HPC Field Research Articles

Building bridges of excellence: a comprehensive competence framework for nurses in hospice and palliative care—a mixed method study

BackgroundHospice and Palliative Care (HPC) is in high demand in China; however, the country is facing the shortage of qualified HPC nurses. A well-suited competence framework is needed to promote HPC human resource development. Nevertheless, existing unstandardized single-structured frameworks may not be sufficient to meet this need. This study aimed at constructing a comprehensive multi-structured HPC competence framework for nurses.MethodsThis study employed a mixed-method approach, including a systematic review and qualitative interview for HPC competence profile extraction, a two-round Delphi survey to determine the competences for the framework, and a cross-sectional study for framework structure exploration. The competence profiles were extracted from publications from academic databases and interviews recruiting nurses working in the HPC field. The research team synthesized profiles and transferred them to competences utilizing existing competence dictionaries. These synthesized competences were then subjected to Delphi expert panels to determine the framework elements. The study analyzed theoretical structure of the framework through exploratory factor analysis (EFA) based on a cross-sectional study receiving 491 valid questionnaires.ResultsThe systematic review involved 30 publications from 10 countries between 1995 and 2021, while 13 nurses from three hospitals were interviewed. In total, 87 and 48 competence profiles were respectively extracted from systematic review and interview and later synthesized into 32 competences. After the Delphi survey, 25 competences were incorporated into the HPC competence framework for nurses. The EFA found a two-factor structure, with factor 1 comprising 18 competences namely Basic Competences; factor 2 concluding 7 competences namely Developmental Competences.ConclusionsThe two-factor HPC competence framework provided valuable insights into the need and directions of Chinese HPC nurses’ development.

SEDAR: Soft Error Detection and Automatic Recovery in High Performance Computing Systems


 Reliability and fault tolerance have become aspects of growing relevance in the field of HPC, due to the increased probability that faults of different kinds will occur in these systems. This is fundamentally due to the increasing complexity of the processors, in the search to improve performance, which leads to a rise in the scale of integration and in the number of components that work near their technological limits, being increasingly prone to failures. Another factor that affects is the growth in the size of parallel systems to obtain greater computational power, in terms of number of cores and processing nodes.
 As applications demand longer uninterrupted computation times, the impact of faults grows, due to the cost of relaunching an execution that was aborted due to the occurrence of a fault or concluded with erroneous results. Consequently, it is necessary to run these applications on highly available and reliable systems, requiring strategies capable of providing detection, protection and recovery against faults.
 In the next years it is planned to reach Exa-scale, in which there will be supercomputers with millions of processing cores, capable of performing on the order of 1018 operations per second. This is a great window of opportunity for HPC applications, but it also increases the risk that they will not complete their executions. Recent studies show that, as systems continue to include more processors, the Mean Time Between Errors decreases, resulting in higher failure rates and increased risk of corrupted results; large parallel applications are expected to deal with errors that occur every few minutes, requiring external help to progress efficiently. Silent Data Corruptions are the most dangerous errors that can occur, since they can generate incorrect results in programs that appear to execute correctly. Scientific applications and large-scale simulations are the most affected, making silent error handling the main challenge towards resilience in HPC. In message passing applications, a silent error, affecting a single task, can produce a pattern of corruption that spreads to all communicating processes; in the worst case scenario, the erroneous final results cannot be detected at the end of the execution and will be taken as correct.
 Since scientific applications have execution times of the order of hours or even days, it is essential to find strategies that allow applications to reach correct solutions in a bounded time, despite the underlying failures. These strategies also prevent energy consumption from skyrocketing, since if they are not used, the executions should be launched again from the beginning. However, the most popular parallel programming models used in supercomputers lack support for fault tolerance.

Effects of locus coeruleus activation and inactivation on hippocampal formation theta rhythm in anesthetized rats

Previously obtained data suggests that noradrenaline (NE) released from the efferent locus coeruleus (LC) endings in hippocampal formation (HPC) may serve as an important modulating signal involved in the pharmacological mechanisms responsible for the production of type 2 theta rhythm in rats. Hence, two distinct hypotheses were tested in the present study: 1/ if the decrease in HPC level of NE is correlated with the desynchronization of HPC field potential, then the inhibition of LC would be expected to abolish HPC type 2 theta rhythm; 2/ if the increase in HPC NE level is correlated with synchronization of HPC field potential, then the stimulation of LC would be expected to produce type 2 theta. The experiments were performed using an experimental model of HPC type 2 theta rhythm recorded in urethanized rats. It was demonstrated that electrical stimulation of LC produced type 2 theta rhythm whereas procaine injection into LC, in contrast, reversibly abolished type 2 theta. The possible relation of type 2 theta rhythm with some disturbances of Alzheimer disease are addressed.

Engineering Algorithms for Scalability through Continuous Validation of Performance Expectations

Many libraries in the HPC field use sophisticated algorithms with clear theoretical scalability expectations. However, hardware constraints or programming bugs may sometimes render these expectations inaccurate or even plainly wrong. While algorithm and performance engineers have already been advocating the systematic combination of analytical performance models with practical measurements for a very long time, we go one step further and show how this comparison can become part of automated testing procedures. The most important applications of our method include initial validation, regression testing, and benchmarking to compare implementation and platform alternatives. Advancing the concept of performance assertions, we verify asymptotic scaling trends rather than precise analytical expressions, relieving the developer from the burden of having to specify and maintain very fine-grained and potentially non-portable expectations. In this way, scalability validation can be continuously applied throughout the whole development cycle with very little effort. Using MPI and parallel sorting algorithms as examples, we show how our method can help uncover non-obvious limitations of both libraries and underlying platforms.

Medial septal cholinergic mediation of hippocampal theta rhythm induced by vagal nerve stimulation.

BackgroundElectrical vagal nerve stimulation (VNS) has been used for years to treat patients with drug-resistant epilepsy. This technique also remains under investigation as a specific treatment of patients with Alzheimer’s disease. Recently we discovered that VNS induced hippocampal formation (HPC) type II theta rhythm, which is involved in memory consolidation. In the present study, we have extended our previous observation and addressed the neuronal substrate and pharmacological profile of HPC type II theta rhythm induced by VNS in anesthetized rats.MethodsMale Wistar rats were implanted with a VNS cuff electrode around the left vagus nerve, a tungsten microelectrode for recording the HPC field activity, and a medial septal (MS) cannula for the injection of a local anesthetic, procaine, and muscarinic agents. A direct, brief effect of VNS on the HPC field potential was evaluated before and after medial-septal drug injection.ResultsMedial septal injection of local anesthetic, procaine, reversibly abolished VNS-induced HPC theta rhythm. With the use of cholinergic muscarinic agonist and antagonists, we demonstrated that medial septal M1 receptors are involved in the mediation of the VNS effect on HPC theta field potential.ConclusionThe MS cholinergic M1 receptor mechanism integrates not only central inputs from the brainstem synchronizing pathway, which underlies the production of HPC type II theta rhythm, but also the input from the vagal afferents in the brain stem.

Special issue on high performance computing in modeling and simulation

Special issue on high performance computing in modeling and simulation

Development of theta rhythm in hippocampal formation slices perfused with 5-HT1A antagonist, (S)WAY 100135

Numerous studies have revealed that median raphe nuclei stimulation induces desynchronization of hippocampal field activity in vivo. Some findings provide evidence for tonic regulation of the theta oscillation of the septo-hippocampal system via the serotonergic system. To date the involvement of serotonergic transmission in theta rhythm generation in hippocampal slices has never been investigated. Thus the aim of the present study was to test whether HPC in vitro preparation is capable of producing theta in the presence of compounds modulating the activity of 5-HT1A receptors. To achieve this a series of experiments designed to determine the effect of different concentrations of the 5-HT1A receptor antagonist (S)WAY 100135 on HPC field activity was carried out. The dominant field potential pattern recorded within HPC slices was epileptiform activity, with a maximum frequency ranging from 0.19±0.06Hz to 0.69±0.10Hz. In addition, after the bath application of (S)WAY 100135 in concentrations 3 and 10µM rhythmic epochs in the theta frequency range were also noted. The highest probability of theta rhythm production was observed after the bath perfusion with a solution of (S) WAY 100135 at a concentration of 10μM. These theta rhythm epochs were characterized by a higher-than-average amplitude compared to carbachol-induced theta epochs and shorter time duration, with no apparent differences in the average frequency and duration of intervals between theta epochs. These results obtained herein of in vitro studies provide direct evidence for the involvement of serotonergic receptors in the depression of oscillatory activity in the HPC theta band.

List-based Data Structures for Efficient Management of Advance Reservations

Complex eScience and other sophisticated applications in the field of HPC imply new demands that queuing based resource management systems cannot meet. To guarantee Quality of Service and co-allocation in the Grid, planning based resource management systems implementing advance reservation are needed. These systems face new challenges as a planning based management system has to keep track of the jobs and reservations in the future. Additionally, during the negotiation process of incoming reservations, a good overview of the remaining, not-yet reserved capacity is needed--not only for the current allocation, but also for the whole book-ahead time. Therefore, the resource management problem becomes a two dimensional problem for advance reservations in this field. In this paper different data structures are investigated and discussed in order to fit to planning based resource management. As a result the benefits of using lists of resource allocation or free blocks are exposed. This general idea widely used to manage continuous resources is extended to cover not only the resource dimension but also the time dimension. The list of blocks approach is evaluated in a Grid level and a local resource management system for a computing cluster. The extensive simulations showed a better runtime and higher reservation success rate compared with the currently favored approach of a slotted time and the more sophisticated approach based on AVL trees.

StarPU: a unified platform for task scheduling on heterogeneous multicore architectures

AbstractIn the field of HPC, the current hardware trend is to design multiprocessor architectures featuring heterogeneous technologies such as specialized coprocessors (e.g. Cell/BE) or data‐parallel accelerators (e.g. GPUs). Approaching the theoretical performance of these architectures is a complex issue. Indeed, substantial efforts have already been devoted to efficiently offload parts of the computations. However, designing an execution model that unifies all computing units and associated embedded memory remains a main challenge. We therefore designed StarPU, an original runtime system providing a high‐level, unified execution model tightly coupled with an expressive data management library. The main goal of StarPU is to provide numerical kernel designers with a convenient way to generate parallel tasks over heterogeneous hardware on the one hand, and easily develop and tune powerful scheduling algorithms on the other hand. We have developed several strategies that can be selected seamlessly at run‐time, and we have analyzed their efficiency on several algorithms running simultaneously over multiple cores and a GPU. In addition to substantial improvements regarding execution times, we have obtained consistent superlinear parallelism by actually exploiting the heterogeneous nature of the machine. We eventually show that our dynamic approach competes with the highly optimized MAGMA library and overcomes the limitations of the corresponding static scheduling in a portable way. Copyright © 2010 John Wiley & Sons, Ltd.

Editorial for the ISC’10 Scientific Sessions Proceedings

The International Supercomputing Conference started in 1986 as the “Supercomputer Seminar” organized by Prof. Hans Meuer, then director of the computer center and professor for computer science at the Universitat Mannheim (Germany). Since these early days the annual conference became a major international event in the HPC community. As the conference grew bigger, it moved from Mannheim over Heidelberg and Dresden to Hamburg. In 2010 the conference will celebrate its 25th birthday! About 2,000 attendees and more than 140 exhibitors from over 45 countries are expected to attend, turning ISC’10 into a powerful and memorable event. Over the years we decided to strengthen the scientific part of the conference and present selected talks on relevant research results in the field of HPC. These scientific sessions started in 2007 as a separate day preceding the conference. Slides and accompanying papers were made available via the conference web site. Now, the scientific sessions evolved into an integral part of the conference, being scheduled in the afternoon of the first day. The call for participation was issued in winter 2009 inviting researchers and developers to submit latest results of their work as full research papers to the program committee of the scientific sessions. Altogether we received 25 submissions from authors all over the world. In a peer-reviewing process with an international committee we selected the best 13 papers for publication in this journal and for presentation during the scientific sessions of the conference.

Hippocampal theta-related cellular activity in the superior colliculus of the urethane-anesthetized rat.

In the present study, 93 cells in the superior colliculus (SC) were recorded extracellularly during the simultaneous occurrence of spontaneous theta field activity, sensory-induced (tail pinch) theta field activity, and large amplitude irregular (LIA) field activity, recorded from an electrode located in the stratum moleculare of the hippocampal formation (HPC). The effect of the intravenous administration of atropine sulfate (ATSO4) was also tested on SC cellular activity. The field activities of theta and LIA were recorded from all layers of the SC and were found to be temporally coherent with the same activities recorded simultaneously from the HPC, during all conditions tested. By using the criteria of Colom and Bland (1987) for the classification of theta-related cells, 75 of 93 cells (81%) were found to be related to the generation of theta field activity in the HPC and 18 of 93 (19%) were nonrelated. All cells recorded discharged in a tonic, nonrhythmic pattern during the theta HPC field states. Of the 75 theta-related cells, 61 (81%) were classified as tonic theta-ON cells and 14 (19%) as tonic theta-OFF cells. Although these cell types were found in all three layers of the SC, the majority of tonic theta-ON cells were recorded in the intermediate layer, and the tonic theta-OFF cells were dispersed evenly between the intermediate layer and the deep layer of the SC. The intravenous administration of ATSO4 abolished theta field activity in the HPC and SC, and the theta-related increase in the discharge rate of all tonic theta-ON cells tested. However, the same treatment did not have any effect on the discharge properties of tonic theta-OFF cells. The same stimuli that resulted in the inhibition of the discharge rates of these cells (tail pinch and electrical stimulation of the PH) in the predrug condition did so after the administration of ATSO4.

Distribution and analysis of hippocampal theta-related cells in the pontine region of the urethane-anesthetized rat.

In the present study 99 cells were recorded in the pontine region of urethane-anesthetized rats during: (1) the spontaneous occurrence of hippocampal formation (HPC) theta field activity; (2) sensory-induced (tail pinch) theta field activity; and (3) large amplitude irregular field activity (LIA). Using the criteria of Colom and Bland (Brain Res 1997;422:277-286) for the classification of theta-related cells, 58/99 cells (59%) were involved with changes in activity related to the occurrence of HPC theta field activity, 24/99 (24%) were non-related, and 17/99 (17%) were related to the sensory input (tail pinch). All cells recorded discharged in a tonic, non-rhythmic pattern in relation to the HPC field activity occurring during the three conditions. Of the 58 theta-related cells, 52 (90%) were classified as tonic theta-ON cells and 6 (10%) as tonic theta-OFF cells. There were no clear regional differences in the distribution of cell types. Statistical analysis of the discharge rates of tonic theta-ON cells during spontaneously occurring theta and tail pinch-induced theta (tested on 48 cells) revealed that 22/48 (46%) of these cells discharged at significantly higher rates during the faster theta field frequencies associated with tail pinches while 26/48 (54%) tonic theta-ON cells did not change discharge rate between the spontaneously occurring theta and the tail pinch-induced theta states. In addition, the discharges of 11/52 (21%) tonic theta-ON cells exhibited weak to moderate correlations with the negative peak of HPC theta field activity recorded from the stratum moleculare of the dentate gyrus. Of the 17 cells related to the sensory stimulation (tail pinch), 12 (71%) cells increased discharge rate during the tail pinch and were classified as sensory activated, while 5 (29%) cells decreased discharge rate during the tail pinch and were classified as sensory inactivated. The results supported the following conclusions: (1) the main cells in the pontine region involved with changes in activity related to the occurrence of HPC theta field activity are tonic theta-ON cells and tonic theta-OFF cells; (2) a subpopulation of tonic theta-ON cells coded the increasing intensity of activation of the ascending brainstem HPC synchronizing pathways by an increase in discharge rate; and (3) a smaller population of cells in the rostral pontine region appeared to be related to sensory stimulation, independent of theta-related activity.