Optimal Data-Dependent Hashing for Approximate Near Neighbors

We show an optimal data-dependent hashing scheme for the approximate near neighbor problem. For an $n$-point data set in a $d$-dimensional space our data structure achieves query time $O(d n^{\rho+o(1)})$ and space $O(n^{1+\rho+o(1)} + dn)$, where $\rho=\tfrac{1}{2c^2-1}$ for the Euclidean space and approximation $c>1$. For the Hamming space, we obtain an exponent of $\rho=\tfrac{1}{2c-1}$. Our result completes the direction set forth in [AINR14] who gave a proof-of-concept that data-dependent hashing can outperform classical Locality Sensitive Hashing (LSH). In contrast to [AINR14], the new bound is not only optimal, but in fact improves over the best (optimal) LSH data structures [IM98,AI06] for all approximation factors $c>1$. From the technical perspective, we proceed by decomposing an arbitrary dataset into several subsets that are, in a certain sense, pseudo-random.Comment: 36 pages, 5 figures, an extended abstract appeared in the proceedings of the 47th ACM Symposium on Theory of Computing (STOC 2015

Big data in the new media environment

Bentley et al. argue for the social scientific contextualization of “big data” by proposing a four-quadrant model. We suggest extensions of the east–west (i.e., socially motivated versus independently motivated) decision-making dimension in light of findings from social psychology and neuroscience. We outline a method that leverages linguistic tools to connect insights across fields that address the individuals underlying big-data media streams

Fragment Grammars: Exploring Computation and Reuse in Language

Language relies on a division of labor between stored units and structure building operations which combine the stored units into larger structures. This division of labor leads to a tradeoff: more structure-building means less need to store while more storage means less need to compute structure. We develop a hierarchical Bayesian model called fragment grammar to explore the optimum balance between structure-building and reuse. The model is developed in the context of stochastic functional programming (SFP) and in particular using a probabilistic variant of Lisp known as the Church programming language (Goodman, Mansinghka, Roy, Bonawitz, & Tenenbaum, 2008). We show how to formalize several probabilistic models of language structure using Church, and how fragment grammar generalizes one of them---adaptor grammars (Johnson, Griffiths, & Goldwater, 2007). We conclude with experimental data with adults and preliminary evaluations of the model on natural language corpus data

Examination of the Resonance Contributions to Dileptonic Rare B-Decays

We analyse the long-distance contribution to $B\to X_s\ell^+\ell^-$ differential decay rate when the momentum dependence of $\psi$ and $\psi'$-$\gamma$ conversion strength is taken into account. The results indicate that the resonance to nonresonance interference in the dilepton invariant mass distribution is substantially reduced.Comment: 10 pages, Latex, one figure (included

Lesions mimicking lacrimal gland pleomorphic adenoma

Aim: To report a series of patients with lacrimal gland lesions simulating the clinicoradiological features of lacrimal gland pleomorphic adenoma (LGPA). Methods: Multicentre retrospective, interventional case series. Clinical records of all patients with lesions mimicking LGPA seen in five orbital units were reviewed. Results: The study included 14 patients (seven men and seven women) with a mean age of 50.9 years. The diagnosis of LGPA was made in all cases by experienced orbital surgeons, based on clinicoradiological features, and lacrimal gland excision was performed. Postoperative histology revealed lymphoma (four patients), chronic dacryoadenitis (three patients), adenoid cystic carcinoma (two patients), Sjogren's syndrome (two patients), cavernous haemangioma (one patient), benign lymphoid hyperplasia (one patient) and granulomatous dacryoadenitis (one patient). Comparison with the total number of histologically confirmed LGPA cases seen during the study period revealed that 22.6% of cases of suspected LGPA were misdiagnosed based on clinicoradiological criteria. Conclusions: Many different lesions may mimic the clinicoradiological features of LGPA. The accepted clinicoradiological criteria used for the diagnosis of LGPA have a high false-positive rate, even in experienced hands. Based on this study, the authors believe that fine-needle aspiration biopsy or intraoperative biopsy and frozen section diagnosis may help reduce unnecessary lacrimal gland excision.Venkatesh C Prabhakaran, Paul S Cannon, Alan McNab, Garry Davis, Brett O’Donnell, Peter J Dolman, Raf Ghabrial, Dinesh Selv

Lactobacillus ruminis strains cluster according to their mammalian gut source

peer-reviewedBackground Lactobacillus ruminis is a motile Lactobacillus that is autochthonous to the human gut, and which may also be isolated from other mammals. Detailed characterization of L. ruminis has previously been restricted to strains of human and bovine origin. We therefore sought to expand our bio-bank of strains to identify and characterise isolates of porcine and equine origin by comparative genomics. Results We isolated five strains from the faeces of horses and two strains from pigs, and compared their motility, biochemistry and genetic relatedness to six human isolates and three bovine isolates including the type strain 27780T. Multilocus sequence typing analysis based on concatenated sequence data for six individual loci separated the 16 L. ruminis strains into three clades concordant with human, bovine or porcine, and equine sources. Sequencing the genomes of four additional strains of human, bovine, equine and porcine origin revealed a high level of genome synteny, independent of the source animal. Analysis of carbohydrate utilization, stress survival and technological robustness in a combined panel of sixteen L. ruminis isolates identified strains with optimal survival characteristics suitable for future investigation as candidate probiotics. Under laboratory conditions, six human isolates of L. ruminis tested were aflagellate and non-motile, whereas all 10 strains of bovine, equine and porcine origin were motile. Interestingly the equine and porcine strains were hyper-flagellated compared to bovine isolates, and this hyper-flagellate phenotype correlated with the ability to swarm on solid medium containing up to 1.8% agar. Analysis by RNA sequencing and qRT-PCR identified genes for the biosynthesis of flagella, genes for carbohydrate metabolism and genes of unknown function that were differentially expressed in swarming cells of an equine isolate of L. ruminis. Conclusions We suggest that Lactobacillus ruminis isolates have potential to be used in the functional food industry. We have also identified a MLST scheme able to distinguish between strains of L. ruminis of different origin. Genes for non-digestible oligosaccharide metabolism were identified with a putative role in swarming behaviour.This work was supported by a Principal Investigator Award (07/IN.1/B1780) from Science Foundation Ireland to P.W. O’Toole

Crystalfield symmetries of luminescent Eu3+ centers in GaN : the importance of the 5D0 to 7F1 transition

Eu-doped GaN is a promising material with potential application not only in optoelectronics but also in magneto-optical and quantum optical devices ‘beyond the light emitting diode’. Its interesting spectroscopy is unfortunately complicated by spectral overlaps due to ‘site multiplicity’, the existence in a given sample of multiple composite centers in which Eu ions associate with intrinsic or extrinsic defects. We show here that elementary crystalfield analysis of the 5D0 to 7F1 transition can critically distinguish such sites. Hence, we find that the center involved in the hysteretic photochromic switching (HPS) observed in GaN(Mg):Eu, proposed as the basis of a new solid state qubit material, is not in fact Eu1, as previously reported, but a related defect, Eu1(Mg). Furthermore, the decomposition of the crystalfield distortions of Eu0, Eu1(Mg) and Eu1 into axial and non-axial components strongly suggests reasonable microscopic models for the defects themselves