2,216 research outputs found
Long-range electron transfer in structurally engineered pentaammineruthenium (histidine-62) cytochrome c
In many biological processes, long-range electron transfer (ET) plays a key role. When the three-dimensional structures of proteins are accurately known, use of modified proteins and protein-protein complexes provides an experimental approach to study ET rates between two metal centers. For Ru(His)- modified proteins, the introduction of histidine residues at any desired surface location by site-directed mutagenesis opens the way for systematic investigations of ET pathways
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ERP Correlates of Recognition Memory in Autism Spectrum Disorder
Recognition memory in autism spectrum disorder (ASD) tends to be undiminished compared to that of typically developing (TD) individuals (Bowler et al. 2007), but it is still unknown whether memory in ASD relies on qualitatively similar or different neurophysiology. We sought to explore the neural activity underlying recognition by employing the old/new word repetition event-related potential effect. Behavioural recognition performance was comparable across both groups, and demonstrated superior recognition for low frequency over high frequency words. However, the ASD group showed a parietal rather than anterior onset (300–500 ms), and diminished right frontal old/new effects (800–1500 ms) relative to TD individuals. This study shows that undiminished recognition performance results from a pattern of differing functional neurophysiology in ASD
Heavy Quark Spin Symmetry and Heavy Baryons: Electroweak Decays
Heavy quark spin symmetry is discussed in the context of single and doubly
heavy baryons. A special attention is paid to the constraints/simplifications
that this symmetry imposes on the non-relativistic constituent quark model wave
functions and on the b->c semileptonic decays of these hadrons.Comment: Presented at the 21st European Conference on Few-Body Problems in
Physics, Salamanca, Spain, 30 August - 3 September 201
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Free Recall Learning of Hierarchically Organised Lists by Adults with Asperger's Syndrome: Additional Evidence for Diminished Relational Processing
The Task Support Hypothesis (TSH, Bowler et al. Neuropsychologia 35:65–70 1997) states that individuals with autism spectrum disorder (ASD) show better memory when test procedures provide support for retrieval. The present study aimed to see whether this principle also applied at encoding. Twenty participants with high-functioning ASD and 20 matched comparison participants studied arrays of 112 words over four trials. Words were arranged either under hierarchically embedded category headings (e.g. Instruments—String—Plucked—Violin) or randomly. Both groups showed similar overall recall and better recall for the hierarchically organised words. However, the ASD participants made less use of information about relations between words and more use of item-specific information in their recall, confirming earlier reports of relational difficulties in this population
Two Meson Systems with Ginsparg-Wilson Valence Quarks
Unphysical effects associated with finite lattice spacing and partial
quenching may lead to the presence of unphysical terms in chiral extrapolation
formulae. These unphysical terms must then be removed during data analysis
before physical predictions can be made. In this work, we show that through
next-to-leading order, there are no unphysical counterterms in the
extrapolation formulae, expressed in lattice-physical parameters, for meson
scattering lengths in theories with Ginsparg-Wilson valence quarks. Our work
applies to most sea quark discretization, provided that chiral perturbation
theory is a valid approximation. We demonstrate our results with explicit
computations and show that, in favorable circumstances, the extrapolation
formulae do not depend on the unknown constant C_Mix appearing at lowest order
in the mixed action chiral Lagrangian. We show that the I=1 KK scattering
length does not depend on C_Mix in contrast to the I=3/2 K-pi scattering
length. In addition, we show that these observables combined with f_K / f_pi
and the I=2 pi-pi scattering length share only two linearly independent sets of
counterterms, providing a means to test the mixed action theory at one lattice
spacing. We therefore make a prediction for the I=1 KK scattering length.Comment: 21 pages, 2 figures, 2 tables. Version to be published in PRD.
Improved discussion in Sec. III B. Added reference
Second Stage String Fragmentation Model
A string model, advocated by Bowler, provides a physical and intuitive
picture of heavy quark fragmentation. When supplemented by an ad hoc factor of
(1-z), to suppress fragmentation near z=1, it supplies an excellent fit to the
data. We extend Bowler's model by accounting for the further decay of the
massive mesonic states produced by the initial string breaking. We find that
each subsequent string break and cascade decay beyond the first, introduces a
factor of (1-z). Furthermore we find that including a finite mass for the
quarks, which pop out of the vacuum and split the string, forces the first
string breaking to produce massive states requiring further decay. This
sequence terminates at the second stage of fragmentation where only relatively
"light" heavy meson systems are formed. Thus we naturally account for the
phenomenologically required factor of (1-z). We also predict that the ratio of
(primary) fragments-vector/(vector plus scalar) should be .61. Our second stage
string fragmentation model provides an appealing picture of heavy quark
fragmentation.Comment: 15 page
Revisiting global trends in freshwater insect biodiversity: A reply
Abstract Jähnig et al. make some useful points regarding the conclusions that can be drawn from our meta‐analysis; however, some issues require clarification. First, we never suggested that there was a globally increasing trend of freshwater insect abundances, but only spoke of an average increasing trend in the available data. We also did not suggest that freshwater quality has improved globally, but rather that documented improvements in water quality can explain at least some of the trends we observed. Second, as we acknowledged, our data are not a representative set of freshwater ecosystems around the world, but they are what is currently accessible. Third, there is indeed no doubt that changes in abundance or biomass need not correlate with changes in other aspects of biodiversity, such as species richness or functional composition. Our analysis was specifically focused on trends in community abundance/biomass because it has been the subject of recent study and speculation, and is a widely available metric in long‐term studies. To better understand the recent changes in freshwater insect assemblages, we encourage freshwater ecologists to further open their troves of data from countless long‐term monitoring schemes so that larger and more comprehensive syntheses can be undertaken
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Brief Report: The Role of Task Support in the Spatial and Temporal Source Memory of Adults with Autism Spectrum Disorder
Adults with autism spectrum disorder (ASD) show intact recognition (supported procedure) but impaired recall (unsupported procedure) of incidentally-encoded context. Because this has not been demonstrated for temporal source, we compared the temporal and spatial source memory of adults with ASD and verbally matched typical adults. Because of difficulties with temporal processing in ASD, we predicted ASD adults would benefit from test support for location but not temporal occurrence of studied words. We found similar levels of recognition and source memory for both groups but there was a greater effect of support on memory for location source in the ASD group. The lack of an effect of support for temporal source may simply reflect a difficulty in operationalising temporal cues
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