysed using several time-series models that adjusted for monthly non-malaria admission rates and the seasonality and trends in rainfall.</p> <p>Results</p> <p>Since January 1999 paediatric malaria admissions have significantly declined at all hospitals. This trend was observed against a background of rising or constant non-malaria admissions and unaffected by long-term rainfall throughout the surveillance period. By March 2007 the estimated proportional decline in malaria cases was 63% in Kilifi, 53% in Kwale and 28% in Malindi. Time-series models strongly suggest that the observed decline in malaria admissions was a result of malaria-specific control efforts in the hospital catchment areas.</p> <p>Conclusion</p> <p>This study provides evidence of a changing disease burden on the Kenyan coast and that the most parsimonious explanation is an expansion in the coverage of interventions such as the use of insecticide-treated nets and the availability of anti-malarial medicines. While specific attribution to intervention coverage cannot be computed what is clear is that this area of Kenya is experiencing a malaria epidemiological transition.</p

Malaria-related mortality based on verbal autopsy in an area of low endemicity in a predominantly rural population in Ethiopia

<p>Abstract</p> <p>Background</p> <p>Although malaria is one of the most important causes of death in Ethiopia, measuring the magnitude of malaria-attributed deaths at community level poses a considerable difficulty. Nevertheless, despite its low sensitivity and specificity, verbal autopsy (VA) has been the most important technique to determine malaria-specific cause of death for community-based studies. The present study was undertaken to assess the magnitude of malaria mortality in a predominantly rural population of Ethiopia using VA technique at Butajira Rural Health Programme (BRHP) Demographic Surveillance Site (DSS).</p> <p>Methods</p> <p>A verbal autopsy was carried out for a year from August 2003 to July 2004 for all deaths identified at BRPH-DSS. Two trained physicians independently reviewed each VA questionnaire and indicated the most likely causes of death. Finally, all malaria related deaths were identified and used for analysis.</p> <p>Results</p> <p>A verbal autopsy study was successfully conducted in 325 deaths, of which 42 (13%) were attributed to malaria. The majority of malaria deaths (47.6%) were from the rural lowlands compared to those that occurred in the rural highlands (31%) and urban (21.4%) areas. The proportional mortality attributable to malaria was not statistically significant among the specific age groups and ecological zones. Mortality from malaria was reckoned to be seasonal; 57% occurred during a three-month period at the end of the rainy season between September and November. About 71% of the deceased received some form of treatment before death, while 12 (28.6%) of those who died neither sought care from a traditional healer nor were taken to a conventional health facility before death. Of those who sought treatment, 53.3% were first taken to a private clinic, 40% sought care from public health facilities, and the remaining two (6.7%) received traditional medicine. Only 11.9% of the total malaria-related deaths received some sort of treatment within 24h after the onset of illness.</p> <p>Conclusion</p> <p>The results of this study suggest that malaria plays a considerable role as a cause of death in the study area. Further data on malaria mortality with a relatively large sample size for at least two years will be needed to substantially describe the burden of malaria mortality in the study area.</p

Modulation of Transmission Spectra of Anodized Alumina Membrane Distributed Bragg Reflector by Controlling Anodization Temperature

We have successfully prepared anodized alumina membrane distributed Bragg reflector (DBR) using electrochemical anodization method. The transmission peak of this distributed Bragg reflector could be easily and effectively modulated to cover almost any wavelength range of the whole visible spectrum by adjusting anodization temperature

Viral Paratransgenesis in the Malaria Vector Anopheles gambiae

Paratransgenesis, the genetic manipulation of insect symbiotic microorganisms, is being considered as a potential method to control vector-borne diseases such as malaria. The feasibility of paratransgenic malaria control has been hampered by the lack of candidate symbiotic microorganisms for the major vector Anopheles gambiae. In other systems, densonucleosis viruses (DNVs) are attractive agents for viral paratransgenesis because they infect important vector insects, can be genetically manipulated and are transmitted to subsequent generations. However, An. gambiae has been shown to be refractory to DNV dissemination. We discovered, cloned and characterized the first known DNV (AgDNV) capable of infection and dissemination in An. gambiae. We developed a flexible AgDNV-based expression vector to express any gene of interest in An. gambiae using a two-plasmid helper-transducer system. To demonstrate proof-of-concept of the viral paratransgenesis strategy, we used this system to transduce expression of an exogenous gene (enhanced green fluorescent protein; EGFP) in An. gambiae mosquitoes. Wild-type and EGFP-transducing AgDNV virions were highly infectious to An. gambiae larvae, disseminated to and expressed EGFP in epidemiologically relevant adult tissues such as midgut, fat body and ovaries and were transmitted to subsequent mosquito generations. These proof-of-principle data suggest that AgDNV could be used as part of a paratransgenic malaria control strategy by transduction of anti-Plasmodium peptides or insect-specific toxins in Anopheles mosquitoes. AgDNV will also be extremely valuable as an effective and easy-to-use laboratory tool for transient gene expression or RNAi in An. gambiae

The epidemiology of malaria in adults in a rural area of southern Mozambique

BACKGROUND: Epidemiological studies of malaria in adults who live in malaria endemic areas are scarce. More attention to the natural history of malaria affecting adults is needed to understand the dynamics of malaria infection and its interaction with the immune system. The present study was undertaken to investigate the clinical, parasitological and haematological status of adults exposed to malaria, and to characterize parasites in these individuals who progressively acquire protective immunity. METHODS: A cross-sectional survey of 249 adults was conducted in a malaria endemic area of Mozambique. Clinical, parasitological and haematological status of the study population was recorded. Sub-microscopic infections and multiplicity of infections were investigated using polymerase chain reaction (PCR) and restriction fragment length polymorphism of Plasmodium falciparum merozoite surface protein 2 (msp2). RESULTS: Prevalence of P. falciparum infection by microscopy (14%) and PCR (42%) decreased progressively during adulthood, in parallel with an increase in the prevalence of sub-microscopic infections. Anaemia was only related to parasitaemia as detected by PCR. Multiplicity of infection decreased with age and was higher in subjects with high P. falciparum densities, highlighting density-dependent constraints upon the PCR technique. CONCLUSION: Adults of Manhiça progressively develop non-sterile, protective immunity against P. falciparum malaria. The method of parasite detection has a significant effect on the observed natural history of malaria infections. A more sensitive definition of malaria in adults should be formulated, considering symptoms such as diarrhoea, shivering and headache, combined with the presence of parasitaemia

A blind accuracy assessment of computer-modeled forensic facial reconstruction using computed tomography data from live subjects.

A computer modeling system for facial reconstruction has been developed that employs a touch-based application to create anatomically accurate facial models focusing on skeletal detail. This article discusses the advantages and disadvantages of the system and illustrates its accuracy and reliability with a blind study using computed tomography (CT) data of living individuals. Three-dimensional models of the skulls of two white North American adults (one male, one female) were imported into the computer system. Facial reconstructions were produced by two practitioners following the Manchester method. Two posters were produced, each including a face pool of five surface model images and the facial reconstruction. The face pool related to the sex, age, and ethnic group of the target individual and included the surface model image of the target individual. Fifty-two volunteers were asked to choose the face from the face pool that most resembled each reconstruction. Both reconstructions received majority percentage hit rates that were at least 50% greater than any other face in the pool. The combined percentage hit rate was 50% above chance (70%). A quantitative comparison of the facial morphology between the facial reconstructions and the CT scan models of the subjects was carried out using Rapidform(™) 2004 PP2-RF4. The majority of the surfaces of the facial reconstructions showed less than 2.5 mm error and 90% of the male face and 75% of the female face showed less than 5 mm error. Many of the differences between the facial reconstructions and the facial scans were probably the result of positional effects caused during the CT scanning procedure, especially on the female subject who had a fatter face than the male subject. The areas of most facial reconstruction error were at the ears and nasal tip

Fanconi anaemia with bilateral diffuse pulmonary arterio venous fistulae: a case report

<p>Abstract</p> <p>Background</p> <p>We report a patient with cytogenetically confirmed Fanconi anaemia with associated diffuse bilateral pulmonary arterio-venous fistulae. This is only the second reported case of diffuse pulmonary arterio-venous fistulae with Fanconi anaemia.</p> <p>Case Presentation</p> <p>A 16 year old Sri Lankan boy, with a cytogenetically confirmed Fanconi anaemia was admitted to University Medical Unit, National Hospital of Sri Lanka for further assessment and treatment. Both central and peripheral cyanosis plus clubbing were noted on examination. The peripheral saturation was persistently low on room air and did not improve with supplementary Oxygen. Contrast echocardiography failed to demonstrate an intra cardiac shunt but showed early crossover of contrast, suggesting the possibility of pulmonary arterio-venous fistulae. Computed tomography pulmonary angiogram was inconclusive. Subsequent right heart catheterisation revealed bilateral diffuse arterio-venous fistulae not amenable for device closure or surgical intervention.</p> <p>Conclusion</p> <p>To our knowledge, this is the second reported patient with diffuse pulmonary arterio-venous fistulae associated with Fanconi anaemia. We report this case to create awareness among clinicians regarding this elusive association. We recommend screening patients with Fanconi anaemia using contrast echocardiography at the time of assessment with transthoracic echocardiogram. Though universal screening may be impossible given the cost constraints, such screening should at least be performed in patients with clinical evidence of desaturation or when a therapeutic option such as haematopoietic stem cell transplantation is considered. Treatment of pulmonary arteriovenous fistulae would improve patient outcome as desaturation by shunting worsens the anaemic symptoms by reducing the oxygen carrying capacity of blood.</p