Micromagnetic Simulations of Ferromagnetic Rings

Thin nanomagnetic rings have generated interest for fundamental studies of magnetization reversal and also for their potential in various applications, particularly as magnetic memories. They are a rare example of a geometry in which an analytical solution for the rate of thermally induced magnetic reversal has been determined, in an approximation whose errors can be estimated and bounded. In this work, numerical simulations of soft ferromagnetic rings are used to explore aspects of the analytical solution. The evolution of the energy near the transition states confirms that, consistent with analytical predictions, thermally induced magnetization reversal can have one of two intermediate states: either constant or soliton-like saddle configurations, depending on ring size and externally applied magnetic field. The results confirm analytical predictions of a transition in thermally activated reversal behavior as magnetic field is varied at constant ring size. Simulations also show that the analytic one dimensional model continues to hold even for wide rings

Thermal Stability of the Magnetization in Perpendicularly Magnetized Thin Film Nanomagnets

Understanding the stability of thin film nanomagnets with perpendicular magnetic anisotropy (PMA) against thermally induced magnetization reversal is important when designing perpendicularly magnetized patterned media and magnetic random access memories. The leading-order dependence of magnetization reversal rates are governed by the energy barrier the system needs to surmount in order for reversal to proceed. In this paper we study the reversal dynamics of these systems and compute the relevant barriers using the string method of E, Vanden-Eijnden, and Ren. We find the reversal to be often spatially incoherent; that is, rather than the magnetization flipping as a rigid unit, reversal proceeds instead through a soliton-like domain wall sweeping through the system. We show that for square nanomagnetic elements the energy barrier increases with element size up to a critical length scale, beyond which the energy barrier is constant. For circular elements the energy barrier continues to increase indefinitely, albeit more slowly beyond a critical size. In both cases the energy barriers are smaller than those expected for coherent magnetization reversal.Comment: 5 pages, 4 Figure

Stability of 2pi domain walls in ferromagnetic nanorings

The stability of 2pi domain walls in ferromagnetic nanorings is investigated via calculation of the minimum energy path that separates a 2pi domain wall from the vortex state of a ferromagnetic nanoring. Trapped domains are stable when they exist between certain types of transverse domain walls, i.e., walls in which the edge defects on the same side of the magnetic strip have equal sign and thus repel. Here the energy barriers between these configurations and vortex magnetization states are obtained using the string method. Due to the geometry of a ring, two types of 2pi walls must be distinguished that differ by their overall topological index and exchange energy. The minimum energy path corresponds to the expulsion of a vortex. The energy barrier for annihilation of a 2pi wall is compared to the activation energy for transitions between the two ring vortex states.Comment: 4 pages, 2 figure

Glucagon receptor antagonist and GIP agonist combination for diet induced obese mice.

Ablation of glucagon receptor signaling represents a potential treatment option for type 2 diabetes (T2DM). Additionally, activation of glucose-dependent insulinotropic polypeptide (GIP) receptor signaling also holds therapeutic promise for T2DM. Therefore, this study examined both independent and combined metabolic actions of desHis1Pro4Glu9(Lys12PAL)-glucagon (glucagon receptor antagonist) andd-Ala2GIP (GIP receptor agonist) in diet-induced obese mice. Glucagon receptor binding has been linked to alpha-helical structure and desHis1Pro4Glu9(Lys12PAL)-glucagon displayed enhanced alpha-helical content compared with native glucagon. In clonal pancreatic BRIN-BD11 beta-cells, desHis1Pro4Glu9(Lys12PAL)-glucagon was devoid of any insulinotropic or cAMP-generating actions, and did not impeded-Ala2GIP-mediated (P&lt;0.01 toP&lt;0.001) effects on insulin and cAMP production. Twice-daily injection of desHis1Pro4Glu9(Lys12PAL)-glucagon ord-Ala2GIP alone, and in combination, in high-fat-fed mice failed to affect body weight or energy intake. Circulating blood glucose levels were significantly (P&lt;0.05 toP&lt;0.01) decreased by all treatments regimens, with plasma and pancreatic insulin elevated (P&lt;0.05 toP&lt;0.001) in all mice receivingd-Ala2GIP. Interestingly, plasma glucagon concentrations were decreased (P&lt;0.05) by sustained glucagon inhibition (day 28), but increased (P&lt;0.05) byd-Ala2GIP therapy, with a combined treatment resulting in glucagon concentration similar to saline controls. All treatments improved (P&lt;0.01) intraperitoneal and oral glucose tolerance, and peripheral insulin sensitivity.d-Ala2GIP-treated mice showed increased glucose-induced insulin secretion in response to intraperitoneal and oral glucose. Metabolic rate and ambulatory locomotor activity were increased (P&lt;0.05 toP&lt;0.001) in all desHis1Pro4Glu9(Lys12PAL)-glucagon-treated mice. These studies highlight the potential of glucagon receptor inhibition alone, and in combination with GIP receptor activation, for T2DM treatment.</jats:p

Developing the Warwick Patient Experiences Framework (WaPEF): Utilising patient-based evidence to shape clinical guidelines International Journal of Quality in Healthcare

Objective This paper presents the development of the Warwick Patient Experiences Framework (WaPEF) and describes how it informed the development of the NICE Guidance and Quality Standard, ‘Patient experience in adult NHS services: improving the experience of care for people using adult NHS services’. Design The WaPEF was developed using a thematic qualitative overview that utilized a systematic review approach. Search strategies were developed, inclusion and exclusion criteria developed and data extracted from papers. Results The WaPEF identifies seven key generic themes that are important to a high-quality patient experience: patient as active participant, responsiveness of services, an individualized approach, lived experience, continuity of care and relationships, communication, information and support. Conclusions The WaPEF is the first patient experiences framework with an explicit link to an underpinning patient evidence base, linking themes and sub-themes with specific references. The WaPEF informed the structure and content of the NICE Patient Experiences Guidance. The guidance, published in February 2012, will form a key part of the NHS Outcomes Framework in the UK for the future evaluation of health and social care. The proposed framework could be adapted to other country contexts and settings

Undergraduate medical research: the student perspective

Background: Research training is essential in a modern undergraduate medical curriculum. Our evaluation aimed to (a) gauge students&#x2019; awareness of research activities, (b) compare students&#x2019; perceptions of their transferable and research-specific skills competencies, (c) determine students&#x2019; motivation for research and (d) obtain students&#x2019; personal views on doing research. Methods: Undergraduate medical students (N=317) completed a research skills questionnaire developed by the Centre for Excellence in Teaching and Learning in Applied Undergraduate Research Skills (CETL-AURS) at Reading University. The questionnaire assessed students&#x2019; transferable skills, research-specific skills (e.g., study design, data collection and data analysis), research experience and attitude and motivation towards doing research. Results: The majority of students are motivated to pursue research. Graduate entrants and male students appear to be the most confident regarding their research skills competencies. Although all students recognise the role of research in medical practice, many are unaware of the medical research activities or successes within their university. Of those who report no interest in a career incorporating research, a common perception was that researchers are isolated from patients and clinical practice. Discussion: Students have a narrow definition of research and what it entails. An explanation for why research competence does not align more closely with research motivation is derived from students&#x2019; lack of understanding of the concept of translational research, as well as a lack of awareness of the research activity being undertaken by their teachers and mentors. We plan to address this with specific research awareness initiatives

Malignant hyperthermia

Malignant hyperthermia (MH) is a pharmacogenetic disorder of skeletal muscle that presents as a hypermetabolic response to potent volatile anesthetic gases such as halothane, sevoflurane, desflurane and the depolarizing muscle relaxant succinylcholine, and rarely, in humans, to stresses such as vigorous exercise and heat. The incidence of MH reactions ranges from 1:5,000 to 1:50,000–100,000 anesthesias. However, the prevalence of the genetic abnormalities may be as great as one in 3,000 individuals. MH affects humans, certain pig breeds, dogs, horses, and probably other animals. The classic signs of MH include hyperthermia to marked degree, tachycardia, tachypnea, increased carbon dioxide production, increased oxygen consumption, acidosis, muscle rigidity, and rhabdomyolysis, all related to a hypermetabolic response. The syndrome is likely to be fatal if untreated. Early recognition of the signs of MH, specifically elevation of end-expired carbon dioxide, provides the clinical diagnostic clues. In humans the syndrome is inherited in autosomal dominant pattern, while in pigs in autosomal recessive. The pathophysiologic changes of MH are due to uncontrolled rise of myoplasmic calcium, which activates biochemical processes related to muscle activation. Due to ATP depletion, the muscle membrane integrity is compromised leading to hyperkalemia and rhabdomyolysis. In most cases, the syndrome is caused by a defect in the ryanodine receptor. Over 90 mutations have been identified in the RYR-1 gene located on chromosome 19q13.1, and at least 25 are causal for MH. Diagnostic testing relies on assessing the in vitro contracture response of biopsied muscle to halothane, caffeine, and other drugs. Elucidation of the genetic changes has led to the introduction, on a limited basis so far, of genetic testing for susceptibility to MH. As the sensitivity of genetic testing increases, molecular genetics will be used for identifying those at risk with greater frequency. Dantrolene sodium is a specific antagonist of the pathophysiologic changes of MH and should be available wherever general anesthesia is administered. Thanks to the dramatic progress in understanding the clinical manifestation and pathophysiology of the syndrome, the mortality from MH has dropped from over 80% thirty years ago to less than 5%