390 research outputs found
An asynchronous spike event coding scheme for programmable analog arrays
This paper presents a spike event coding scheme for the communication of analog signals in programmable analog arrays. In the scheme presented here no events are transmitted when the signals are constant leading to low power dissipation and traffic reduction in analog arrays. The design process and the implementation of the scheme in a programmable array context are explained. The validation of the presented scheme is performed using a speech signal. Finally, we demonstrate how the event coded scheme can perform summation of analog signals without additional hardware
A CMOS implementation of a spike event coding scheme for analog arrays
This paper presents a CMOS circuit implementation of a spike event coding/decoding scheme for transmission of analog signals in a programmable analog array. This scheme uses spikes for a time representation of analog signals. No spikes are transmitted using this scheme when signals are constant, leading to low power dissipation and traffic reduction in a shared channel. A proof-of-concept chip was designed in a 0.35 mum process and experimental results are presented
Sea Changes Ashore : The Ocean and Iceland's Herring Captial
The story of SiglufjörĂ°ur (Siglufjordur), a north Iceland village that became the "Herring Capital of the World," provides a case study of complex interactions between physical, biological, and social systems. SiglufjörĂ°ur's natural capital - a good harbor and proximity to prime herring grounds - contributed to its development as a major fishing center during the first half of the 20th century. This herring fishery was initiated by Norwegians, but subsequently expanded by Icelanders to such an extent that the fishery, and SiglufjörĂ°ur in particular, became engines helping to pull the whole Icelandic economy. During the golden years of this "herring adventure," SiglufjörĂ°ur opened unprecedented economic and social opportunities. Unfortunately, the fishing boom reflected unsustainably high catch rates. In the years following World War II, overfishing by an international fleet eroded the once-huge herring stock. Then, in the mid-1960s, large-scale physical changes took place in the seas north of Iceland. These physical changes had ecological consequences that led to the loss of the herring's main food supply. Severe environmental stress, combined with heavy fishing pressure, drove the herring stocks toward collapse. SiglufjörĂ°ur found itself first marginalized, then shut out as the herring progressively vanished. During the decades following the 1968 collapse, this former boomtown has sought alternatives for sustainable development.L'histoire de SiglufjörĂ°ur (Siglufjordur), un village du nord de l'Islande qui acquit le statut de «Capitale mondiale du hareng», offre une Ă©tude de cas des interactions complexes qui ont lieu entre des systĂšmes physiques, biologiques et sociaux. Le capital naturel de SiglufjörĂ°ur - un bon port et la proximitĂ© de bancs de harengs exceptionnels - a contribuĂ© Ă sa mise en valeur comme grand centre de pĂȘche durant la premiĂšre moitiĂ© du XXe siĂšcle. La pĂȘche au hareng, pratiquĂ©e tout d'abord par les NorvĂ©giens, prit un tel essor avec les Islandais qu'elle devint, avec SiglufjörĂ°ur en particulier, le moteur qui contribua Ă faire marcher toute l'Ă©conomie de l'Islande. Durant les annĂ©es fastes de cette «Úre du hareng», il y eut Ă SiglufjörĂ°ur des ouvertures Ă©conomiques et sociales sans prĂ©cĂ©dent. Malheureusement, le boom de la pĂȘche reprĂ©sentait des taux de prises trop Ă©levĂ©s pour ĂȘtre durables. Au cours des annĂ©es qui suivirent la DeuxiĂšme Guerre mondiale, la surpĂȘche pratiquĂ©e par une flottille internationale fit baisser le stock de harengs jadis abondant. Puis au milieu des annĂ©es 1960, il se produisit, dans les eaux situĂ©es au nord de l'Islande, des changements Ă grande Ă©chelle sur le plan physique. Ces derniers eurent des consĂ©quences Ă©cologiques qui aboutirent Ă la disparition de la source principale de nourriture du hareng. Un stress environnemental trĂšs fort, joint Ă des pressions pour augmenter encore plus les prises, mena les stocks de harengs Ă l'effondrement. SiglufjörĂ°ur se trouva tout d'abord marginalisĂ©, puis, Ă mesure que le hareng disparaissait, carrĂ©ment exclu. Durant les dĂ©cennies suivant l'effondrement de 1968, cette ancienne ville champignon a tentĂ© de trouver des solutions de rechange pour se dĂ©velopper de façon durable
Re-Focusing - Building a Future for Entrepreneurial Education & Learning
The field of entrepreneurship has struggled with fundamental
questions concerning the subjectâs nature and purpose. To whom and to
what means are educational and training agendas ultimately directed?
Such questions have become of central importance to policy makers,
practitioners and academics alike. There are suggestions that university
business schools should engage more critically with the lived experiences
of practising entrepreneurs through alternative pedagogical approaches
and methods, seeking to account for and highlighting the social, political
and moral aspects of entrepreneurial practice. In the UK, where funding in
higher education has become increasingly dependent on student fees,
there are renewed pressures to educate students for entrepreneurial
practice as opposed to educating them about the nature and effects of
entrepreneurship. Government and EU policies are calling on business
schools to develop and enhance entrepreneurial growth and skill sets, to
make their education and training programmes more proactive in
providing innovative educational practices which help and facilitate life
experiences and experiential learning. This paper makes the case for
critical frameworks to be applied so that complex social processes
become a source of learning for educators and entrepreneurs and so that
innovative pedagogical approaches can be developed in terms both of
context (curriculum design) and process (delivery methods)
Characteristics of pebble- and cobble-sized clasts along the Curiosity rover traverse from Bradbury Landing to Rocknest
We have assessed the characteristics of clasts along Curiosity's traverse to shed light on the processes important in the genesis, modification, and transportation of surface materials. Pebble- to cobble-sized clasts at Bradbury Landing, and subsequentl
PPPC 4 DM ID: A Poor Particle Physicist Cookbook for Dark Matter Indirect Detection
We provide ingredients and recipes for computing signals of TeV-scale Dark
Matter annihilations and decays in the Galaxy and beyond. For each DM channel,
we present the energy spectra of electrons and positrons, antiprotons,
antideuterons, gamma rays, neutrinos and antineutrinos e, mu, tau at
production, computed by high-statistics simulations. We estimate the Monte
Carlo uncertainty by comparing the results yielded by the Pythia and Herwig
event generators. We then provide the propagation functions for charged
particles in the Galaxy, for several DM distribution profiles and sets of
propagation parameters. Propagation of electrons and positrons is performed
with an improved semi-analytic method that takes into account
position-dependent energy losses in the Milky Way. Using such propagation
functions, we compute the energy spectra of electrons and positrons,
antiprotons and antideuterons at the location of the Earth. We then present the
gamma ray fluxes, both from prompt emission and from Inverse Compton scattering
in the galactic halo. Finally, we provide the spectra of extragalactic gamma
rays. All results are available in numerical form and ready to be consumed.Comment: 57 pages with many figures and tables. v4: updated to include a 125
higgs boson, computation and discussion of extragalactic spectra corrected,
some other typos fixed; all these corrections and updates are reflected on
the numerical ingredients available at
http://www.marcocirelli.net/PPPC4DMID.html they correspond to Release 2.
Protocol for a nested case-control study design for omics investigations in the Environmental Determinants of Islet Autoimmunity cohort
Background: The Environmental Determinants of Islet Autoimmunity (ENDIA) pregnancy-birth cohort investigates the developmental origins of type 1 diabetes (T1D), with recruitment between 2013 and 2019. ENDIA is the first study in the world with comprehensive data and biospecimen collection during pregnancy, at birth and through childhood from at-risk children who have a first-degree relative with T1D. Environmental exposures are thought to drive the progression to clinical T1D, with pancreatic islet autoimmunity (IA) developing in genetically susceptible individuals. The exposures and key molecular mechanisms driving this progression are unknown. Persistent IA is the primary outcome of ENDIA; defined as a positive antibody for at least one of IAA, GAD, ZnT8 or IA2 on two consecutive occasions and signifies high risk of clinical T1D.Method: A nested case-control (NCC) study design with 54 cases and 161 matched controls aims to investigate associations between persistent IA and longitudinal omics exposures in ENDIA. The NCC study will analyse samples obtained from ENDIA children who have either developed persistent IA or progressed to clinical T1D (cases) and matched control children at risk of developing persistent IA. Control children were matched on sex and age, with all four autoantibodies absent within a defined window of the case's onset date. Cases seroconverted at a median of 1.37âyears (IQR 0.95, 2.56). Longitudinal omics data generated from approximately 16,000 samples of different biospecimen types, will enable evaluation of changes from pregnancy through childhood.Conclusions: This paper describes the ENDIA NCC study, omics platform design considerations and planned univariate and multivariate analyses for its longitudinal data. Methodologies for multivariate omics analysis with longitudinal data are discovery-focused and data driven. There is currently no single multivariate method tailored specifically for the longitudinal omics data that the ENDIA NCC study will generate and therefore omics analysis results will require either cross validation or independent validation.KEY MESSAGESThe ENDIA nested case-control study will utilize longitudinal omics data on approximately 16,000 samples from 190 unique children at risk of type 1 diabetes (T1D), including 54 who have developed islet autoimmunity (IA), followed during pregnancy, at birth and during early childhood, enabling the developmental origins of T1D to be explored.Helena Oakey ... Lynne C. Giles ... Rebecca L. Thomson ... Pat Ashwood ... Emma J. Knight ... Simon C. Barry ... Kelly McGorm ... Jennifer J. Couper ... Megan A. S. Penno ... the ENDIA Study Group ... et al
Virus infection and grazing exert counteracting influences on survivorship of native bunchgrass seedlings competing with invasive exotics
1. âInvasive annual grasses introduced by European settlers have largely displaced native grassland vegetation in California and now form dense stands that constrain the establishment of native perennial bunchgrass seedlings. Bunchgrass seedlings face additional pressures from both livestock grazing and barley and cereal yellow dwarf viruses (B/CYDVs), which infect both young and established grasses throughout the state. 2. âPrevious work suggested that B/CYDVs could mediate apparent competition between invasive exotic grasses and native bunchgrasses in California. 3. âTo investigate the potential significance of virus-mediated mortality for early survivorship of bunchgrass seedlings, we compared the separate and combined effects of virus infection, competition and simulated grazing in a field experiment. We infected two species of young bunchgrasses that show different sensitivity to B/CYDV infection, subjected them to competition with three different densities of exotic annuals crossed with two clipping treatments, and monitored their growth and first-year survivorship. 4. âAlthough virus infection alone did not reduce first-year survivorship, it halved the survivorship of bunchgrasses competing with exotics. Within an environment in which competition strongly reduces seedling survivorship (as in natural grasslands), virus infection therefore has the power to cause additional seedling mortality and alter patterns of establishment. 5. âSurprisingly, clipping did not reduce bunchgrass survivorship further, but rather doubled it and disproportionately increased survivorship of infected bunchgrasses. 6. âTogether with previous work, these findings show that B/CYDVs can be potentially powerful elements influencing species interactions in natural grasslands. 7. âMore generally, our findings demonstrate the potential significance of multitrophic interactions in virus ecology. Although sometimes treated collectively as plant âpredatorsâ, viruses and herbivores may exert influences that are distinctly different, even counteracting
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