A self-adaptive hardware with resistive switching synapses for experience-based neurocomputing

: Neurobiological systems continually interact with the surrounding environment to refine their behaviour toward the best possible reward. Achieving such learning by experience is one of the main challenges of artificial intelligence, but currently it is hindered by the lack of hardware capable of plastic adaptation. Here, we propose a bio-inspired recurrent neural network, mastered by a digital system on chip with resistive-switching synaptic arrays of memory devices, which exploits homeostatic Hebbian learning for improved efficiency. All the results are discussed experimentally and theoretically, proposing a conceptual framework for benchmarking the main outcomes in terms of accuracy and resilience. To test the proposed architecture for reinforcement learning tasks, we study the autonomous exploration of continually evolving environments and verify the results for the Mars rover navigation. We also show that, compared to conventional deep learning techniques, our in-memory hardware has the potential to achieve a significant boost in speed and power-saving

Haplotypes versus genotypes on pedigrees

Abstract. Genome sequencing will soon produce haplotype data for individuals. For pedigrees of related individuals, sequencing appears to be an attractive alternative to genotyping. However, methods for pedigree analysis with haplotype data have not yet been developed, and the computational complexity of such problems has been an open question. Furthermore, it is not clear in which scenarios haplotype data would provide better estimates than genotype data for quantities such as recombination rates. To answer these questions, a reduction is given from genotype problem instances to haplotype problem instances, and it is shown that solving the haplotype problem yields the solution to the genotype problem, up to constant factors or coefficients. The pedigree analysis problems we will consider are the likelihood, maximum probability haplotype, and minimum recombination haplotype problems. Two algorithms are introduced: an exponential-time hidden Markov model (HMM) for haplotype data where some individuals are untyped, and a linear-time algorithm for pedigrees having haplotype data for all individuals. Recombination estimates from the general haplotype HMM algorithm are compared to recombination estimates produced by a genotype HMM. Having haplotype data on all individuals produces better estimates. However, having several untyped individuals can drastically reduce the utility of haplotype data. Pedigree analysis, both linkage and association studies, has a long history of important contributions to genetics, including disease-gene finding and some of the first genetic maps for humans. Recent contributions include fine-scale recombination maps in humans [4], regions linked to Schizophrenia that might be missed by genome-wide association studies [11], and insights into the relationship between cystic fibrosis and fertility [13]. Algorithms for pedigree problems are of great interest to the computer science community, in part because of connections to machine learning algorithms, optimization methods, and combinatorics [7, 16

Transcriptional landscape of the human and fly genomes: Nonlinear and multifunctional modular model of transcriptomes

Regions of the genome not coding for proteins or not involved in cis-acting regulatory activities are frequently viewed as lacking in functional value. However, a number of recent large-scale studies have revealed significant regulated transcription of unannotated portions of a variety of plant and animal genomes, allowing a new appreciation of the widespread transcription of large portions of the genome. High-resolution mapping of the sites of transcription of the human and fly genomes has provided an alternative picture of the extent and organization of transcription and has offered insights for biological functions of some of the newly identified unannotated transcripts. Considerable portions of the unannotated transcription observed are developmental or cell-type-specific parts of protein-coding transcripts, often serving as novel, alternative 5′ transcriptional start sites. These distal 5′ portions are often situated at significant distances from the annotated gene and alternatively join with or ignore portions of other intervening genes to comprise novel unannotated protein-coding transcripts. These data support an interlaced model of the genome in which many regions serve multifunctional purposes and are highly modular in their utilization. This model illustrates the underappreciated organizational complexity of the genome and one of the functional roles of transcription from unannotated portions of the genome. Copyright 2006, Cold Spring Harbor Laboratory Press © 2006 Cold Spring Harbor Laboratory Press

Technical standardization of laparoscopic splenectomy: experience with 105 cases.

BACKGROUND: Some reports have suggested that laparoscopic splenectomy (LS) can be successfully performed in adults. However, several aspects of this procedure remain as yet undefined; therefore, several attempts have been made to modify the standard technique to try to optimize the procedure. Herein we analyze our experience with 105 laparoscopic splenectomies. METHODS: From 1993 to 2000, 105 patients underwent LS at our hospital. Twelve of these patients also underwent a concomitant cholecystectomy. There were 66 women and 39 men whose ages ranged between 4 and 78 years (median, 27.7). All patients underwent an elective laparoscopic splenectomy. Seventy five patients had thrombocytopenia (ITP), 14 had hereditary spherocytosis, eight were affected by b-thalassemia, two had splenic cysts, two had lymphoma, (two had myeloid chronic leukemia, one patient presented with a splenic abscess and one had incurred an iatrogenic spleen lesion during adrenalectomy. The first patients in this series were positioned in dorsal decubitus; however, as the team's experience increased, the right lateral decubitus became the position of choice because it provides better exposure of the splenic hilum. This procedure requires the use of only four trocars. RESULTS: Mean operating time was 95 min (range, 35-320). Hospital stay ranged from 2 to 21 days (median, 4.5). There was only one conversion to open surgery. One patient died in the postoperative period due to the evolution of a preexisting malignant disease. We recorded nine complications-four subphrenic abscesses, two cases of pleuritis, two episodes of postoperative bleeding, and one intestinal infarction 16 days after surgery. Only two patients needed redo surgery. CONCLUSIONS: We believe that the laparoscopic approach is a valid alternative to open splenectomy, but mastery of some of the technical details of this procedure could greatly help avoid its complications. On the basis of our experience, it seems that the lateral approach should be considered the position of choice because it provides exposure and easier dissection of the splenic hilar structures. We also found that a 30 degrees scope and an ultrasonic dissector allowed for perfect vision and optimal hemostasis during the procedure. At the end of procedure, the spleen should be fragmented and then extracted using an extraction bag

Multiple binary OxRAMs as synapses for convolutional neural networks

International audienceOxide-based resistive memory (OxRAM) devices find applications in memory, logic, and neuromorphic computing systems. Among the different dielectrics proposed in OxRAM stacks, hafnium oxide, HfO$_2$, attracted growing interest because of its compatibility with typical BEOL advanced CMOS processing and promising performances in terms of endurance (higher than Flash) and switching speed (few tens of ns). This chapter describes an artificial synapse composed of multiple binary HfO$_2$-based OxRAM cells connected in parallel, thereby providing synaptic analog behavior. The VRRAM technology is presented as a possible solution to gain area with respect to planar approaches by realizing one VRRAM pillar per synapse. The HfO$_2$-based OxRAM synapse has been proposed for hardware implementation of power efficient Convolutional Neural Networks for visual pattern recognition applications. Finally, the synaptic weight resolution and the robustness to device variability of the network have been investigated. Statistical evaluation of device variability is obtained on a 16 kbit OxRAM memory array integrated into advanced 28nm CMOS technology

Diffuse scattering in metallic tin polymorphs

The lattice dynamics of the metallic tin β and γ polymorphs has been studied by a combination of diffuse scattering, inelastic xray scattering and density functional perturbation theory. The nonsymmorphic space group of the β tin structure results in unusual asymmetry of thermal diffuse scattering. Strong resemblance of the diffuse scattering intensity distribution in β and γ -tin were observed, reflecting the structural relationship between the two phases and revealing the qualitative similarity of the underlying electronic potential. The strong influence of the electron subsystem on interionic interactions creates anomalies in the phonon dispersion relations. All observed features are described in great detail by the density functional perturbation theory for both β and γ -tin at arbitrary momentum transfers. The combined approach delivers thus a complete picture of the lattice dynamics in harmonic description.©2014 IOP Publishing Ltd Printed in the UK

About the intrinsic resistance variability in HfO<inf>2</inf>-based RRAM devices

Resistive memories (RRAM) are attracting a wide interest as candidates for the next generation memory technology, in particular for embedded and, more generally, for low power applications like IoT. However, their variability still remains a concern as the latter has been proven to be an intrinsic feature linked to the filamentary switching mechanism. In this paper we will review some recent key results by our and other groups that show the fundamental variability limits of the HfO2-based technology and some possible alternatives