LENS® and SFF: Enabling Technologies for Optimized Structures

Optimized, lightweight, high-strength structures are needed in many applications from aerospace to automotive. In pursuit of such structures, there have been proposed analytical solutions and some specialized FEA solutions for specific structures such as automobile frames. However, generalized 3D optimization methods have been unavailable for use by most designers. Moreover, in the cases where optimized structural solutions are available, they are often hollow, curving, thin wall structures that cannot be fabricated by conventional manufacturing methods. Researchers at Sandia National Laboratories and the University of Rhode Island teamed to solve these problems. The team has been pursuing two methods of optimizing models for generalized loading conditions, and also has been investigating the methods needed to fabricate these structures using Laser Engineered Net Shaping™ (LENS®) and other rapid prototyping methods. These solid freeform fabrication (SFF) methods offer the unique ability to make hollow, high aspect ratio features out of many materials. The manufacturing development required for LENS to make these complex structures has included the addition of rotational axes to Sandia’s LENS machine bringing the total to 5 controlled axes. The additional axes have required new efforts in process planning. Several of the unique structures that are only now possible through the use of SFF technology are shown as part of the discussion of this exciting new application for SFF.Mechanical Engineerin

Effective pre-school, primary and secondary education project (EPPSE 3-14): students’ reports of their experiences of school in Year 9

The Effective Pre-school, Primary and Secondary Education Project (EPPSE) has inves tigated the academic and social behavioural (+ in the later stages the affective) development of approximately 3,000 children from the age of 3+ years since 1997. This report presents the results of analyses related to student’s experiences in Year 9 (age 14), with the purpose of creating measures of both school and classroom life as experienced by students. These measures have been used in the analysis of academic and social-behavioural outcomes as well as dispositions to investigate whether a student’s reported experience of school can significantly predict outcomes in other areas. The findings highlight the importance of the ‘student voice’ and provide an insight into the experiences of teenagers in the first decade of the 21st Century

Influences on students’ attainment and progress in Key Stage 3: academic outcomes in English, Maths and Science in Year 9

The Effective Pre-school, Primary and Secondary Education Project (EPPSE) has investigated the academic and social-behavioural development of approximately 3,000 children from the age of 3+ years since 1997. This Research Brief focuses on the relationships between a range of individual student, family, home, pre-, primary and secondary school characteristics and students\u27 academic attainment in English, maths and science in Year 9 at secondary school (age 14). It compares the latest findings with those found for students\u27 attainment at younger ages. It also highlights the influences of secondary school on students\u27 attainment in the core curriculum areas and studies their academic progress across Key Stage 3 between the ages of 11 and 14

Effective Pre-school, Primary and Secondary Education 3-14 Project (EPPSE 3-14): influences on students’ dispositions in Key Stage 3: exploring enjoyment of school, popularity, anxiety, citizenship values and academic self-concept in Year 9

The Effective Pre-school, Primary and Secondary Education Project (EPPSE) has investigated the academic and social-behavioural development of approximately 3,000 children from the age of 3+ years since 1997. This Report and Research Brief reports on students’ dispositions when they were age 14 (Year 9) in six main areas: ‘enjoyment of school’, ‘academic self concept’ (English and maths), ‘popularity’, ‘citizenship values’ and ‘anxiety’. It examines how these dispositions have changed during Key Stage 3 (KS3) and the relationships between dispositions and a range of individual student, family, home, pre-, primary and secondary school measures. It shows how school experiences help to shape dispositions, and also explores the relationships between dispositions to school and students’ academic and social-behavioural outcomes. The findings highlight the importance of the ‘student voice’ and provides an insight into the experiences of teenagers in the first decade of the 21st Century

Effective Pre-school, Primary and Secondary Education 3-14 Project (EPPSE 3-14): influences on students’ dispositions in Key Stage 3: exploring enjoyment of school, popularity, anxiety, citizenship values and academic self-concept in Year 9

The Effective Pre-school, Primary and Secondary Education Project (EPPSE) has investigated the academic and social-behavioural development of approximately 3,000 children from the age of 3+ years since 1997. This Report and Research Brief reports on students’ dispositions when they were age 14 (Year 9) in six main areas: ‘enjoyment of school’, ‘academic self concept’ (English and maths), ‘popularity’, ‘citizenship values’ and ‘anxiety’. It examines how these dispositions have changed during Key Stage 3 (KS3) and the relationships between dispositions and a range of individual student, family, home, pre-, primary and secondary school measures. It shows how school experiences help to shape dispositions, and also explores the relationships between dispositions to school and students’ academic and social-behavioural outcomes. The findings highlight the importance of the ‘student voice’ and provides an insight into the experiences of teenagers in the first decade of the 21st Century

Effects and underlying mechanisms of refractory period pacing on repolarization dynamics in the human heart

Repolarization alternans is related to the initiation of life threatening cardiac arrhythmias. Experimental and computational studies suggest that the abolishment of alternans using dynamic pacing protocols may prevent abnormal heart rhythms. In a recent animal study, refractory period pacing (RPP) on every other beat has shown promising results in alternans reduction. However, the cellular mechanisms underlying this therapy and its efficiency in human patients remain unclear. In this study, in vivo unipolar electrograms acquired during RPP from 240 epicardial sites from one patient were analysed. Current clamp of 18 channels was performed in silico to elucidate the ionic mechanisms underlying action potential modulation by RPP. Its efficacy with positive and negative polarities was tested on a population of 87 calibrated human ventricular models exhibiting alternans. In vivo electrograms showed significant changes in T-wave alternans when applying RPP. In silico, results showed APD shortening for RPP with positive polarity and APD prolongation with RPP negative. Under current clamp protocols, voltage rectification of L-type Ca(2)+ (ICaL) and inward rectifier K+ (IK1) currents were identified as the key determinants for the observed changes. RPP pacing successfully reduced alternans on the in silico models using a negative polarity stimulus in the short beat

A cortical potential reflecting cardiac function

Emotional trauma and psychological stress can precipitate cardiac arrhythmia and sudden death through arrhythmogenic effects of efferent sympathetic drive. Patients with preexisting heart disease are particularly at risk. Moreover, generation of proarrhythmic activity patterns within cerebral autonomic centers may be amplified by afferent feedback from a dysfunctional myocardium. An electrocortical potential reflecting afferent cardiac information has been described, reflecting individual differences in interoceptive sensitivity (awareness of one's own heartbeats). To inform our understanding of mechanisms underlying arrhythmogenesis, we extended this approach, identifying electrocortical potentials corresponding to the cortical expression of afferent information about the integrity of myocardial function during stress. We measured changes in cardiac response simultaneously with electroencephalography in patients with established ventricular dysfunction. Experimentally induced mental stress enhanced cardiovascular indices of sympathetic activity (systolic blood pressure, heart rate, ventricular ejection fraction, and skin conductance) across all patients. However, the functional response of the myocardium varied; some patients increased, whereas others decreased, cardiac output during stress. Across patients, heartbeat-evoked potential amplitude at left temporal and lateral frontal electrode locations correlated with stress-induced changes in cardiac output, consistent with an afferent cortical representation of myocardial function during stress. Moreover, the amplitude of the heartbeat-evoked potential in the left temporal region reflected the proarrhythmic status of the heart (inhomogeneity of left ventricular repolarization). These observations delineate a cortical representation of cardiac function predictive of proarrhythmic abnormalities in cardiac repolarization. Our findings highlight the dynamic interaction of heart and brain in stress-induced cardiovascular morbidity

Regional differences in APD restitution can initiate wavebreak and re-entry in cardiac tissue: A computational study

Background Regional differences in action potential duration (APD) restitution in the heart favour arrhythmias, but the mechanism is not well understood. Methods We simulated a 150 × 150 mm 2D sheet of cardiac ventricular tissue using a simplified computational model. We investigated wavebreak and re-entry initiated by an S1S2S3 stimulus protocol in tissue sheets with two regions, each with different APD restitution. The two regions had a different APD at short diastolic interval (DI), but similar APD at long DI. Simulations were performed twice; once with both regions having steep (slope > 1), and once with both regions having flat (slope < 1) APD restitution. Results Wavebreak and re-entry were readily initiated using the S1S2S3 protocol in tissue sheets with two regions having different APD restitution properties. Initiation occurred irrespective of whether the APD restitution slopes were steep or flat. With steep APD restitution, the range of S2S3 intervals resulting in wavebreak increased from 1 ms with S1S2 of 250 ms, to 75 ms (S1S2 180 ms). With flat APD restitution, the range of S2S3 intervals resulting in wavebreak increased from 1 ms (S1S2 250 ms), to 21 ms (S1S2 340 ms) and then 11 ms (S1S2 400 ms). Conclusion Regional differences in APD restitution are an arrhythmogenic substrate that can be concealed at normal heart rates. A premature stimulus produces regional differences in repolarisation, and a further premature stimulus can then result in wavebreak and initiate re-entry. This mechanism for initiating re-entry is independent of the steepness of the APD restitution curve

Measurement of the 18Ne(a,p_0)21Na reaction cross section in the burning energy region for X-ray bursts

The 18Ne(a,p)21Na reaction provides one of the main HCNO-breakout routes into the rp-process in X-ray bursts. The 18Ne(a,p_0)21Na reaction cross section has been determined for the first time in the Gamow energy region for peak temperatures T=2GK by measuring its time-reversal reaction 21Na(p,a)18Ne in inverse kinematics. The astrophysical rate for ground-state to ground-state transitions was found to be a factor of 2 lower than Hauser-Feshbach theoretical predictions. Our reduced rate will affect the physical conditions under which breakout from the HCNO cycles occurs via the 18Ne(a,p)21Na reaction.Comment: 5 pages, 3 figures, accepted for publication on Physical Review Letter