Measuring β-cell function in vivo to understand the pathophysiology of type 2 diabetes

Diabetes arises when insulin secretion is inadequate for the prevailing metabolic conditions. As such appropriate measurement of β-cell function is necessary for a better understanding of the pathophysiology of prediabetes and diabetes. Unfortunately this is not a straightforward process and requires utilization of mathematical modelling to best appreciate its complexities. This is because insulin concentrations in the plasma represent a balance between the processes of secretion, hepatic extraction and clearance. In isolation such simple measures reveal very little about β-cell function. Moreover, since insulin lowers glucose accounting for the effect of the former on the latter it is a key part of understanding insulin action. The development of the minimal model has allowed simultaneous measurement of the dynamic relationship between insulin secretion and insulin action and produces a quantitative number – the Disposition Index – which quantifies β-cell function. At present this remains the best functional measure of islet health, however, it may not capture other phenotypes such as β-cell senescence or the effect of incretin hormones on β-cell function. Future ongoing development and interaction with other technologies, such as functional imaging, should enhance the contribution of this functional testing to the prevention, treatment and understanding of type 2 diabetes.peer-reviewe

An Emancipatory Study Exploring the Educational Experiences of Unaccompanied Children and Young People

This research was set within the context of the refugee crisis and children and young people’s (CYP) rights. This study aimed to explore the educational experiences of unaccompanied children and young people (UCYP), a particularly high-risk group who are separated from their parents due to reasons such as war, persecution or violence, and whom do not have the protection of a responsible adult. A systematic literature review indicated a paucity of research around UCYP’s educational experiences from their perspective. To address this gap, qualitative emancipatory and exploratory research was undertaken which encompassed the following research question: ‘What factors contribute to UCYP’s positive experiences within the education setting?’ The research employed a participatory approach and used visual participatory methods (camera walking tours and collages) to explore the views of five UCYP (aged 16 to 18) attending an English for Speakers of Other Languages (ESOL) course within college. Data was produced in the form of photographs with accompanying written text, notes from discussions with UCYP, and collages created from magazine and newspaper cuttings. The visual and written data was analysed using thematic analysis. The research indicated that the education setting provided an environment within which UCYP could fulfil a range of needs (physical, social, emotional, and spiritual). It provided a secure base where they could meet their basic needs for food and shelter and develop relationships with teachers and peers which was important for their sense of belonging and wellbeing. Furthermore, the young people held high aspirations for themselves and their future, and saw education, and speaking English, as essential for meeting these goals. The researcher reflected on the strengths and limitations in undertaking a participatory design and in conducting emancipatory research. Implications for EP practice were outlined which includes promoting the importance of relationships and cultural diversity through consultation and training and using visual participatory approaches to promote the voice of CYP

Monitoring magnetosheath-magnetosphere interconnection topology from the aurora

International audienceA strong southward rotation of the IMF (BZ from 5 to -6 nT in ~ 20 s) on 4 January 1995 caused an abrupt reconfiguration of midday aurorae and plasma convection consisting of the following: (1) the red-line aurora associated with magnetosheath plasma transfer at the low-latitude magnetopause appeared at the same time that (2) the green-line aurora from precipitating energetic plasma sheet particles equatorward of the cusp (near the open-closed field line boundary) weakened visibly and shifted equatorward, (3) the high-latitude aurora during the previous northward IMF, which is associated with lobe reconnection, persisted briefly (3 min) and brightened, before it disappeared from the field-of-view, (4) the activation of a strong convection bay (DPY current) at cusp and sub-cusp latitudes when the field turned strongly south, (5) a distinct wave motion of the plasma sheet outer boundary, as inferred from the aurora, which correlates closely with Pc 5 magnetic pulsations. Our interpretation of the dramatic reconfiguration is that reconnection poleward of the cusp coexisted briefly with reconnection at sub-cusp latitudes. The latter provided a magnetic field connection which enabled, on the one hand, magnetosheath particles to enter and cause the red-line cusp aurora, and on the other hand, allowed for magnetospheric energetic particles to escape and weaken the outer plasma sheet source of the green-line emission. The coexistence of the two cusp auroras reflects the time required for one field line topology to replace another, which, under the prevailing high speed wind ( ~ 650 km/s), lasts ~ 3?4 min. The motion of open flux tubes propagating from equator to pole during this transition is traced in the aurora by a poleward moving form. The waves on the outer boundary of the plasma sheet are most likely due to the Kelvin-Helmholtz instability. The study illustrates the ability of local auroral observations to monitor even a global change in magnetospheric magnetic topology

Plasma flows, Birkeland currents and auroral forms in relation to the Svalgaard-Mansurov effect

The traditional explanation of the polar cap magnetic deflections, referred to as the Svalgaard-Mansurov effect, is in terms of currents associated with ionospheric flow resulting from the release of magnetic tension on newly open magnetic field lines. In this study, we aim at an updated description of the sources of the Svalgaard-Mansurov effect based on recent observations of configurations of plasma flow channels, Birkeland current systems and aurorae in the magnetosphere-ionosphere system. Central to our description is the distinction between two different flow channels (FC 1 and FC 2) corresponding to two consecutive stages in the evolution of open field lines in Dungey cell convection, with FC 1 on newly open, and FC 2 on old open, field lines. Flow channel FC 1 is the result of ionospheric Pedersen current closure of Birkeland currents flowing along newly open field lines. During intervals of nonzero interplanetary magnetic field <I>B</I>_y component FC 1 is observed on either side of noon and it is accompanied by poleward moving auroral forms (PMAFs/prenoon and PMAFs/postnoon). In such cases the next convection stage, in the form of flow channel FC 2 on the periphery of the polar cap, is particularly important for establishing an IMF <I>B</I>_y-related convection asymmetry along the dawn-dusk meridian, which is a central element causing the Svalgaard-Mansurov effect. FC 2 flows are excited by the ionospheric Pedersen current closure of the northernmost pair of Birkeland currents in the four-sheet current system, which is coupled to the tail magnetopause and flank low-latitude boundary layer. This study is based on a review of recent statistical and event studies of central parameters relating to the magnetosphere-ionosphere current systems mentioned above. Temporal-spatial structure in the current systems is obtained by ground-satellite conjunction studies. On this point we emphasize the important information derived from the continuous ground monitoring of the dynamical behaviour of aurora and plasma convection during intervals of well-organised solar wind plasma and magnetic field conditions in interplanetary coronal mass ejections (ICMEs) during their Earth passage

Glycosylated haemoglobin (HbA1c) and cortisol levels on admission to intensive care as predictors of outcome

Objective: To evaluate the predictive value of glycosylated haemoglobin and cortisol on admission, in critical care patients. Design: Prospective, observational, single centre study. Setting: 14 bedded Intensive care unit of a tertiary-level university hospital. Patients: 124 consecutive emergency medical and surgical patients. Methods: Data collected on admission included patient demographics, medical history, medication, diagnosis, type of nutrition, TISS28 score, serum blood glucose, Glycosylated haemoglobin (HbA1c), cortisol, mean arterial blood pressure, and the use of inotropes in the first 24hrs. Daily baseline tests included complete blood count, urea and electrolytes, creatinine, twice weekly liver function tests. The primary outcome measure was intensive care unit mortality. Secondary outcome measures were ITU stay, days of ventilation, peak urea, peak creatinine, lowest platelet count, peak bilirubin, lowest Pa/FiO2, and the number of transfusions. Measurements and results: 124 patients (mean age 56.2 years SD 23.2) were included. Regression analysis was used to identify any potential predictors of outcome: HbA1c levels on admission were not found to be significantly associated with mortality (p=0.51), or any other secondary endpoints listed above. However, subgroup analysis revealed a predictive role of HbA1c with regards to length of ITU stay (p= 0.01) and number of days of ventilation (p=0.007) in those patients with a history of diabetes. Glucose level on admission emerged as an independent marker of mortality (p=0.009). Conclusions: This study suggests that HbA1c may not be a predictor of outcome in the general ITU population but may be of predictive value in diabetic ITU patients. On the other hand, blood glucose levels on admission emerged as a predictor of mortality, whilst no association was found between HbA1c and cortisol levels on admission.peer-reviewe

Plasma flow channels at the dawn/dusk polar cap boundaries: momentum transfer on old open field lines and the roles of IMF B-y and conductivity gradients

Using DMSP F13 data in conjunction with IMF data we investigate the newly discovered channels of enhanced (1.5–3 km/s) antisunward convection occurring at the dawn (06:00–09:00 MLT) or dusk (15:00–18:00 MLT) flanks of the polar cap for different combinations of IMF By polarity, hemisphere (NH/SH) and the dawn/dusk MLTs. Dawn-side cases where this flow channel appears occur for the following combinations: NH-dawn/By\u3e0 and SH-dawn/By\u3c0. The dusk-side cases are: NH-dusk/By\u3c0 and SH-dusk/By\u3e0. The flow channels are placed in the context of particle precipitation regimes/boundaries and ionospheric conductivity gradients. They are found to be threaded by old open field lines ( time since reconnection \u3e10 min) characterized by polar rain precipitation. In the dawn-side cases (NH-dawn/By\u3e0 and SH-dawn/By\u3c0) and in a Parker spiral field, the polar rain contains the solar wind strahl component. The convection enhancement is attributed to the Pedersen current closure of Birkeland current sheets (C1 and C2) in the polar cap (C1) and at the polar cap boundary (C2). The low ionospheric conductivity in the polar cap, particularly in the winter hemisphere, is compensated by an enhanced electric field driving the flow channel there. This is momentum transfer from the solar wind via dynamo action taking place in the combined current system of the high- and low-latitude boundary layers (HBL/LLBL). The conductivity gradient at the polar cap boundary contributes to establishing the convection channel and the associated enhancement of the dawn-dusk convection asymmetry extending beyond the dawn-dusk terminator during intervals of nonzero IMF By component. The HBL/LLBL-ionosphere coupling via Birkeland currents C1/C2 is a source of dawn-dusk convection asymmetry and Svalgaard-Mansurov effect which must be added to the effect of magnetic tension acting on newly open field lines

Aspects of magnetosphere–ionosphere coupling in sawtooth substorms: a case study

In a case study we report on repetitive substorm activity during storm time which was excited during Earth passage of an interplanetary coronal mass ejection (ICME) on 18 August 2003. Applying a combination of magnetosphere and ground observations during a favourable multi-spacecraft configuration in the plasma sheet (GOES-10 at geostationary altitude) and in the tail lobes (Geotail and Cluster-1), we monitor the temporal–spatial evolution of basic elements of the substorm current system. Emphasis is placed on activations of the large-scale substorm current wedge (SCW), spanning the 21:00–03:00 MLT sector of the near-Earth plasma sheet (GOES-10 data during the interval 06:00–12:00 UT), and magnetic perturbations in the tail lobes in relation to ground observations of auroral electrojets and convection in the polar cap ionosphere. The joint ground–satellite observations are interpreted in terms of sequential intensifications and expansions of the outer and inner current loops of the SCW and their respective associations with the westward electrojet centred near midnight (24:00 MLT) and the eastward electrojet observed at 14:00–15:00 MLT. Combined magnetic field observations across the tail lobe from Cluster and Geotail allow us to make estimates of enhancements of the cross-polar-cap potential (CPCP) amounting to ≈ 30–60 kV (lower limits), corresponding to monotonic increases of the PCN index by 1.5 to 3 mV m−1 from inductive electric field coupling in the magnetosphere–ionosphere (M–I) system during the initial transient phase of the substorm expansion

Polar observations of ion/electron bursts at the pre-dawn polar cap boundary: evidence for internal reconnection of overdraped lobe flux

Observations made by Polar of ion-electron bursts on the dawn side of the polar cap are presented. They occurred when conditions external to the magnetosphere corresponded to that of the sheath region of a magnetic cloud, which was characterized by very high densities/dynamic pressure and a magnetic field which was strong in all components and which was tilted antisunward (Bx\u3c0) and northward (Bz\u3e0) with its clock angle lying between 20 and 90° (By: 8–15 nT). A clear temporal development in the energy range spanned by the individual ion bursts (from 0.2–2 keV to 1–10 keV) was present. We relate this to a corresponding temporal evolution in the cloud sheath field and plasma. We analyze the solar wind-magnetosphere aspects of the observations using the concepts of (i) (i) overdraped lobe flux, (ii) Bx- and By-regulated sequential reconnections in opposite hemispheres (magnetopause and internal modes), and (iii) newly-closed magnetic flux. In particular, we find that the most energetic ion bursts (accompanied by bi-directionally streaming electrons at 1–10 keV and intense magnetosheath-origin fluxes) are located on newly closed field lines generated by internal reconnection occurring between overdraped lobe field lines and the closed geomagnetic field. This result corroborates a topology of lobe reconnection under conditions of dipole tilt and/or nonzero IMF Bx component advanced by Watanabe et al. (2006), which in our case is adapted to nonzero IMF By conditions