Computer-assisted radiographic calculation of spinal curvature in brachycephalic "screw-Tailed" dog breeds with congenital thoracic vertebral malformations: reliability and clinical evaluation

The objectives of this study were: To investigate computer-assisted digital radiographic measurement of Cobb angles in dogs with congenital thoracic vertebral malformations, to determine its intra- and inter-observer reliability and its association with the presence of neurological deficits. Medical records were reviewed (2009–2013) to identify brachycephalic screw-tailed dog breeds with radiographic studies of the thoracic vertebral column and with at least one vertebral malformation present. Twenty-eight dogs were included in the study. The end vertebrae were defined as the cranial end plate of the vertebra cranial to the malformed vertebra and the caudal end plate of the vertebra caudal to the malformed vertebra. Three observers performed the measurements twice. Intraclass correlation coefficients were used to calculate the intra- and inter-observer reliabilities. The intraclass correlation coefficient was excellent for all intra- and inter-observer measurements using this method. There was a significant difference in the kyphotic Cobb angle between dogs with and without associated neurological deficits. The majority of dogs with neurological deficits had a kyphotic Cobb angle higher than 35°. No significant difference in the scoliotic Cobb angle was observed. We concluded that the computer assisted digital radiographic measurement of the Cobb angle for kyphosis and scoliosis is a valid, reproducible and reliable method to quantify the degree of spinal curvature in brachycephalic screw-tailed dog breeds with congenital thoracic vertebral malformations

Ab initio modeling of oxygen impurity atom incorporation into uranium mononitride surface and subsurface vacancies

The incorporation of oxygen atoms has been simulated into either nitrogen or uranium vacancy at the UN(001) surface, sub-surface or central layers. For calculations on the corresponding slab models both the relativistic pseudopotentials and the method of projector augmented-waves (PAW) as implemented in the VASP computer code have been used. The energies of O atom incorporation and solution within the defective UN surface have been calculated and discussed. For different configurations of oxygen ions at vacancies within the UN(001) slab, the calculated density of states and electronic charge re-distribution was analyzed. Considerable energetic preference of O atom incorporation into the N-vacancy as compared to U-vacancy indicates that the observed oxidation of UN is determined mainly by the interaction of oxygen atoms with the surface and sub-surface N vacancies resulting in their capture by the vacancies and formation of O-U bonds with the nearest uranium atoms. Keywords: Density functional calculations, uranium mononitride, surface, defects, N and U vacancie

Family-centered care in early intervention : perceptions of practice

A study was conducted in order to investigate the perceptions of both primary caregivers and early intervention (EI) occupational therapists (OTs) in regards to the implementation and importance of family-centered care (FCC). [This is an excerpt from the abstract. For the complete abstract, please see the document.

Neutron time-of-flight measurements of charged-particle energy loss in inertial confinement fusion plasmas

Neutron spectra from secondary ^{3}H(d,n)α reactions produced by an implosion of a deuterium-gas capsule at the National Ignition Facility have been measured with order-of-magnitude improvements in statistics and resolution over past experiments. These new data and their sensitivity to the energy loss of fast tritons emitted from thermal ^{2}H(d,p)^{3}H reactions enable the first statistically significant investigation of charged-particle stopping via the emitted neutron spectrum. Radiation-hydrodynamic simulations, constrained to match a number of observables from the implosion, were used to predict the neutron spectra while employing two different energy loss models. This analysis represents the first test of stopping models under inertial confinement fusion conditions, covering plasma temperatures of k_{B}T≈1-4  keV and particle densities of n≈(12-2)×10^{24}  cm^{-3}. Under these conditions, we find significant deviations of our data from a theory employing classical collisions whereas the theory including quantum diffraction agrees with our data

Dry process fluorination of uranium dioxide using ammonium bifluoride

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2003.Includes bibliographical references (p. 59-60).An experimental study was conducted to determine the practicality of various unit operations for fluorination of uranium dioxide. The objective was to prepare ammonium uranium fluoride double salts from uranium dioxide and ammonium bifluoride, then decompose these salts to uranium tetrafluoride through heating to temperatures near 425 °C in either a fluidized bed or a stirred bed. Fluorination in the stirred bed was attempted without pretreatment of the reagents. For the fluidized bed experiments, reagents were ball-milled prior to being heated in the bed. Experiments were conducted in either argon or 4% hydrogen in argon. The ball mill appeared to be an effective technique for fluorinating uranium dioxide with ammonium bifluoride. Samples changed color from brown to bright green, and no oxides could be detected in the x-ray diffraction pattern of the product. It was found that stainless steel is a suitable material of construction for reaction vessels, whereas mild steel parts corroded quickly. Only a small degree of fluidization provided adequate mixing in fluidized beds, but a paddle mixing the stirred beds left an unmixed region around the bed perimeter. Results from the stirred beds showed the initial fluorination reaction completed only when the reagents were heated to 110 °C for at least three hours under argon. Decomposition took place under argon with a temperature ramp up to 425 °C. The product UF4 contained less than 1% oxide as an impurity, and the decomposition appeared to be complete. Fluidized beds were run with both argon and 4% hydrogen in argon as carrier gases. Experiments with 4% hydrogen in argon produced uranium tetrafluoride, with ammonium uranium pentafluoride and uranium dioxide as impurties. Experiments in argon produced uranium tetrafluoride, with uranyl difluoride, ammonium diuranyl pentafluoride and triuranium octoxide as impurities. Minimum temperatures and times needed to decompose the double salt in the fluidized beds were 200 minutes at 115 °C, a 500-minute ramp to 425 °C, and 200 minutes at 425 °C. The intermediate double salt produced at 110 °C appeared to be triammonium uranium septafluoride.by Charles Burnett Yeamans.S.M

Indications of flow near maximum compression in layered deuterium-tritium implosions at the National Ignition Facility

An accurate understanding of burn dynamics in implosions of cryogenically layered deuterium (D) and tritium (T) filled capsules, obtained partly through precision diagnosis of these experiments, is essential for assessing the impediments to achieving ignition at the National Ignition Facility. We present measurements of neutrons from such implosions. The apparent ion temperatures T[subscript ion] are inferred from the variance of the primary neutron spectrum. Consistently higher DT than DD T[subscript ion] are observed and the difference is seen to increase with increasing apparent DT T[subscript ion]. The line-of-sight rms variations of both DD and DT T[subscript ion] are small, ∼ 150 eV, indicating an isotropic source. The DD neutron yields are consistently high relative to the DT neutron yields given the observed T[subscript ion]. Spatial and temporal variations of the DT temperature and density, DD-DT differential attenuation in the surrounding DT fuel, and fluid motion variations contribute to a DT T[subscript ion] greater than the DD T[subscript ion], but are in a one-dimensional model insufficient to explain the data. We hypothesize that in a three-dimensional interpretation, these effects combined could explain the results.Lawrence Livermore National Laboratory (Contract No. DE-AC52- 07NA27344

Component acquisition and single-source vendor management strategy in a defense application

Thesis (M.B.A.)--Massachusetts Institute of Technology, Sloan School of Management; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; in conjunction with the Leaders for Manufacturing Program at MIT, 2009.Includes bibliographical references (p. 51-52).Building an aircraft carrier is one of the most complex manufacturing undertakings in the world. Each component must be designed, tested and manufactured to not only Northrop Grumman Shipbuilding's (NGSB) exceptionally high standards, but also to the standards, requirements and approvals of both the Navy and the US Federal Government. As a result of these standards and requirements, lead times for construction materials can exceed two years, while a similar component, purchased for industrial use may have a lead time of 90 days. To add to the complexity, the scheduled delivery date for the carrier is fixed, and compressed so that engineering design and construction must take place concurrently. In essence, the ship is under construction years before the design is complete. As a result of concurrent engineering, a complex procurement process and a limited vendor base, some material is chronically late to the Required-in-Yard (RIY) date, causing deviations from the optimal construction schedule and impacting the cost of the ship. This thesis analyzes the current CVN 78 valve purchasing process to identify opportunities to leverage the product model and existing process infrastructure to improve material delivery to schedule and decrease construction costs for CVN 79. It is the goal of this research to improve the supply chain to support the preferred construction schedule, while reducing cost and risk associated with component acquisition. This thesis begins with an analysis of the current supply chain system within NGSB New Carrier Construction.(cont.) It then explores the current state of vendor relations between NGSB and the supply base. The cost impact for delaying construction due to delinquent valves is identified and presented. Then specific vendor management strategies are examined. This thesis proposes a framework for improving on-time delivery of the component and lowering overall supply chain cost by (1) pursuing strategic alliances with valve vendors, (2) providing greater visibility of demand earlier in the engineering design cycle and (3) using this visibility to drive procurement timing to improve delivery to scheduled need date. The thesis presents a case study in vendor collaboration and provides recommendations. Finally, it discusses the impact of applying the framework to similar components within the New Carrier Construction Program and the potential application of the framework to NGSB's other active programs and shipbuilding locations.by Lory Hammer.S.M.M.B.A

Fusion Energy Output Greater than the Kinetic Energy of an Imploding Shell at the National Ignition Facility

A series of cryogenic, layered deuterium-tritium (DT) implosions have produced, for the first time, fusion energy output twice the peak kinetic energy of the imploding shell. These experiments at the National Ignition Facility utilized high density carbon ablators with a three-shock laser pulse (1.5 MJ in 7.5 ns) to irradiate low gas-filled (0.3  mg/cc of helium) bare depleted uranium hohlraums, resulting in a peak hohlraum radiative temperature ∼290  eV. The imploding shell, composed of the nonablated high density carbon and the DT cryogenic layer, is, thus, driven to velocity on the order of 380  km/s resulting in a peak kinetic energy of ∼21  kJ, which once stagnated produced a total DT neutron yield of 1.9×10¹⁶ (shot N170827) corresponding to an output fusion energy of 54 kJ. Time dependent low mode asymmetries that limited further progress of implosions have now been controlled, leading to an increased compression of the hot spot. It resulted in hot spot areal density (ρr∼0.3  g/cm²) and stagnation pressure (∼360  Gbar) never before achieved in a laboratory experiment