Enhancing the CO2 trapping capacity of Saudi Arabian basalt via nanofluid treatment: Implications for CO2 geo-storage.

Mineralization reactions in basaltic formations have gained recent interest as an effective method for CO2 geo-storage in order to mitigate anthropogenic greenhouse gas emissions. The CO2/rock interactions, including interfacial tension and wettability, are crucial factors in determining the CO2 trapping capacity and the feasibility of CO2 geological storage in these formations. The Red Sea geological coast in Saudi Arabia has many basaltic formations, and their wetting characteristics are rarely reported in the literature. Moreover, organic acid contamination is inherent in geo-storage formations and significantly impacts their CO2 geo-storage capacities. Hence, to reverse the organic effect, the influence of various SiO2 nanofluid concentrations (0.05-0.75 wt%) on the CO2-wettability of organic-acid aged Saudi Arabian (SA) basalt is evaluated herein at 323 K and various pressures (0.1-20 MPa) via contact angle measurements. The SA basalt substrates are characterized via various techniques, including atomic force microscopy, energy dispersive spectroscopy, scanning electron microscopy, and others. In addition, the CO2 column heights that correspond to the capillary entry pressure before and after nanofluid treatment are calculated. The results show that the organic acid-aged SA basalt substrates become intermediate-wet to CO2-wet under reservoir pressure and temperature conditions. When treated with SiO2 nanofluids, however, the SA basalt substrates become weakly water-wet, and the optimum performance is observed at an SiO2 nanofluid concentration of 0.1 wt%. At 323 K and 20 MPa, the CO2 column height corresponding to the capillary entry pressure increases from -957 m for the organic-aged SA basalt to 6253 m for the 0.1 wt% nano-treated SA basalt. The results suggest that the CO2 containment security of organic-acid-contaminated SA basalt can be enhanced by SiO2 nanofluid treatment. Thus, the results of this study may play a significant role in assessing the trapping of CO2 in SA basaltic formations.

A coupled phase-field and reactive-transport framework for fracture propagation in poroelastic media.

We present a novel approach to model hydro-chemo-mechanical responses in rock formations subject to fracture propagation within chemically active rock formations. The framework developed integrates the mechanisms of reactive transport, fluid flow and transport in porous media, and phase-field modelling of fracture propagation in poroelastic media. The solution approach integrates the geochemical package PHREEQC with a finite-element open-source platform, FEniCs. The PHREEQC solver is used to calculate the localized chemical reaction, including solid dissolution/precipitation. The resulting solid weakening by chemical damage is estimated from the reaction-induced porosity change. The proposed coupled model was verified with previous numerical results and applied to a synthetic case exhibiting hydraulic fracturing enhanced with chemical damage. Simulation results suggest that mechanical failure could be accelerated in the presence of ongoing chemical processes due to rock weakening and porosity changes, allowing the nucleation, growth, and development of fractures.

The effect of particle shape on discharge and clogging.

Granular flow is common across different fields from energy resource recovery and mineral processing to grain transport and traffic flow. Migrating particles may jam and form arches that span constrictions and hinder particle flow. Most studies have investigated the migration and clogging of spherical particles, however, natural particles are rarely spherical, but exhibit eccentricity, angularity and roughness. New experiments explore the discharge of cubes, 2D crosses, 3D crosses and spheres under dry conditions and during particle-laden fluid flow. Variables include orifice-to-particle size ratio and solidity. Cubes and 3D crosses are the most prone to clogging because of their ability to interlock or the development of face-to-face contacts that can resist torque and enhance bridging. Spheres arriving to the orifice must be correctly positioned to create stable bridges, while flat 2D crosses orient their longest axes in the direction of flowlines across the orifice and favor flow. Intermittent clogging causes kinetic retardation in particle-laden flow even in the absence of inertial effects; the gradual increase in the local particle solidity above the constriction enhances particle interactions and the probability of clogging. The discharge volume before clogging is a Poisson process for small orifice-to-particle size ratio; however, the clogging probability becomes history-dependent for non-spherical particles at large orifice-to-particle size ratio and high solidities, i.e., when particle-particle interactions and interlocking gain significance.

Infant human immunodeficiency virus diagnosis in resource-limited settings: issues, technologies, and country experiences.

Diagnosing human immunodeficiency virus (HIV) infection in infants is difficult because maternal HIV antibodies cross the placenta, causing positive serologic tests in HIV-exposed infants for the first several months of life. Early definitive diagnosis of HIV requires virologic testing such as polymerase chain reaction (PCR), which is the diagnostic standard in resource-rich settings but has been too complex and expensive for widespread use in most countries with high HIV prevalence. Early PCR testing can help HIV-infected infants access treatment, provide psychosocial benefits for families of uninfected infants, and help programs for prevention of mother-to-child transmission of HIV monitor their effectiveness. HIV testing, including PCR, is increasingly available for infants in resource-limited settings, but there are many barriers and complex policy decisions that need to be addressed before universal early testing can become standard. This paper reviews challenges and progress in the field and suggests ways to facilitate early infant testing in resource-limited settings.

Auditory target processing in methadone substituted opiate addicts: the effect of nicotine in controls.

BACKGROUND: The P300 component of the auditory evoked potential is an indicator of attention dependent target processing. Only a few studies have assessed cognitive function in substituted opiate addicts by means of evoked potential recordings. In addition, P300 data suggest that chronic nicotine use reduces P300 amplitudes. While nicotine and opiate effects combine in addicted subjects, here we investigated the P300 component of the auditory event related potential in methadone substituted opiate addicts with and without concomitant non-opioid drug use in comparison to a group of control subjects with and without nicotine consumption. METHODS: We assessed 47 opiate addicted out-patients under current methadone substitution and 65 control subjects matched for age and gender in an 2-stimulus auditory oddball paradigm. Patients were grouped for those with and without additional non-opioid drug use and controls were grouped for current nicotine use. P300 amplitude and latency data were analyzed at electrodes Fz, Cz and Pz. RESULTS: Patients and controls did not differ with regard to P300 amplitudes and latencies when whole groups were compared. Subgroup analyses revealed significantly reduced P300 amplitudes in controls with nicotine use when compared to those without. P300 amplitudes of methadone substituted opiate addicts were in between the two control groups and did not differ with regard to additional non-opioid use. Controls with nicotine had lower P300 amplitudes when compared to patients with concomitant non-opioid drugs. No P300 latency effects were found. CONCLUSION: Attention dependent target processing as indexed by the P300 component amplitudes and latencies is not reduced in methadone substituted opiate addicts when compared to controls. The effect of nicotine on P300 amplitudes in healthy subjects exceeds the effects of long term opioid addiction under methadone substitution.

Qualitative assessment of the integration of HIV services with infant routine immunization visits in Tanzania.

BACKGROUND: In 2009, a project was implemented in 8 primary health clinics throughout Tanzania to explore the feasibility of integrating pediatric HIV prevention services with routine infant immunization visits. METHODS: We conducted interviews with 64 conveniently sampled mothers of infants who had received integrated HIV and immunization services and 16 providers who delivered the integrated services to qualitatively identify benefits and challenges of the intervention midway through project implementation. FINDINGS: Mothers' perceived benefits of the integrated services included time savings, opportunity to learn their child's HIV status and receive HIV treatment, if necessary. Providers' perceived benefits included reaching mothers who usually would not come for only HIV testing. Mothers and providers reported similar challenges, including mothers' fear of HIV testing, poor spousal support, perceived mandatory HIV testing, poor patient flow affecting confidentiality of service delivery, heavier provider workloads, and community stigma against HIV-infected persons; the latter a more frequent theme in rural compared with urban locations. INTERPRETATION: Future scale-up should ensure privacy of these integrated services received at clinics and community outreach to address stigma and perceived mandatory testing. Increasing human resources for health to address higher workloads and longer waiting times for proper patient flow is necessary in the long term.

Evaluation of using routine infant immunization visits to identify and follow-up HIV-exposed infants and their mothers in Tanzania.

BACKGROUND: Without treatment, approximately half of HIV-infected infants die by age 2 years, and 80% die before age 5 years. Early identification of HIV-infected and HIV-exposed infants provides opportunities for life-saving interventions. We evaluated integration of HIV-related services with routine infant immunization in Tanzania. METHODS: During April 2009 to March 2010, at 4 urban and 4 rural sites, mothers' HIV status was determined at first-month immunization using antenatal cards. HIV-exposed infants were offered HIV testing and follow-up care. Impact of integrated service delivery was assessed by comparing average monthly vaccine doses administered during the study period and a 2-year baseline period; acceptance was assessed by interviewing mothers and service providers. FINDINGS: During 7569 visits, 308 HIV-exposed infants were identified and registered; of these, 290 (94%) were tested, 15 (5%) were HIV infected. At urban sites, first-month vaccine doses remained stable (+2% for pentavalent vaccine and -4% for polio vaccine), and vaccine doses given later in life (pentavalent, polio, and measles) increased 12%, 8%, and 11%, respectively. At rural sites, first-month vaccine doses decreased 33% and 35% and vaccine doses given later in life decreased 23%, 28%, and 28%. Mothers and service providers generally favored integrated services; however, HIV-related stigma and inadequate confidentiality controls of HIV testing were identified, particularly at rural sites. INTERPRETATION: Integration of HIV-related services at immunization visits identified HIV-exposed infants, HIV-infected infants, and HIV-infected mothers; however, decreases in vaccine doses administered at rural sites were concerning. HIV-related service integration with immunization visits needs careful monitoring to ensure optimum vaccine delivery.

Hospitalization and mortality among primarily nonbreastfed children during a large outbreak of diarrhea and malnutrition in Botswana, 2006.

BACKGROUND: In 2006, a pediatric diarrhea outbreak occurred in Botswana, coinciding with heavy rains. Surveillance recorded a 3 times increase in cases and a 25 fold increase in deaths between January and March. Botswana has high HIV prevalence among pregnant women (33.4% in 2005), and an estimated 35% of all infants under the age of 6 months are not breastfed. METHODS: We followed all children <5 years old with diarrhea in the country's second largest referral hospital at the peak of the outbreak by chart review, interviewed mothers, and conducted laboratory testing for HIV and enteric pathogens. RESULTS: Of 153 hospitalized children with diarrhea, 97% were <2 years old; 88% of these were not breastfeeding. HIV was diagnosed in 18% of children and 64% of mothers. Cryptosporidium and enteropathogenic Escherichia coli were common; many children had multiple pathogens. Severe acute malnutrition (kwashiorkor or marasmus) developed in 38 (25%) patients, and 33 (22%) died. Kwashiorkor increased risk for death (relative risk 2.0; P = 0.05); only one breastfeeding child died. Many children who died had been undersupplied with formula. CONCLUSIONS: Most of the severe morbidity and mortality in this outbreak occurred in children who were HIV negative and not breastfed. Feeding and nutritional factors were the most important determinants of severe illness and death. Breastfeeding is critical to infant survival in the developing world, and support for breastfeeding among HIV-negative women, and HIV-positive women who cannot formula feed safely, may prevent further high-mortality outbreaks.

Cost-effectiveness of routine rapid human immunodeficiency virus antibody testing before DNA-PCR testing for early diagnosis of infants in resource-limited settings.

BACKGROUND: Infants born to HIV-infected women should receive HIV testing to allow early diagnosis and treatment. Recommendations for resource-limited settings stress laboratory-based virologic assays. While effective, these tests are logistically complex and expensive. This study explored the cost-effectiveness of incorporating initial screening with rapid HIV tests (RHT) into the conventional testing algorithm to screen-out HIV-uninfected infants, thereby reducing the need for costly virologic testing. METHODS: Data on HIV prevalence, RHT sensitivity and specificity, and costs were collected from 820 HIV-exposed children (1.5-18 months) attending 2 postnatal screening programs in Uganda during July 2005 to December 2006. Cost-effectiveness models compared the conventional testing algorithm DNA polymerase chain reaction (DNA-PCR with Roche Amplicor v1.5) with a modified algorithm (initial RHT to screen-out HIV-uninfected infants before DNA-PCR). RESULTS: The model estimated that the conventional algorithm would identify 94.3% (91.8%-94.7%) of HIV-infected infants, compared with 87.8% (79.4%-90.5%) for a modified algorithm using RHT (HIV 1/2 Determine) and excluding the need for DNA-PCR for HIV antibody-negative infants. Costs per infant were $23.47 ($23.32-$23.76) for the conventional algorithm and between $22.75 ($21.89-$23.31) and $7.58 ($6.41-$10.75) for the modified algorithm, depending on infant age and symptoms. Compared with the conventional algorithm, costs per HIV-infected infant identified using the modified algorithm were higher in 1.5-to 3-month-old infants, but significantly lower in 3-month-old and older infants. Models replicating the whole infant testing program showed the modified algorithm would have marginally lower sensitivity, but would reduce total program costs by 27% to 40%, producing an incremental cost-effectiveness ratio of $1489 ($686-$6781) for the conventional versus modified algorithms. CONCLUSIONS: Screening infants with RHT before DNA-PCR is cost-effective in infants 3 months old or older. Incorporating RHT into early infant testing programs could improve cost-effectiveness and reduce program costs.