1,255 research outputs found

    Hemispheric specialization in selective attention and short-term memory: a fine-coarse model of left- and right-ear disadvantages.

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    Serial short-term memory is impaired by irrelevant sound, particularly when the sound changes acoustically. This acoustic effect is larger when the sound is presented to the left compared to the right ear (a left-ear disadvantage). Serial memory appears relatively insensitive to distraction from the semantic properties of a background sound. In contrast, short-term free recall of semantic-category exemplars is impaired by the semantic properties of background speech and is relatively insensitive to the sound’s acoustic properties. This semantic effect is larger when the sound is presented to the right compared to the left ear (a right-ear disadvantage). In this paper, we outline a speculative neurocognitive ïŹne-coarse model of these hemispheric differences in relation to short-term memory and selective attention, and explicate empirical directions in which this model can be critically evaluated

    Pathway-Dependent Post-assembly Modification of an Anthracene-Edged MII4L6 Tetrahedron

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    FeII4L6 tetrahedral cage 1 undergoes post-assembly modification (PAM) via a Diels–Alder cycloaddition of the anthracene panels of the cage with tetracyanoethylene (TCNE). The modified cage 2 possesses an enclosed cavity suitable for encapsulation of the fullerene C60, whereas original cage 1 forms a unique covalent adduct through a Diels–Alder cycloaddition of three of its anthracene ligands with C60. This adduct undergoes further PAM via reaction of the remaining three ligands with TCNE, enabling the isolation of two distinct products depending on the order of addition of C60 and TCNE. Modified cage 2 was also able to bind an anionic guest, [Co(C2B9H11)2]−, which was not encapsulated by the original cage, demonstrating the potential of PAM for tuning the binding properties of supramolecular hosts

    Desarrollo y política social en åreas no metropolitanas. Estados Unidos de América

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    It is interesting to envisage the situation of social and economic development in non-metropolitan areas of the United States, understating that 80% of the population of American citizens currently live in cities.This work is based on research on rural economy done by the members of the Economic Research Service (ERS). The data used in this analysis came from a variety of federal sources. The most recent data available was used for this study, from different series emitted at different times, so that the newest data comes from 2003 and 2005.Resulta interesante visualizar la situaciĂłn de desarrollo social y econĂłmico en ĂĄreas de los Estados Unidos de AmĂ©rica no metropolitanas, entendiendo que un 80 % de la poblaciĂłn de ciudadanos estadounidenses viven actualmente en ciudades.El presente trabajo, se basa en las investigaciones de la economĂ­a rural de los miembros del Servicio de Investigaciones EconĂłmicas (ERS), siendo el origen de los datos utilizados en este anĂĄlisis, una variedad de fuentes federales, en la que se utilizan los datos mĂĄs recientes disponibles, de series diversas emitidas en diferentes Ă©pocas, por lo cual los datos mĂĄs nuevos fluctĂșan entre los años 2003 y 2005

    The phonon theory of liquid thermodynamics

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    Heat capacity of matter is considered to be its most important property because it holds information about system's degrees of freedom as well as the regime in which the system operates, classical or quantum. Heat capacity is well understood in gases and solids but not in the third state of matter, liquids, and is not discussed in physics textbooks as a result. The perceived difficulty is that interactions in a liquid are both strong and system-specific, implying that the energy strongly depends on the liquid type and that, therefore, liquid energy can not be calculated in general form. Here, we develop a phonon theory of liquids where this problem is avoided. The theory covers both classical and quantum regimes. We demonstrate good agreement of calculated and experimental heat capacity of 21 liquids, including noble, metallic, molecular and hydrogen-bonded network liquids in a wide range of temperature and pressure.Comment: 7 pages, 4 figure

    Mitochondrial genome sequences illuminate maternal lineages of conservation concern in a rare carnivore

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    <p>Abstract</p> <p>Background</p> <p>Science-based wildlife management relies on genetic information to infer population connectivity and identify conservation units. The most commonly used genetic marker for characterizing animal biodiversity and identifying maternal lineages is the mitochondrial genome. Mitochondrial genotyping figures prominently in conservation and management plans, with much of the attention focused on the non-coding displacement ("D") loop. We used massively parallel multiplexed sequencing to sequence complete mitochondrial genomes from 40 fishers, a threatened carnivore that possesses low mitogenomic diversity. This allowed us to test a key assumption of conservation genetics, specifically, that the D-loop accurately reflects genealogical relationships and variation of the larger mitochondrial genome.</p> <p>Results</p> <p>Overall mitogenomic divergence in fishers is exceedingly low, with 66 segregating sites and an average pairwise distance between genomes of 0.00088 across their aligned length (16,290 bp). Estimates of variation and genealogical relationships from the displacement (<it>D</it>) loop region (299 bp) are contradicted by the complete mitochondrial genome, as well as the protein coding fraction of the mitochondrial genome. The sources of this contradiction trace primarily to the near-absence of mutations marking the D-loop region of one of the most divergent lineages, and secondarily to independent (recurrent) mutations at two nucleotide position in the D-loop amplicon.</p> <p>Conclusions</p> <p>Our study has two important implications. First, inferred genealogical reconstructions based on the fisher D-loop region contradict inferences based on the entire mitogenome to the point that the populations of greatest conservation concern cannot be accurately resolved. Whole-genome analysis identifies Californian haplotypes from the northern-most populations as highly distinctive, with a significant excess of amino acid changes that may be indicative of molecular adaptation; D-loop sequences fail to identify this unique mitochondrial lineage. Second, the impact of recurrent mutation appears most acute in closely related haplotypes, due to the low level of evolutionary signal (unique mutations that mark lineages) relative to evolutionary noise (recurrent, shared mutation in unrelated haplotypes). For wildlife managers, this means that the populations of greatest conservation concern may be at the highest risk of being misidentified by D-loop haplotyping. This message is timely because it highlights the new opportunities for basing conservation decisions on more accurate genetic information.</p

    Dynamical Belyi maps

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    We study the dynamical properties of a large class of rational maps with exactly three ramification points. By constructing families of such maps, we obtain infinitely many conservative maps of degree dd; this answers a question of Silverman. Rather precise results on the reduction of these maps yield strong information on the rational dynamics.Comment: 21 page

    Life history parameters in acellular extrinsic fiber cementum microstructure

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    Life-history parameters such as pregnancies, skeletal trauma, and renal disease have previously been identified from hypomineralized growth layers (incremental lines) of acellular extrinsic fiber cementum (AEFC). The precise periodicity of these growth layers remains vaguely approximated, so causal life-history explanations using tooth cementum cannot yet be rigorously calculated or tested. On the other hand, we show how life history parameters in AEFC can be identified by two contrasting elemental detection methods. Based on our results we reject the possibility of accurate estimation of pregnancies and other life history parameters from cementum using scanning electron microscopy alone. Here, we propose a new methodological approach for cementum research, Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), to measure degree and distribution of mineralization of cementum growth layers. Our results show that Tof-SIMS can significantly increase our knowledge of cementum composition and is therefore a powerful new tool for life history researchers

    Covalent Post-assembly Modification Triggers Multiple Structural Transformations of a Tetrazine-Edged Fe4L6 Tetrahedron

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    Covalent post-assembly modification (PAM) reactions are useful synthetic tools for functionalizing and stabilizing self-assembled metal-organic complexes. Recently, PAM reactions have also been explored as stimuli for triggering supramolecular structural transformations. Herein we demonstrate the use of inverse electron-demand Diels-Alder (IEDDA) PAM reactions to induce supramolecular structural transformations starting from a tetrazine-edged FeII4L6 tetrahedral precursor. Following PAM, this tetrahedron rearranged to form three different architectures depending on the addition of other stimuli: an electron-rich aniline or a templating anion. By tracing the stimulus-response relationships within the system, we deciphered a network of transformations that mapped different combinations of stimuli onto specific transformation products. Given the many functions being developed for self-assembled three-dimensional architectures, this newly established ability to control the interconversion between structures using combinations of different stimulus types may serve as the basis for switching the functions expressed within a system.D.A.R. acknowledges the Gates Cambridge Trust. B.S.P. acknowledges the Royal Commission for the Exhibition of 1851 Fellowship and Corpus Christi College, Cambridge. This work was supported by the UK Engineering and Physical Sciences Research Council (EP/M01083X/1)
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