Lack of continuity between Cronobacter biotypes and species as determined using multilocus sequence typing

The accuracy of the Cronobacter biotyping scheme was compared with the 7-loci multilocus sequence typing scheme. Biotyping did not reliably assign species level identification, as only half (17/31) of the biotype variants were unique to any of the seven Cronobacter species and the remaining biotypes were shared across the genus

An N-body Integrator for Gravitating Planetary Rings, and the Outer Edge of Saturn's B Ring

A new symplectic N-body integrator is introduced, one designed to calculate the global 360 degree evolution of a self-gravitating planetary ring that is in orbit about an oblate planet. This freely-available code is called epi_int, and it is distinct from other such codes in its use of streamlines to calculate the effects of ring self-gravity. The great advantage of this approach is that the perturbing forces arise from smooth wires of ring matter rather than discreet particles, so there is very little gravitational scattering and so only a modest number of particles are needed to simulate, say, the scalloped edge of a resonantly confined ring or the propagation of spiral density waves. The code is applied to the outer edge of Saturn's B ring, and a comparison of Cassini measurements of the ring's forced response to simulations of Mimas' resonant perturbations reveals that the B ring's surface density at its outer edge is 195+-60 gm/cm^2 which, if the same everywhere across the ring would mean that the B ring's mass is about 90% of Mimas' mass. Cassini observations show that the B ring-edge has several free normal modes, which are long-lived disturbances of the ring-edge that are not driven by any known satellite resonances. Although the mechanism that excites or sustains these normal modes is unknown, we can plant such a disturbance at a simulated ring's edge, and find that these modes persist without any damping for more than ~10^5 orbits or ~100 yrs despite the simulated ring's viscosity of 100 cm^2/sec. These simulations also indicate that impulsive disturbances at a ring can excite long-lived normal modes, which suggests that an impact in the recent past by perhaps a cloud of cometary debris might have excited these disturbances which are quite common to many of Saturn's sharp-edged rings.Comment: 55 pages, 13 figures, accepted for publication in the Astrophysical Journa

A dynamic HAZOP case study using the Texas City refinery explosion

© 2016 Elsevier Ltd. The catastrophic explosion that occurred at Texas City on 23 March 2005 during the start-up of the raffinate splitter resulted in an estimated 15 deaths and 180 injuries. Since the incident, several studies have investigated the root causes of the disaster. Some contributing factors to the incident include wider organisational, process safety management, and human elements. There have also been some attempts to model the sequence of events before the incident, and the consequences of the resulting fires and explosions. This study provides a dynamic model of the sequence of events leading up to the incident and replicates the reported process variables during the isomerisation unit start-up on the day of the incident. The resulting simulation model is used as the framework for a dynamic hazard and operability (HAZOP) study

The 200 MeV Pi+ induced single-nucleon removal from 24Mg

Nuclear gamma-rays in coincidence with outgoing pions or protons following single nucleon removal from Mg-24 by 200 MeV pions (+) were detected with Ge(Li) detectors. Differential cross sections are reported for gamma-rays from the first excited mirror states of Na-23 and Mg-23 in coincidence with positive pions or protons detected in particle telescopes at 30, 60, 90, 120, and 150 deg; angle-integrated absolute cross sections and cross section ratios are calculated. These results are compared with the predictions of a Pauli-blocked plane-wave impulse approximation (PWIA) and the intranuclear cascade (INC) and nucleon charge exchange (NCX) reaction models. The PWIA and the INC calculations generally agree with the angular dependence of the experimental results but not the absolute magnitude. The NCX calculation does not reproduce the observed cross section charge ratios

A New Prescription for Protogalactic Feedback and Outflows: Where Have All the Baryons Gone?

Up to half of the baryons inferred to once have been in our galaxy have not yet been detected. Ejection would seem to provide the most attractive explanation. Previous numerical studies may have underestimated the role of winds. I propose a solution involving a multiphase model of the protogalactic interstellar medium and the possibility of driving a superwind. Simulations do not yet incorporate the small-scale physics that, I argue, drives mass-loading of the cold phase gas and enhances the porosity, thereby ensuring that winds are driven at a rate that depends primarily on the star formation rate. The occurrence of hypernovae, as claimed for metal-poor and possibly also for starburst environments, and the possibility of a top-heavy primordial stellar initial mass function are likely to have played important roles in allowing winds to prevail in massive gas-rich starbursting protogalaxies as well as in dwarfs. I discuss why such outflows are generically of order the rate of star formation and may have been a common occurrence in the past.Comment: MNRAS, in press (2003): minor revisions include

NBA 2K

The NBA 2K games have come a long way from an emerging basketball game to now becoming the biggest basketball game ever created. From its graphics, gameplay, community, and many more reasons why the game became so successful today, NBA 2K has evolved into the best basketball game by improving its overall structure every year-round