Beyond von-Neumann computing with nanoscale phase-change memory devices

OnlineOpen ArticleThis is the final version of the article. Available from the publisher via the DOI in this record.Historically, the application of phase-change materials and devices has been limited to the provision of non-volatile memories. Recently however the potential has been demonstrated for using phase-change devices as the basis for new forms of brain-like computing, by exploiting their multi-level resistance capability to provide electronic mimics of biological synapses. Here we exploit a different and previously under-explored property also intrinsic to phase-change materials and devices, namely accumulation, to demonstrate that nanoscale electronic phase-change devices can also provide a powerful form of arithmetic computing. We carry out complicated arithmetic operations, including parallel factorization and fractional division, using simple nanoscale phase-change cells that process and store data simultaneously and at the same physical location, promising a most efficient and effective means for implementing 'beyond von-Neumann' computing. We also show that this same accumulation property can be used to provide a particularly simple form phase-change integrate-and-fire 'neuron' which, by combining both phase-change synapse and neuron electronic mimics, potentially opens up a route to the realization of all-phase-change neuromorphic processing.The authors gratefully acknowledge EPSRC for grant funding (EP/ F015046/1). They also would like to thank Dr. A Pauza, formerly of Plasmon Data Systems Ltd, for help in preparation of the GST samples. Professor Peter Ashwin from the University of Exeter is also acknowledged for helpful discussions and guidance in the formulation of the GCA simulator. The authors are also very grateful to Mr. David Anderson of the University of Exeter for valuable assistance with the lithography of the pseudo-devices

Graduated dark energy: Observational hints of a spontaneous sign switch in the cosmological constant

We study the cosmological constant in the standard CDM model by introducing the graduated dark energy (gDE) characterised by a minimal dynamical deviation from the null inertial mass density of the in the form inert / < 0 with < 1 being a ratio of two odd integers, for which its energy density dynamically takes negative values in the nite past. For large negative values of , it creates a phenomenological model described by a smooth function that approximately describes the spontaneously switching sign in the late universe to become positive today. We confront the model with the latest combined observational data sets of PLK+BAO+SN+H. It is striking that the data predict bimodal posterior probability distributions for the parameters of the model along with large negative values; the new maximum signi cantly excludes the , and the old maximum contains the . The improvement in the goodness of the t for the reaches highly signi cant levels, 2 min = 6:4, for the new maxima, while it remains at insigni cant levels, 2 min . 0:02, for the old maxima. We show that, in contrast to the old maxima, which do not distinguish from the , the new maxima agree with the model-independent H0 measurements, high-precision Ly- data, and model-independent Omh2 diagnostic estimates. Our results provide strong hints of a spontaneous sign switch in the cosmological constant and lead us to conjecture that the universe has transitioned from AdS vacua to dS vacua, at a redshift z 2:32 and triggered the late-time acceleration, and suggests looking for such mechanisms in string theory constructions

Screening Λ in a new modified gravity model

Abstract We study a new model of Energy-Momentum Squared Gravity (EMSG), called Energy-Momentum Log Gravity (EMLG), constructed by the addition of the term $$f(T_{\mu \nu }T^{\mu \nu })=\alpha \ln (\lambda \,T_{\mu \nu }T^{\mu \nu })$$f(TμνTμν)=αln(λTμνTμν), envisaged as a correction, to the Einstein–Hilbert action with cosmological constant $$\Lambda$$Λ. The choice of this modification is made as a specific way of including new terms in the right-hand side of the Einstein field equations, resulting in constant effective inertial mass density and, importantly, leading to an explicit exact solution of the matter energy density in terms of redshift. We look for viable cosmologies, in particular, an extension of the standard $$\Lambda$$ΛCDM model. EMLG provides an effective dynamical dark energy passing below zero at large redshifts, accommodating a mechanism for screening $$\Lambda$$Λ in this region, in line with suggestions for alleviating some of the tensions that arise between observational data sets within the standard $$\Lambda$$ΛCDM model. We present a detailed theoretical investigation of the model and then constrain the free parameter $$\alpha '$$α′, a normalisation of $$\alpha$$α, using the latest observational data. The data does not rule out the $$\Lambda$$ΛCDM limit of our model ($$\alpha '= 0$$α′=0), but prefers slightly negative values of the EMLG model parameter ($$\alpha '= -0.032\pm 0.043$$α′=-0.032±0.043), which leads to the screening of $$\Lambda$$Λ. We also discuss how EMLG relaxes the persistent tension that appears in the measurements of $$H_0$$H0 within the standard $$\Lambda$$ΛCDM model.</jats:p

The diagnosis of clinically significant oesophageal Candida infections: a reappraisal of clinicopathological findings

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154961/1/his14063_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154961/2/his14063.pd

Stoichiometrically driven disorder and local diffusion in NMC cathodes

Major structural differences in lithium nickel manganese cobalt oxides (NMC) prepared under identical conditions have been uncovered using neutron powder diffraction. Sample NMC-622 was obtained as a single R[3 with combining macron]m crystal structure with little defects, whereas NMC-811 showed significant Li deficiency and NMC-433 formed three distinct phases; ordered R[3 with combining macron]m, disordered R[3 with combining macron]m and a C2/m phase. Local diffusion behaviour was also studied by muon spin relaxation (μSR). It was observed that single phase R[3 with combining macron]m NMC-622 showed a higher lithium diffusion coefficient (4.4 × 10−11 cm2 s−1) compared to lithium deficient NMC-811 (2.9 × 10−11 cm2 s−1), or the highly disordered NMC-433 (3.4 × 10−11 cm2 s−1). Furthermore, activation energies for the Li diffusion process were estimated to be 58 meV, 61 meV and 28 meV for NMC-811, NMC-622 and NMC-433, respectively

Multiple diffusion pathways in LixNi0.77Co0.14Al0.09O2 (NCA) Li-ion battery cathodes

Experimental evidence for the presence of two computationally theorised diffusion pathways, namely the oxygen dumbbell hop (ODH) and tetrahedral site hop (TSH), has been given for the first time by muon spin relaxation (µSR) on sub-stoichiometric LixNi0.77Co0.14Al0.09O2. µSR has proven to be a powerful tool that is able to discriminate between diffusion pathways that occur on different timescales on a local level, where bulk electrochemical techniques cannot. Whereas the estimated values of DLi at lithium concentrations of 0.87 and 0.71 were found to be on the order of 10-11 by electrochemical impedance spectroscopy, contributions to diffusion from ODH and TSH were determined to be on the order of 10-11 and 10-10 cm2 s-1, and a factor of four decrease in Ea for both samples, in excellent agreement with theoretical calculations on related compounds. Rietveld refinement of both X-ray and neutron diffraction data was also used to interrogate the local structure of the materials where no contribution from Li+/Ni2+ cation mixing was observed

Critical influence of surface nitrogen species on the activity of N-doped TiO thin-films during photodegradation of stearic acid under UV light irradiation

Atmospheric-pressure chemical vapour deposition (APCVD) was used to produce a series of nitrogen-doped titania (N-TiO) thin-films using tert-butylamine as the nitrogen source. The films were deposited as the anatase phase on glass and quartz substrates and characterised using X-ray diffraction, optical and vibrational spectroscopy and electron microscopy. The nature and location of the nitrogen species present on the surface and bulk of the films was studied by X-ray photoelectron spectroscopy. Thorough comparison amongst films with similar structural and morphological features allowed the role of nitrogen species to be evaluated during photo-oxidation of a model organic pollutant (stearic acid). Sequential photocatalytic experiments revealed a drastic decrease in the UV activity of the films which were correlated with changes involving surface nitrogen groups. The existence of concomitant nitrogen species with similar binding energies (ca. 400eV) but different chemical nature is proposed, as well as the direct participation of at least one of these species in the oxidation reaction. A similar mechanism for the visible light activity of N-TiO materials is also suggested. © 2014

inGeno – an integrated genome and ortholog viewer for improved genome to genome comparisons

BACKGROUND: Systematic genome comparisons are an important tool to reveal gene functions, pathogenic features, metabolic pathways and genome evolution in the era of post-genomics. Furthermore, such comparisons provide important clues for vaccines and drug development. Existing genome comparison software often lacks accurate information on orthologs, the function of similar genes identified and genome-wide reports and lists on specific functions. All these features and further analyses are provided here in the context of a modular software tool "inGeno" written in Java with Biojava subroutines. RESULTS: InGeno provides a user-friendly interactive visualization platform for sequence comparisons (comprehensive reciprocal protein – protein comparisons) between complete genome sequences and all associated annotations and features. The comparison data can be acquired from several different sequence analysis programs in flexible formats. Automatic dot-plot analysis includes output reduction, filtering, ortholog testing and linear regression, followed by smart clustering (local collinear blocks; LCBs) to reveal similar genome regions. Further, the system provides genome alignment and visualization editor, collinear relationships and strain-specific islands. Specific annotations and functions are parsed, recognized, clustered, logically concatenated and visualized and summarized in reports. CONCLUSION: As shown in this study, inGeno can be applied to study and compare in particular prokaryotic genomes against each other (gram positive and negative as well as close and more distantly related species) and has been proven to be sensitive and accurate. This modular software is user-friendly and easily accommodates new routines to meet specific user-defined requirements

Comparison of the CDC Backpack aspirator and the Prokopack aspirator for sampling indoor- and outdoor-resting mosquitoes in southern Tanzania.

BACKGROUND\ud \ud Resting mosquitoes can easily be collected using an aspirating device. The most commonly used mechanical aspirator is the CDC Backpack aspirator. Recently, a simple, and low-cost aspirator called the Prokopack has been devised and proved to have comparable performance. The following study evaluates the Prokopack aspirator compared to the CDC backpack aspirator when sampling resting mosquitoes in rural Tanzania.\ud \ud METHODS\ud \ud Mosquitoes were sampled in- and outdoors of 48 typical rural African households using both aspirators. The aspirators were rotated between collectors and households in a randomized, Latin Square design. Outdoor collections were performed using artificial resting places (large barrel and car tyre), underneath the outdoor kitchen (kibanda) roof and from a drop-net. Data were analysed with generalized linear models.\ud \ud RESULTS\ud \ud The number of mosquitoes collected using the CDC Backpack and the Prokopack aspirator were not significantly different both in- and outdoors (indoors p = 0.735; large barrel p = 0.867; car tyre p = 0.418; kibanda p = 0.519). The Prokopack was superior for sampling of drop-nets due to its smaller size. The number mosquitoes collected per technician was more consistent when using the Prokopack aspirator. The Prokopack was more user-friendly: technicians preferred using the it over the CDC backpack aspirator as it weighs considerably less, retains its charge for longer and is easier to manoeuvre.\ud \ud CONCLUSIONS\ud \ud The Prokopack proved in the field to be more advantageous than the CDC Backpack aspirator. It can be self assembled using simple, low-cost and easily attainable materials. This device is a useful tool for researchers or vector-control surveillance programs operating in rural Africa, as it is far simpler and quicker than traditional means of sampling resting mosquitoes. Further longitudinal evaluations of the Prokopack aspirator versus the gold standard pyrethrum spray catch for indoor resting catches are recommended

Identification and characterization of a novel non-structural protein of bluetongue virus

Bluetongue virus (BTV) is the causative agent of a major disease of livestock (bluetongue). For over two decades, it has been widely accepted that the 10 segments of the dsRNA genome of BTV encode for 7 structural and 3 non-structural proteins. The non-structural proteins (NS1, NS2, NS3/NS3a) play different key roles during the viral replication cycle. In this study we show that BTV expresses a fourth non-structural protein (that we designated NS4) encoded by an open reading frame in segment 9 overlapping the open reading frame encoding VP6. NS4 is 77–79 amino acid residues in length and highly conserved among several BTV serotypes/strains. NS4 was expressed early post-infection and localized in the nucleoli of BTV infected cells. By reverse genetics, we showed that NS4 is dispensable for BTV replication in vitro, both in mammalian and insect cells, and does not affect viral virulence in murine models of bluetongue infection. Interestingly, NS4 conferred a replication advantage to BTV-8, but not to BTV-1, in cells in an interferon (IFN)-induced antiviral state. However, the BTV-1 NS4 conferred a replication advantage both to a BTV-8 reassortant containing the entire segment 9 of BTV-1 and to a BTV-8 mutant with the NS4 identical to the homologous BTV-1 protein. Collectively, this study suggests that NS4 plays an important role in virus-host interaction and is one of the mechanisms played, at least by BTV-8, to counteract the antiviral response of the host. In addition, the distinct nucleolar localization of NS4, being expressed by a virus that replicates exclusively in the cytoplasm, offers new avenues to investigate the multiple roles played by the nucleolus in the biology of the cell