Diophantine networks

We introduce a new class of deterministic networks by associating networks with Diophantine equations, thus relating network topology to algebraic properties. The network is formed by rep- resenting integers as vertices and by drawing cliques between M vertices every time that M dis- tinct integers satisfy the equation. We analyse the network generated by the Pythagorean equation x2+y2 = z2 showing that its degree distribution is well approximated by a power law with exponen- tial cut-o®. We also show that the properties of this network di®er considerably from the features of scale-free networks generated through preferential attachment. Remarkably we also recover a power law for the clustering coe±cient. We then study the network associated with the equation x2 + y2 = z showing that the degree distribution is consistent with a power-law for several decades of values of k and that, after having reached a minimum, the distribution begins rising again. The power law exponent, in this case, is given by ° » 4:5 We then analyse clustering and ageing and compare our results to the ones obtained in the Pythagorean case

IEEE 802.11n MAC frame aggregation mechanisms for next-generation high-throughput WLANs [Medium access control protocols for wireless LANs]

IEEE 802.11n is an ongoing next-generation wireless LAN standard that supports a very highspeed connection with more than 100 Mb/s data throughput measured at the medium access control layer. This article investigates the key MAC enhancements that help 802.11n achieve high throughput and high efficiency. A detailed description is given for various frame aggregation mechanisms proposed in the latest 802.11n draft standard. Our simulation results confirm that A-MSDU, A-MPDU, and a combination of these methods improve extensively the channel efficiency and data throughput. We analyze the performance of each frame aggregation scheme in distinct scenarios, and we conclude that overall, the two-level aggregation is the most efficacious

A Methodology for Afterburner Evaluation

A preliminary investigation of the performance of an afterburner module proposed by the Gas Turbine Research Establishment, Bangalore for the Kaveri engine has been carried out. The investigation, which was both theoretical and experimental, evaluated the af-terburner configuration on the basis of flame stability, combustion efficiency and total pressure loss. An evaluation methodology, which was formulated, has been employed to arrive at design modifications for improved performance

Efficient simulations with electronic open boundaries

We present a reformulation of the Hairy Probe method for introducing electronic open boundaries that is appropriate for steady state calculations involving non-orthogonal atomic basis sets. As a check on the correctness of the method we investigate a perfect atomic wire of Cu atoms, and a perfect non-orthogonal chain of H atoms. For both atom chains we find that the conductance has a value of exactly one quantum unit, and that this is rather insensitive to the strength of coupling of the probes to the system, provided values of the coupling are of the same order as the mean inter-level spacing of the system without probes. For the Cu atom chain we find in addition that away from the regions with probes attached, the potential in the wire is uniform, while within them it follows a predicted exponential variation with position. We then apply the method to an initial investigation of the suitability of graphene as a contact material for molecular electronics. We perform calculations on a carbon nanoribbon to determine the correct coupling strength of the probes to the graphene, and obtain a conductance of about two quantum units corresponding to two bands crossing the Fermi surface. We then compute the current through a benzene molecule attached to two graphene contacts and find only a very weak current because of the disruption of the π-conjugation by the covalent bond between the benzene and the graphene. In all cases we find that very strong or weak probe couplings suppress the current

The cost to see the Wizard: buy-ins and trade-offs in neurological rehabilitation

This scientific commentary refers to ‘A decision-neuroscientific intervention to improve cognitive recovery after stroke’ by Studer et al. (doi:10.1093/brain/awab128)

Late onset Ito's nevus

Dermal melanocytoses include a variety of congenital and acquired melanocytic lesions characterised by the presence of multiple spindle-shaped dendritic melanocytes in the dermis. These lesions are commonly found in the skin of Asians, but they can also appear in Caucasians. The Mongolian spot, nevi of Ota and Ito are the most common morphological forms. We report a case of a 24-year-old Caucasian woman presented with a 10-months history of progressive darkening of the right side of her upper back. Cutaneous examination revealed a macular blue-grey hyperpigmentation of the right side of her upper back. Biopsy specimen from the macule showed multiple darkly pigmented, spindle-shaped dendritic melanocytes in the superficial dermis, interstitially arranged between collagen bundles. The diagnosis of nevus of Ito was established. Our patient is maintaining vigilance in dermatology consultation

Hemangioma Cavernoso da Supra-Renal

INTRODUÇÃO: O hemangioma cavernoso da glândula supra-renal é um tumor benigno, raro, com menos de uma centena de casos reportados na literatura. É caracterizado na sua constituição por formações vasculares dilatadas e delimitadas por células endoteliais. Apresenta-se caracteristicamente como um incidentaloma e o seu diagnóstico é habitualmente estabelecido apenas no pós-operatório. CASO CLÍNICO: Doente de 73 anos referenciada por nódulo de 45mm da glândula supra-renal esquerda diagnosticado incidentalmente no seguimento de lesão quística renal. A avaliação imagiológica por TC revelou nódulo sólido de 45x28mm na glândula supra-renal esquerda. Realizou estudo para avaliar a autonomia do nódulo, e que revelou uma hipersecreção adrenérgica. Colocada a hipótese diagnóstica de feocromocitoma e proposta para cirurgia ablativa. Foi submetida a suprarrenalectomia esquerda laparoscópica, que decorreu sem intercorrências. O resultado histológico da peça operatória revelou um hemangioma cavernoso da supra-renal. DISCUSSÃO / CONCLUSÃO: A forma de apresentação mais comum do hemangioma cavernoso da supra-renal é a de um incidentaloma, implicando o diagnóstico diferencial com os vários tipos de lesões ocupando espaço deste órgão. Este facto associado à falta de especificidade dos exames pré-operatórios e à raridade da patologia compromete a acuidade diagnóstica. No presente caso, assim como na maioria dos reportados na literatura, esta patologia foi somente estabelecida no pós-operatório através do resultado anátomo-patológico

HTR4 gene structure and altered expression in the developing lung

Background: Meta-analyses of genome-wide association studies (GWAS) have identified single nucleotide polymorphisms (SNPs) spanning the 5-hydroxytryptamine receptor 4 (5-HT4R) gene (HTR4) associated with lung function. The aims of this study were to i) investigate the expression profile of HTR4 in adult and fetal lung tissue and cultured airway cells, ii) further define HTR4 gene structure and iii) explore the potential functional implications of key SNPs using a bioinformatic approach

Adaptive Seeding for Gaussian Mixture Models

We present new initialization methods for the expectation-maximization algorithm for multivariate Gaussian mixture models. Our methods are adaptions of the well-known $K$-means++ initialization and the Gonzalez algorithm. Thereby we aim to close the gap between simple random, e.g. uniform, and complex methods, that crucially depend on the right choice of hyperparameters. Our extensive experiments indicate the usefulness of our methods compared to common techniques and methods, which e.g. apply the original $K$-means++ and Gonzalez directly, with respect to artificial as well as real-world data sets.Comment: This is a preprint of a paper that has been accepted for publication in the Proceedings of the 20th Pacific Asia Conference on Knowledge Discovery and Data Mining (PAKDD) 2016. The final publication is available at link.springer.com (http://link.springer.com/chapter/10.1007/978-3-319-31750-2 24