| 1. |
- Beal, Jacob, et al.
(author)
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Robust estimation of bacterial cell count from optical density
- 2020
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In: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Journal article (peer-reviewed)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Huang, Zi-Nan, et al.
(author)
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Analysis of the stress field in the reactor vessel of the China Initiative Accelerator Driven System during postulated ULOF and UTOP transients
- 2023
-
In: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 194
-
Journal article (peer-reviewed)abstract
- The China Initiative Accelerator Driven System (CiADS) was proposed by China Academy of Science since 2015. The subcritical reactor in CiADS is a liquid Lead Bismuth Eutectic (LBE) cooled fast reactor. When the reactor core is in operation, the LBE coolant will directly contact and corrode the inner surface of reactor vessel. Due to the high temperature, the corrosion will be more severe. If the stress on the reactor vessel exceeds the limit, the plastic deformation will occur, leading to the generation and expansion of defects and cracks, and the safety of the reactor will be affected. Therefore, evaluating the stress field of the reactor vessel under different operating conditions is a very important research project. In this paper, the finite element analysis software ADINA was applied to analyze the reactor vessel in CiADS, and the ASME Code was used as stress assessment standards. We can preliminarily prove that the stress assessments of the vessel during the postulated Unprotected Loss of Flow (ULOF) accidents satisfy the requirements of ASME Code. The limit reactivity insertion to protect the vessel from plastic deformation is 0.58$ in the postulated Unprotected Transient over Power (UTOP) accidents based on our current results. Therefore, we can preliminarily conclude that the current material selection and structural design of the reactor vessel in CiADS could survive most of the postulated transient accidents considering the stress effect.
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| 3. |
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| 4. |
- Saunois, Marielle, et al.
(author)
-
The Global Methane Budget 2000–2017
- 2020
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In: Earth System Science Data. - : Copernicus GmbH. - 1866-3516 .- 1866-3508. ; 12:3, s. 1561-1623
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Journal article (peer-reviewed)abstract
- Understanding and quantifying the global methane (CH4) budget is important for assessing realistic pathways to mitigate climate change. Atmospheric emissions and concentrations of CH4 continue to increase, making CH4 the second most important human-influenced greenhouse gas in terms of climate forcing, after carbon dioxide (CO2). The relative importance of CH4 compared to CO2 depends on its shorter atmospheric lifetime, stronger warming potential, and variations in atmospheric growth rate over the past decade, the causes of which are still debated. Two major challenges in reducing uncertainties in the atmospheric growth rate arise from the variety of geographically overlapping CH4 sources and from the destruction of CH4 by short-lived hydroxyl radicals (OH). To address these challenges, we have established a consortium of multidisciplinary scientists under the umbrella of the Global Carbon Project to synthesize and stimulate new research aimed at improving and regularly updating the global methane budget. Following Saunois et al. (2016), we present here the second version of the living review paper dedicated to the decadal methane budget, integrating results of top-down studies (atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up estimates (including process-based models for estimating land surface emissions and atmospheric chemistry, inventories of anthropogenic emissions, and data-driven extrapolations).For the 2008–2017 decade, global methane emissions are estimated by atmospheric inversions (a top-down approach) to be 576 Tg CH4 yr−1 (range 550–594, corresponding to the minimum and maximum estimates of the model ensemble). Of this total, 359 Tg CH4 yr−1 or ∼ 60 % is attributed to anthropogenic sources, that is emissions caused by direct human activity (i.e. anthropogenic emissions; range 336–376 Tg CH4 yr−1 or 50 %–65 %). The mean annual total emission for the new decade (2008–2017) is 29 Tg CH4 yr−1 larger than our estimate for the previous decade (2000–2009), and 24 Tg CH4 yr−1 larger than the one reported in the previous budget for 2003–2012 (Saunois et al., 2016). Since 2012, global CH4 emissions have been tracking the warmest scenarios assessed by the Intergovernmental Panel on Climate Change. Bottom-up methods suggest almost 30 % larger global emissions (737 Tg CH4 yr−1, range 594–881) than top-down inversion methods. Indeed, bottom-up estimates for natural sources such as natural wetlands, other inland water systems, and geological sources are higher than top-down estimates. The atmospheric constraints on the top-down budget suggest that at least some of these bottom-up emissions are overestimated. The latitudinal distribution of atmospheric observation-based emissions indicates a predominance of tropical emissions (∼ 65 % of the global budget, < 30∘ N) compared to mid-latitudes (∼ 30 %, 30–60∘ N) and high northern latitudes (∼ 4 %, 60–90∘ N). The most important source of uncertainty in the methane budget is attributable to natural emissions, especially those from wetlands and other inland waters.Some of our global source estimates are smaller than those in previously published budgets (Saunois et al., 2016; Kirschke et al., 2013). In particular wetland emissions are about 35 Tg CH4 yr−1 lower due to improved partition wetlands and other inland waters. Emissions from geological sources and wild animals are also found to be smaller by 7 Tg CH4 yr−1 by 8 Tg CH4 yr−1, respectively. However, the overall discrepancy between bottom-up and top-down estimates has been reduced by only 5 % compared to Saunois et al. (2016), due to a higher estimate of emissions from inland waters, highlighting the need for more detailed research on emissions factors. Priorities for improving the methane budget include (i) a global, high-resolution map of water-saturated soils and inundated areas emitting methane based on a robust classification of different types of emitting habitats; (ii) further development of process-based models for inland-water emissions; (iii) intensification of methane observations at local scales (e.g., FLUXNET-CH4 measurements) and urban-scale monitoring to constrain bottom-up land surface models, and at regional scales (surface networks and satellites) to constrain atmospheric inversions; (iv) improvements of transport models and the representation of photochemical sinks in top-down inversions; and (v) development of a 3D variational inversion system using isotopic and/or co-emitted species such as ethane to improve source partitioning.The data presented here can be downloaded from https://doi.org/10.18160/GCP-CH4-2019 (Saunois et al., 2020) and from the Global Carbon Project.
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| 5. |
- Tang, Hu, et al.
(author)
-
Boron-Rich Molybdenum Boride with Unusual Short-Range Vacancy Ordering, Anisotropic Hardness, and Superconductivity
- 2020
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In: Chemistry of Materials. - : AMER CHEMICAL SOC. - 0897-4756 .- 1520-5002. ; 32:1, s. 459-467
-
Journal article (peer-reviewed)abstract
- Determination of the structures of materials involving more light elements such as boron-rich compounds is challenging and technically important in understanding their varied compositions and superior functionalities. Here we resolve the long-standing uncertainties in structure and composition about the highest boride (termed MoB4, Mo1-xB3, or MoB3) through the rapid formation of large sized boron-rich molybdenum boride under pressure. Using high-quality single-crystal X-ray diffraction analysis and aberration-corrected scanning transmission electron microscopy, we reveal that boron-rich molybdenum boride with a composition of Mo0.757B3 exhibits P6(3)/mmc symmetry with a partial occupancy of 0.514 in 211 Mo sites (Mol), and direct observations reveal the short-range ordering of cation vacancies in (010) crystal planes. Large anisotropic Young's moduli and Vickers hardness are seen for Mo0.757B3, which may be attributed by its two-dimensional boron distributions. Mo0.757B3 is also found to be superconducting with a transition temperature (T-c) of 2.4 K, which was confirmed by measurements of resistivity and magnetic susceptibility. Theoretical calculations suggest that the partial occupancy of Mo atoms plays a crucial role in the emergence of superconductivity.
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| 6. |
- Zhang, Ting, et al.
(author)
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The evolution of parasitism from mutualism in wasps pollinating the fig, Ficus microcarpa, in Yunnan Province, China
- 2021
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences (PNAS). - 0027-8424 .- 1091-6490. ; 118:32
-
Journal article (peer-reviewed)abstract
- Theory identifies factors that can undermine the evolutionary stability of mutualisms. However, theory's relevance to mutualism stability in nature is controversial. Detailed comparative studies of parasitic species that are embedded within otherwise mutualistic taxa (e.g., fig pollinator wasps) can identify factors that potentially promote or undermine mutualism stability. We describe results from behavioral, morphological, phylogenetic, and experimental studies of two functionally distinct, but closely related, Eupristina wasp species associated with the monoecious host fig, Ficus microcarpa, in Yunnan Province, China. One (Eupristina verticillata) is a competent pollinator exhibiting morphologies and behaviors consistent with observed seed production. The other (Eupristina sp.) lacks these traits, and dramatically reduces both female and male reproductive success of its host. Furthermore, observations and experiments indicate that individuals of this parasitic species exhibit greater relative fitness than the pollinators, in both indirect competition (individual wasps in separate fig inflorescences) and direct competition (wasps of both species within the same fig). Moreover, phylogenetic analyses suggest that these two Eupristina species are sister taxa. By the strictest definition, the nonpollinating species represents a "cheater" that has descended from a beneficial pollinating mutualist. In sharp contrast to all 15 existing studies of actively pollinated figs and their wasps, the local F. microcarpa exhibit no evidence for host sanctions that effectively reduce the relative fitness of wasps that do not pollinate. We suggest that the lack of sanctions in the local hosts promotes the loss of specialized morphologies and behaviors crucial for pollination and, thereby, the evolution of cheating.
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| 7. |
- Abbafati, Cristiana, et al.
(author)
-
- 2020
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Journal article (peer-reviewed)
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| 8. |
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| 9. |
- Andersson, Måns
(author)
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Leveraging Intermediate Representations for High-Performance Portable Discrete Fourier Transform Frameworks : with Application to Molecular Dynamics
- 2023
-
Licentiate thesis (other academic/artistic)abstract
- The Discrete Fourier Transform (DFT) and its improved formulations, the Fast Fourier Transforms (FFTs), are vital for scientists and engineers in a range of domains from signal processing to the solution of partial differential equations. A growing trend in Scientific Computing is heterogeneous computing, where accelerators are used instead or together with CPUs. This has led to problems for developers in unifying portability, performance, and productivity. This thesis first motivates this work by showing the importance of having efficient DFT calculations, describes the DFT algorithm and a formulation based on matrix-factorizations which has been developed to formulate FFT algorithms and express their parallelism to exploit modern computer architectures, such as accelerators.The first paper is a motivating study of the breakdown of the performance and scalability of the high-performance Molecular Dynamics code GROMACS where DFT calculations are a main performance bottleneck. In particular, the long-range interactions are solved with the Particle-Mesh Ewald algorithm which uses a three-dimensional Fast Fourier Transform. The two following papers present two approaches to leverage factorization with the help of two different frameworks using Intermediate Representation and compiler technology, for the development of fast and portable code. The second paper presents a front-end and a pipeline for code generation in a domain-specific language based on Multi-Level Intermediate Representation (MLIR) for developing Fast Fourier Transform libraries. The last paper investigates and optimizes an implementation of an important kernel within the matrix-factorization framework: the batched DFT. It is implemented with data-centric programming and a data-centric intermediate representation called Stateful Dataflow multi-graphs (SDFG). The paper evaluates strategies for complex-valued data layout for performance and portability and we show that there is a trade-off between portability and maintainability in using the native complex data type and that an SDFG-level abstraction could be beneficial for developing higher-level applications.
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| 10. |
- Araújo De Medeiros, Daniel
(author)
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Emerging Paradigms in the Convergence of Cloud and High-Performance Computing
- 2023
-
Licentiate thesis (other academic/artistic)abstract
- Traditional HPC scientific workloads are tightly coupled, while emerging scientific workflows exhibit even more complex patterns, consisting of multiple characteristically different stages that may be IO-intensive, compute-intensive, or memory-intensive. New high-performance computer systems are evolving to adapt to these new requirements and are motivated by the need for performance and efficiency in resource usage. On the other hand, cloud workloads are loosely coupled, and their systems have matured technologies under different constraints from HPC.In this thesis, the use of cloud technologies designed for loosely coupled dynamic and elastic workloads is explored, repurposed, and examined in the landscape of HPC in three major parts. The first part deals with the deployment of HPC workloads in cloud-native environments through the use of containers and analyses the feasibility and trade-offs of elastic scaling. The second part relates to the use of workflow management systems in HPC workflows; in particular, a molecular docking workflow executed through Airflow is discussed. Finally, object storage systems, a cost-effective and scalable solution widely used in the cloud, and their usage in HPC applications through MPI I/O are discussed in the third part of this thesis.
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| 11. |
- Araújo De Medeiros, Daniel, et al.
(author)
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Kub : Enabling Elastic HPC Workloads on Containerized Environments
- 2023
-
In: Proceedings of the 35th International Symposium on Computer Architecture and High Performance Computing (SBAC-PAD). - : Institute of Electrical and Electronics Engineers (IEEE).
-
Conference paper (peer-reviewed)abstract
- The conventional model of resource allocation in HPC systems is static. Thus, a job cannot leverage newly available resources in the system or release underutilized resources during the execution. In this paper, we present Kub, a methodology that enables elastic execution of HPC workloads on Kubernetes so that the resources allocated to a job can be dynamically scaled during the execution. One main optimization of our method is to maximize the reuse of the originally allocated resources so that the disruption to the running job can be minimized. The scaling procedure is coordinated among nodes through remote procedure calls on Kubernetes for deploying workloads in the cloud. We evaluate our approach using one synthetic benchmark and two production-level MPI-based HPC applications - GRO-MACS and CM1. Our results demonstrate that the benefits of adapting the allocated resources depend on the workload characteristics. In the tested cases, a properly chosen scaling point for increasing resources during execution achieved up to 2x speedup. Also, the overhead of checkpointing and data reshuffling significantly influences the selection of optimal scaling points and requires application-specific knowledge.
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| 12. |
- Araújo De Medeiros, Daniel, et al.
(author)
-
LibCOS : Enabling Converged HPC and Cloud Data Stores with MPI
- 2023
-
In: Proceedings of International Conference on High Performance Computing in Asia-Pacific Region, HPC Asia 2023. - New York, NY, USA : Association for Computing Machinery (ACM). ; , s. 106-116
-
Conference paper (peer-reviewed)abstract
- Recently, federated HPC and cloud resources are becoming increasingly strategic for providing diversified and geographically available computing resources. However, accessing data stores across HPC and cloud storage systems is challenging. Many cloud providers use object storage systems to support their clients in storing and retrieving data over the internet. One popular method is REST APIs atop the HTTP protocol, with Amazon's S3 APIs being supported by most vendors. In contrast, HPC systems are contained within their networks and tend to use parallel file systems with POSIX-like interfaces. This work addresses the challenge of diverse data stores on HPC and cloud systems by providing native object storage support through the unified MPI I/O interface in HPC applications. In particular, we provide a prototype library called LibCOS that transparently enables MPI applications running on HPC systems to access object storage on remote cloud systems. We evaluated LibCOS on a Ceph object storage system and a traditional HPC system. In addition, we conducted performance characterization of core S3 operations that enable individual and collective MPI I/O. Our evaluation in HACC, IOR, and BigSort shows that enabling diverse data stores on HPC and Cloud storage is feasible and can be transparently achieved through the widely adopted MPI I/O. Also, we show that a native object storage system like Ceph could improve the scalability of I/O operations in parallel applications.
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| 13. |
- Barucca, G., et al.
(author)
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Study of excited Ξ baryons with the P¯ ANDA detector
- 2021
-
In: European Physical Journal A. - : Springer Nature. - 1434-6001 .- 1434-601X. ; 57:4
-
Journal article (peer-reviewed)abstract
- The study of baryon excitation spectra provides insight into the inner structure of baryons. So far, most of the world-wide efforts have been directed towards N∗ and Δ spectroscopy. Nevertheless, the study of the double and triple strange baryon spectrum provides independent information to the N∗ and Δ spectra. The future antiproton experiment P¯ANDA will provide direct access to final states containing a Ξ¯ Ξ pair, for which production cross sections up to μb are expected in p¯p reactions. With a luminosity of L= 10 31 cm- 2 s- 1 in the first phase of the experiment, the expected cross sections correspond to a production rate of ∼106events/day. With a nearly 4 π detector acceptance, P¯ANDA will thus be a hyperon factory. In this study, reactions of the type p¯p → Ξ¯ +Ξ∗ - as well as p¯p → Ξ¯ ∗ +Ξ- with various decay modes are investigated. For the exclusive reconstruction of the signal events a full decay tree fit is used, resulting in reconstruction efficiencies between 3 and 5%. This allows high statistics data to be collected within a few weeks of data taking.
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| 14. |
- Barucca, G., et al.
(author)
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The potential of Λ and Ξ- studies with PANDA at FAIR
- 2021
-
In: European Physical Journal A. - : Springer Nature. - 1434-6001 .- 1434-601X. ; 57:4
-
Journal article (peer-reviewed)abstract
- The antiproton experiment PANDA at FAIR is designed to bring hadron physics to a new level in terms of scope, precision and accuracy. In this work, its unique capability for studies of hyperons is outlined. We discuss ground-state hyperons as diagnostic tools to study non-perturbative aspects of the strong interaction, and fundamental symmetries. New simulation studies have been carried out for two benchmark hyperon-antihyperon production channels: p¯ p→ Λ¯ Λ and p¯ p→ Ξ¯ +Ξ-. The results, presented in detail in this paper, show that hyperon-antihyperon pairs from these reactions can be exclusively reconstructed with high efficiency and very low background contamination. In addition, the polarisation and spin correlations have been studied, exploiting the weak, self-analysing decay of hyperons and antihyperons. Two independent approaches to the finite efficiency have been applied and evaluated: one standard multidimensional efficiency correction approach, and one efficiency independent approach. The applicability of the latter was thoroughly evaluated for all channels, beam momenta and observables. The standard method yields good results in all cases, and shows that spin observables can be studied with high precision and accuracy already in the first phase of data taking with PANDA.
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| 15. |
- Chen, Heping, et al.
(author)
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Real-Time Cerebral Vessel Segmentation in Laser Speckle Contrast Image Based on Unsupervised Domain Adaptation
- 2021
-
In: Frontiers in Neuroscience. - : Frontiers Media SA. - 1662-4548 .- 1662-453X. ; 15
-
Journal article (peer-reviewed)abstract
- Laser speckle contrast imaging (LSCI) is a full-field, high spatiotemporal resolution and low-cost optical technique for measuring blood flow, which has been successfully used for neurovascular imaging. However, due to the low signal-noise ratio and the relatively small sizes, segmenting the cerebral vessels in LSCI has always been a technical challenge. Recently, deep learning has shown its advantages in vascular segmentation. Nonetheless, ground truth by manual labeling is usually required for training the network, which makes it difficult to implement in practice. In this manuscript, we proposed a deep learning-based method for real-time cerebral vessel segmentation of LSCI without ground truth labels, which could be further integrated into intraoperative blood vessel imaging system. Synthetic LSCI images were obtained with a synthesis network from LSCI images and public labeled dataset of Digital Retinal Images for Vessel Extraction, which were then used to train the segmentation network. Using matching strategies to reduce the size discrepancy between retinal images and laser speckle contrast images, we could further significantly improve image synthesis and segmentation performance. In the testing LSCI images of rodent cerebral vessels, the proposed method resulted in a dice similarity coefficient of over 75%.
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| 16. |
- Cheng, Chao, et al.
(author)
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Mosaic chromosomal alterations are associated with increased lung cancer risk : insight from the INTEGRAL-ILCCO cohort analysis
- 2023
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In: Journal of Thoracic Oncology. - : Elsevier. - 1556-0864 .- 1556-1380.
-
Journal article (peer-reviewed)abstract
- Introduction: Mosaic chromosomal alterations (mCAs) detected in white blood cells represent a type of clonal hematopoiesis (CH) that is understudied compared with CH-related somatic mutations. A few recent studies indicated their potential link with nonhematological cancers, especially lung cancer. Methods: In this study, we investigated the association between mCAs and lung cancer using the high-density genotyping data from the OncoArray study of INTEGRAL-ILCCO, the largest single genetic study of lung cancer with 18,221 lung cancer cases and 14,825 cancer-free controls. Results: We identified a comprehensive list of autosomal mCAs, ChrX mCAs, and mosaic ChrY (mChrY) losses from these samples. Autosomal mCAs were detected in 4.3% of subjects, in addition to ChrX mCAs in 3.6% of females and mChrY losses in 9.6% of males. Multivariable logistic regression analysis indicated that the presence of autosomal mCAs in white blood cells was associated with an increased lung cancer risk after adjusting for key confounding factors, including age, sex, smoking status, and race. This association was mainly driven by a specific type of mCAs: copy-neutral loss of heterozygosity on autosomal chromosomes. The association between autosome copy-neutral loss of heterozygosity and increased risk of lung cancer was further confirmed in two major histologic subtypes, lung adenocarcinoma and squamous cell carcinoma. In addition, we observed a significant increase of ChrX mCAs and mChrY losses in smokers compared with nonsmokers and racial differences in certain types of mCA events. Conclusions: Our study established a link between mCAs in white blood cells and increased risk of lung cancer.
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| 17. |
- Cllasun, Hüsrev, et al.
(author)
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FPGA-accelerated simulation of variable latency memory systems
- 2022
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In: MEMSYS 2022 - Proceedings of the International Symposium on Memory Systems. - : Association for Computing Machinery (ACM).
-
Conference paper (peer-reviewed)abstract
- With the growing complexity of memory types, organizations, and placement, efficient use of memory systems remains a key objective to processing data-rich workloads. Heterogeneous memories including HBM, conventional DRAM, and persistent memory, both locally and network-attached, exhibit a wide range of latencies and bandwidths. The delivered performance to an application may vary widely depending on workload and interference from competing clients. Evaluating the impact on applications to these emerging memory systems challenges traditional simulation techniques. In this work, we describe VLD-sim, an FPGA-accelerated simulator designed to evaluate application performance in the presence of varying non-deterministic latency. VLD-sim implements a statistical approach in which memory system access latency is non-deterministic, as would occur when request traffic is generated from a large collection of possibly unrelated threads and compute nodes. VLD-sim runs on a Multi-Processor System on Chip with hard CPU plus configurable logic to enable fast evaluation of workloads or of individual applications. We evaluate VLD-sim with CPU-only and near memory accelerator-enabled applications and compare against an idealized fixed latency baseline. Our findings reveal and quantify performance impact on applications due to non-deterministic latency. With high flexibility and and fast execution time, VLD-sim enables system level evaluation of a large memory architecture design space.
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| 18. |
- Faj, Jennifer, et al.
(author)
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MPI Performance Analysis in Vlasiator : Unraveling Communication Bottlenecks
- 2023
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In: SC23 Proccedings. - Denver, Colorado, USA.
-
Conference paper (peer-reviewed)abstract
- Vlasiator is a popular and powerful massively parallel code for accurate magnetospheric and solar wind plasma simulations. This work provides an in-depth analysis of Vlasiator, focusing on MPI performance using the Integrated Performance Monitoring (IPM) tool. We show that MPI non-blocking point-to-point communication accounts for most of the communication time. The communication topology shows a large number of MPI messages exchanging data in a six-dimensional grid. We also show that relatively large messages are used in MPI communication, reaching up to 256MB. As a communication-bound application, we found that using OpenMP in Vlasiator is critical for eliminating intra-node communication. Our results provide important insights for optimizing Vlasiator for the upcoming Exascale machines.
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| 19. |
- Faj, Jennifer, et al.
(author)
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Quantum Computer Simulations at Warp Speed : Assessing the Impact of GPU Acceleration
- 2023
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In: Proceedings 2023 IEEE 19th International Conference on e-Science, e-Science 2023. - : Institute of Electrical and Electronics Engineers (IEEE).
-
Conference paper (peer-reviewed)abstract
- Quantum computer simulators are crucial for the development of quantum computing. This work investigates GPU and multi-GPU systems' suitability and performance impact on a widely used simulation tool - the state vector simulator Qiskit Aer. In particular, we evaluate the performance of both Qiskit's default Nvidia Thrust backend and the recent Nvidia cuQuantum backend on Nvidia A100 GPUs. We provide a benchmark suite of representative quantum applications for characterization. For simulations with a large number of qubits, the two GPU backends can provide up to 14× speedup over the CPU backend, with Nvidia cuQuantum providing a further 1.5-3× speedup over the default Thrust backend. Our evaluation on a single GPU identifies the most important functions in Nvidia Thrust and cuQuantum for different quantum applications and their compute and memory bottlenecks. We also evaluate the gate fusion and cache-blocking optimizations on different quantum applications. Finally, we evaluate large-number qubit quantum applications on multi-GPU and identify data movement between host and GPU as the limiting factor for the performance.
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| 20. |
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| 21. |
- Kristan, Matej, et al.
(author)
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The Ninth Visual Object Tracking VOT2021 Challenge Results
- 2021
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In: 2021 IEEE/CVF INTERNATIONAL CONFERENCE ON COMPUTER VISION WORKSHOPS (ICCVW 2021). - : IEEE COMPUTER SOC. - 9781665401913 ; , s. 2711-2738
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Conference paper (peer-reviewed)abstract
- The Visual Object Tracking challenge VOT2021 is the ninth annual tracker benchmarking activity organized by the VOT initiative. Results of 71 trackers are presented; many are state-of-the-art trackers published at major computer vision conferences or in journals in recent years. The VOT2021 challenge was composed of four sub-challenges focusing on different tracking domains: (i) VOT-ST2021 challenge focused on short-term tracking in RGB, (ii) VOT-RT2021 challenge focused on "real-time" short-term tracking in RGB, (iii) VOT-LT2021 focused on long-term tracking, namely coping with target disappearance and reappearance and (iv) VOT-RGBD2021 challenge focused on long-term tracking in RGB and depth imagery. The VOT-ST2021 dataset was refreshed, while VOT-RGBD2021 introduces a training dataset and sequestered dataset for winner identification. The source code for most of the trackers, the datasets, the evaluation kit and the results along with the source code for most trackers are publicly available at the challenge website(1).
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| 22. |
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| 23. |
- Lee, Hanna, et al.
(author)
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Metabolic phenotype and microbiome of infants fed formula containing Lactobacillus paracasei strain F-19
- 2022
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In: Frontiers in Pediatrics. - : Frontiers Media S.A.. - 2296-2360. ; 10
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Journal article (peer-reviewed)abstract
- Early childhood nutrition drives the development of the gut microbiota. In contrast to breastfeeding, feeding infant formula has been shown to impact both the gut microbiota and the serum metabolome toward a more unfavorable state. It is thought that probiotics may alter the gut microbiota and hence create a more favorable metabolic outcome. To investigate the impact of supplementation with Lactobacillus paracasei spp. paracasei strain F-19 on the intestinal microbiota and the serum metabolome, infants were fed a formula containing L. paracasei F19 (F19) and compared to a cohort of infants fed the same standard formula without the probiotic (SF) and a breast-fed reference group (BF). The microbiome, as well as serum metabolome, were compared amongst groups. Consumption of L. paracasei F19 resulted in lower community diversity of the gut microbiome relative to the SF group that made it more similar to the BF group at the end of the intervention (4 months). It also significantly increased lactobacilli and tended to increase bifidobacteria, also making it more similar to the BF group. The dominant genus in the microbiome of all infants was Bifidobacterium throughout the intervention, which was maintained at 12 months. Although the serum metabolome of the F19 group was more similar to the group receiving the SF than the BF group, increases in serum TCA cycle intermediates and decreases in several amino acids in the metabolome of the F19 group were observed, which resulted in a metabolome that trended toward the BF group. Overall, L. paracasei F19 supplementation did not override the impact of formula-feeding but did impact the microbiome and the serum metabolome in a way that may mitigate some unfavorable metabolic impacts of formula-feeding.
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| 24. |
- Lee, Hanna, et al.
(author)
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Milk Fat Globule Membrane as a Modulator of Infant Metabolism and Gut Microbiota : A Formula Supplement Narrowing the Metabolic Differences between Breastfed and Formula-Fed Infants
- 2021
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In: Molecular Nutrition & Food Research. - : Wiley-VCH Verlagsgesellschaft. - 1613-4125 .- 1613-4133. ; 65:3
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Journal article (peer-reviewed)abstract
- Scope Milk fat globule membrane (MFGM) is an important component of milk that has previously been removed in the manufacture of infant formulas, but has recently gained attention owing to its potential to improve immunological, cognitive, and metabolic health. The goal of this study is to determine whether supplementing MFGM in infant formula would drive desirable changes in metabolism and gut microbiota to elicit benefits observed in prior studies. Methods and Results The serum metabolome and fecal microbiota are analyzed using H-1 NMR spectroscopy and 16S rRNA gene sequencing respectively in a cohort of Chinese infants given a standard formula or a formula supplemented with an MFGM-enriched whey protein fraction. Supplementing MFGM suppressed protein degradation pathways and the levels of insulinogenic amino acids that are typically enhanced in formula-fed infants while facilitating fatty acid oxidation and ketogenesis, a feature that may favor brain development. MFGM supplementation did not induce significant compositional changes in the fecal microbiota but suppressed microbial diversity and altered microbiota-associated metabolites. Conclusion Supplementing MFGM in a formula reduced some metabolic gaps between formula-fed and breastfed infants.
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| 25. |
- Li, Xiaonan, et al.
(author)
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Serum cytokine patterns are modulated in infants fed formula with probiotics or milk fat globule membranes : A randomized controlled trial
- 2021
-
In: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 16
-
Journal article (peer-reviewed)abstract
- Background: Proteins and lipids of milk fat globule membrane (MFGM) and probiotics are immunomodulatory. We hypothesized that Lactobacillus paracasei ssp. paracasei strain F19 (F19) would augment vaccine antibody and T helper 1 type immune responses whereas MFGM would produce an immune response closer to that of breastfed (BF) infants.Objective: To compare the effects of supplementing formula with F19 or bovine MFGM on serum cytokine and vaccine responses of formula-fed (FF) and BF infants.Design: FF infants were randomized to formula with F19 (n = 195) or MFGM (n = 192), or standard formula (SF) (n = 194) from age 21±7 days until 4 months. A BF group served as reference (n = 208). We analyzed seven cytokines (n = 398) in serum at age 4 months using magnetic bead-based multiplex technology. Using ELISA, we analyzed anti-diphtheria IgG (n = 258) and anti-poliovirus IgG (n = 309) concentrations in serum before and after the second and third immunization, respectively.Results: Compared with SF, the F19 group had greater IL-2 and lower IFN-γ concentrations (p<0.05, average effect size 0.14 and 0.39). Compared with BF, the F19 group had greater IL-2, IL-4 and IL-17A concentrations (p<0.05, average effect size 0.42, 0.34 and 0.26, respectively). The MFGM group had lower IL-2 and IL-17A concentrations compared with SF (p<0.05, average effect size 0.34 and 0.31). Cytokine concentrations were comparable among the MFGM and BF groups. Vaccine responses were comparable among the formula groups.Conclusions: Contrary to previous studies F19 increased IL-2 and lowered IFN-γ production, suggesting that the response to probiotics differs across populations. The cytokine profile of the MFGM group approached that of BF infants, and may be associated with the previous finding that infectious outcomes for the MFGM group in this cohort were closer to those of BF infants, as opposed to the SF group. These immunomodulatory effects support future clinical evaluation of infant formula with F19 or MFGM.
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| 26. |
- Liang, Yajun, et al.
(author)
-
Metabolic syndrome in patients with first-ever ischemic stroke : prevalence and association with coronary heart disease
- 2022
-
In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 12:1
-
Journal article (peer-reviewed)abstract
- The metabolic syndrome (MetS) has been well linked with coronary heart disease (CHD) in the general population, but studies have rarely explored their association among patients with stroke. We examine prevalence of MetS and its association with CHD in patients with first-ever ischemic stroke. This hospital-based study included 1851 patients with first-ever ischemic stroke (mean age 61.2 years, 36.5% women) who were hospitalized into two university hospitals in Shandong, China (January 2016–February 2017). Data were collected through interviews, physical examinations, and laboratory tests. MetS was defined following the National Cholesterol Education Program (NCEP) criteria, the International Diabetes Federation (IDF) criteria, and the Chinese Diabetes Society (CDS) criteria. CHD was defined following clinical criteria. Data were analyzed using binary logistic regression models. The overall prevalence of MetS was 33.4% by NECP criteria, 47.2% by IDF criteria, and 32.5% by CDS criteria, with the prevalence being decreased with age and higher in women than in men (p < 0.05). High blood pressure, high triglycerides, and low HDL-C were significantly associated with CHD (multi-adjusted odds ratio [OR] range 1.27–1.38, p < 0.05). The multi-adjusted OR of CHD associated with MetS defined by the NECP criteria, IDF criteria, and CDS criteria (vs. no MetS) was 1.27 (95% confidence interval 1.03–1.57), 1.44 (1.18–1.76), and 1.27 (1.03–1.57), respectively. In addition, having 1–2 abnormal components (vs. none) of MetS was associated with CHD (multi-adjusted OR range 1.66–1.72, p < 0.05). MetS affects over one-third of patients with first-ever ischemic stroke. MetS is associated with an increased likelihood of CHD in stroke patients.
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| 27. |
- Liu, Lang, et al.
(author)
-
Quantitative investigation on micro-parameters of cemented paste backfill and its sensitivity analysis
- 2020
-
In: Journal of Central South University. - : Springer. - 2095-2899 .- 2227-5223. ; 27:1, s. 267-276
-
Journal article (peer-reviewed)abstract
- The mechanical properties of cemented paste backfill (CPB) depend heavily on its pore structural characteristics and micro-structural changes. In order to explore the variation mechanisms of macro-mechanical characteristics and micro-structure of CPB. CPB specimens with different mass concentrations prepared from the full tailings of Xianglushan Tungsten Ore were micro-tests. Moreover, acquired pore digital images were processed by using the pores (particles) and cracks analysis system (PCAS), and a sensitivity analysis was performed. The results show that as the mass concentration of CPB increases from 70% to 78%, the porosity, the average pore area and the number of pores drop overall, leading to a decline in the pores opening degree and enhancing the mechanical characteristics. As the mass concentration of CPB increases, the trend of fractal dimension, probability entropy and roundness is reduced, constant and increased, which can result in an enhancement of the uniformity, an unchanged directionality and more round pores. According to the definition of sensitivity, the sensitivities of various micro-parameters were calculated and can be ranked as porosity > average pore area > number of pores > roundness > fractal dimension > probability entropy.
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| 28. |
- Liu, Xueyang, et al.
(author)
-
Accelerator integration in a tile-based SoC: lessons learned with a hardware floating point compression engine
- 2023
-
In: Proceedings of 2023 SC Workshops of the International Conference on High Performance Computing, Network, Storage, and Analysis, SC Workshops 2023. - : Association for Computing Machinery (ACM). ; , s. 1662-1669
-
Conference paper (peer-reviewed)abstract
- Heterogeneous Intellectual Property (IP) hardware acceleration engines have emerged as a viable path forward to improving performance in the waning of Moore's Law and Dennard scaling. In this study, we design, prototype, and evaluate the HPC-specialized ZHW floating point compression accelerator as a resource on a System on Chip (SoC). Our full hardware/software implementation and evaluation reveal inefficiencies at the system level that significantly throttle the potential speedup of the ZHW accelerator. By optimizing data movement between CPU, memory, and accelerator, 6.9X is possible compared to a RISC-V64 core, and 2.9X over a Mac M1 ARM core.
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| 29. |
- Lv, Jiezhao, et al.
(author)
-
Numerical Investigation of the Stimulated Growth of Single-Crystal Fibers by Point-Effect-Induced Fluid Dynamics
- 2022
-
In: Crystal Growth & Design. - : AMER CHEMICAL SOC. - 1528-7483 .- 1528-7505. ; 22:12, s. 7031-7039
-
Journal article (peer-reviewed)abstract
- Using molecular dynamics analysis and a two-component diffusion model that accounts for the time-dependent crystal surface chemical reaction, we show by extensive numerical simulations that the recently observed prismatic facet growth suppression in single-crystal fibers is the combined action of self-shielding by crystal surface selectivity and self-channeling arising from a point effect due to fibers small diameters and large aspect ratios. We further show that the self-channeling leads to a pyramidal-face-aiming solute flow, resulting in accelerated single-crystal fiber growth. This mesoscopic stimulated matter growth acceleration theory can satisfactorily explain all experimental results reported to date. This new crystal fiber growth technology opens a realm of application possibilities for single-crystal fiber architectures in chip-size photonics.
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| 30. |
- Markidis, Stefano, et al.
(author)
-
Kinetic Modeling in the Magnetosphere
- 2021
-
In: Magnetospheres in the Solar System. - : Wiley. ; , s. 607-615
-
Book chapter (other academic/artistic)abstract
- This paper presents the state of the art of kinetic modeling techniques for simulating plasma kinetic dynamics in magnetospheres. We describe the key numerical techniques for enabling large-scale kinetic simulations of magnetospheres: parameter scaling, implicit Particle-in-Cell schemes and fluid-kinetic coupling. We show an application of these techniques to study particle acceleration and heating in asymmetric magnetic reconnection in the Ganymede magnetosphere.
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| 31. |
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| 32. |
- Miao, Bai-Ge, et al.
(author)
-
Active pollination in a functionally dioecious Ficus species : An interplay between pollinator behaviour and floral morphology
- 2023
-
In: Flora. - : Elsevier. - 0367-2530 .- 1618-0585. ; 302
-
Journal article (peer-reviewed)abstract
- Active pollination has evolved four times in brood site pollination mutualisms. When pollination is active, the pollinator's behaviour specifically evolves to ensure flower fertilisation. In functionally dioecious Ficus species, the male figs host pollinating wasp larvae, while wasps cannot breed in the female figs because the styles are longer than the wasp ovipositor. Here we investigate the dioecious Ficus hispida. We show that in male figs, every time the wasp has laid an egg into a pistillate flower, it removes one pollen grain from its pollen pockets and places it on the hypopygium. When the wasp inserts its ovipositor into the next flower, the pollen grain is deposited deep within the style. Each ovipositor insertion results in flower pollination and insect oviposition. Because of systematic pollination of the flowers into which the eggs are laid, the wasp larvae benefit from feeding on fertilised endosperm while no seed are produced. In female figs, after probing a flower, the wasp presents pollination behaviour only every five visits. However, if it does occur, this behaviour lasts longer than in male figs and results in the deposition of on average 10 pollen grains on the hypopygium. The exposed sticky papillae on the stigmatic surface collect pollen from the hypopygium and pollen tubes may grow to neighbouring stigmas, ensuring secondary dispersal and efficient ovule fertilisation. Overall, our study demonstrates that the floral morphology of male figs facilitates precise pollen deposition, beneficial for the wasp progeny, while the floral morphology of female figs compensates for wasp pollination behaviour that is not selected in those figs. We conclude that the morphology of the arena in which interactions with its pollinator are played out is the result of selection on the plant to maximize its male and female fitness. Incidentally, this morphology stabilises the mutualistic interaction.
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| 33. |
- Ou, Yangmei, et al.
(author)
-
Developing D-pi-D hole-transport materials for perovskite solar cells : the effect of the pi-bridge on device performance
- 2021
-
In: Materials Chemistry Frontiers. - : Royal Society of Chemistry (RSC). - 2052-1537. ; 5:2, s. 876-884
-
Journal article (peer-reviewed)abstract
- Three cost-effective D-pi-D hole transport materials (HTMs) with different pi-bridges, including biphenyl (SY1), phenanthrene (SY2), and pyrene (SY3), have been synthesized via a one-pot reaction with cheap commercially available starting materials for application in organic-inorganic hybrid perovskite solar cells (PSCs). The effects of the various pi-bridges on the photophysical, electrochemical, and electrical properties, and film morphologies of the materials, as well as on the photovoltaic properties of the PSCs, have been systematically investigated accordingly. Our results clearly show that HTM-SY3 with pyrene as the pi-bridge exhibits higher hole mobility and better hole extraction/transport and film formation abilities than the other two HTMs. Devices that employed SY3 as the HTM show impressive power conversion efficiency (PCE) values of 19.08% and 13.41% in (FAPbI(3))(0.85)(MAPbBr(3))(0.15)- and CsPbI2Br-based PSCs, respectively, which are higher than those of the reference HTM-SY1- and SY2-based ones. Our studies demonstrate a promising strategy to rationally design and synthesize low-cost and efficient HTMs through structural engineering for use in PSCs.
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| 34. |
- Pecunia, Vincenzo, et al.
(author)
-
Roadmap on energy harvesting materials
- 2023
-
In: Journal of Physics. - : IOP Publishing. - 2515-7639. ; 6:4
-
Journal article (peer-reviewed)abstract
- Ambient energy harvesting has great potential to contribute to sustainable development and address growing environmental challenges. Converting waste energy from energy-intensive processes and systems (e.g. combustion engines and furnaces) is crucial to reducing their environmental impact and achieving net-zero emissions. Compact energy harvesters will also be key to powering the exponentially growing smart devices ecosystem that is part of the Internet of Things, thus enabling futuristic applications that can improve our quality of life (e.g. smart homes, smart cities, smart manufacturing, and smart healthcare). To achieve these goals, innovative materials are needed to efficiently convert ambient energy into electricity through various physical mechanisms, such as the photovoltaic effect, thermoelectricity, piezoelectricity, triboelectricity, and radiofrequency wireless power transfer. By bringing together the perspectives of experts in various types of energy harvesting materials, this Roadmap provides extensive insights into recent advances and present challenges in the field. Additionally, the Roadmap analyses the key performance metrics of these technologies in relation to their ultimate energy conversion limits. Building on these insights, the Roadmap outlines promising directions for future research to fully harness the potential of energy harvesting materials for green energy anytime, anywhere.
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| 35. |
- Peng, Bo, et al.
(author)
-
Multigap topology and non-Abelian braiding of phonons from first principles
- 2022
-
In: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 105:8
-
Journal article (peer-reviewed)abstract
- Non-Abelian states of matter, in which the final state depends on the order of the interchanges of two quasipar-ticles, can encode information immune from environmental noise with the potential to provide a robust platform for topological quantum computation. We demonstrate that phonons can carry non-Abelian frame charges at the band-crossing points of their frequency spectrum, and that external stimuli can drive their braiding. We present a general framework to understand the topological configurations of phonons from first-principles calculations using a topological invariant called Euler class, and provide a complete analysis of phonon braiding by combining different topological configurations. Taking a well-known dielectric material Al2O3 as a representative example, we demonstrate that electrostatic doping gives rise to phonon band inversions that can induce redistribution of the frame charges, leading to non-Abelian braiding of phonons. Our work provides a quasiparticle platform for realizable non-Abelian braiding in reciprocal space, and expands the tool set for studying braiding processes.
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| 36. |
- Peng, Bo, et al.
(author)
-
Phonons as a platform for non-Abelian braiding and its manifestation in layered silicates
- 2022
-
In: Nature Communications. - : Springer Nature. - 2041-1723. ; 13:1
-
Journal article (peer-reviewed)abstract
- Multi-gap topology is a new avenue in topological phases of matter but it remains difficult to verify in real materials. Here, the authors predict multi-gap topologies and associated phase transitions driven by braiding processes in the phonon spectra of monolayer silicates, providing clear signatures for experimental verification. Topological phases of matter have revolutionised the fundamental understanding of band theory and hold great promise for next-generation technologies such as low-power electronics or quantum computers. Single-gap topologies have been extensively explored, and a large number of materials have been theoretically proposed and experimentally observed. These ideas have recently been extended to multi-gap topologies with band nodes that carry non-Abelian charges, characterised by invariants that arise by the momentum space braiding of such nodes. However, the constraints placed by the Fermi-Dirac distribution to electronic systems have so far prevented the experimental observation of multi-gap topologies in real materials. Here, we show that multi-gap topologies and the accompanying phase transitions driven by braiding processes can be readily observed in the bosonic phonon spectra of known monolayer silicates. The associated braiding process can be controlled by means of an electric field and epitaxial strain, and involves, for the first time, more than three bands. Finally, we propose that the band inversion processes at the Gamma point can be tracked by following the evolution of the Raman spectrum, providing a clear signature for the experimental verification of the band inversion accompanied by the braiding process.
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| 37. |
- Peng, Ivy Bo, et al.
(author)
-
OpenCUBE: Building an Open Source Cloud Blueprint with EPI Systems
- 2024
-
In: Euro-Par 2023: Parallel Processing Workshops - Euro-Par 2023 International Workshops, 2023, Revised Selected Papers. - : Springer Nature. ; , s. 260-264
-
Conference paper (peer-reviewed)abstract
- OpenCUBE aims to develop an open-source full software stack for Cloud computing blueprint deployed on EPI hardware, adaptable to emerging workloads across the computing continuum. OpenCUBE prioritizes energy awareness and utilizes open APIs, Open Source components, advanced SiPearl Rhea processors, and RISC-V accelerator. The project leverages representative workloads, such as cloud-native workloads and workflows of weather forecast data management, molecular docking, and space weather, for evaluation and validation.
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| 38. |
- Qin, Zhilian, et al.
(author)
-
Vertical distributions of organic carbon fractions under paddy and forest soils derived from black shales : Implications for potential of long-term carbon storage
- 2021
-
In: Catena (Cremlingen. Print). - : Elsevier. - 0341-8162 .- 1872-6887. ; 198, s. 1-8
-
Journal article (peer-reviewed)abstract
- Black shales are characterized by a high content of organic carbon (C). Few studies have focused on the influence of land use on soil organic C (SOC) fractions from soils derived from black shale (black shale soils). The objective of this study was to elucidate the influence of land use on SOC fractions in black shale soils combining chemical determination and stable C isotope analysis techniques. Herein, we determined labile organic C (LOC), semilabile organic C (Semi-LOC), and recalcitrant organic C (ROC) fractions in various depths of soils in paddy fields (0-70 cm) and forests (0-120 cm) from black shale distribution region in Hunan province, China, and then investigated delta C-13 values of these soils. Results showed that the contents of LOC, Semi-LOC, and ROC in paddy soils (1.63-7.35 g kg(-1), 0.35-1.21 g kg(-1), and 3.75-14.8 g kg(-1), respectively) and forest soils (0.73-4.94 g kg(-1), 0.12-0.89 g kg(-1), and 1.44-8.96 g kg(-1), respectively) are significantly decreased with increasing depth. The contribution made by LOC to SOC in paddy soils was significantly lower than that in forest soils, while the contribution made by ROC to SOC was significantly higher in paddy soils than that in forest soils. In these two land uses, the delta C-13 values were higher in SOC compared to the ROC fraction, while the delta C-13 values were close in the ROC fraction below 20 cm soil depth. Our study indicated that i) new C is mainly limited to the surface soil layer (0-10 cm) in forests, while it can be leached along the soil profiles in paddy fields; ii) the estimated ROC pool is similar to 900 Pg within the 0-100 cm soil layer in terrestrial ecosystems, which should better represent the ability of soil C sequestration.
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| 39. |
- Schieffer, Gabin, et al.
(author)
-
Boosting the Performance of Object Tracking with a Half-Precision Particle Filter on GPU
- 2024
-
In: Euro-Par 2023: Parallel Processing Workshops - Euro-Par 2023 International Workshops, Limassol, Cyprus, August 28 – September 1, 2023, Revised Selected Papers. - : Springer Nature. ; , s. 294-305
-
Conference paper (peer-reviewed)abstract
- High-performance GPU-accelerated particle filter methods are critical for object detection applications, ranging from autonomous driving, robot localization, to time-series prediction. In this work, we investigate the design, development and optimization of particle-filter using half-precision on CUDA cores and compare their performance and accuracy with single- and double-precision baselines on Nvidia V100, A100, A40 and T4 GPUs. To mitigate numerical instability and precision losses, we introduce algorithmic changes in the particle filters. Using half-precision leads to a performance improvement of 1.5–2 × and 2.5–4.6 × with respect to single- and double-precision baselines respectively, at the cost of a relatively small loss of accuracy.
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| 40. |
- Stavert, Ann R., et al.
(author)
-
Regional trends and drivers of the global methane budget
- 2022
-
In: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 28:1, s. 182-200
-
Journal article (peer-reviewed)abstract
- The ongoing development of the Global Carbon Project (GCP) global methane (CH4) budget shows a continuation of increasing CH4 emissions and CH4 accumulation in the atmosphere during 2000–2017. Here, we decompose the global budget into 19 regions (18 land and 1 oceanic) and five key source sectors to spatially attribute the observed global trends. A comparison of top-down (TD) (atmospheric and transport model-based) and bottom-up (BU) (inventory- and process model-based) CH4 emission estimates demonstrates robust temporal trends with CH4 emissions increasing in 16 of the 19 regions. Five regions—China, Southeast Asia, USA, South Asia, and Brazil—account for >40% of the global total emissions (their anthropogenic and natural sources together totaling >270 Tg CH4 yr−1 in 2008–2017). Two of these regions, China and South Asia, emit predominantly anthropogenic emissions (>75%) and together emit more than 25% of global anthropogenic emissions. China and the Middle East show the largest increases in total emission rates over the 2000 to 2017 period with regional emissions increasing by >20%. In contrast, Europe and Korea and Japan show a steady decline in CH4 emission rates, with total emissions decreasing by ~10% between 2000 and 2017. Coal mining, waste (predominantly solid waste disposal) and livestock (especially enteric fermentation) are dominant drivers of observed emissions increases while declines appear driven by a combination of waste and fossil emission reductions. As such, together these sectors present the greatest risks of further increasing the atmospheric CH4 burden and the greatest opportunities for greenhouse gas abatement.
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| 41. |
- Wahlgren, Jacob, et al.
(author)
-
A Quantitative Approach for Adopting Disaggregated Memory in HPC Systems
- 2023
-
In: Proceedings of the International Conference for High Performance Computing, Networking, Storage and Analysis, SC 2023. - : Association for Computing Machinery (ACM).
-
Conference paper (peer-reviewed)abstract
- Memory disaggregation has recently been adopted in data centers to improve resource utilization, motivated by cost and sustainability. Recent studies on large-scale HPC facilities have also highlighted memory underutilization. A promising and non-disruptive option for memory disaggregation is rack-scale memory pooling, where node-local memory is supplemented by shared memory pools. This work outlines the prospects and requirements for adoption and clarifies several misconceptions. We propose a quantitative method for dissecting application requirements on the memory system from the top down in three levels, moving from general, to multi-tier memory systems, and then to memory pooling. We provide a multi-level profiling tool and LBench to facilitate the quantitative approach. We evaluate a set of representative HPC workloads on an emulated platform. Our results show that prefetching activities can significantly influence memory traffic profiles. Interference in memory pooling has varied impacts on applications, depending on their access ratios to memory tiers and arithmetic intensities. Finally, in two case studies, we show the benefits of our findings at the application and system levels, achieving 50% reduction in remote access and 13% speedup in BFS, and reducing performance variation of co-located workloads in interference-aware job scheduling.
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| 42. |
- Wang, Di-Si, et al.
(author)
-
Analysis of the Accelerator-Driven System Fuel Assembly during the Steam Generator Tube Rupture Accident
- 2021
-
In: Materials. - : MDPI AG. - 1996-1944. ; 14:8
-
Journal article (peer-reviewed)abstract
- China is developing an ADS (Accelerator-Driven System) research device named the China initiative accelerator-driven system (CiADS). When performing a safety analysis of this new proposed design, the core behavior during the steam generator tube rupture (SGTR) accident has to be investigated. The purpose of our research in this paper is to investigate the impact from different heating conditions and inlet steam contents on steam bubble and coolant temperature distributions in ADS fuel assemblies during a postulated SGTR accident by performing necessary computational fluid dynamics (CFD) simulations. In this research, the open source CFD calculation software OpenFOAM, together with the two-phase VOF (Volume of Fluid) model were used to simulate the steam bubble behavior in heavy liquid metal flow. The model was validated with experimental results published in the open literature. Based on our simulation results, it can be noticed that steam bubbles will accumulate at the periphery region of fuel assemblies, and the maximum temperature in fuel assembly will not overwhelm its working limit during the postulated SGTR accident when the steam content at assembly inlet is less than 15%.
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| 43. |
- Wang, Di -Si, et al.
(author)
-
Finite element analysis of the main reactor vessel in the China Initiative Accelerator Driven System
- 2023
-
In: Engineering Failure Analysis. - : Elsevier BV. - 1350-6307 .- 1873-1961. ; 146
-
Journal article (peer-reviewed)abstract
- The China Initiative Accelerator Driven System (CiADS) was proposed by China Academy of Science since 2015. The reactor in CiADS is a subcritical fast neutron reactor cooled by a liquid lead-bismuth eutectic. The reactor operates at high temperature and bears high thermal stress. In addition to the heavy weight of the whole reactor, the vessel will bear large effective stress. If the effective stress exceeds the limit of the material, defects and cracks may occur on the main reactor vessel, which will affect the safety performances of the reactor. Therefore, it is very important to analyze the effective stress field of the reactor vessel. In this paper, the finite element analysis software ADINA was applied to analyze the reactor vessel in CiADS. We can preliminarily prove that the maximum effective stress that the vessel will bear during the postulated Unprotected Loss of Flow (ULOF) and Unprotected Transient over Power (UTOP) accidents is less than the yield strength of 316L stainless steel. Therefore, we can preliminarily conclude that the current ma-terial selection and structural design of the CiADS vessel could survive the postulated transient accidents considering the effective stress effect.
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| 44. |
- Wang, Peng, et al.
(author)
-
Linking Emergence to the Complex Product System
- 2020
-
In: IEEE Access. - : Institute of Electrical and Electronics Engineers (IEEE). - 2169-3536. ; 8, s. 34286-34298
-
Journal article (peer-reviewed)abstract
- The increasing complexity of product calls for manufacturing integration, while in turn high integration brings the problems of system level complexity. This paper proposes that complex product system (CoPS) should be managed as a dynamical system. The dynamical characteristics of CoPS are discussed from the perspective of emergence. A conceptual model is established to analyze the cause, process and result of the CoPS emergence. The mechanism of inner state emergence in CoPS is interpreted by formal languages to provide a point view of state space. It is concluded that the behavior of CoPS, especially the complexity, exhibits the 'entity is greater than the sum of the parts' phenomena when satisfying given necessary conditions. A novel methodology is then established to evaluate this emergence-based complexity. The feasibility and application of the novel complexity measurement is verified by an example of turbine housing production process. Further discussions are made on how to manage the potential emerging complexity based on the proposed measurement.
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| 45. |
- Wang, Peng, et al.
(author)
-
The Existence of Autonomous Chaos in EDM Process
- 2022
-
In: Machines. - : MDPI AG. - 2075-1702. ; 10:4
-
Journal article (peer-reviewed)abstract
- The dynamical evolution of electrical discharge machining (EDM) has drawn immense research interest. Previous research on mechanism analysis has discussed the deterministic nonlinearity of gap states at pulse-on discharging duration, while describing the pulse-off deionization process separately as a stochastic evolutionary process. In this case, the precise model describing a complete machining process, as well as the optimum performance parameters of EDM, can hardly be determined. The main purpose of this paper is to clarify whether the EDM system can maintain consistency in dynamic characteristics within a discharge interval. A nonlinear self-maintained equivalent model is first established, and two threshold conditions are obtained by the Shilnikov theory. The theoretical results prove that the EDM system could lead to chaos without external excitation. The time series of the deionization process recorded in the EDM experiments are then analyzed to further validate this theoretical conclusion. Qualitative chaotic analyses verify that the autonomous EDM process has chaotic characteristics. Quantitative methods are used to estimate the chaotic feature of the autonomous EDM process. By comparing the quantitative results of the autonomous EDM process with the non-autonomous EDM process, a deduction is further made that the EDM system will evolve towards steady chaos under an autonomous state.
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| 46. |
- Williams, Jeremy J., et al.
(author)
-
Characterizing the Performance of the Implicit Massively Parallel Particle-in-Cell iPIC3D Code
- 2023
-
In: SC23 Proccedings. - Denver, Colorado, USA.
-
Conference paper (peer-reviewed)abstract
- Optimizing iPIC3D, an implicit Particle-in-Cell (PIC) code,for large-scale 3D plasma simulations is crucial for spaceand astrophysical applications. This work focuses on characterizing iPIC3D’s communication efficiency through strategic measures like optimal node placement, communicationand computation overlap, and load balancing. Profiling andtracing tools are employed to analyze iPIC3D’s communication efficiency and provide practical recommendations. Implementing optimized communication protocols addressesthe Geospace Environmental Modeling (GEM) magnetic reconnection challenges in plasma physics with more precisesimulations. This approach captures the complexities of 3Dplasma simulations, particularly in magnetic reconnection,advancing space and astrophysical research.
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| 47. |
- Williams, Jeremy J., et al.
(author)
-
Leveraging HPC Profiling and Tracing Tools to Understand the Performance of Particle-in-Cell Monte Carlo Simulations
- 2024
-
In: Euro-Par 2023: Parallel Processing Workshops - Euro-Par 2023 International Workshops, Limassol, Cyprus, August 28 – September 1, 2023, Revised Selected Papers. - : Springer Science and Business Media Deutschland GmbH. ; , s. 123-134
-
Conference paper (peer-reviewed)abstract
- Large-scale plasma simulations are critical for designing and developing next-generation fusion energy devices and modeling industrial plasmas. BIT1 is a massively parallel Particle-in-Cell code designed for specifically studying plasma material interaction in fusion devices. Its most salient characteristic is the inclusion of collision Monte Carlo models for different plasma species. In this work, we characterize single node, multiple nodes, and I/O performances of the BIT1 code in two realistic cases by using several HPC profilers, such as perf, IPM, Extrae/Paraver, and Darshan tools. We find that the BIT1 sorting function on-node performance is the main performance bottleneck. Strong scaling tests show a parallel performance of 77% and 96% on 2,560 MPI ranks for the two test cases. We demonstrate that communication, load imbalance and self-synchronization are important factors impacting the performance of the BIT1 on large-scale runs.
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| 48. |
- Zhang, Ying, et al.
(author)
-
Capture of novel sp3 hybridized Z-BN by compressing boron nitride nanotubes with small diameter
- 2022
-
In: Diamond and related materials. - : Elsevier. - 0925-9635 .- 1879-0062. ; 130
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Journal article (peer-reviewed)abstract
- Experimental synthesis of new sp3 hybridized carbon/boron nitride structures remains challenging despite that numerous sp3 structures have been proposed in theory. Here, we showed that compressed multi-walled boron nitride nanotubes (MWBNNTs) and boron nitride peapods (C60@BNNTs) with small diameters could transform into a new sp3 hybridized boron nitride allotrope (Z-BN). This strategy is considered from the topological transition point of view in boron nitride nanotubes upon compression. Due to the increased curvature in compressed small-diameter MWBNNTs, the uncommon 4- and 8-membered rings in Z-BN could be more favorably formed. And the irreversible tube collapse is proved to be a critical factor for the capture of the formed Z-BN, because of the competition between the resilience of tube before collapse and the stress limitation for the lattice stabilization of Z-BN upon decompression. In this case, Z-BN starts to form above 19.0 GPa, which is fully reversible below 45 GPa and finally becomes quenchable at 93.5 GPa. This collapse-induced capture of the high-pressure phase could also be extended to other tubular materials for quenching novel sp3 structures.
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| 49. |
- Zhao, Shijing, et al.
(author)
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Elucidating the reaction pathway of crystalline multi-metal borides for highly efficient oxygen-evolving electrocatalysts
- 2022
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In: Journal of Materials Chemistry A. - : ROYAL SOC CHEMISTRY. - 2050-7488 .- 2050-7496. ; 10:3, s. 1569-1578
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Journal article (peer-reviewed)abstract
- Understanding the fundamental principle of catalytic performance and the mechanism of multimetal-based electrocatalysts is essential for the rational design of advanced renewable energy systems. Here, highly crystalline MMMoB4 (M = Fe, Co) compounds with controllable compositions of multiple active metal atoms and polyacene-type boron networks were synthesized delicately by a one-step high-pressure technique to explore electrocatalytic selectivity and activity. CoFeMoB4 and Co2MoB4 are revealed to be highly active and durable oxygen evolution reaction (OER) electrocatalysts under alkaline conditions. The mutually promotive activation of metals with amorphous clusters and ultra-small grains on the surface are responsible for the enhanced activity of CoFeMoB4. More specifically, Co and Fe coupling in CoFeMoB4 facilitates surface reconstruction into active Co hydroxide and Fe oxyhydroxide, in contrast to Co oxyhydroxide in Co2MoB4 and Fe oxides in Fe2MoB4. Dissolving Mo may provide potential space for adsorbing hydroxyl, and the optimized electronic structure with boron is mainly responsible for the long-term durability. In contrast, Mo atoms are responsible for hydrogen evolution reaction (HER) properties, and the optimized d-band center and density of states at the Fermi level make Co2MoB4 a superior HER catalyst. Our findings provide insight into distinguishing the catalytic pathway of multi-metal borides with improved OER activity and different roles of Mo and Co/Fe in the HER and OER.
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