1,111 research outputs found
When is the Haar measure a Pietsch measure for nonlinear mappings?
We show that, as in the linear case, the normalized Haar measure on a compact
topological group is a Pietsch measure for nonlinear summing mappings on
closed translation invariant subspaces of . This answers a question posed
to the authors by J. Diestel. We also show that our result applies to several
well-studied classes of nonlinear summing mappings. In the final section some
problems are proposed
All-optical 3D atomic loops generated with Bessel light fields
The propagation invariance of Bessel beams as well as their transversal
structure are used to perform a comparative analysis of their effect on cold
atoms for four different configurations and combinations thereof. We show that,
even at temperatures for which the classical description of the atom center of
mass motion is valid, the interchange of momentum, energy and orbital angular
momentum between light and atoms yields efficient tools for all-optical
trapping, transporting and, in general, manipulating the state of motion of
cold atoms.Comment: 13 pages, 9 figure
A Poisson hierarchical modelling approach to detecting copy number variation in sequence coverage data.
BACKGROUND: The advent of next generation sequencing technology has accelerated efforts to map and catalogue copy number variation (CNV) in genomes of important micro-organisms for public health. A typical analysis of the sequence data involves mapping reads onto a reference genome, calculating the respective coverage, and detecting regions with too-low or too-high coverage (deletions and amplifications, respectively). Current CNV detection methods rely on statistical assumptions (e.g., a Poisson model) that may not hold in general, or require fine-tuning the underlying algorithms to detect known hits. We propose a new CNV detection methodology based on two Poisson hierarchical models, the Poisson-Gamma and Poisson-Lognormal, with the advantage of being sufficiently flexible to describe different data patterns, whilst robust against deviations from the often assumed Poisson model. RESULTS: Using sequence coverage data of 7 Plasmodium falciparum malaria genomes (3D7 reference strain, HB3, DD2, 7G8, GB4, OX005, and OX006), we showed that empirical coverage distributions are intrinsically asymmetric and overdispersed in relation to the Poisson model. We also demonstrated a low baseline false positive rate for the proposed methodology using 3D7 resequencing data and simulation. When applied to the non-reference isolate data, our approach detected known CNV hits, including an amplification of the PfMDR1 locus in DD2 and a large deletion in the CLAG3.2 gene in GB4, and putative novel CNV regions. When compared to the recently available FREEC and cn.MOPS approaches, our findings were more concordant with putative hits from the highest quality array data for the 7G8 and GB4 isolates. CONCLUSIONS: In summary, the proposed methodology brings an increase in flexibility, robustness, accuracy and statistical rigour to CNV detection using sequence coverage data
The Level of NMDA Receptor in the Membrane Modulates Amyloid-ÎČ Association and Perforation
Alzheimerâs disease is a neurodegenerative disorder that affects mostly the elderly. The main histopathological markers are the senile plaques formed by amyloid-ÎČ peptide (AÎČ) aggregates that can perforate the plasma membrane of cells, increasing the intracellular calcium levels and releasing synaptic vesicles that finally lead to a delayed synaptic failure. Several membrane proteins and lipids interact with AÎČ affecting its toxicity in neurons. Here, we focus on NMDA receptors (NMDARs) as proteins that could be modulating the association and neurotoxic perforation induced by AÎČ on the plasma membrane. In fact, our results showed that decreasing NMDARs, using enzymatic or siRNA approaches, increased the association of AÎČ to the neurons. Furthermore, overexpression of NMDARs also resulted in an enhanced association between NMDA and AÎČ. Functionally, the reduction in membrane NMDARs augmented the process of membrane perforation. On the other hand, overexpressing NMDARs had a protective effect because AÎČ was now unable to cause membrane perforation, suggesting a complex relationship between AÎČ and NMDARs. Because previous studies have recognized that AÎČ oligomers are able to increase membrane permeability and produce amyloid pores, the present study supports the conclusion that NMDARs play a critical protective role on AÎČ actions in hippocampal neurons. These results could explain the lack of correlation between brain AÎČ burden and clinically observed dementia
Sharp values for the constants in the polynomial Bohnenblust-Hille inequality
In this paper we prove that the complex polynomial Bohnenblust-Hille constant
for -homogeneous polynomials in is exactly
. We also give the exact value of the real polynomial
Bohnenblust-Hille constant for -homogeneous polynomials in .
Finally, we provide lower estimates for the real polynomial Bohnenblust-Hille
constant for polynomials in of higher degrees.Comment: 16 page
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