An experimental study of the flow of gas along synthetic faults of varying orientation to the stress field: implications for performance assessment of radioactive waste disposal

Critical stress theory states that fault transmissivity is strongly dependent upon orientation with respect to the stress tensor. This paper describes an experimental study aimed at verifying critical stress theory using a bespoke angled shear rig designed to examine the relationship between gas flows along a kaolinite-filled synthetic fault as a function of fault dip. A total of 22 gas injection experiments were conducted on faults oriented 0°, 15°, 30°, and 45° to horizontal; both with and without active shear. Gas flow was seen to be complex; repeat gas injection testing showed a consistent gas entry pressure but considerably different, nonrepeatable, gas peak or breakthrough pressure. Gas flow occurred along discrete, dilatant pathways. The physics governing the pressure at which these features formed was repeatable; however, permeability was dependent on the number, distribution, and geometry of the resultant pathways. The nonrepeatable gas response suggests that the number of pathways was dependent on very subtle variations in gouge properties. No fault orientations were seen to exhibit nonflow characteristics, although critical stress theory predicted that two of the investigated fault angles should be effective seals. However, a small variation in gas entry pressure was seen with fault angle as a result of varying normal and shear stress acting on the gouge material. Shear was seen to enhance gas movement by reducing gas entry pressure and increased permeability once gas became mobile. Therefore, in kaolinite gouge-filled faults, shear is not an effective self-sealing mechanism to gas flow

The role of the stress-path and importance of stress history on the flow of water along fractures and faults; an experimental study conducted on kaolinite gouge and Callovo-Oxfordian mudstone

The flow of water along discontinuities, such as fractures or faults, is of paramount importance in understanding the hydromechanical response of an underground geological disposal facility for radioactive waste. This paper reports four experiments conducted on kaolinite gouge on a 30° slip-plane and on realistic fractures created in Callovo-Oxfordian mudstone (COx) from France. Test histories were conducted that initially loaded the gouge material in step changes in vertical stress, followed by unloading of the sample in similar steps. This loading-unloading history showed considerable hysteresis in hydraulic flow, with only partial recovery of fracture transmissivity. This demonstrates the importance of stress history on fracture flow; consideration of just the current stress acting upon a fracture or fault may result in inaccuracies of predicted hydraulic flow. The stress dependency of fracture flow in both kaolinite and COx can be described by a power-law or cubic relationship, which is likely to be dependent on the fracture roughness, thickness of gouge material, saturation state, permeability of the host material, and clay mineralogy (i.e. swelling potential). The observed response of fracture transmissivity to normal stress in COx is a complex superposition of mechanical response of the fracture and the swelling of clay in the fracture surface. The stress-dependency of flow was also seen to be dependent on orientation with respect to bedding. A fracture perpendicular with bedding accommodates greater compression and results in a lower transmissivity. The orientation dependence is related to the anisotropic swelling characteristics of CO

Fewer and better-educated children: Expanded choices in schooling and fertility in rural Pakistan

This report presents the results of a longitudinal study of changing educational opportunities in rural Punjab and N.W.F.P. from 1997 to 2004. The purpose of the study was to answer two major research questions: what were the effects of changes in schooling opportunities in the community over the past six years on enrollment and attainment, and what were the effects on family planning and fertility behavior? This study builds on an earlier study undertaken in 1997. As noted in this report, the study is innovative in several ways: (1) it is longitudinal; (2) it combines consideration of three dimensions of schooling opportunity structures in the community—access, choice, and quality; (3) it considers the availability of school choice, in particular private versus government and religious versus secular, as a factor in educational attainment and performance; and (4) it defines schooling opportunity structures separately for boys and girls on all three dimensions—quality, choice, and access. The longitudinal nature of the study has two dimensions: a school component and a household-based component. All schools visited in the first survey were revisited in the second survey as were women previously interviewed in 1997

Preventing ethics dumping: the challenges for Kenyan research ethics committees

Ethics dumping is the practice of undertaking research in a low- or middle-income setting which would not be permitted, or would be severely restricted, in a high-income setting. Whilst Kenya operates a sophisticated research governance system, resource constraints and the relatively low number of accredited research ethics committees limit the capacity for ensuring ethical compliance. As a result, Kenya has been experiencing cases of ethics dumping. This article presents 11 challenges in the context of preventing ethics dumping in Kenya, namely variations in governance standards, resistance to double ethics review, resource constraints, unresolved issues in the management of biological samples, unresolved issues in the management of primary data, unsuitable informed consent procedures, cultural insensitivity, differing standards of care, reluctance to provide feedback to research communities, power differentials which facilitate the exploitation of local researchers and lack of local relevance and/or affordability of the resultant products. A reflective approach for researchers, built around the values of fairness, respect, care and honesty, is presented as a means of taking shared responsibility for preventing ethics dumping

Helicobacter pylori and cancer among adults in Uganda

Data from Africa on infection with Helicobacter pylori (H. pylori) are sparse. Therefore, as part of an epidemiological study of cancer in Uganda, we investigated the prevalence and determinants of antibodies against H. pylori among 854 people with different cancer types and benign tumours. Patients were recruited from hospitals in Kampala, Uganda, interviewed about various demographic and lifestyle factors and tested for antibodies against H. pylori. In all patients combined, excluding those with stomach cancer (which has been associated with H. pylori infection), the prevalence of antibodies was 87% (723/833) overall, but declined with increasing age (p = 0.02) and was lower among people who were HIV seropositive compared to seronegative (p <0.001). Otherwise, there were few consistent epidemiological associations. Among those with stomach cancer, 18/21 (86%) had anti-H. pylori antibodies (odds ratio 0.8, 95% confidence intervals 0.2–2.9, p = 0.7; estimated using all other patients as controls, with adjustment for age, sex and HIV serostatus). No other cancer site or type was significantly associated with anti-H. pylori antibodies. The prevalence of H. pylori reported here is broadly in accord with results from other developing countries, although the determinants of infection and its' role in the aetiology of gastric cancer in Uganda remain unclear

Adolescents and Youth in Pakistan 2001-2002: A Nationally Representative Survey

Published by the Population Council\u27s Islamabad office, this is the first comprehensive survey of Pakistani youth. The report provides an unprecedented view of young people\u27s experiences with and attitudes about education, employment, families, and marriage. The report findings confirm the large differences in the current situation of adolescents and youth, males versus females, from different strata of residence and economic status. Addressing these requires government intervention, changes in attitude, and input from the media, women and youth groups, and members of civil society

Gendered immobility: influence of social roles and local context on mobility decisions in Pakistan

This paper examines the instances of one-day immobility in Pakistan and reports its socio-demographic determinants using the nationally representative dataset of the 2007 Pakistan Time Use Survey. Of 37,830 time diary respondents, nearly 30% did not report travel during the diary day. Homemakers and those out of the workforce were more likely to be immobile than employed or student respondents. Immobility rates were very high among women (55%) as compared to men (4%). Among women, those between 20 and 34 years of age, married, with children, having better education, dependent on other household members and those living in higher income households were more likely to be immobile. The excessive gender nature of immobility seems to be triggered by a gender-based sociocultural environment, which restricts female mobility due to family honor concerns. Other than this, those living in the provinces of Sindh and Khyber Pakhtunkhwa or in urban areas were more likely to be immobile than those living in Punjab and Sindh provinces or in rural areas. The significant geographic effect at broader spatial scale is caused by the demographic structure as well as due to differences in the social and cultural context of these areas. Finally, questions regarding the measurement of immobility and the potential implications of increased female immobility are discussed