Identifying networks with common organizational principles

Many complex systems can be represented as networks, and the problem of network comparison is becoming increasingly relevant. There are many techniques for network comparison, from simply comparing network summary statistics to sophisticated but computationally costly alignment-based approaches. Yet it remains challenging to accurately cluster networks that are of a different size and density, but hypothesized to be structurally similar. In this paper, we address this problem by introducing a new network comparison methodology that is aimed at identifying common organizational principles in networks. The methodology is simple, intuitive and applicable in a wide variety of settings ranging from the functional classification of proteins to tracking the evolution of a world trade network.Comment: 26 pages, 7 figure

Speech and language therapy versus placebo or no intervention for speech problems in Parkinson's disease

Parkinson's disease patients commonly suffer from speech and vocal problems including dysarthric speech, reduced loudness and loss of articulation. These symptoms increase in frequency and intensity with progression of the disease). Speech and language therapy (SLT) aims to improve the intelligibility of speech with behavioural treatment techniques or instrumental aids

MeerKAT HI line observations of the nearby interacting galaxy pair NGC 1512/1510

We present MeerKAT HI line observations of the nearby interacting galaxy pair NGC 1512/1510. The MeerKAT data yield high-fidelity image sets characterised by an excellent combination of high angular resolution (~20") and and sensitivity (~0.08 Msun/pc^2), thereby offering the most detailed view of this well-studied system's neutral atomic hydrogen content, especially the HI co-located with the optical components of the galaxies. The stellar bulge and bar of NGC 1512 are located within a central HI depression where surface densities fall below 1 Msun/pc^2, while the galaxy's starburst ring coincides with a well-defined HI annulus delimited by a surface density of 3 Msun/pc^2. In stark contrast, the star-bursting companion, NGC 1510, has its young stellar population precisely matched to the highest HI over-densities we measure (~12.5 Msun/pc^2). The improved quality of the MeerKAT data warrants the first detailed measurements of the lengths and masses of the system's tidally-induced HI arms. We measure the longest of the two prominent HI arms to extend over ~27 kpc and to contain more than 30% of the system's total HI mass. We quantitatively explore the spatial correlation between HI and far-ultraviolet flux over a large range of HI mass surface densities spanning the outer disk. The results indicate the system's HI content to play an important role in setting the pre-conditions required for wide-spread, high-mass star formation. This work serves as a demonstration of the remarkable efficiency and accuracy with which MeerKAT can image nearby systems in HI line emission.Comment: 12 pages, 11 figures. Submitted only to arXi

Spectral evidence for a powerful compact jet from XTE J1118+480

We present observations of the X-ray transient XTE J1118+480 during its Low/Hard X-ray state outburst in 2000, at radio and sub-millimetre wavelengths with the VLA, Ryle Telescope, MERLIN and JCMT. The high-resolution MERLIN observations reveal all the radio emission (at 5 GHz) to come from a compact core with physical dimensions smaller than 65*d(kpc) AU. The combined radio data reveal a persistent and inverted radio spectrum, with spectral index \~+0.5. The source is also detected at 350 GHz, on an extrapolation of the radio spectrum. Flat or inverted radio spectra are now known to be typical of the Low/Hard X-ray state, and are believed to arise in synchrotron emission from a partially self-absorbed jet. Comparison of the radio and sub-millimetre data with reported near-infrared observations suggest that the synchrotron emission from the jet extends to the near-infrared, or possibly even optical regimes. In this case the ratio of jet power to total X-ray luminosity is likely to be P_J/L_X >> 0.01, depending on the radiative efficiency and relativistic Doppler factor of the jet. Based on these arguments we conclude that during the period of our observations XTE J1118+480 was producing a powerful outflow which extracted a large fraction of the total accretion power.Comment: Accepted for publication as a Letter in MNRA

Distance, dissimilarity index, and network community structure

We address the question of finding the community structure of a complex network. In an earlier effort [H. Zhou, {\em Phys. Rev. E} (2003)], the concept of network random walking is introduced and a distance measure defined. Here we calculate, based on this distance measure, the dissimilarity index between nearest-neighboring vertices of a network and design an algorithm to partition these vertices into communities that are hierarchically organized. Each community is characterized by an upper and a lower dissimilarity threshold. The algorithm is applied to several artificial and real-world networks, and excellent results are obtained. In the case of artificially generated random modular networks, this method outperforms the algorithm based on the concept of edge betweenness centrality. For yeast's protein-protein interaction network, we are able to identify many clusters that have well defined biological functions.Comment: 10 pages, 7 figures, REVTeX4 forma

Expression, purification, crystallization and preliminary crystallographic analysis of BipD, a component of the Burkholderia pseudomallei type III secretion system

A construct consisting of residues 10–310 of mature BipD, a component of the B. pseudomallei type III secretion system, has been crystallized. Native BipD crystals and SeMet and K2PtCl4 derivative crystals have undergone preliminary crystallographic analysis

Attractiveness of periodic orbits in parametrically forced systemswith time-increasing friction

We consider dissipative one-dimensional systems subject to a periodic force and study numerically how a time-varying friction affects the dynamics. As a model system, particularly suited for numerical analysis, we investigate the driven cubic oscillator in the presence of friction. We find that, if the damping coefficient increases in time up to a final constant value, then the basins of attraction of the leading resonances are larger than they would have been if the coefficient had been fixed at that value since the beginning. From a quantitative point of view, the scenario depends both on the final value and the growth rate of the damping coefficient. The relevance of the results for the spin-orbit model are discussed in some detail.Comment: 30 pages, 6 figure

Harvest and Non-Harvest Mortality Relationships for Lesser Scaup Breeding in Southwestern Montana

Since the mid-to-late 1990s, lesser scaup (Aythya affinis) populations have remained more than 20% below the population goal set forth in the North American Waterfowl Management Plan.  Accordingly, considerable attention has been directed towards understanding what factors may be limiting their population, including the role of harvest.  Red Rock Lakes National Wildlife Refuge (RRL) in southwestern Montana is the site of a long-term study of lesser scaup ecology and demography.  Preliminary harvest estimates indicate that this population is harvested at rates similar to the continental population with juveniles experiencing an annual average harvest rate of 9.1% (95% CI = 7.7 - 10.7%) and adults an average annual harvest rate of 3.6% (95% CI = 2.2 - 6.1%).  Since 2005, ~1,300 female have been banded on the study site and an additional ~1,000 females have been nasal-marked.  In addition, ~1,400 resightings have been collected for nasal-marked hens on the study site and ~340 dead recoveries from our study population have been reported from Canada to Mexico.  With results obtained from multistrata models that utilize these multiple encounter types, I will present (1) estimates of harvest and natural mortality rates for female lesser scaup banded and nasal-marked at RRL from 2005-2016; (2) how non-harvest mortality varies in relation to harvest mortality over the same period; (3) an assessment of how these rates respond to changes in hunting regulations.  These results will be used to help inform lesser scaup harvest demography, a key structural uncertainty in current harvest models identified in the draft Scaup Conservation Action Plan

Harvest and Non-Harvest Mortality Relationships for Lesser Scaup Breeding in Southwestern Montana

Since the mid-to-late 1990s, lesser scaup (Aythya affinis) populations have remained more than 20% below the population goal set forth in the North American Waterfowl Management Plan.  Accordingly, considerable attention has been directed towards understanding what factors may be limiting their population, including the role of harvest.  Red Rock Lakes National Wildlife Refuge (RRL) in southwestern Montana is the site of a long-term study of lesser scaup ecology and demography with data from which survival and harvest rates can be estimated using capture-mark-recapture statistical techniques.  The role of harvest in regulating duck population dynamics, including lesser scaup, is clouded with uncertainty.  Decades of research into the additive or compensatory nature of harvest mortality has yielded little consensus as to which of these hypotheses prevail in North American duck populations.  The most limiting factor to assessing these relationships stems from lacking estimates of population size during waterfowl hunting seasons.  We assessed the relationship between survival rates and harvest rates for lesser scaup females breeding at RRL for an 11 years, beginning in 2005.  Consistent with predictions of density dependence regulation of natural mortality rates during the non-breeding season, we found evidence suggesting adult female survival rates fluctuate in response to harvest regulations, an index of population size, and the total number of lesser scaup harvested in the Pacific and Central Flyways