Efficient detection of contagious outbreaks in massive metropolitan encounter networks

Physical contact remains difficult to trace in large metropolitan networks, though it is a key vehicle for the transmission of contagious outbreaks. Co-presence encounters during daily transit use provide us with a city-scale time-resolved physical contact network, consisting of 1 billion contacts among 3 million transit users. Here, we study the advantage that knowledge of such co-presence structures may provide for early detection of contagious outbreaks. We first examine the "friend sensor" scheme --- a simple, but universal strategy requiring only local information --- and demonstrate that it provides significant early detection of simulated outbreaks. Taking advantage of the full network structure, we then identify advanced "global sensor sets", obtaining substantial early warning times savings over the friends sensor scheme. Individuals with highest number of encounters are the most efficient sensors, with performance comparable to individuals with the highest travel frequency, exploratory behavior and structural centrality. An efficiency balance emerges when testing the dependency on sensor size and evaluating sensor reliability; we find that substantial and reliable lead-time could be attained by monitoring only 0.01% of the population with the highest degree.Comment: 4 figure

The Determination of Degradation Products of Lewisite and/or Mustard Gas in Water by High Performance Liquid Chromatography

Lewisite (L) and mustard gas (HD) are highly toxic vesicant warfare agents that are very sparingly soluble in water and thereby converted quantitatively to the stable and soluble degradation products 2-chlorovinylarsonous acid (CVAA), 2-chloro vinylarsonic acid (CVAOA), 2,2’-dihydroxyethyl sulphide and 2,2’-dichlorodiethyl sulphoxide. A new method based on reversed-phase high performance liquid chromatography (RP-HPLC) has been developed for the simultaneous detection of CVAOA, CVAA, 2,2’-dichlorodiethyl sulphoxide, 2,2’-dihydroxyethyl sulphide. The effects of eluent and pH on the separation efficiency were studied. UV spectra of CVAOA, CVAA, 2,2’-dichlorodiethyl sulphoxide and 2,2’-dihydroxyethyl sulphide were recorded. Good separation was achieved by HPLC using a 250 × 4.6 mm column with 5 μm ODS C18 after optimization of all relevant parameters. The calibration curves ofCVAOA,CVAA, 2,2’-dichlorodiethyl sulphoxide and 2,2’-dihydroxyethyl sulphide showed high linearity over a concentration range of 5–500, 2–500, 5–500, 50–1000 mg L–1, respectively. The detection limits at a signal-to-noise ratio of 3 were 0.001, 0.2, 2, 20mgL–1. The method may be beneficial for studying the distribution of lewisite-and/or mustard gas and their degradation products in the environment.Keywords: High performance liquid chromatography, 2-chlorovinylarsonic acid, -chlorovinylarsonous acid, 2,2’-dichlorodiethylsulphoxide, 2,2’-dihydroxyethyl sulphide

The Extreme Spin of the Black Hole in Cygnus X-1

The compact primary in the X-ray binary Cygnus X-1 was the first black hole to be established via dynamical observations. We have recently determined accurate values for its mass and distance, and for the orbital inclination angle of the binary. Building on these results, which are based on our favored (asynchronous) dynamical model, we have measured the radius of the inner edge of the black hole's accretion disk by fitting its thermal continuum spectrum to a fully relativistic model of a thin accretion disk. Assuming that the spin axis of the black hole is aligned with the orbital angular momentum vector, we have determined that Cygnus X-1 contains a near-extreme Kerr black hole with a spin parameter a/M>0.95 (3\sigma). For a less probable (synchronous) dynamical model, we find a/M>0.92 (3\sigma). In our analysis, we include the uncertainties in black hole mass, orbital inclination angle and distance, and we also include the uncertainty in the calibration of the absolute flux via the Crab. These four sources of uncertainty totally dominate the error budget. The uncertainties introduced by the thin-disk model we employ are particularly small in this case given the extreme spin of the black hole and the disk's low luminosity.Comment: Paper III of three papers on Cygnus X-1; 21 pages including 5 figures and 12 tables, ApJ in press. The paper is significantly restructured; two further tests of the robustness of our spin measurement are presented, and our error analysis has been substantially improved; the conclusions are unchange

Dirac-Electrons-Mediated Magnetic Proximity Effect in Topological Insulator / Magnetic Insulator Heterostructures

The possible realization of dissipationless chiral edge current in a topological insulator / magnetic insulator heterostructure is based on the condition that the magnetic proximity exchange coupling at the interface is dominated by the Dirac surface states of the topological insulator. Here we report a polarized neutron reflectometry observation of Dirac electrons mediated magnetic proximity effect in a bulk-insulating topological insulator (Bi$_{0.2}$Sb$_{0.8}$)$_{2}$Te$_{3}$ / magnetic insulator EuS heterostructure. We are able to maximize the proximity induced magnetism by applying an electrical back gate to tune the Fermi level of topological insulator to be close to the charge neutral point. A phenomenological model based on diamagnetic screening is developed to explain the suppressed proximity induced magnetism at high carrier density. Our work paves the way to utilize the magnetic proximity effect at the topological insulator/magnetic insulator hetero-interface for low-power spintronic applications.Comment: 5 pages main text with 4 figures; 2 pages supplemental materials; suggestions and discussions are welcome

Firefly: Embracing Future Web Technologies

At IPAC/Caltech, we have developed the Firefly web archive and visualization system. Used in production for the last eight years in many missions, Firefly gives the scientist significant capabilities to study data. Firefly provided the first completely web based FITS viewer as well as a growing set of tabular and plotting visualizers. Further, it will be used for the science user interface of the LSST telescope which goes online in 2021. Firefly must meet the needs of archive access and visualization for the 2021 LSST telescope and must serve astronomers beyond the year 2030. Recently, our team has faced the fact that the technology behind Firefly software was becoming obsolete. We were searching for ways to utilize the current breakthroughs in maintaining stability, testability, speed, and reliability of large web applications, which Firefly exemplifies. In the last year, we have ported the Firefly to cutting edge web technologies. Embarking on this massive overhaul is no small feat to say the least. Choosing the technologies that will maintain a forward trajectory in a future development project is always hard and often overwhelming. When a team must port 150,000 lines of code for a production-level product there is little room to make poor choices. This paper will give an overview of the most modern web technologies and lessons learned in our conversion from GWT based system to React/Redux based system

Diversity of antimicrobial resistance, stress resistance, and virulence factors of Salmonella, Shiga toxin-producing Escherichia coli, and Listeria monocytogenes from produce, spices, and tree nuts by whole genome sequencing

IntroductionThe objective of this study was to analyze antimicrobial resistance (AMR), stress resistance, and virulence factors through whole genome sequencing (WGS) of 192 isolates comprising 164 Salmonella isolates, 8 non-O157 Shiga toxin-producing Escherichia coli (STEC) isolates, and 20 Listeria monocytogenes isolates.MethodsThese isolates were sourced from a national survey conducted between 2010 and 2017, involving 31,322 samples of produce (31 isolates), nuts (43 isolates), and spices (118 isolates).ResultsThe findings yielded several key insights: (1) Within all Salmonella isolates studied, the most prevalent Salmonella serotypes included Give, Kentucky, Senftenberg, Mbandaka, Anatum, Newport, and Weltevreden. (2) All eight non-O157 STEC isolates were found to carry the genes blaEC, acrF, and mdtM, while all 20 L. monocytogenes isolates possessed fosX and lin genes. The Salmonella isolates displayed diverse AMR gene profiles, with 3.65% exhibiting multi-drug resistance. (3) Both Salmonella and non-O157 STEC isolates were discovered to carry stress genes associated with acid resistance, but none of the L. monocytogenes isolates carried an acid resistance gene. Salmonella isolates were found to carry multiple metal-resistance genes. The non-O157 STEC isolates universally exhibited acid resistance genes, and 4 out of the 20 L. monocytogenes isolates were equipped with resistance genes against biocides. (4) All of the STEC isolates (100%) carried stx1 and stx2 genes, while none of them carried eae and wyz genes. Most L. monocytogenes isolates were found to contain 29 virulence genes and 1 pathogenicity island. All Salmonella isolates carried SPI-9, but lacked SPI-7, SPI-10, SPI-11, SPI-12, mig-5, prefA, tviA, and viaB genes.ConclusionThese findings on AMR, stress resistance, and virulence factors among the investigated isolates highlight the potential risks they pose to public health and provide the scientific foundation for the development of preventative and control strategies and guidance pertaining to these major foodborne pathogens