Scanning Transmission Ion Microscopy as it Complements Particle Induced X-Ray Emission Microanalysis

The early uses of Scanning Transmission Ion Microscopy (STIM) with MeV ions are reviewed. The transformation of STIM energy-loss images into maps of areal density is discussed, and is illustrated with images of a fruit fly head (Drosophila melanogaster). Freeze-dried male heads are transparent to 4-MeV protons in the dorsal and frontal directions, but in the sagittal direction the brain is opaque. STIM with molecular ions is shown to be useful for increasing contrast in low density areas. For recording registered STIM and PIXE images without changing accelerator parameters, apertures are used to accomplish the required change in beam intensity (a factor of 105). Molecular ions are used to assess contamination of the microbeam by scattered ions. Pixel by pixel ratios of x-ray intensity to areal density are taken to obtain maps of element concentrations. Calcium and iron maps are shown. Inner parts of the fly head are clearly seen in the concentration maps. The PIXE exposure caused differential displacements of inner parts of the head by 15 μm or less. Weight loss during the PIXE exposure was measured to be 3%

Size of Outbreaks Near the Epidemic Threshold

The spread of infectious diseases near the epidemic threshold is investigated. Scaling laws for the size and the duration of outbreaks originating from a single infected individual in a large susceptible population are obtained. The maximal size of an outbreak n_* scales as N^{2/3} with N the population size. This scaling law implies that the average outbreak size scales as N^{1/3}. Moreover, the maximal and the average duration of an outbreak grow as t_* ~ N^{1/3} and ~ ln N, respectively.Comment: 4 pages, 5 figure

Unsung heroes: who supports social work students on placement?

Since the introduction of the three year degree programme in 2003, social work education has undergone a number of significant changes. The time students spend on placement has been increased to two hundred days, and the range of placement opportunities and the way in which these placements have been configured has significantly diversified. A consistent feature over the years, however, has been the presence of a Practice Educator (PE) who has guided, assessed and taught the student whilst on placement. Unsurprisingly, the role of the PE and the pivotal relationship they have with the student has been explored in the past and features in social work literature. This paper, however, concentrates on a range of other relationships which are of significance in providing support to students on placement. In particular it draws on research to discuss the role of the university contact tutor, the place of the wider team in which the student is sited, and the support offered by family, friends and others. Placements and the work undertaken by PE’s will continue to be integral to the delivery of social work education. It is, however, essential to recognise and value the often over looked role of others in providing support to students on placement

Modeling the Dust Properties of z ~ 6 Quasars with ART^2 -- All-wavelength Radiative Transfer with Adaptive Refinement Tree

The detection of large quantities of dust in z ~ 6 quasars by infrared and radio surveys presents puzzles for the formation and evolution of dust in these early systems. Previously (Li et al. 2007), we showed that luminous quasars at z > 6 can form through hierarchical mergers of gas-rich galaxies. Here, we calculate the dust properties of simulated quasars and their progenitors using a three-dimensional Monte Carlo radiative transfer code, ART^2 -- All-wavelength Radiative Transfer with Adaptive Refinement Tree. ART^2 incorporates a radiative equilibrium algorithm for dust emission, an adaptive grid for inhomogeneous density, a multiphase model for the ISM, and a supernova-origin dust model. We reproduce the SED and dust properties of SDSS J1148+5251, and find that the infrared emission are closely associated with the formation and evolution of the quasar host. The system evolves from a cold to a warm ULIRG owing to heating and feedback from stars and AGN. Furthermore, the AGN has significant implications for the interpretation of observation of the hosts. Our results suggest that vigorous star formation in merging progenitors is necessary to reproduce the observed dust properties of z~6 quasars, supporting a merger-driven origin for luminous quasars at high redshifts and the starburst-to-quasar evolutionary hypothesis. (Abridged)Comment: 26 pages, 22 figures, accepted by ApJ. Version with full resolution images is available at http://www.cfa.harvard.edu/~yxli/ARTDUST/astroph0706.3706.pd

Comparison of prasugrel and clopidogrel used as antiplatelet medication for endovascular treatment of unruptured intracranial aneurysms: A meta-analysis

BACKGROUND: Clopidogrel is routinely used to decrease ischemic complications during neurointerventional procedures. However, the efficacy may be limited by antiplatelet resistance. PURPOSE: Our aim was to analyze the efficacy of prasugrel compared with clopidogrel in the cerebrovascular field. DATA SOURCES: A systematic search of 2 large databases was performed for studies published from 2000 to 2018. STUDY SELECTION: According to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we included studies reporting treatment-related outcomes of patients undergoing neurointerventional procedures under prasugrel, and studies comparing prasugrel and clopidogrel. DATA ANALYSIS: Random-effects meta-analysis was used to pool the overall rate of complications, ischemic and hemorrhagic events, and influence of the dose of prasugrel. DATA SYNTHESIS: In the 7 included studies, 682 and 672 unruptured intracranial aneurysms were treated under prasugrel (cases) and clopidogrel (controls), respectively. Low-dose (20 mg/5 mg; loading and maintenance doses) prasugrel compared with the standard dose of clopidogrel (300 mg/75 mg) showed a significant reduction in the complication rate (OR 0.36; 95% CI, 0.17–74, P .006; I2 0%). Overall, the ischemic complication rate was significantly higher in the clopidogrel group (40/672 6%; 95% CI, 3%–13%; I2 83% versus 16/682 2%; 95% CI, 1%–5%; I2 73%; P .03). Low and high loading doses of prasugrel were associated with 0.6% (5/535; 95% CI, 0.1%–1.6%; I2 0%) and 9.3% (13/147; 95% CI, 0.2%–18%; I2 60%) intraperiprocedural hemorrhages, respectively (P .001), whereas low and high maintenance doses of prasugrel were associated with 0% (0/433) and 0.9% (2/249; 95% CI, 0.3%–2%; I2 0%) delayed hemorrhagic events, respectively (P .001). LIMITATIONS: Retrospective series and heterogeneous endovascular treatments were limitations. CONCLUSIONS: In our study, low-dose prasugrel compared with clopidogrel premedication was associated with an effective reduction of the ischemic events with an acceptable rate of hemorrhagic complications

Analytical solution of a one-dimensional Ising model with zero temperature dynamics

The one-dimensional Ising model with nearest neighbour interactions and the zero-temperature dynamics recently considered by Lefevre and Dean -J. Phys. A: Math. Gen. {\bf 34}, L213 (2001)- is investigated. By introducing a particle-hole description, in which the holes are associated to the domain walls of the Ising model, an analytical solution is obtained. The result for the asymptotic energy agrees with that found in the mean field approximation.Comment: 6 pages, no figures; accepted in J. Phys. A: Math. Gen. (Letter to the Editor