A conceptual model of community dynamics during the transport stage of the invasion process: a case study of ships’ ballast

Aim: After J. L. Lockwood, P. Cassey and T. Blackburn (2009, Diversity and Distributions, 15, 904–910) first described a theoretical relationship between propagule pressure and colonization pressure, two empirical studies demonstrated that the transport stage of the invasion process can profoundly influence the strength of the relationship among multiple events, as well as predictions of introduction risk. However, studies exploring dynamics of transported communities are rare, as repeated-measures sampling during transportation by any vector is logistically difficult. We constructed a conceptual model of community dynamics during transportation and supported it by empirical data for propagule pressure and colonization pressure of plankton. Location: Global. Methods: A conceptual model of community dynamics was developed based on lognormal species abundance distribution and the simulation model of J. L. Lockwood, P. Cassey and T. Blackburn (2009, Diversity and Distributions, 15, 904–910). We considered four cases: case ‘A’ – no reduction in propagule nor colonization pressure; case ‘B’ – strong reduction in propagule and mild reduction in colonization pressure; case ‘C’ – mild reduction in propagule and strong reduction in colonization pressure; and case ‘D’ – strong reduction in both propagule and colonization pressures. Results: The cases ‘B’, ‘C’ and ‘D’ were supported by empirical data for invertebrates, dinoflagellates and diatoms from ships’ ballast tanks, respectively. Propagule pressure of invertebrates, dinoflagellates and diatoms decreased 99.95%, 80% and 94% in 25 days, respectively, while colonization pressure decreased 34%, 57% and 64%. Main conclusions: Transport affects both propagule pressure and colonization pressure of taxa, with the magnitude of change dependent on length of transport and taxon-specific survival and reproduction. Our model demonstrates that introduction risk varies substantially across and within taxa depending on the occurrence and severity of selection pressures during transportation which serve to change species abundance distributions

Search for Short-Term Periodicities in the Sun's Surface Rotation: A Revisit

The power spectral analyses of the Sun's surface equatorial rotation rate determined from the Mt. Wilson daily Doppler velocity measurements during the period 3 December 1985 to 5 March 2007 suggests the existence of 7.6 year, 2.8 year, 1.47 year, 245 day, 182 day and 158 day periodicities in the surface equatorial rotation rate during the period before 1996. However, there is no variation of any kind in the more accurately measured data during the period after 1995. That is, the aforementioned periodicities in the data during the period before the year 1996 may be artifacts of the uncertainties of those data due to the frequent changes in the instrumentation of the Mt. Wilson spectrograph. On the other hand, the temporal behavior of most of the activity phenomena during cycles 22 (1986-1996) and 23 (after 1997) is considerably different. Therefore, the presence of the aforementioned short-term periodicities during the last cycle and absence of them in the current cycle may, in principle, be real temporal behavior of the solar rotation during these cycles.Comment: 11 pages, 6 figures, accepted for publication in Solar Physic

Utilization of case presentations in medical microbiology to enhance relevance of basic science for medical students

Background : Small-group case presentation exercises (CPs) were created to increase course relevance for medical students taking Medical Microbiology (MM) and Infectious Diseases (ID) Methods : Each student received a unique paper case and had 10 minutes to review patient history, physical exam data, and laboratory data. Students then had three minutes to orally present their case and defend why they ruled in or out each of the answer choices provided, followed by an additional three minutes to answer questions. Results : Exam scores differed significantly between students who received the traditional lecture-laboratory curriculum (Group I) and students who participated in the CPs (Group II). In MM, median unit exam and final exam scores for Group I students were 84.4% and 77.8%, compared to 86.0% and 82.2% for Group II students (P < 0.018; P < 0.001; Mann-Whitney Rank Sum Test). Median unit and final ID exam scores for Group I students were 84.0% and 80.0%, compared to 88.0% and 86.7% for Group II students (P < 0.001; P < 0.001). Conclusion : Students felt that the CPs improved their critical thinking and presentation skills and helped to prepare them as future physicians

Ecological Invasion, Roughened Fronts, and a Competitor's Extreme Advance: Integrating Stochastic Spatial-Growth Models

Both community ecology and conservation biology seek further understanding of factors governing the advance of an invasive species. We model biological invasion as an individual-based, stochastic process on a two-dimensional landscape. An ecologically superior invader and a resident species compete for space preemptively. Our general model includes the basic contact process and a variant of the Eden model as special cases. We employ the concept of a "roughened" front to quantify effects of discreteness and stochasticity on invasion; we emphasize the probability distribution of the front-runner's relative position. That is, we analyze the location of the most advanced invader as the extreme deviation about the front's mean position. We find that a class of models with different assumptions about neighborhood interactions exhibit universal characteristics. That is, key features of the invasion dynamics span a class of models, independently of locally detailed demographic rules. Our results integrate theories of invasive spatial growth and generate novel hypotheses linking habitat or landscape size (length of the invading front) to invasion velocity, and to the relative position of the most advanced invader.Comment: The original publication is available at www.springerlink.com/content/8528v8563r7u2742

Acceleration of Relativistic Protons during the 20 January 2005 Flare and CME

The origin of relativistic solar protons during large flare/CME events has not been uniquely identified so far.We perform a detailed comparative analysis of the time profiles of relativistic protons detected by the worldwide network of neutron monitors at Earth with electromagnetic signatures of particle acceleration in the solar corona during the large particle event of 20 January 2005. The intensity-time profile of the relativistic protons derived from the neutron monitor data indicates two successive peaks. We show that microwave, hard X-ray and gamma-ray emissions display several episodes of particle acceleration within the impulsive flare phase. The first relativistic protons detected at Earth are accelerated together with relativistic electrons and with protons that produce pion decay gamma-rays during the second episode. The second peak in the relativistic proton profile at Earth is accompanied by new signatures of particle acceleration in the corona within approximatively 1 solar radius above the photosphere, revealed by hard X-ray and microwave emissions of low intensity, and by the renewed radio emission of electron beams and of a coronal shock wave. We discuss the observations in terms of different scenarios of particle acceleration in the corona.Comment: 22 pages, 5 figure

Narrowband Searches for Continuous and Long-duration Transient Gravitational Waves from Known Pulsars in the LIGO-Virgo Third Observing Run

Isolated neutron stars that are asymmetric with respect to their spin axis are possible sources of detectable continuous gravitational waves. This paper presents a fully coherent search for such signals from eighteen pulsars in data from LIGO and Virgo's third observing run (O3). For known pulsars, efficient and sensitive matched-filter searches can be carried out if one assumes the gravitational radiation is phase-locked to the electromagnetic emission. In the search presented here, we relax this assumption and allow both the frequency and the time derivative of the frequency of the gravitational waves to vary in a small range around those inferred from electromagnetic observations. We find no evidence for continuous gravitational waves, and set upper limits on the strain amplitude for each target. These limits are more constraining for seven of the targets than the spin-down limit defined by ascribing all rotational energy loss to gravitational radiation. In an additional search, we look in O3 data for long-duration (hours-months) transient gravitational waves in the aftermath of pulsar glitches for six targets with a total of nine glitches. We report two marginal outliers from this search, but find no clear evidence for such emission either. The resulting duration-dependent strain upper limits do not surpass indirect energy constraints for any of these targets. © 2022. The Author(s). Published by the American Astronomical Society

Search for Gravitational Waves Associated with Gamma-Ray Bursts Detected by Fermi and Swift during the LIGO-Virgo Run O3b

We search for gravitational-wave signals associated with gamma-ray bursts (GRBs) detected by the Fermi and Swift satellites during the second half of the third observing run of Advanced LIGO and Advanced Virgo (2019 November 1 15:00 UTC-2020 March 27 17:00 UTC). We conduct two independent searches: A generic gravitational-wave transients search to analyze 86 GRBs and an analysis to target binary mergers with at least one neutron star as short GRB progenitors for 17 events. We find no significant evidence for gravitational-wave signals associated with any of these GRBs. A weighted binomial test of the combined results finds no evidence for subthreshold gravitational-wave signals associated with this GRB ensemble either. We use several source types and signal morphologies during the searches, resulting in lower bounds on the estimated distance to each GRB. Finally, we constrain the population of low-luminosity short GRBs using results from the first to the third observing runs of Advanced LIGO and Advanced Virgo. The resulting population is in accordance with the local binary neutron star merger rate. © 2022. The Author(s). Published by the American Astronomical Society