410 research outputs found
A Survey on FPGA-Based Heterogeneous Clusters Architectures
In recent years, the most powerful supercomputers have already reached megawatt power consumption levels, an important issue that challenges sustainability and shows the impossibility of maintaining this trend. To this date, the prevalent approach to supercomputing is dominated by CPUs and GPUs. Given their fixed architectures with generic instruction sets, they have been favored with lots of tools and mature workflows which led to mass adoption and further growth. However, reconfigurable hardware such as FPGAs has repeatedly proven that it offers substantial advantages over this supercomputing approach concerning performance and power consumption. In this survey, we review the most relevant works that advanced the field of heterogeneous supercomputing using FPGAs focusing on their architectural characteristics. Each work was divided into three main parts: network, hardware, and software tools. All implementations face challenges that involve all three parts. These dependencies result in compromises that designers must take into account. The advantages and limitations of each approach are discussed and compared in detail. The classification and study of the architectures illustrate the trade-offs of the solutions and help identify open problems and research lines
Remote Laboratory for E-Learning of Systems on Chip and Their Applications to Nuclear and Scientific Instrumentation
Configuring and setting up a remote access laboratory for an advanced online school on fully programmable System-on-Chip (SoC) proved to be an outstanding challenge. The school, jointly organized by the International Centre for Theoretical Physics (ICTP) and the International Atomic Energy Agency (IAEA), focused on SoC and its applications to nuclear and scientific instrumentation and was mainly addressed to physicists, computer scientists and engineers from developing countries. The use of e-learning tools, which some of them adopted and others developed, allowed the school participants to directly access both integrated development environment software and programmable SoC platforms. This facilitated the follow-up of all proposed exercises and the final project. During the four weeks of the training activity, we faced and overcame different technology and communication challenges, whose solutions we describe in detail together with dedicated tools and design methodology. We finally present a summary of the gained experience and an assessment of the results we achieved, addressed to those who foresee to organize similar initiatives using e-learning for advanced training with remote access to SoC platforms
Cross Section Ratios between different CM energies at the LHC: opportunities for precision measurements and BSM sensitivity
The staged increase of the LHC beam energy provides a new class of
interesting observables, namely ratios and double ratios of cross sections of
various hard processes. The large degree of correlation of theoretical
systematics in the cross section calculations at different energies leads to
highly precise predictions for such ratios. We present in this letter few
examples of such ratios, and discuss their possible implications, both in terms
of opportunities for precision measurements and in terms of sensitivity to
Beyond the Standard Model dynamics.Comment: 19 pages, 9 figure
Impact-parameter dependent nuclear parton distribution functions: EPS09s and EKS98s and their applications in nuclear hard processes
We determine the spatial (impact parameter) dependence of nuclear parton
distribution functions (nPDFs) using the -dependence of the spatially
independent (averaged) global fits EPS09 and EKS98. We work under the
assumption that the spatial dependence can be formulated as a power series of
the nuclear thickness functions . To reproduce the -dependence over the
entire range we need terms up to . As an outcome, we release two
sets, EPS09s (LO, NLO, error sets) and EKS98s, of spatially dependent nPDFs for
public use. We also discuss the implementation of these into the existing
calculations. With our results, the centrality dependence of nuclear
hard-process observables can be studied consistently with the globally fitted
nPDFs for the first time. As an application, we first calculate the LO nuclear
modification factor for primary partonic-jet production in
different centrality classes in Au+Au collisions at RHIC and Pb+Pb collisions
at LHC. Also the corresponding central-to-peripheral ratios are
studied. We also calculate the LO and NLO nuclear modification factors for
single inclusive neutral pion production, , at mid- and
forward rapidities in different centrality classes in d+Au collisions at RHIC.
In particular, we show that our results are compatible with the PHENIX
mid-rapidity data within the overall normalization uncertainties given by the
experiment. Finally, we show our predictions for the corresponding
modifications in the forthcoming p+Pb collisions at LHC.Comment: 36 page
MINLO: Multi-scale improved NLO
In the present work we consider the assignment of the factorization and
renormalization scales in hadron collider processes with associated jet
production, at next-to-leading order (NLO) in perturbation theory. We propose a
simple, definite prescription to this end, including Sudakov form factors to
consistently account for the distinct kinematic scales occuring in such
collisions. The scheme yields results that are accurate at NLO and, for a large
class of observables, it resums to all orders the large logarithms that arise
from kinematic configurations involving disparate scales. In practical terms
the method is most simply understood as an NLO extension of the matrix element
reweighting procedure employed in tree level matrix element-parton shower
merging algorithms. By way of a proof-of-concept, we apply the method to Higgs
and Z boson production in association with up to two jets.Comment: 27 pages, 17 figure
Higgs Physics: Theory
I review the theoretical aspects of the physics of Higgs bosons, focusing on
the elements that are relevant for the production and detection at present
hadron colliders. After briefly summarizing the basics of electroweak symmetry
breaking in the Standard Model, I discuss Higgs production at the LHC and at
the Tevatron, with some focus on the main production mechanism, the gluon-gluon
fusion process, and summarize the main Higgs decay modes and the experimental
detection channels. I then briefly survey the case of the minimal
supersymmetric extension of the Standard Model. In a last section, I review the
prospects for determining the fundamental properties of the Higgs particles
once they have been experimentally observed.Comment: 21 pages, 15 figures. Talk given at the XXV International Symposium
on Lepton Photon Interactions at High Energies (Lepton Photon 11), 22-27
August 2011, Mumbai, Indi
Phenotypic and genotypic monitoring of Schistosoma mansoni in Tanzanian schoolchildren five years into a preventative chemotherapy national control programme
We conducted combined in vitro PZQ efficacy testing with population genetic analyses of S. mansoni collected from children from two schools in 2010, five years after the introduction of a National Control Programme. Children at one school had received four annual PZQ treatments and the other school had received two mass treatments in total. We compared genetic differentiation, indices of genetic diversity, and estimated adult worm burden from parasites collected in 2010 with samples collected in 2005 (before the control programme began) and in 2006 (six months after the first PZQ treatment). Using 2010 larval samples, we also compared the genetic similarity of those with high and low in vitro sensitivity to PZQ
Observation of Spontaneous Brillouin Cooling
While radiation-pressure cooling is well known, the Brillouin scattering of
light from sound is considered an acousto-optical amplification-only process.
It was suggested that cooling could be possible in multi-resonance Brillouin
systems when phonons experience lower damping than light. However, this regime
was not accessible in traditional Brillouin systems since backscattering
enforces high acoustical frequencies associated with high mechanical damping.
Recently, forward Brillouin scattering in microcavities has allowed access to
low-frequency acoustical modes where mechanical dissipation is lower than
optical dissipation, in accordance with the requirements for cooling. Here we
experimentally demonstrate cooling via such a forward Brillouin process in a
microresonator. We show two regimes of operation for the Brillouin process:
acoustical amplification as is traditional, but also for the first time, a
Brillouin cooling regime. Cooling is mediated by an optical pump, and scattered
light, that beat and electrostrictively attenuate the Brownian motion of the
mechanical mode.Comment: Supplementary material include
Three-dimensional cephalometric evaluation of maxillary growth following in utero repair of cleft lip and alveolar-like defects in the mid-gestational sheep model
Objective: To evaluate maxillary growth following in utero repair of surgically created cleft lip and alveolar (CLA)-like defects by means of three-dimensional (3D) computer tomographic (CT) cephalometric analysis in the mid-gestational sheep model. Methods: In 12 sheep fetuses a unilateral CLA-like defect was created in utero (untreated control group: 4 fetuses). Four different bone grafts were used for the alveolar defect closure. After euthanasia, CT scans of the skulls of the fetuses, 3D re-constructions, and a 3D-CT cephalometric analysis were performed. Results: The comparisons between the operated and nonoperated skull sides as well as of the maxillary asymmetry among the experimental groups revealed no statistically significant differences of the 12 variables used. Conclusions: None of the surgical approaches used for the in utero correction of CLA-like defects seem to affect significantly postsurgical maxillary growth; however, when bone graft healing takes place, a tendency for almost normal maxillary growth can be observed. Copyright (c) 2006 S. Karger AG, Basel
2D-fluoroscopic navigated percutaneous screw fixation of pelvic ring injuries - a case series
<p>Abstract</p> <p>Background</p> <p>Screw fixation of pelvic ring fractures is a common, but demanding procedure and navigation techniques were introduced to increase the precision of screw placement. The purpose of this case series was the evaluation of screw misplacement rate and functional outcome of percutaneous screw fixation of pelvic ring disruptions using a 2D navigation system.</p> <p>Methods</p> <p>Between August 2004 and December 2007, 44 of 442 patients with pelvic injuries were included for closed reduction and percutaneous screw fixation of disrupted pelvic ring lesions using an optoelectronic 2D-fluoroscopic based navigation system. Operating and fluoroscopy time were measured, as well as peri- and postoperative complications documented. Screw position was assessed by postoperative CT scans. Quality of live was evaluated by SF 36-questionnaire in 40 of 44 patients at mean follow up 15.5 ± 1.2 month.</p> <p>Results</p> <p>56 iliosacral- and 29 ramus pubic-screws were inserted (mean operation time per screw 62 ± 4 minutes, mean fluoroscopy time per screw 123 ± 12 seconds). In post-operative CT-scans the screw position was assessed and graded as follows: I. secure positioning, completely in the cancellous bone (80%); II. secure positioning, but contacting cortical bone structures (14%); III. malplaced positioning, penetrating the cortical bone (6%). The malplacements predominantly occurred in bilateral overlapping screw fixation. No wound infection or iatrogenic neurovascular damage were observed. Four re-operations were performed, two of them due to implant-misplacement and two of them due to implant-failure.</p> <p>Conclusion</p> <p>2D-fluoroscopic navigation is a safe tool providing high accuracy of percutaneous screw placement for pelvic ring fractures, but in cases of a bilateral iliosacral screw fixation an increased risk for screw misplacement was observed. If additional ramus pubic screw fixations are performed, the retrograde inserted screws have to pass the iliopubic eminence to prevent an axial screw loosening.</p
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