Thermal Neutron Characterization and Dose Modeling of a Plutonium-239/Beryllium Alpha-Neutron Source

Determination of neutron dose can be challenging and requires knowledge of neutron energy and neutron flux. A plutonium-239/beryllium (239PuBe) alpha-neutron source was used to irradiate bacterial samples to create neutron dose response. The goal of this project was to characterize the thermal neutron flux of the 239PuBe alpha-neutron source and model the neutron dose using version MCNPX of the Monte-Carlo N-Particle transport codes. The 37 GBq 239PuBe alpha-neutron source was placed in a neutron “howitzer,” that is, a 2-ft diameter moderating barrel with four radial irradiation ports. Multi-foil activation was used at various distances to determine thermal neutron flux, which was then used to verify a MCNPX code representing the system. Dysprosium thermal foils were used with cadmium covers. The MCNPX code was then adapted for dosimetric modeling. That is, the F5 tally, with a dose function, was used in place of the F4 tally. The four irradiation ports were found to have average thermal neutron fluxes of 5334 ± 829, 2928 ± 451, 1289 ± 199, and 1211 ± 186 neutrons cm-2 s-1 at 3.58, 9.04, 12.8, and 13.7 cm from the 239PuBe alpha-neutron source, respectively. The adapted MCNPX code calculated theoretical total ambient dose equivalent rates of 1717 ± 90.2, 703 ± 37.0, 286 ± 15.0, and 174 ± 9.18 mrem hr-1 at 4, 8, 14, and 18 cm from the 239PuBe alpha-neutron source, respectively. The theoretical direct (uncollided) ambient dose equivalent rates at the same distances were 837 ± 44.0, 272 ± 14.3, 100 ± 5.29, and 63.1 ± 3.32 mrem hr-1, respectively. Rough estimates of the absorbed dose rates were made from the ambient dose equivalent rates and a recommendation of 23.6 cm from the PuBe source was made to achieve an absorbed dose rate of roughly 10 mGy d-1

Hydrogen bonding structure of confined water templated by a metal-organic framework with open metal sites.

Water in confinement exhibits properties significantly different from bulk water due to frustration in the hydrogen-bond network induced by interactions with the substrate. Here, we combine infrared spectroscopy and many-body molecular dynamics simulations to probe the structure and dynamics of confined water as a function of relative humidity within a metal-organic framework containing cylindrical pores lined with ordered cobalt open coordination sites. Building upon the agreement between experimental and theoretical spectra, we demonstrate that water at low relative humidity binds initially to open metal sites and subsequently forms disconnected one-dimensional chains of hydrogen-bonded water molecules bridging between cobalt atoms. With increasing relative humidity, these water chains nucleate pore filling, and water molecules occupy the entire pore interior before the relative humidity reaches 30%. Systematic analysis of rotational and translational dynamics indicates heterogeneity in this pore-confined water, with water molecules displaying variable mobility as a function of distance from the interface

Motor Symptoms as a Prodrome to Schizophrenia

Schizophrenia occurs in 1% of the population and is severely impairing to those afflicted. Thereby, it is of the utmost importance to recognize and treat the disorder as early as possible. For the last several decades research has attempted to elucidate a variety of predictive factors in order to aid in the identification of patients at high risk of developing a schizophrenia spectrum disorder. These factors have included premorbid or prodromal movement symptoms. The literature has identified motor aberrations beginning early in life, in some cases even in infancy, ranging from neonatal hypotonicity to facial and upper body dyskinesia. These motor symptoms have not only been demonstrated to aid in predicting conversion to schizophrenia but carry prognostic importance for other outcomes as well. We present the case of a 34-year-old male who developed abnormal motor symptoms several years prior to the onset of psychosis. Our case builds upon the current body of literature by demonstrating the importance of spontaneous dyskinesia in the evaluation of populations at high risk for the development of a schizophrenia spectrum illnesses

THE EFFECT OF CAMERA PAN ON THE TWO-DIMENSIONAL DIRECT LINEAR TRANSFORMATION AND SCALAR RECONSTRUCTION TECHNIQUES WHEN APPLIED TO ERGOMETER ROWING

Changes in camera pan may affect reconstruction accuracy of two-dimensional (2D) kinematic data collected in on-water rowing testing. The 2D direct linear transformation (2D-DLT) may assist in improving reconstruction accuracy of rowing kinematics when a perpendicular camera changes position. Accuracy of the 2D-DLT and scalar reconstruction techniques was compared using coefficient of multiple correlations (CMCs), range of motion difference (ROMDiff) and root mean square error (RMSE). 2DDLT was found to have significantly greater accuracy (CMC and RMSE;

A 2-DIMENSIONAL VIDEO BASED MODEL FOR USE IN ERGOMETER ROWING KINEMATICS

Motion capture of the rowing stroke using accurate 3D opto-reflective systems has been limited by the constraints of the surrounding hydrodynamic environment. As a consequence 2D lower-extremity kinematic models have been used in an attempt to counter these logistical issues (Lamb, 1989). Despite this, there is limited research supporting the accuracy of a 2D video based model (2DVBM) for motion capture of the rowing stroke. The purpose of this study was to assess the accuracy of a 2DVBM against the conventional gait model using a 3D opto-reflective system

DO GYMNASTS EXPERIENCE SYMMETRICAL LIMB LOADING WHEN PERFORMING FOUNDATION GYMNASTICS SKILLS?

Uneven asymmetrical landings in artistic gymnastics is considered a risk factor for injury. The aim of this research was to investigate if gymnasts experience asymmetrical upper and lower limb loading when performing foundation gymnastics skills on floor. Sixteen competitive level gymnasts (male= 8, female= 8) performed seven different gymnastics skills while wearing four inertial measurement units located bilaterally on the distal forearm and tibias. Every gymnastics skill showed significant inter-limb asymmetry (range z= -5.8, -6.0,