Microdosimetric measurements of shielding effects for iron particles at 500 MeV/nucleon incident upon aluminum and polyethylene

2007 Fall.Includes bibliographical references (pages 58-59).The radiation environment in space is very different than on the earth. One portion of the radiation present in space is galactic cosmic radiation (GCR). GCR is composed of protons, alpha particles, and high Z and energy (HZE) particles. One of the most significant HZE particle species in terms of absorbed dose is iron. One of the dosimetry instruments used on the Space Shuttle and the International Space Station is the tissue equivalent proportional counter (TEPC). It is used to measure absorbed dose and estimate the average quality factor of radiation exposure during manned space missions. TEPCs measure energy deposition in volumes of simulated tissue with dimensions on the order of microns. Spectra of energy depositions are used to calculate values of frequency mean lineal energy, ȳF, and dose mean lineal energy, ȳD. The value of ȳF can be used to calculate the absorbed dose per particle. Previous studies have found that the choice of ȳF or ȳD to approximate particle linear energy transfer (LET), and thus the quality factor, depends on the momentum of the particle and for iron, the value of ȳD is equivalent. However, the presence of material causes HZE particles to slow down and/or fragment. Thus radiation of one HZE particle species incident on one side of shielding material, insufficient to stop all radiation, will produce a wide range of particles and energies on the other side. This study exposed a spherical TEPC, in conjunction with a particle spectrometer, to iron particles at 500 MeV/nucleon, produced at the Heavy Ion Medical Accelerator in Chiba, Japan, with and without shielding material. The shielding material used, in separate measurements, was 1.65 cm Al and 5 cm polyethylene (each has 4.5 g cm-2 density thickness). The density thickness is similar to what is used on the Space Shuttle and International Space Station. The absorbed dose per particle was measured and the average LET of the radiation was estimated for each shielding scenario. For iron particles at 500 MeV/nucleon, the shielding did not cause a change in the absorbed dose per particle. But the shielding reduced the average quality factor of the radiation and polyethylene was better than aluminum, at the same density thickness

Waves in the Red Sea : response to monsoonal and mountain gap winds

Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Continental Shelf Research 65 (2013): 1-13, doi:10.1016/j.csr.2013.05.017.An unstructured grid, phase-averaged wave model forced with winds from a high resolution atmospheric model is used to evaluate wind wave conditions in the Red Sea over an approximately 2-year period. The Red Sea lies in a narrow rift valley, and the steep topography surrounding the basin steers the dominant wind patterns and consequently the wave climate. At large scales, the model results indicated that the primary seasonal variability in waves was due to the monsoonal wind reversal. During the winter, monsoon winds from the southeast generated waves with mean significant wave heights in excess of 2 m and mean periods of 8 s in the southern Red Sea, while in the northern part of the basin waves were smaller, shorter period, and from northwest. The zone of convergence of winds and waves typically occurred around 19-20˚N, but the location varied between 15 to 21.5˚N. During the summer, waves were generally smaller and from the northwest over most of the basin. While the seasonal winds oriented along the axis of the Red Sea drove much of the variability in the waves, the maximum wave heights in the simulations were not due to the monsoonal winds but instead were generated by localized mountain wind jets oriented across the basin (roughly east-west). During the summer, a mountain wind jet from the Tokar Gap enhanced the waves in the region of 18 and 20˚N, with monthly mean wave heights exceeding 2 m and maximum wave heights of 14 m during a period when the rest of the Red Sea was relatively calm. Smaller mountain gap wind jets along the northeast coast created large waves during the fall and winter, with a series of jets providing a dominant source of wave energy during these periods. Evaluation of the wave model results against observations from a buoy and satellites found that the spatial resolution of the wind model significantly affected the quality of the wave model results. Wind forcing from a 10-km grid produced higher skills for waves than winds from a 30-km grid, largely due to under-prediction of the mean wind speed and wave height with the coarser grid. The 30-km grid did not resolve the mountain gap wind jets, and thus predicted lower wave heights in the central Red Sea during the summer and along the northeast coast in the winter.This research is based on work supported by Award No. USA00001, USA00002, KSA00011, made by the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia

Foreground and Source of a Cluster of Ultra-high Energy Cosmic Rays

We investigate the origin of a nearly pointlike cluster of 5 ultrahigh energy cosmic rays at RA ~169.2deg and dec ~56.8deg, using Sloan Digital Sky Survey and other data. No particular source candidates are found near the estimated source direction, but the direction is exceptional in having a likely merging pair of galaxy clusters at 140/h Mpc, with an unusually low foreground density. Large scale shocks or another product of the merging galaxy clusters may accelerate the UHECRs, or the merging galaxy clusters may be coincidental and the UHECRs may be accelerated in a rare event of an unexceptional progenitor. Low magnetic deflections in the foreground void may explain why this is the only identified pointlike cluster of so many UHECRs.Comment: 5 p

Controlled Delivery of Sdf-1 Alpha and Igf-1: Cxcr4(+) Cell Recruitment and Functional Skeletal Muscle Recovery

Therapeutic delivery of regeneration-promoting biological factors directly to the site of injury has demonstrated its efficacy in various injury models. Several reports describe improved tissue regeneration following local injection of tissue specific growth factors, cytokines and chemokines. Evidence exists that combined cytokine/growth factor treatment is superior for optimizing tissue repair by targeting different aspects of the regeneration response. The purpose of this study was to evaluate the therapeutic potential of the controlled delivery of stromal cell-derived factor-1alpha (SDF-1 alpha) alone or in combination with insulin-like growth factor-I (SDF-1 alpha/IGF-I) for the treatment of tourniquet-induced ischemia/reperfusion injury (TK-I/R) of skeletal muscle. We hypothesized that SDF-1 alpha will promote sustained stem cell recruitment to the site of muscle injury, while IGF-I will induce progenitor cell differentiation to effectively restore muscle contractile function after TK-I/R injury while concurrently reducing apoptosis. Utilizing a novel poly-ethylene glycol PEGylated fibrin gel matrix (PEG-Fib), we incorporated SDF-1 alpha alone (PEG-Fib/SDF-1 alpha) or in combination with IGF-I (PEG-Fib/SDF-1 alpha/IGF-I) for controlled release at the site of acute muscle injury. Despite enhanced cell recruitment and revascularization of the regenerating muscle after SDF-1 alpha treatment, functional analysis showed no benefit from PEG-Fib/SDF-1 alpha therapy, while dual delivery of PEG-Fib/SDF-1 alpha/IGF-I resulted in IGF-I-mediated improvement of maximal force recovery and SDF-1 alpha-driven in vivo neovasculogenesis. Histological data supported functional data, as well as highlighted the important differences in the regeneration process among treatment groups. This study provides evidence that while revascularization may be necessary for maximizing muscle force recovery, without modulation of other effects of inflammation it is insufficient.Kinesiology and Health Educatio

Community leadership network - more than an aspiration 'Through the School Gates'

This paper focuses on the National College for School Leadership's 'Community Leadership Network' which comprises ten areas in England (rural and urban). The paper argues that models of school leadership should aim to service and build capacity for interdependent relationships between institutions and communities beyond the school gates. Through a case study of Winsford Networked Learning Community (North of England) and its use of facilitation tools it will lay out the problems and possibilities of building this capacit