Investigations of meltwater refreezing and density variations in the snowpack and firn within the percolation zone of the Greenland Ice Sheet

The mass balance of polythermal ice masses is critically dependent on the proportion of surface-generated meltwater that subsequently refreezes in the snowpack and firn. In order to quantify this effect and to characterize its spatial variability, we measured near-surface (26%, resulting in a 32% increase in net accumulation. This 'seasonal densification' increased at lower elevations, rising to 47% 10 km closer to the ice-sheet margin at 1860 m a. s. l. Density/depth profiles from nine sites within 1 km2 at ∼1945 m a.s.l. reveal complex stratigraphies that change over short spatial scales and seasonally. We conclude that estimates of mass-balance change cannot be calculated solely from observed changes in surface elevation, but that near-surface densification must also be considered. However, predicting spatial and temporal variations in densification may not be straightforward. Further, the development of complex firn-density profiles both masks discernible annual layers in the near-surface firn and ice stratigraphy and is likely to introduce error into radar-derived estimates of surface elevation

Permeability evolution during progressive development of deformation bands in porous sandstones

[1] Triaxial deformation experiments were carried out on large (0.1 m) diameter cores of a porous sandstone in order to investigate the evolution of bulk sample permeability as a function of axial strain and effective confining pressure. The log permeability of each sample evolved via three stages: (1) a linear decrease prior to sample failure associated with poroelastic compaction, (2) a transient increase associated with dynamic stress drop, and (3) a systematic quasi-static decrease associated with progressive formation of new deformation bands with increasing inelastic axial strain. A quantitative model for permeability evolution with increasing inelastic axial strain is used to analyze the permeability data in the postfailure stage. The model explicitly accounts for the observed fault zone geometry, allowing the permeability of individual deformation bands to be estimated from measured bulk parameters. In a test of the model for Clashach sandstone, the parameters vary systematically with confining pressure and define a simple constitutive rule for bulk permeability of the sample as a function of inelastic axial strain and effective confining pressure. The parameters may thus be useful in predicting fault permeability and sealing potential as a function of burial depth and faul

Study of Gas-Fluidization Dynamics with Laser-Polarized Xe-129

Abstract We report initial NMR studies of gas dynamics in a particle bed fluidized by laser-polarized xenon ( 129 Xe) gas. We have made preliminary measurements of two important characteristics: gas exchange between the bubble and emulsion phases and the gas velocity distribution in the bed. We used T 2 * contrast to differentiate the bubble and emulsion phases by choosing solid particles with large magnetic susceptibility. Experimental tests demonstrated that this method was successful in eliminating 129 Xe magnetization in the emulsion phase, which enabled us to observe the time dependence of the bubble magnetization. By employing the pulsed field gradient method, we also measured the gas velocity distribution within the bed. These results clearly show the onset of bubbling and can be used to deduce information about gas and particle motion in the fluidized bed.

Corporate Governance in Microfinance Institutions: Board Composition and the Ability to Face Institutional Voids

Manuscript Type: Empirical Research Question/Issue: We utilize institutional theory to examine corporate governance in microfinance institutions (MFIs). Many MFIs operate at the bottom of the economic pyramid (BOP), which is usually agrarian, impoverished, and plagued with institutional voids. We investigate the link between the composition of the boards of MFIs and the ability of the MFIs to face institutional voids to ensure organizational viability. Research Findings/Insights: We find that MFIs with boards that have more socio-economic expertise and female representation are better able to lower the MFI’s costs of operating at the BOP. However, this relationship weakens when the effectiveness of agrarian institutions at the BOP is low. When agrarian institutions are ineffective, the board of the MFI may have difficulty in helping the MFI reduce its costs of operating at the BOP. Agrarian crises arising from ineffective agrarian institutions tend to aggravate the various institutional voids present at the BOP, making it harder for the board to guide the MFI around the institutional voids. Theoretical/Academic Implications: We extend institutional theory to understand how boards direct and control firms operating at the BOP to face institutional voids. In some cases, a firm can fill an institutional void. However, because other institutional voids exist, the board must also help the firm develop workarounds to ensure organizational viability. We extend existing literature on board composition to highlight how human capital and gender diversity of boards can help improve the viability of firms operating at the BOP. Practitioner/Policy Implications: MFIs with high operating costs may benefit from electing a board with socio-economic expertise and female representatives. Governments and policy makers can work toward building effective social, economic, and political institutions to help create contexts that are favorable to firms (such as MFIs) that often find it difficult to operate at the BOP

What are emergency ambulance services doing to meet the needs of people who call frequently? A national survey of current practice in the United Kingdom

Background Emergency ambulance services are integral to providing a service for those with unplanned urgent and life-threatening health conditions. However, high use of the service by a small minority of patients is a concern. Our objectives were to describe: service-wide and local policies or pathways for people classified as Frequent Caller; call volume; and results of any audit or evaluation. Method We conducted a national survey of current practice in ambulance services in relation to the management of people who call the emergency ambulance service frequently using a structured questionnaire for completion by email and telephone interview. We analysed responses using a descriptive and thematic approach. Results Twelve of 13 UK ambulance services responded. Most services used nationally agreed definitions for ‘Frequent Caller’, with 600–900 people meeting this classification each month. Service-wide policies were in place, with local variations. Models of care varied from within-service care where calls are flagged in the call centre; contact made with callers; and their General Practitioner (GP) with an aim of discouraging further calls, to case management through cross-service, multi-disciplinary team meetings aiming to resolve callers’ needs. Although data were available related to volume of calls and number of callers meeting the threshold for definition as Frequent Caller, no formal audits or evaluations were reported. Conclusions Ambulance services are under pressure to meet challenging response times for high acuity patients. Tensions are apparent in the provision of care to patients who have complex needs and call frequently. Multi-disciplinary case management approaches may help to provide appropriate care, and reduce demand on emergency services. However, there is currently inadequate evidence to inform commissioning, policy or practice development

Development of a new quality of life measure for Duchenne muscular dystrophy using mixed methods

Objective Based on concerns over existing patient reported outcome measures (PROMs) for assessing quality of life (QoL) in Duchenne muscular dystrophy (DMD), we describe the mixed methods development of a new QoL PROM for use in boys and men with DMD: the DMD-QoL. Methods The DMD-QoL was developed in 3 stages. First, draft items were generated from 18 semi-structured qualitative interviews with boys and men with DMD, analysed using framework analysis. Second, cognitive debriefing interviews with patients (n = 10), clinicians (n = 8), and patients' parents (n = 10) were undertaken and a reduced item set selected and refined. Third, psychometric data on the draft items from a cross-sectional online survey (n = 102), and stakeholder input from patients and patients' parents, was used to produce the final questionnaire. Patient and public involvement and engagement was embedded throughout the process. Results From an initial draft of 47 items, a revised set of 27 items was produced at stage 2, and this set was further refined at stage 3 to generate the DMD-QoL, a 14-item QoL PROM. The DMD-QoL is designed for use from 7 years of age by proxy report and from 10 years of age by self or proxy report. The final measure showed good psychometric properties. Conclusions The DMD-QoL is a new 14-item QoL PROM for boys and men with DMD, with demonstrable content and face validity

Does co-creation impact public service delivery?:The importance of state and governance traditions

Co-creation in public service delivery requires partnerships between citizens and civil servants. The authors argue that whether or not these partnerships will be successful depends on state and governance traditions (for example a tradition of authority sharing or consultation). These traditions determine the extent to which co-creation can become institutionalized in a country’s governance framework

A Low Protein Diet Increases the Hypoxic Tolerance in Drosophila

Dietary restriction is well known to increase the life span of a variety of organisms from yeast to mammals, but the relationships between nutrition and the hypoxic tolerance have not yet been considered. Hypoxia is a major cause of cell death in myocardial infarction and stroke. Here we forced hypoxia-related death by exposing one-day-old male Drosophila to chronic hypoxia (5% O(2)) and analysed their survival. Chronic hypoxia reduced the average life span from 33.6 days to 6.3 days when flies were fed on a rich diet. A demographic analysis indicated that chronic hypoxia increased the slope of the mortality trajectory and not the short-term risk of death. Dietary restriction produced by food dilution, by yeast restriction, or by amino acid restriction partially reversed the deleterious action of hypoxia. It increased the life span of hypoxic flies up to seven days, which represented about 25% of the life time of an hypoxic fly. Maximum survival of hypoxic flies required only dietary sucrose, and it was insensitive to drugs such as rapamycin and resveratrol, which increase longevity of normoxic animals. The results thus uncover a new link between protein nutrition, nutrient signalling, and resistance to hypoxic stresses

PH wave-front propagation in the urea-urease reaction

The urease-catalyzed hydrolysis of urea displays feedback that results in a switch from acid (pH ∼3) to base (pH ∼9) after a controllable period of time (from 10 to \u3e5000 s). Here we show that the spatially distributed reaction can support pH wave fronts propagating with a speed of the order of 0.1-1 mm min-1. The experimental results were reproduced qualitatively in reaction-diffusion simulations including a Michaelis-Menten expression for the urease reaction with a bell-shaped rate-pH dependence. However, this model fails to predict that at lower enzyme concentrations, the unstirred reaction does not always support fronts when the well-stirred reaction still rapidly switches to high pH. © 2012 by the Biophysical Society