236 research outputs found
Numerical Simulations of the Dynamical Behavior of the SK Model
We study the dynamical behavior of the Sherrington Kirkpatrick model. Thanks
to the APE supercomputer we are able to analyze large lattice volumes, and to
investigate the low region. We present a determination of the remnant
magnetization and of its time decay exponent, of the energy time decay
exponent, and we discuss aging phenomena in the model.Comment: 11 pages including 8 figures. Revised version with major
restructurin
APEnet+: a 3D toroidal network enabling Petaflops scale Lattice QCD simulations on commodity clusters
Many scientific computations need multi-node parallelism for matching up both
space (memory) and time (speed) ever-increasing requirements. The use of GPUs
as accelerators introduces yet another level of complexity for the programmer
and may potentially result in large overheads due to the complex memory
hierarchy. Additionally, top-notch problems may easily employ more than a
Petaflops of sustained computing power, requiring thousands of GPUs
orchestrated with some parallel programming model. Here we describe APEnet+,
the new generation of our interconnect, which scales up to tens of thousands of
nodes with linear cost, thus improving the price/performance ratio on large
clusters. The project target is the development of the Apelink+ host adapter
featuring a low latency, high bandwidth direct network, state-of-the-art wire
speeds on the links and a PCIe X8 gen2 host interface. It features hardware
support for the RDMA programming model and experimental acceleration of GPU
networking. A Linux kernel driver, a set of low-level RDMA APIs and an OpenMPI
library driver are available, allowing for painless porting of standard
applications. Finally, we give an insight of future work and intended
developments
GPU peer-to-peer techniques applied to a cluster interconnect
Modern GPUs support special protocols to exchange data directly across the
PCI Express bus. While these protocols could be used to reduce GPU data
transmission times, basically by avoiding staging to host memory, they require
specific hardware features which are not available on current generation
network adapters. In this paper we describe the architectural modifications
required to implement peer-to-peer access to NVIDIA Fermi- and Kepler-class
GPUs on an FPGA-based cluster interconnect. Besides, the current software
implementation, which integrates this feature by minimally extending the RDMA
programming model, is discussed, as well as some issues raised while employing
it in a higher level API like MPI. Finally, the current limits of the technique
are studied by analyzing the performance improvements on low-level benchmarks
and on two GPU-accelerated applications, showing when and how they seem to
benefit from the GPU peer-to-peer method.Comment: paper accepted to CASS 201
NaNet:a low-latency NIC enabling GPU-based, real-time low level trigger systems
We implemented the NaNet FPGA-based PCI2 Gen2 GbE/APElink NIC, featuring
GPUDirect RDMA capabilities and UDP protocol management offloading. NaNet is
able to receive a UDP input data stream from its GbE interface and redirect it,
without any intermediate buffering or CPU intervention, to the memory of a
Fermi/Kepler GPU hosted on the same PCIe bus, provided that the two devices
share the same upstream root complex. Synthetic benchmarks for latency and
bandwidth are presented. We describe how NaNet can be employed in the prototype
of the GPU-based RICH low-level trigger processor of the NA62 CERN experiment,
to implement the data link between the TEL62 readout boards and the low level
trigger processor. Results for the throughput and latency of the integrated
system are presented and discussed.Comment: Proceedings for the 20th International Conference on Computing in
High Energy and Nuclear Physics (CHEP
Anti-Vascular Endothelial Growth Factors Protect Retinal Pigment Epithelium Cells Against Oxidation by Modulating Nitric Oxide Release and Autophagy
Background/Aims: the anti-vascular endothelial growth factors (VEGF), Aflibercept and Ranibizumab, are used for the treatment of macular degeneration. Here we examined the involvement of nitric oxide (NO), mitochondria function and of apoptosis/autophagy in their antioxidant effects in human retinal pigment epithelium cells (RPE). Methods: RPE were exposed to Ranibizumab/Aflibercept in the absence or presence of NO synthase (NOS) inhibitor and of autophagy activator/blocker, rapamicyn/3-methyladenine. Specific kits were used for cell viability, NO and reactive oxygen species detection and mitochondrial membrane potential measurement, whereas Western Blot was performed for apoptosis/ autophagy markers and other kinases detection. Results: In RPE cultured in physiological conditions, Aflibercept/Ranibizumab increased NO release in a dose and time-dependent way. Opposite results were obtained in RPE pretreated with hydrogen peroxide. Moreover, both the anti-VEGF agents were able to prevent the fall of cell viability and of mitochondrial membrane potential. Those effects were reduced by the NOS inhibitor and 3-methyladenine and were potentiated by rapamycin. Finally, Aflibercept and Ranibizumab counteracted the changes of apoptosis/autophagy markers, NOS, Phosphatidylinositol-3-Kinase/Protein Kinase B and Extracellular signal–regulated kinases 1/2 caused by peroxidation. Conclusion: Aflibercept and Ranibizumab protect RPE against peroxidation through the modulation of NO release, apoptosis and autophagy
Three-dimensional facial morphometry in patients rehabilitated with implant-supported prostheses
The aim of the present study was to assess a low-cost, non-invasive facial morphometric digitizer to assist the practitioner in three-dimensional soft-tissue changes before and after oral rehabilitation. The method should provide quantitative data to support an objective assessment of the facial esthetic outcome [1]. Twenty-two patients aged 45-82 years, all with edentulous maxilla and mandible, were assessed both before and after receiving their definitive complete implant-supported prostheses (each received 4-11 implants in each dental arch; full-arch fixed prostheses were made). The three-dimensional coordinates of 50 soft-tissue facial landmarks were collected with a non-invasive digitizer; labial and facial areas, volumes, angles and distances were compared without/ with the prostheses [2]. Dental prostheses induced significant reductions in the nasolabial, mentolabial and interlabial angles, with increased labial prominence (p<0.05, Wilcoxon test). Lip vermilion area and volume significantly increased; significant increments were found in the vertical and anteroposterior labial dimensions. The presence of the dental prostheses significantly (p<0.001) modified the three-dimensional positions of several soft-tissue facial landmarks. The current approach enabled quantitative evaluation of the final soft-tissue results of oral rehabilitation with implant-supported prostheses, without submitting the patients to invasive procedures. The method could assess the three-dimensional appearance of the facial soft tissues of the patient while planning the provisional prosthetic restoration, providing quantitative information to prepare the best definitive prosthesis. Dote ricerca: FSE, Regione Lombardi
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