ν-inflaton dark matter

We present a unified model where the same scalar field can drive inflation and account for the present dark matter abundance. This scenario is based on the incomplete decay of the inflaton field into right-handed neutrino pairs, which is accomplished by imposing a discrete interchange symmetry on the inflaton and on two of the right-handed neutrinos. We show that this can lead to a successful reheating of the Universe after inflation, while leaving a stable inflaton remnant at late times. This remnant may be in the form of WIMP-like inflaton particles or of an oscillating inflaton condensate, depending on whether or not the latter evaporates and reaches thermal equilibrium with the cosmic plasma. We further show that this scenario is compatible with generating light neutrino masses and mixings through the seesaw mechanism, predicting at least one massless neutrino, and also the observed baryon asymmetry via thermal leptogenesis.publishe

Exploring Graphics Processor Performance for General Purpose Applications

Abstract In our experiments we compare the execution on a midclass GPU (NVIDIA GeForce FX 5700LE) with a high-end CPU (Pentium 4 3.2GHz). The results show that to achieve high speedup with the GPU you need to: (1) format the vectors into two-dimensional arrays; (2) process large data arrays; and (3

Reliability Analysis of Compressed CNNs

The use of artificial intelligence, Machine Learning and in particular Deep Learning (DL), have recently become a effective and standard de-facto solution for complex problems like image classification, sentiment analysis or natural language processing. In order to address the growing demand of performance of ML applications, research has focused on techniques for compressing the large amount of the parameters required by the Deep Neural Networks (DNN) used in DL. Some of these techniques include parameter pruning, weight-sharing, i.e. clustering of the weights, and parameter quantization. However, reducing the amount of parameters can lower the fault tolerance of DNNs, already sensitive to software and hardware faults caused by, among others, high particles strikes, row hammer or gradient descent attacks, et cetera. In this work we analyze the sensitivity to faults of widely used DNNs, in particular Convolutional Neural Networks (CNN), that have been compressed with the use of pruning, weight clustering and quantization. Our analysis shows that in DNNs that employ all such compression mechanisms, i.e. with their memory footprint reduced up to 86.3x, random single bit faults can result in accuracy drops up to 13.56%

Hybrid2: Combining Caching and Migration in Hybrid Memory Systems

This paper considers a hybrid memory system composed of memory technologies with different characteristics; in particular a small, near memory exhibiting high bandwidth, i.e., 3D-stacked DRAM, and a larger, far memory offering capacity at lower bandwidth, i.e., off-chip DRAM. In the past,the near memory of such a system has been used either as a DRAM cache or as part of a flat address space combined with a migration mechanism. Caches and migration offer different tradeoffs (between performance, main memory capacity, data transfer costs, etc.) and share similar challenges related todata-transfer granularity and metadata management. This paper proposes Hybrid2 , a new hybrid memory system architecture that combines a DRAM cache with a migration scheme. Hybrid 2 does not deny valuable capacity from the memory system because it uses only a small fraction of the near memory as a DRAM cache; 64MB in our experiments.It further leverages the DRAM cache as a staging area to select the data most suitable for migration. Finally, Hybrid2 alleviates the metadata overheads of both DRAM caches and migration using a common mechanism. Using near to far memory ratios of 1:16, 1:8 and 1:4 in our experiments, Hybrid2 on average outperforms current state-of-the-art migration schemes by 7.9%, 9.1% and 6.4%, respectively. In the same system configurations, compared to DRAM caches Hybrid2 gives away on average only 0.3%, 1.2%, and 5.3% of performance offering 5.9%, 12.1%, and 24.6% more main memory capacity, respectively

AVR: Reducing Memory Traffic with Approximate Value Reconstruction

This paper describes Approximate Value Reconstruction (AVR), an architecture for approximate memory compression. AVR reduces the memory traffic of applications that tolerate approximations in their dataset. Thereby, it utilizes more efficiently off-chip bandwidth improving significantly system performance and energy efficiency. AVR compresses memory blocks using low latency downsampling that exploits similarities between neighboring values and achieves aggressive compression ratios, up to 16:1 in our implementation. The proposed AVR architecture supports our compression scheme maximizing its effect and minimizing its overheads by (i) co-locating in the Last Level Cache (LLC) compressed and uncompressed data, (ii) efficiently handling LLC evictions, (iii) keeping track of badly compressed memory blocks, and (iv) avoiding LLC pollution with unwanted decompressed data. For applications that tolerate aggressive approximation in large fractions of their data, AVR reduces memory traffic by up to 70%, execution time by up to 55%, and energy costs by up to 20% introducing less than 1% error to the application output

Influence of diagenetic processes and terrestrial/anthropogenic sources in the REE contents of the Cascais submarine canyon (Iberian western coast)

ABSTRACT: Temporal variations of rare earth elements (REE) and their fractionation patterns, major elements, Pb and Hg were determined in two multicores collected at 445 and 2100 m water depth (mwd) in the Cascais submarine canyon (CSC). The PAAS-normalized REE patterns suggest mixing of Tagus estuarine and marine sediments, marked by MREE (Nd‐Dy series) enrichment and by positive Eu-anomaly, with marine sediments. The positive Eu/Eu* implies incorporation of detrital feldspar minerals derived from the estuary. Ce/Ce*, (La/Yb)PAAS and (Nd/Yb)PAAS show differences between the two cores. Core 252-35 from the shallower site is enriched in HREE (Ho‐Lu series) over LREE (La‐Pr series), a pattern also found in the Tagus estuary in the vicinity of an abandoned chemical complex, where the environment is affected by the legacy of massive-sulfide ores processing. There seems to be only limited down-canyon sediment transport to the deeper reaches where core 252-32 was collected. This deeper site shows Ce/Ce* peaks coinciding with low (La/Yb)PAAS values suggesting preferential diagenetic remobilization of LREE relative to HREE. Upcore Pb/Al and Hg/Corg trends observed in both cores indicate dispersion of the anthropogenic component from the estuary through the CSC, which is less obvious from the ∑REE/Al trends particularly in the deeper site. This may suggest the influence of diagenetic processes in the REE signal, associated with relatively low sediment accumulation rates.info:eu-repo/semantics/publishedVersio

Alterações recentes nas razões isotópicas de Pb em sedimentos do Canhão Submarino de Cascais, Portugal

Temporal variations in lead concentrations and stable lead isotopic ratios in two sediment cores from the Cascais Canyon shows changes in sources of Pb during the last two centuries. The increase of total Pb contents wIth the evolution of Pb ratio recorded in both cores reveals the Increase of Pb from industrial sources. Nevertheless, this increase is lower in deeper core location (252-32) due to dilution and mixing with uncontaminated marine materials. An isotopic shift towards lower Pb/Pb in the shallower core (252-35) during the 1970s may reflect the increasing number of vehicles in the Lisboa area during that time

Local, national and international dialogues

UID/SOC/04647/2013 SFRH/BPD/112462/2015; SFRH/BPD/77611/2011Although the institutionalization of sociology in Portugal was only made possible after the revolution of 1974, it is currently characterized by a remarkable vitality, apparent for instance in the number and diversity of members of the Associação Portuguesa de Sociologia as well as that of participants at its national conferences. However, significant challenges have also emerged, stemming not only from the expansion and diversification of sociologists, but also from the economic crisis, austerity policies, the enlargement of social science specializations, and the pressures in politics and the media to give advantage to business, law and engineering professionals, courses and research. The present paper will be organized in three sections. Firstly, we will analyse the existing courses of sociology in Portugal (at BA, master and PhD level) as well as the regional location, activity sectors and professional positions of those who have graduated in sociology. Secondly, we will discuss the participation of those different profiles in the Associação Portuguesa de Sociologia throughout time and the ongoing efforts to improve such participation. According to Burawoy’s typology, we suggest that, despite some tensions, academic and critical sociologies have been developed and working together in Portugal, but the connection with a large group of applied sociologists has weakened over time. Public sociology may be the missed link to foster a dialogue among sociologists and other sectors of society. Our national association’s current strategy to develop such links will be sketched. Thirdly, we will present a broad overview of the internationalization of Portuguese sociology, through collaboration in projects and networks, especially with Europe and Portuguese-speaking countries like Brazil and Angola.publishersversionpublishe

LEGaTO: first steps towards energy-efficient toolset for heterogeneous computing

LEGaTO is a three-year EU H2020 project which started in December 2017. The LEGaTO project will leverage task-based programming models to provide a software ecosystem for Made-in-Europe heterogeneous hardware composed of CPUs, GPUs, FPGAs and dataflow engines. The aim is to attain one order of magnitude energy savings from the edge to the converged cloud/HPC.Peer ReviewedPostprint (author's final draft