753 research outputs found
White paper: A plan for cooperation between NASA and DARPA to establish a center for advanced architectures
Large, complex computer systems require many years of development. It is recognized that large scale systems are unlikely to be delivered in useful condition unless users are intimately involved throughout the design process. A mechanism is described that will involve users in the design of advanced computing systems and will accelerate the insertion of new systems into scientific research. This mechanism is embodied in a facility called the Center for Advanced Architectures (CAA). CAA would be a division of RIACS (Research Institute for Advanced Computer Science) and would receive its technical direction from a Scientific Advisory Board established by RIACS. The CAA described here is a possible implementation of a center envisaged in a proposed cooperation between NASA and DARPA
The Emergence of Miller's Magic Number on a Sparse Distributed Memory
Human memory is limited in the number of items held in one's mindâa limit known as âMiller's magic numberâ. We study the emergence of such limits as a result of the statistics of large bitvectors used to represent items in memory, given two postulates: i) the Sparse Distributed Memory; and ii) chunking through averaging. Potential implications for theoretical neuroscience are discussed
Geometric Algebra Model of Distributed Representations
Formalism based on GA is an alternative to distributed representation models
developed so far --- Smolensky's tensor product, Holographic Reduced
Representations (HRR) and Binary Spatter Code (BSC). Convolutions are replaced
by geometric products, interpretable in terms of geometry which seems to be the
most natural language for visualization of higher concepts. This paper recalls
the main ideas behind the GA model and investigates recognition test results
using both inner product and a clipped version of matrix representation. The
influence of accidental blade equality on recognition is also studied. Finally,
the efficiency of the GA model is compared to that of previously developed
models.Comment: 30 pages, 19 figure
Incremental dimension reduction of tensors with random index
We present an incremental, scalable and efficient dimension reduction
technique for tensors that is based on sparse random linear coding. Data is
stored in a compactified representation with fixed size, which makes memory
requirements low and predictable. Component encoding and decoding are performed
on-line without computationally expensive re-analysis of the data set. The
range of tensor indices can be extended dynamically without modifying the
component representation. This idea originates from a mathematical model of
semantic memory and a method known as random indexing in natural language
processing. We generalize the random-indexing algorithm to tensors and present
signal-to-noise-ratio simulations for representations of vectors and matrices.
We present also a mathematical analysis of the approximate orthogonality of
high-dimensional ternary vectors, which is a property that underpins this and
other similar random-coding approaches to dimension reduction. To further
demonstrate the properties of random indexing we present results of a synonym
identification task. The method presented here has some similarities with
random projection and Tucker decomposition, but it performs well at high
dimensionality only (n>10^3). Random indexing is useful for a range of complex
practical problems, e.g., in natural language processing, data mining, pattern
recognition, event detection, graph searching and search engines. Prototype
software is provided. It supports encoding and decoding of tensors of order >=
1 in a unified framework, i.e., vectors, matrices and higher order tensors.Comment: 36 pages, 9 figure
MitÀ voimme oppia maailmalla jÀrjestetyistÀ perusturvaan liittyvistÀ kokeista? : Katsaus kenttÀkoeasetelmiin
TÀmÀn työpaperin tarkoituksena on esitellÀ ulkomailla tehtyjÀ tai suunnitteilla olevia perustulokokeita, jotka voivat olla hyödyksi Suomessa vireillÀ olevan perustulokokeilun valmistelu-työssÀ. Kuvailemme myös muita kenttÀkokeita, joiden koeasetelmista voidaan Suomessakin ottaa oppia. KÀymme lisÀksi lÀpi perustulokokeiden vaikutusten arvioimisen kannalta keskeistÀ taloustieteellistÀ teoriaa.
LÀhteinÀ olemme kÀyttÀneet akateemisia tutkimusjulkaisuja. TÀmÀ on rajannut tarkastelusta pois kokeet tai kokeilut, joista ei ole tehty kunnollisia selvityksiÀ tai analyysejÀ. Alankomaissa suunnitteilla olevien kokeiden tiedot perustuvat niitÀ valmistelevien tutkijoiden haastatteluihin. Kuvailemme työpaperissa lyhyesti, minkÀlaisia eri kokeet ovat olleet ja minkÀlaisia tuloksia niistÀ on saatu. NÀihin havaintoihin perustuen olemme valmistelleet listan keskeisimmistÀ opeista, jotka kannattaa huomioida suomalaisen perustulokenttÀkokeen valmistelussa. NÀmÀ opit on jaettu kolmeen aihealueeseen: tutkimuskysymykset, koeasetelma ja tulosten arvioiminen.
Yksi olennaisimmista tutkimuskysymyksistÀ perustulokokeessa on selvittÀÀ, miten ilman tiukkoja ehtoja ja tulorajoja myönnettÀvÀ rahaetuus vaikuttaa työn tarjontaan. SitÀ olisi hyvÀ tutkia erilaisilla perustulotason ja veroasteiden yhdistelmillÀ, jotta voidaan ymmÀrtÀÀ sekÀ tulo- ettÀ substituutiovaikutuksia. Subjektiivisen hyvinvoinnin ja stressitasojen mittaaminen voi auttaa havaitsemaan perustulon vaikutuksia herkemmin ja yksilöllisemmin kuin pelkÀn työn tarjonnan tarkastelu. Siksi myös niitÀ tulisi seurata kokeessa.
Laadullisesti hyvÀn koeasetelman edellytyksenÀ on riittÀvÀn iso otoskoko, joka mahdollistaa eri ihmisryhmien tarkemman tarkastelun. Koehenkilöt tulee valita arpomalla ja vapaaehtoisten kÀyttöÀ koehenkilöinÀ tulisi vÀlttÀÀ. Koska tietylle alueelle rajautuva koe vÀhentÀÀ tulosten yleistettÀvyyttÀ, olisi valtakunnallinen koe suotuisin vaihtoehto. Kokeen on kestettÀvÀ myös riittÀvÀn pitkÀÀn, jotta kÀyttÀytymisvaikutuksia ehditÀÀn havaita.
Tulosten arviointiin liittyen suosittelemme, ettÀ kokeiltavan ohjelman arviointi otetaan huomioon jo suunnittelu- ja toteutusvaiheessa. Tuloksia arvioitaessa oikean ajankohdan valitseminen aineistosta on yhtÀ lailla tÀrkeÀÀ. LisÀksi kokeen aineiston avoimuus parantaa tutkimuksen laatua.
MikÀÀn aiemmin suoritetuista perustulokokeista ei pysty antamaan suoraan vastauksia, miten perustulon kÀyttöönotto vaikuttaisi ihmisten kÀyttÀytymiseen Suomessa, koska ne on tehty Suomen nykytilasta poikkeavissa olosuhteissa. Muista kokeista voidaan kuitenkin ammentaa ideoita siihen, miten perustulokokeilu Suomessa kannattaisi toteuttaa
Metal and metalloid exposure and oxidative status in free-living individuals of Myotis daubentonii
Metal elements, ubiquitous in the environment, can cause negative effects in long-lived organisms even after low but prolonged exposure. Insectivorous bats living near metal emission sources can be vulnerable to such contaminants. Although it is known that bats can bioaccumulate metals, little information exists on the effects of metal elements on their physiological status. For example, oxidative status markers are known to vary after detoxification processes and immune reactions. Here, for two consecutive summers, we sampled individuals from a natural population of the insectivorous bat, Myotis daubentonii, inhabiting a site close to a metal emission source. We quantified metals and metalloids (As, Ca, Cd, Co, Cu, Mn, Ni, Pb, Se, Zn) from individual fecal pellets. We measured enzymatic antioxidants (GP, CAT, SOD), total glutathione (tGSH) and ratio between reduced and oxidized glutathione (GSH:GSSG) from their red blood cells together with biometrics, hematocrit and parasite prevalence. In general, metal concentrations in feces of M. daubentonii reflected the exposure to ambient contamination. This was especially evident in the higher concentrations of Cd, Co, Cu and Ni close to a smelter compared to a site with less contaminant exposure. Annual differences were also observed for most elements quantified. Sex-specific differences were observed for calcium and zinc excretion. SOD and CAT enzymatic activities were associated with metal levels (principal components of six metal elements), suggesting early signs of chronic stress in bats. The study also shows promise for the use of non-invasive sampling to assess the metal exposure on an individual basis and metal contamination in the environment.Peer reviewe
Cartoon Computation: Quantum-like computing without quantum mechanics
We present a computational framework based on geometric structures. No
quantum mechanics is involved, and yet the algorithms perform tasks analogous
to quantum computation. Tensor products and entangled states are not needed --
they are replaced by sets of basic shapes. To test the formalism we solve in
geometric terms the Deutsch-Jozsa problem, historically the first example that
demonstrated the potential power of quantum computation. Each step of the
algorithm has a clear geometric interpetation and allows for a cartoon
representation.Comment: version accepted in J. Phys.A (Letter to the Editor
ORP2 couples LDL-cholesterol transport to FAK activation by endosomal cholesterol/PI(4,5)P-2 exchange
Low-density lipoprotein (LDL)-cholesterol delivery from late endosomes to the plasma membrane regulates focal adhesion dynamics and cell migration, but the mechanisms controlling it are poorly characterized. Here, we employed auxin-inducible rapid degradation of oxysterol-binding protein-related protein 2 (ORP2/OSBPL2) to show that endogenous ORP2 mediates the transfer of LDL-derived cholesterol from late endosomes to focal adhesion kinase (FAK)-/integrin-positive recycling endosomes in human cells. In vitro, cholesterol enhances membrane association of FAK to PI(4,5)P-2-containing lipid bilayers. In cells, ORP2 stimulates FAK activation and PI(4,5)P-2 generation in endomembranes, enhancing cell adhesion. Moreover, ORP2 increases PI(4,5)P-2 in NPC1-containing late endosomes in a FAK-dependent manner, controlling their tubulovesicular trafficking. Together, these results provide evidence that ORP2 controls FAK activation and LDL-cholesterol plasma membrane delivery by promoting bidirectional cholesterol/PI(4,5)P-2 exchange between late and recycling endosomes.Peer reviewe
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