RTSim: A cycle-accurate simulator for racetrack memories

Racetrack memories (RTMs) have drawn considerable attention from computer architects of late. Owing to the ultra-high capacity and comparable access latency to SRAM, RTMs are promising candidates to revolutionize the memory subsystem. In order to evaluate their performance and suitability at various levels in the memory hierarchy, it is crucial to have RTM-specific simulation tools that accurately model their behavior and enable exhaustive design space exploration. To this end, we propose RTSim, an open source cycle-accurate memory simulator that enables performance evaluation of the domain-wall-based racetrack memories. The skyrmions-based RTMs can also be modeled with RTSim because they are architecturally similar to domain-wall-based RTMs. RTSim is developed in collaboration with physicists and computer scientists. It accurately models RTM-specific shift operations, access ports management and the sequence of memory commands beside handling the routine read/write operations. RTSim is built on top of NVMain2.0, offering larger design space for exploration

Shiftsreduce: Minimizing shifts in racetrack memory 4.0

Racetrack memories (RMs) have significantly evolved since their conception in 2008, making them a serious contender in the field of emerging memory technologies. Despite key technological advancements, the access latency and energy consumption of an RM-based system are still highly influenced by the number of shift operations. These operations are required to move bits to the right positions in the racetracks. This article presents data-placement techniques for RMs that maximize the likelihood that consecutive references access nearby memory locations at runtime, thereby minimizing the number of shifts. We present an integer linear programming (ILP) formulation for optimal data placement in RMs, and we revisit existing offset assignment heuristics, originally proposed for random-access memories. We introduce a novel heuristic tailored to a realistic RM and combine it with a genetic search to further improve the solution. We show a reduction in the number of shifts of up to 52.5%, outperforming the state of the art by up to 16.1%

Magnetic racetrack memory: from physics to the cusp of applications within a decade

Racetrack memory (RTM) is a novel spintronic memory-storage technology that has the potential to overcome fundamental constraints of existing memory and storage devices. It is unique in that its core differentiating feature is the movement of data, which is composed of magnetic domain walls (DWs), by short current pulses. This enables more data to be stored per unit area compared to any other current technologies. On the one hand, RTM has the potential for mass data storage with unlimited endurance using considerably less energy than today's technologies. On the other hand, RTM promises an ultrafast nonvolatile memory competitive with static random access memory (SRAM) but with a much smaller footprint. During the last decade, the discovery of novel physical mechanisms to operate RTM has led to a major enhancement in the efficiency with which nanoscopic, chiral DWs can be manipulated. New materials and artificially atomically engineered thin-film structures have been found to increase the speed and lower the threshold current with which the data bits can be manipulated. With these recent developments, RTM has attracted the attention of the computer architecture community that has evaluated the use of RTM at various levels in the memory stack. Recent studies advocate RTM as a promising compromise between, on the one hand, power-hungry, volatile memories and, on the other hand, slow, nonvolatile storage. By optimizing the memory subsystem, significant performance improvements can be achieved, enabling a new era of cache, graphical processing units, and high capacity memory devices. In this article, we provide an overview of the major developments of RTM technology from both the physics and computer architecture perspectives over the past decade. We identify the remaining challenges and give an outlook on its future

Physical Fitness Training in Patients with Subacute Stroke (PHYS-STROKE): multicentre, randomised controlled, endpoint blinded trial

OBJECTIVE: To determine the safety and efficacy of aerobic exercise on activities of daily living in the subacute phase after stroke. DESIGN: Multicentre, randomised controlled, endpoint blinded trial. SETTING: Seven inpatient rehabilitation sites in Germany (2013-17). PARTICIPANTS: 200 adults with subacute stroke (days 5-45 after stroke) with a median National Institutes of Health stroke scale (NIHSS, range 0-42 points, higher values indicating more severe strokes) score of 8 (interquartile range 5-12) were randomly assigned (1:1) to aerobic physical fitness training (n=105) or relaxation sessions (n=95, control group) in addition to standard care. INTERVENTION: Participants received either aerobic, bodyweight supported, treadmill based physical fitness training or relaxation sessions, each for 25 minutes, five times weekly for four weeks, in addition to standard rehabilitation therapy. Investigators and endpoint assessors were masked to treatment assignment. MAIN OUTCOME MEASURES: The primary outcomes were change in maximal walking speed (m/s) in the 10 m walking test and change in Barthel index scores (range 0-100 points, higher scores indicating less disability) three months after stroke compared with baseline. Safety outcomes were recurrent cardiovascular events, including stroke, hospital readmissions, and death within three months after stroke. Efficacy was tested with analysis of covariance for each primary outcome in the full analysis set. Multiple imputation was used to account for missing values. RESULTS: Compared with relaxation, aerobic physical fitness training did not result in a significantly higher mean change in maximal walking speed (adjusted treatment effect 0.1 m/s (95% confidence interval 0.0 to 0.2 m/s), P=0.23) or mean change in Barthel index score (0 (-5 to 5), P=0.99) at three months after stroke. A higher rate of serious adverse events was observed in the aerobic group compared with relaxation group (incidence rate ratio 1.81, 95% confidence interval 0.97 to 3.36). CONCLUSIONS: Among moderately to severely affected adults with subacute stroke, aerobic bodyweight supported, treadmill based physical fitness training was not superior to relaxation sessions for maximal walking speed and Barthel index score but did suggest higher rates of adverse events. These results do not appear to support the use of aerobic bodyweight supported fitness training in people with subacute stroke to improve activities of daily living or maximal walking speed and should be considered in future guidelines. TRIAL REGISTRATION: ClinicalTrials.gov NCT01953549

Einfluss der Eindeichung auf Pestizidrückstände in Böden eines landwirtschaftlichen Gebietes des Red River Deltas, Vietnam

Fruchtbare Böden und eine hohe Verfügbarkeit von Wasser machen Deltaregionen zu den wichtigsten landwirtschaftlichen Produktionsflächen. Zur Sicherstellung hoher Erträge werden insbesondere in Reismonokulturen, Pestizide in einer erhöhten Menge und Häufigkeit eingesetzt. Während das Verhalten dieser Stoffe im Nassreisanbau bereits in früheren Studien beschrieben wurde, hat diese Studie zum Ziel den Einfluss von Deich-Konstruktionen auf die räumliche Verteilung der Pestizide zu untersuchen. Dazu wurden Boden- und Sedimentproben im Delta des Roten Flusses im Landkreis Giao Thuy entnommen. Dieses Gebiet ist von einem Meer- und Flussdeich mit verschiedenen Einlass- und Abflussschleusen umgeben. Dadurch findet eine Regulation der Wasserbewirtschaftung statt und das eingedeichte Gebiet wird vor Überschwemmung, Stürmen und das Eindringen von Salzwasser geschützt. In der Vergangenheit beobachteten regionale Behörden eine Abnahme der Wasserqualität vom Flussdeich hin zum Meerdeich. Dies ist vermutlich auf einen verringerten Wasseraustausch zurückzuführen, hervorgerufen durch das Deichsystem, was zu einer Akkumulation der Pestizidrückstände innerhalb des eingedeichten Gebietes führt. Um diese Hypothese zu prüfen, wurden Boden- und Sedimentproben von Reisflächen, Bewässerungsgräben und auch von Salzwasseraquakulturflächen außerhalb des eingedeichten Gebietes entnommen und anschließend auf Rückstände von 12 verschiedenen Pestiziden hin untersucht. Die Pestizide wurden wie folgt bestimmt: Extraktion mittels accelerated solvent extraction (ASE), gefolgt von einer Aufreinigung nach Laabs et al. (2007) und der Quantifizierung mittels Gaschromatographie gekoppelt an ein Massenspektrometer (GC-MS). Vorläufige Ergebnisse lassen vermuten, dass Chlorpyrifos, Propiconazole und Isoprothiolane häufig in den Proben der Reisflächen vorhanden sind. In Reisflächen nahe des Meerdeiches wurden keine erhöhten Pestizidkonzentrationen ermittelt. Die Pestizidrückstände in den Proben der Reisflächen sind eher der direkten Applikation verschuldet, wohingegen die Kanalproben keiner direkten Applikation ausgesetzt sind

Electric and magnetic dipole transitions to bound states in 206Pb

Nuclear resonance fluorescence measurements with linearly polarized bremsstrahlung were performed to determine parities of bound dipole transitions in 206Pb. A new 1+ level at 5800 keV was found, which has almost the same strength as the isoscalar M1 transition in 208Pb. Twenty-four further dipole states in 206Pb below 7.6 MeV possess negative parity

Cue properties change timing strategies in group movement synchronisation

To maintain synchrony in group activities, each individual within the group must continuously correct their movements to remain in time with the temporal cues available. Cues might originate from one or more members of the group. Current research suggests that when synchronising movements, individuals optimise their performance in terms of minimising variability of timing errors (asynchronies) between external cues and their own movements. However, the cost of this is an increase in the timing variability of their own movements. Here we investigate whether an individual’s timing strategy changes according to the task, in a group scenario. To investigate this, we employed a novel paradigm that positioned six individuals to form two chains with common origin and termination on the circumference of a circle. We found that participants with access to timing cues from only one other member used a strategy to minimise their asynchrony variance. In contrast, the participant at the common termination of the two chains, who was required to integrate timing cues from two members, used a strategy that minimised movement variability. We conclude that humans are able to flexibly switch timekeeping strategies to maintain task demands and thus optimise the temporal performance of their movements

SAM levels, gene expression of SAM synthetase, methionine synthase and ACC oxidase, and ethylene emission from N. suaveolens flowers

S′adenosyl-l-methionine (SAM) is a ubiquitous methyl donor and a precursor in the biosynthesis of ethylene, polyamines, biotin, and nicotianamine in plants. Only limited information is available regarding its synthesis (SAM cycle) and its concentrations in plant tissues. The SAM concentrations in flowers of Nicotiana suaveolens were determined during day/night cycles and found to fluctuate rhythmically between 10 and 50 nmol g−1 fresh weight. Troughs of SAM levels were measured in the evening and night, which corresponds to the time when the major floral scent compound, methyl benzoate, is synthesized by a SAM dependent methyltransferase (NsBSMT) and when this enzyme possesses its highest activity. The SAM synthetase (NsSAMS1) and methionine synthase (NsMS1) are enzymes, among others, which are involved in the synthesis and regeneration of SAM. Respective genes were isolated from a N. suaveolens petal cDNA library. Transcript accumulation patterns of both SAM regenerating enzymes matched perfectly those of the bifunctional NsBSMT; maximum mRNA accumulations of NsMS1 and NsSAMS1 were attained in the evening. Ethylene, which is synthesized from SAM, reached only low levels of 1–2 ppbv in N. suaveolens flowers. It is emitted in a burst at the end of the life span of the flowers, which correlates with the increased expression of the 1-aminocyclopropane-1-carboxylate oxidase (NsACO)