135 research outputs found
Memory-efficient array redistribution through portable collective communication
Modern large-scale deep learning workloads highlight the need for parallel
execution across many devices in order to fit model data into hardware
accelerator memories. In these settings, array redistribution may be required
during a computation, but can also become a bottleneck if not done efficiently.
In this paper we address the problem of redistributing multi-dimensional array
data in SPMD computations, the most prevalent form of parallelism in deep
learning. We present a type-directed approach to synthesizing array
redistributions as sequences of MPI-style collective operations. We prove
formally that our synthesized redistributions are memory-efficient and perform
no excessive data transfers. Array redistribution for SPMD computations using
collective operations has also been implemented in the context of the XLA SPMD
partitioner, a production-grade tool for partitioning programs across
accelerator systems. We evaluate our approach against the XLA implementation
and find that our approach delivers a geometric mean speedup of ,
with maximum speedups as a high as , while offering provable memory
guarantees, making our system particularly appealing for large-scale models.Comment: minor errata fixe
Nanoparticle detection in an open-access silicon microcavity
We report on the detection of free nanoparticles in a micromachined,
open-access Fabry-P\'erot microcavity. With a mirror separation of m,
a radius of curvature of mm, and a beam waist of m, the mode
volume of our symmetric infrared cavity is smaller than pL. The small
beam waist, together with a finesse exceeding 34,000, enables the detection of
nano-scale dielectric particles in high vacuum. This device allows monitoring
of the motion of individual nm radius silica nanospheres in real time.
We observe strong coupling between the particles and the cavity field, a
precondition for optomechanical control. We discuss the prospects for optical
cooling and detection of dielectric particles smaller than nm in radius
and amu in mass.Comment: 4 pages, 3 figure
Three-dimensional graphene on a nano-porous 4H-SiC backbone: a novel material for food sensing applications
Sensors which are sensitive to volatile organic compounds and thus able to
monitor the conservation state of food, are precious because they work
non-destructively and allow to avoid direct contact with the food, ensuring
hygienic conditions. In particular, the monitoring of rancidity would solve a
widespread issue in food storage. The sensor discussed here is produced
utilizing a novel three-dimensional arrangement of graphene, which is grown on
a crystalline silicon carbide (SiC) wafer previously porousified by chemical
etching. This approach allows a very high surface-to.volume ratio. Furthermore,
the structure of the sensor surface features a large amount of edges, dangling
bounds, and active sites, which make the sensor, on a chemically robust
skeleton, chemically active, particularly to hydrogenated molecules. The
interaction of the sensor with such compounds is read out by measuring the
sensor resistance in a four wire configuration. The sensor performance has been
assessed on three hazelnut samples: sound hazelnuts, spoiled hazelnuts, and
stink bug hazelnuts. A resistance variation of about DeltaR = 0.13 (0.02) Ohm
between sound and damaged hazelnuts has been detected. Our measurements confirm
the ability of the sensor to discriminate between sound and damaged hazelnuts.
The sensor signal is stable for days, providing the possibility to use this
sensor for the monitoring of the storage state of fats and foods in general.Comment: 11 pages, 6 figures 1 tabl
Metal Nanoparticle-Functionalized Three-Dimensional Graphene: a versatile platform towards sensors and energy-related applications
We demonstrate the first successful functionalization of epitaxial
three-dimensional graphene with metal nanoparticles. The functionalization is
obtained by immersing the 3D graphene in a nanoparticle colloidal solution.
This method is versatile and here is demonstrated for gold and palladium, but
can be extended to other types and shapes of nanoparticles. We have measured
the nanoparticle density on the top-surface and in the porous layer volume by
Scanning Electron Microscopy and Scanning Transmission Electron Microscopy.
Samples exhibit a high coverage of nanoparticles with minimal clustering. High
quality graphene has been demonstrated to promote the functionalization leading
to higher nanoparticle density, both on the surface and in the pores. X-ray
Photoelectron Spectroscopy allowed to verify the absence of contamination after
the functionalization process. Moreover, it confirmed the thermal stability of
the Au- and Pd-functionalized three-dimensional graphene up to 530{\deg}C. Our
approach opens up new avenues for utilizing three-dimensional graphene as a
versatile platform for catalytic applications, sensors, and energy storage and
conversion
Marcus or Mira - Investigating the Perception of Virtual Agent Gender in Virtual Reality Role Play-Training
Immersive virtual training environments are used in various domains. In this work we focus on role-play training in virtual reality. In virtual role-play training conversations and interactions with virtual agents are often fundamental to the training. Therefore, the appearance and behavior of the agents plays an important role when designing role-play training.We focus on the gender appearance of agents, as gender is an important aspect for differentiation between characters. We conducted a study with 40 participants in which we investigated how agents gender appearance influences the perception of the agents´ personality traits and the self-perception of a participants’ assumed role in a training for social skills. This work contributes towards understanding the design-space of virtual agent design, virtual agent gender identity, and the design and development of immersive virtual reality role-play training
Clinical review: Practical recommendations on the management of perioperative heart failure in cardiac surgery
Acute cardiovascular dysfunction occurs perioperatively in more than 20% of cardiosurgical patients, yet current acute heart failure (HF) classification is not applicable to this period. Indicators of major perioperative risk include unstable coronary syndromes, decompensated HF, significant arrhythmias and valvular disease. Clinical risk factors include history of heart disease, compensated HF, cerebrovascular disease, presence of diabetes mellitus, renal insufficiency and high-risk surgery. EuroSCORE reliably predicts perioperative cardiovascular alteration in patients aged less than 80 years. Preoperative B-type natriuretic peptide level is an additional risk stratification factor. Aggressively preserving heart function during cardiosurgery is a major goal. Volatile anaesthetics and levosimendan seem to be promising cardioprotective agents, but large trials are still needed to assess the best cardioprotective agent(s) and optimal protocol(s). The aim of monitoring is early detection and assessment of mechanisms of perioperative cardiovascular dysfunction. Ideally, volume status should be assessed by 'dynamic' measurement of haemodynamic parameters. Assess heart function first by echocardiography, then using a pulmonary artery catheter (especially in right heart dysfunction). If volaemia and heart function are in the normal range, cardiovascular dysfunction is very likely related to vascular dysfunction. In treating myocardial dysfunction, consider the following options, either alone or in combination: low-to-moderate doses of dobutamine and epinephrine, milrinone or levosimendan. In vasoplegia-induced hypotension, use norepinephrine to maintain adequate perfusion pressure. Exclude hypovolaemia in patients under vasopressors, through repeated volume assessments. Optimal perioperative use of inotropes/vasopressors in cardiosurgery remains controversial, and further large multinational studies are needed. Cardiosurgical perioperative classification of cardiac impairment should be based on time of occurrence (precardiotomy, failure to wean, postcardiotomy) and haemodynamic severity of the patient's condition (crash and burn, deteriorating fast, stable but inotrope dependent). In heart dysfunction with suspected coronary hypoperfusion, an intra-aortic balloon pump is highly recommended. A ventricular assist device should be considered before end organ dysfunction becomes evident. Extra-corporeal membrane oxygenation is an elegant solution as a bridge to recovery and/or decision making. This paper offers practical recommendations for management of perioperative HF in cardiosurgery based on European experts' opinion. It also emphasizes the need for large surveys and studies to assess the optimal way to manage perioperative HF in cardiac surgery
The SysteMHC Atlas project.
Mass spectrometry (MS)-based immunopeptidomics investigates the repertoire of peptides presented at the cell surface by major histocompatibility complex (MHC) molecules. The broad clinical relevance of MHC-associated peptides, e.g. in precision medicine, provides a strong rationale for the large-scale generation of immunopeptidomic datasets and recent developments in MS-based peptide analysis technologies now support the generation of the required data. Importantly, the availability of diverse immunopeptidomic datasets has resulted in an increasing need to standardize, store and exchange this type of data to enable better collaborations among researchers, to advance the field more efficiently and to establish quality measures required for the meaningful comparison of datasets. Here we present the SysteMHC Atlas (https://systemhcatlas.org), a public database that aims at collecting, organizing, sharing, visualizing and exploring immunopeptidomic data generated by MS. The Atlas includes raw mass spectrometer output files collected from several laboratories around the globe, a catalog of context-specific datasets of MHC class I and class II peptides, standardized MHC allele-specific peptide spectral libraries consisting of consensus spectra calculated from repeat measurements of the same peptide sequence, and links to other proteomics and immunology databases. The SysteMHC Atlas project was created and will be further expanded using a uniform and open computational pipeline that controls the quality of peptide identifications and peptide annotations. Thus, the SysteMHC Atlas disseminates quality controlled immunopeptidomic information to the public domain and serves as a community resource toward the generation of a high-quality comprehensive map of the human immunopeptidome and the support of consistent measurement of immunopeptidomic sample cohorts
Approaches to fattening dairy calves
Innovative organic producers have developed alternative systems for fattening calves, bulls and steers from dairy farming. This technical guide presents the systems and shows what to pay attention to when fattening calves
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