21,321 research outputs found
Byzantium, its Slavic Elements and their Culture (sixth to ninth centuries)
No abstractNo abstrac
Novel diagnostic and prognostic biomarkers in biliary tract cancer.
The worldwide incidence of biliary tract carcinoma (BTC, tumours of the bile ducts and gall-bladder) continues to rise, with the only potentially curative treatment remaining surgical resection or transplantation, possible in only a minority of patients. Late presentation and a paucity of effective treatments mandate the development of techniques for early lesion detection
High-density SNP association study of the 17q21 chromosomal region linked to autism identifies CACNA1G as a novel candidate gene.
Chromosome 17q11-q21 is a region of the genome likely to harbor susceptibility to autism (MIM(209850)) based on earlier evidence of linkage to the disorder. This linkage is specific to multiplex pedigrees containing only male probands (MO) within the Autism Genetic Resource Exchange (AGRE). Earlier, Stone et al.(1) completed a high-density single nucleotide polymorphism association study of 13.7 Mb within this interval, but common variant association was not sufficient to account for the linkage signal. Here, we extend this single nucleotide polymorphism-based association study to complete the coverage of the two-LOD support interval around the chromosome 17q linkage peak by testing the majority of common alleles in 284 MO trios. Markers within an interval containing the gene, CACNA1G, were found to be associated with Autism Spectrum Disorder at a locally significant level (P=1.9 × 10(-5)). While establishing CACNA1G as a novel candidate gene for autism, these alleles do not contribute a sufficient genetic effect to explain the observed linkage, indicating that there is substantial genetic heterogeneity despite the clear linkage signal. The region thus likely harbors a combination of multiple common and rare alleles contributing to the genetic risk. These data, along with earlier studies of chromosomes 5 and 7q3, suggest few if any major common risk alleles account for Autism Spectrum Disorder risk under major linkage peaks in the AGRE sample. This provides important evidence for strategies to identify Autism Spectrum Disorder genes, suggesting that they should focus on identifying rare variants and common variants of small effect
Biomolecular imaging and electronic damage using X-ray free-electron lasers
Proposals to determine biomolecular structures from diffraction experiments
using femtosecond X-ray free-electron laser (XFEL) pulses involve a conflict
between the incident brightness required to achieve diffraction-limited atomic
resolution and the electronic and structural damage induced by the
illumination. Here we show that previous estimates of the conditions under
which biomolecular structures may be obtained in this manner are unduly
restrictive, because they are based on a coherent diffraction model that is not
appropriate to the proposed interaction conditions. A more detailed imaging
model derived from optical coherence theory and quantum electrodynamics is
shown to be far more tolerant of electronic damage. The nuclear density is
employed as the principal descriptor of molecular structure. The foundations of
the approach may also be used to characterize electrodynamical processes by
performing scattering experiments on complex molecules of known structure.Comment: 16 pages, 2 figure
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Optimizing Quantum Models of Classical Channels: The Reverse Holevo Problem
Given a classical channel—a stochastic map from inputs to outputs—the input can often be transformed into an intermediate variable that is informationally smaller than the input. The new channel accurately simulates the original but at a smaller transmission rate. Here, we examine this procedure when the intermediate variable is a quantum state. We determine when and how well quantum simulations of classical channels may improve upon the minimal rates of classical simulation. This inverts Holevo’s original question of quantifying the capacity of quantum channels with classical resources: We determine the lowest-capacity quantum channel required to simulate a classical channel. We also show that this problem is equivalent to another, involving the local generation of a distribution from common entanglement
Order-Order Morphological Transitions for Dual Stimulus Responsive Diblock Copolymer Vesicles
A series of non-ionic poly(glycerol monomethacrylate)−
poly(2-hydroxypropyl methacrylate) (PGMA−PHPMA) diblock copolymer
vesicles has been prepared by reversible addition−fragmentation
chain transfer (RAFT) aqueous dispersion polymerization of HPMA at
70 °C at low pH using a carboxylic acid-based chain transfer agent. The
degree of polymerization (DP) of the PGMA block was fixed at 43, and
the DP of the PHPMA block was systematically varied from 175 to 250 in
order to target vesicle phase space. Based on our recent work describing
the analogous PGMA−PHPMA diblock copolymer worms [Lovett, J. R.;
et al. Angew. Chem. 2015, 54, 1279−1283], such diblock copolymer vesicles were expected to undergo an order−order
morphological transition via ionization of the carboxylic acid end-group on switching the solution pH. Indeed, irreversible vesicleto-sphere
and vesicle-to-worm transitions were observed for PHPMA DPs of 175 and 200, respectively, as judged by
turbidimetry, transmission electron microscopy (TEM), and dynamic light scattering (DLS) studies. However, such
morphological transitions are surprisingly slow, with relatively long time scales (hours) being required at 20 °C. Moreover, no
order−order morphological transitions were observed for vesicles comprising longer membrane-forming blocks (e.g., PGMA43−
PHPMA225−250) on raising the pH from pH 3.5 to pH 6.0. However, in such cases the application of a dual stimulus comprising
the same pH switch immediately followed by cooling from 20 to 5 °C, induces an irreversible vesicle-to-sphere transition. Finally,
TEM and DLS studies conducted in the presence of 100 mM KCl demonstrated that the pH-responsive behavior arising from
end-group ionization could be suppressed in the presence of added electrolyte. This is because charge screening suppresses the
subtle change in the packing parameter required to drive the morphological transition
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