Synthesis and characterization of F-doped Cs{sub 0.33}WO{sub 3−x}F{sub x} particles with improved near infrared shielding ability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jingxiao; Luo, Jiayu; Shi, Fei, E-mail: shifei@dlpu.edu.cn

2015-01-15

F-doped Cs{sub 0.33}WO{sub 3−x}F{sub x} particles were successfully synthesized by the hydrothermal method with hydrofluoric acid as fluorine source, and a new kind of heat insulating films were prepared from dispersion of Cs{sub 0.33}WO{sub 3−x}F{sub x} nanoparticles in polyvinyl alcohol (PVA) aqueous solution. The effects of F doping on the crystal structure and morphology of Cs{sub 0.33}WO{sub 3−x}F{sub x} particles as well as the near-infrared (NIR) shielding ability and heat insulation properties of Cs{sub 0.33}WO{sub 3−x}F{sub x} films were investigated. The results indicated that HF acid addition could promote the formation of rod-like Cs{sub 0.33}WO{sub 3−x}F{sub x} particles during hydrothermalmore » synthesis and increase the yield of Cs{sub 0.33}WO{sub 3−x}F{sub x} powders. Moreover, the as-prepared films from dispersion solution of Cs{sub 0.33}WO{sub 3−x}F{sub x} particles exhibited higher near-infrared (NIR) shielding ability and heat insulating properties than that of the undoped Cs{sub 0.33}WO{sub 3} film. Particularly, the as-prepared Cs{sub 0.33}WO{sub 3−x}F{sub x} sample with F/W (molar ratio)=0.45 showed best NIR shielding ability and transparent heat insulating performance. The formation mechanism of nanorod-like particles and the effects of F doping on the properties of Cs{sub 0.33}WO{sub 3−x}F{sub x} products were discussed. - Graphical abstract: F-doped Cs{sub 0.33}WO{sub 3−x}F{sub x} particles were successfully synthesized by the hydrothermal method with hydrofluoric acid as fluorine source. HF acid addition in the precursor solution could increase the yield of Cs{sub 0.33}WO{sub 3−x}F{sub x} powders and promote the formation of rod-like Cs{sub 0.33}WO{sub 3−x}F{sub x} particles. Moreover, the as-prepared Cs{sub 0.33}WO{sub 3−x}F{sub x} films from dispersion solution of Cs{sub 0.33}WO{sub 3−x}F{sub x} particles exhibited higher near-infrared (NIR) shielding ability and heat insulating properties than that of the

Comparison of Ion Chemistries in Octafluoro-2-butene (2-C4F8) and in Octfluorocyclobutane (c-C4F8)

NASA Astrophysics Data System (ADS)

Jiao, Charles; Dejoseph, Charles; Garscadden, Alan

2007-10-01

2-C4F8 is one of the promising candidates to replace c-C4F8 that has been widely used for dielectric etching but is not environmentally friendly. In this study we have investigated electron impact ionization and ion-molecule reactions of 2-C4F8 using Fourier transform mass spectrometry (FTMS), and compared the results with those of c-C4F8 we have studied previously. Electron impact ionization of 2-C4F8 produces 15 ionic species including C4F7,8^+, C3F3,5,6^+, C2F4^+ and CF1-3^+ as the major ions. The total ionization cross section of 2-C4F8 reaches a maximum of 1.8x10-15 cm^2 at 90 eV. The ionization is dominated by the channel forming the parent ion C4F8^+ from 12 to 18 eV, and by the channel forming C3F5^+ from 18 to 70 eV. After 70 eV, CF3^+ becomes the dominant product ion. Among the major ions generated from the electron impact ionization of 2-C4F8, only CF^+, CF2^+ and CF3^+ are found to react with 2-C4F8, via F^- abstraction or charge transfer mechanism. The charge transfer reaction of Ar^++2-C4F8 produces primarily C4F7^+.

Centrosymmetric [N(CH3)4]2TiF6 vs. noncentrosymmetric polar [C(NH2)3]2TiF6: A hydrogen-bonding effect on the out-of-center distortion of TiF6 octahedra

NASA Astrophysics Data System (ADS)

Kim, Eun-ah; Lee, Dong Woo; Ok, Kang Min

2012-11-01

The syntheses, structures, and characterization of organically templated zero-dimensional titanium fluoride materials, A2TiF6 (A[N(CH3)4] or [C(NH2)3]), are reported. Phase pure samples of A2TiF6 were synthesized by either solvothermal reaction method or a simple mixing method. While [N(CH3)4]2TiF6 crystallizes in a centrosymmetric space group, R-3, [C(NH2)3]2TiF6 crystallizes in a noncentrosymmetric polar space group, Cm. The asymmetric out-of-center distortion of TiF6 octahedra in polar [C(NH2)3]2TiF6 are attributable to the hydrogen-bonding interactions between the fluorine atoms in TiF6 octahedra and the nitrogen atoms in the [C(NH2)3]+ cation. Powder second-harmonic generation (SHG) measurements on the [C(NH2)3]2TiF6, using 1064 nm radiation, indicate the material has SHG efficiency of 25× that of α-SiO2, which indicates an average nonlinear optical susceptibility, exp of 2.8 pm/V. Additional SHG measurements reveal that the material is not phase-matchable (Type 1). The magnitudes of out-of-center distortions and dipole moment calculations for TiF6 octahedra will be also reported.

Adaptation of a haptic robot in a 3T fMRI.

PubMed

Snider, Joseph; Plank, Markus; May, Larry; Liu, Thomas T; Poizner, Howard

2011-10-04

Functional magnetic resonance imaging (fMRI) provides excellent functional brain imaging via the BOLD signal with advantages including non-ionizing radiation, millimeter spatial accuracy of anatomical and functional data, and nearly real-time analyses. Haptic robots provide precise measurement and control of position and force of a cursor in a reasonably confined space. Here we combine these two technologies to allow precision experiments involving motor control with haptic/tactile environment interaction such as reaching or grasping. The basic idea is to attach an 8 foot end effecter supported in the center to the robot allowing the subject to use the robot, but shielding it and keeping it out of the most extreme part of the magnetic field from the fMRI machine (Figure 1). The Phantom Premium 3.0, 6DoF, high-force robot (SensAble Technologies, Inc.) is an excellent choice for providing force-feedback in virtual reality experiments, but it is inherently non-MR safe, introduces significant noise to the sensitive fMRI equipment, and its electric motors may be affected by the fMRI's strongly varying magnetic field. We have constructed a table and shielding system that allows the robot to be safely introduced into the fMRI environment and limits both the degradation of the fMRI signal by the electrically noisy motors and the degradation of the electric motor performance by the strongly varying magnetic field of the fMRI. With the shield, the signal to noise ratio (SNR: mean signal/noise standard deviation) of the fMRI goes from a baseline of ~380 to ~330, and ~250 without the shielding. The remaining noise appears to be uncorrelated and does not add artifacts to the fMRI of a test sphere (Figure 2). The long, stiff handle allows placement of the robot out of range of the most strongly varying parts of the magnetic field so there is no significant effect of the fMRI on the robot. The effect of the handle on the robot's kinematics is minimal since it is lightweight (~2.6

CNT fibers p-doped with F4TCNQ (2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane)

NASA Astrophysics Data System (ADS)

Lepak, Sandra; Boncel, Sławomir; Jóźwik, Iwona; Jakubowska, Małgorzata; Koziol, Krzysztof; Łekawa-Raus, Agnieszka

2017-08-01

Films and fibers made of carbon nanotubes were found to be promising materials for future electrical and electronic engineering. Despite of many advantages provided by these materials, they are not without problems. The biggest issue is that the macroscopic CNT structures, such as films or fibers, have much lower electrical conductivity values than it is for individual carbon nanotubes. And therefore researchers worldwide try to increase electrical properties of those macroscopic structures. One of the approaches scientists are currently investigating is chemical doping. Despite chemical doping has been already reported there is still a huge list of compounds that are capable to increase the conductivity values and has not been tested yet. In this work one of such compounds has been examined. It is a strong p-dopant 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). The solution of F4TCNQ in three different solvents (chloroform, acetic acid and dimethylsulfoxide) has been prepared and applied on purified CNT films. Both electrical conductivity and specific conductivity was measured. The best electrical conductivity value achieved is 5,24·106 S·m-1. Samples were also observed under SEM.

Design of cemented tungsten carbide and boride-containing shields for a fusion power plant

NASA Astrophysics Data System (ADS)

Windsor, C. G.; Marshall, J. M.; Morgan, J. G.; Fair, J.; Smith, G. D. W.; Rajczyk-Wryk, A.; Tarragó, J. M.

2018-07-01

Results are reported on cemented tungsten carbide (cWC) and boride-containing composite materials for the task of shielding the centre column of a superconducting tokamak power plant. The shield is based on five concentric annular shells consisting of cWC and water layers of which the innermost cWC shield can be replaced with boride composites. Sample materials have been fabricated changing the parameters of porosity P, binder alloy fraction f binder and boron weight fraction f boron. For the fabricated materials, and other hypothetical samples with chosen parameters, Monte Carlo studies are made of: (i) the power deposition into the superconducting core, (ii) the fast neutron and gamma fluxes and (iii) the attenuation coefficients through the shield for the deposited power and neutron and gamma fluxes. It is shown that conventional Co-based cWC binder alloy can be replaced with a Fe–Cr alloy (92 wt.% Fe, 8 wt.% Cr), which has lower activation than cobalt with minor changes in shield performance. Boride-based composite materials have been prepared and shown to give a significant reduction in power deposition and flux, when placed close to the superconducting core. A typical shield of cemented tungsten carbide with 10 wt.% of Fe–8Cr binder and 0.1% porosity has a power reduction half-length of 0.06 m. It is shown that the power deposition increases by 4.3% for every 1% additional porosity, and 1.7% for every 1 wt.% additional binder. Power deposition decreased by 26% for an initial 1 wt.% boron addition, but further increases in f boron showed only a marginal decrease. The dependences of power deposited in the core, the maximum neutron and gamma fluxes on the core surface, and the half attenuation distances through the shield have been fitted to within a fractional percentage error by analytic functions of the porosity, metallic binder alloy and boron weight fractions.

NMR Spectra of Oriented Samples of Intercalated Fluorographite and 19F Chemical Shielding Anisotropy of the CIF 3 Molecule

NASA Astrophysics Data System (ADS)

Panich, A. M.

The analysis of 19F NMR spectra of polycrystalline and partially oriented samples of fluorinated graphite (C 2F) n intercalated with chlorine trifluoride has been carried out. Molecular mobility results in almost complete averaging of the dipole-dipole interactions of nuclei, while the essential chemical shielding anisotropy (CSA) is manifested. There is suggested molecular rotation about its C2 axes, which in turn rotates about the normal to the graphite plane. The CSA (σ || - σ ⊥) is determined to be 510 and -640 ppm, respectively, for the two inequivalent fluorine atoms of the molecule. The effect of the "antiparamagnetic" shielding leading to inversion of the chemical shielding tenser [(σ || - σ ⊥) < 0] for the equatorial F atom and anomalous line disposition in the NMR spectrum is discussed.

Added aluminum shielding to attenuate back scatter electrons from intra-oral lead shields.

PubMed

Weidlich, G A; Nuesch, C E; Fuery, J J

1996-01-01

An intra-oral lead shield was developed that consists of a lead base with an aluminum layer that is placed upstream of the lead base. Several such shields with various thicknesses of Al layers were manufactured and quantitatively evaluated in 6 MeV and 12 MeV electron radiation by Thermoluminescent dosimetry (TLD) measurements. The clinical relevance was established by using a 5 cm backscatter block down-stream of the lead shield to simulate anatomical structures of the head and a 0.5 cm superflab bolus upstream of the Al layers of the shield to simulate the patient's lip or cheek. The TLDs were placed between the Al layers of the shield and the superflab to determine the intra-oral skin dose. TLD exposure results revealed that 59.8% of the skin dose at 6 MeV and 45.1% of the skin dose at 12 MeV is due to backscattered electrons. Introduction of a 3.0 mm thick Al layer reduces the backscatter contribution to 13.5% of the back scatter dose at 6 MeV and 56.3% of the back scatter dose at 12 MeV electron radiation.

First-principles prediction of solar radiation shielding performance for transparent windows of GdB{sub 6}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Lihua, E-mail: xiaolihua@git.edu.cn; School of Materials Science and Engineering, Central South University, Changsha, Hunan 410083; Guizhou Special Functional Materials 2011 Collaborative Innovation Center, Guizhou Institute of Technology, Guiyang 550003

2016-04-28

The structural, electronic, magnetic, and optical properties of GdB{sub 6} are studied using the first-principles calculations. Calculated values for magnetic and optical properties and lattice constant are found to be consistent with previously reported experimental results. The calculated results show that GdB{sub 6} is a perfect near-infrared absorption/reflectance material that could serve as a solar radiation shielding material for windows with high visible light transmittance, similar to LaB{sub 6}, which is assigned to its plasma oscillation and a collective oscillation (volume plasmon) of carrier electrons. It was found that the magnetic 4f electrons of Gd are not relevant to themore » important optical properties of GdB{sub 6}. These theoretical studies serve as a reference for future studies.« less

Die Interhalogenkationen [Br2F5]+ und [Br3F8].

PubMed

Ivlev, Sergei; Karttunen, Antti; Buchner, Magnus; Conrad, Matthias; Kraus, Florian

2018-05-02

Wir berichten über die Synthese und Charakterisierung der bislang einzigen Polyhalogenkationen, in denen verbrückende Fluoratome vorliegen. Das [Br2F5]+-Kation enthält eine symmetrische [F2Br-µ-F-BrF2]-Brücke, das [Br3F8]+-Kation enthält unsymmetrische µ-F-Brücken. Die Fluoronium-Ionen wurden in Form ihrer [SbF6]--Salze erhalten und Raman-, und 19F-NMR-spektroskopisch, sowie durch Röntgenbeugung am Einkristall untersucht. Quantenchemische Rechnungen, sowohl für die isolierten Kationen in der Gasphase, als auch für die Festkörper selbst, wurden durchgeführt. Populationsanalysen zeigen, dass die µ-F-Atome die am stärksten negativ partialgeladenen Atome der Kationen sind. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Redetermination of Na(3)TaF(8).

PubMed

Langer, Vratislav; Smrcok, Lubomír; Boca, Miroslav

2010-09-01

The crystal structure of trisodium octafluoridotantalate, Na(3)TaF(8), has been redetermined using diffractometer data collected at 153 K, resulting in more accurate bond distances and angles than obtained from a previous structure determination based on film data. The structure is built from layers running along [101], which are formed by distorted [TaF(8)] antiprisms and [NaF(6)] rectangular bipyramids sharing edges and corners. The individual layers are separated by eight-coordinated Na ions. Two atoms in the asymmetric unit are in special positions: the Ta atom is on a twofold axis in Wyckoff position 4e and one of the Na ions lies on an inversion centre in Wyckoff site 4d.

Shielding Design for the South Pole nToF Diagnostic at the NIF

NASA Astrophysics Data System (ADS)

Khater, Hesham; Sitaraman, Shiva; Hall, James; Hatarik, Robert; Caggiano, Joseph; Waltz, Cory

2017-09-01

Neutron time of flight (nToF) detectors are fielded at the National Ignition Facility (NIF) to measure neutron yield, ion temperature, and downscattering in the cold fuel for D-T implosions. Anisotropically assembled cold fuel may generate different nToF data when measured by detectors located at the Target Chamber equator and poles. A collimated nToF line of sight has been fielded near the Target Chamber South Pole (SP) to examine any possible anisotropy in the cold fuel. The SP nToF detector is located in the lowest floor level of the NIF's Target Bay and at a distance of 18 m from the Target Chamber Center. The detector utilizes a solid bibenzyl scintillator and four photomultiplier tubes. The line of sight includes a port collimator that is attached to the Target Chamber and a bore hole collimator in the concrete floor above the detector. In addition, a beam line get lost hole is constructed in the Target Bay floor to minimize the backscattered radiation at the detector location. Initial measurements indicated the need for installation of additional shielding to eliminate gamma background during the period before arrival of the 14.1 MeV neutrons to the detector. A set of MCNP Monte Carlo simulations with the full Target Bay model were conducted to provide an estimate of the expected neutron and gamma backgrounds during D-T shots. A new shielding scheme is designed to reduce the gamma background by an order of magnitude.

Smart window coating based on F-TiO2-KxWO3 nanocomposites with heat shielding, ultraviolet isolating, hydrophilic and photocatalytic performance

PubMed Central

Liu, Tongyao; Liu, Bin; Wang, Jing; Yang, Linfen; Ma, Xinlong; Li, Hao; Zhang, Yihong; Yin, Shu; Sato, Tsugio; Sekino, Tohru; Wang, Yuhua

2016-01-01

A series of smart window coated multifunctional NIR shielding-photocatalytic films were fabricated successfully through KxWO3 and F-TiO2 in a low-cost and environmentally friendly process. Based on the synergistic effect of KxWO3 and F-TiO2, the optimal proportion of KxWO3 to F-TiO2 was investigated and the FT/2KWO nanocomposite film exhibited strong near-infrared, ultraviolet light shielding ability, good visible light transmittance, high photocatalytic activity and excellent hydrophilic capacity. This film exhibited better thermal insulation capacity than ITO and higher photocatalytic activity than P25. Meanwhile, the excellent stability of this film was examined by the cycle photocatalytic degradation and thermal insulation experiments. Overall, this work is expected to provide a possibility in integrating KxWO3 with F-TiO2, so as to obtain a multifunctional NIR shielding-photocatalytic nanocomposite film in helping solve the energy crisis and deteriorating environmental issues. PMID:27265778

C6, C7, and C8 perfluoroalkyl-substituted phosphinic acids.

PubMed

Singh, R P; Shreeve, J M

2000-04-17

Reaction of red phosphorus with RfI in a 1:2 molar ratio at 230 degrees C led to the formation of a mixture of (Rf)2PI and (Rf)PI2 (Rf = C6F13, C7F15, C8F17) in about a 70:30 ratio, respectively. These mixtures were separated by vacuum distillation. (Rf)2PI (Rf = C6F13, C7F15) are yellow liquids whereas (C8F17)2PI is a yellow solid. Oxidation of (Rf)2PI with excess NO2 led to (Rf)2P(O)OH (Rf = C6F13, C7F15, C8F17) in > 90% isolated yields after aqueous hydrolysis of the anhydride intermediates. These highly fluorinated phosphinic acids are white solids with sharp melting points and are highly soluble in methyl sulfoxide (DMSO) and 1,1,2-trichlorotrifluoroethane. However, solubility in chloroform and methylene dichloride is low. These perfluoroalkylphosphinic acids were characterized by IR, NMR (1H, 19F, and 31P), and mass spectra and elemental analysis.

Characterization of a genetically engineered mouse model of hemophilia A with complete deletion of the F8 gene.

PubMed

Chao, B N; Baldwin, W H; Healey, J F; Parker, E T; Shafer-Weaver, K; Cox, C; Jiang, P; Kanellopoulou, C; Lollar, P; Meeks, S L; Lenardo, M J

2016-02-01

ESSENTIALS: Anti-factor VIII (FVIII) inhibitory antibody formation is a severe complication in hemophilia A therapy. We genetically engineered and characterized a mouse model with complete deletion of the F8 coding region. F8(TKO) mice exhibit severe hemophilia, express no detectable F8 mRNA, and produce FVIII inhibitors. The defined background and lack of FVIII in F8(TKO) mice will aid in studying FVIII inhibitor formation. The most important complication in hemophilia A treatment is the development of inhibitory anti-Factor VIII (FVIII) antibodies in patients after FVIII therapy. Patients with severe hemophilia who express no endogenous FVIII (i.e. cross-reacting material, CRM) have the greatest incidence of inhibitor formation. However, current mouse models of severe hemophilia A produce low levels of truncated FVIII. The lack of a corresponding mouse model hampers the study of inhibitor formation in the complete absence of FVIII protein. We aimed to generate and characterize a novel mouse model of severe hemophilia A (designated the F8(TKO) strain) lacking the complete coding sequence of F8 and any FVIII CRM. Mice were created on a C57BL/6 background using Cre-Lox recombination and characterized using in vivo bleeding assays, measurement of FVIII activity by coagulation and chromogenic assays, and anti-FVIII antibody production using ELISA. All F8 exonic coding regions were deleted from the genome and no F8 mRNA was detected in F8(TKO) mice. The bleeding phenotype of F8(TKO) mice was comparable to E16 mice by measurements of factor activity and tail snip assay. Similar levels of anti-FVIII antibody titers after recombinant FVIII injections were observed between F8(TKO) and E16 mice. We describe a new C57BL/6 mouse model for severe hemophilia A patients lacking CRM. These mice can be directly bred to the many C57BL/6 strains of genetically engineered mice, which is valuable for studying the impact of a wide variety of genes on FVIII inhibitor formation on a

K(3)TaF(8) from laboratory X-ray powder data.

PubMed

Smrcok, Lubomír; Cerný, Radovan; Boca, Miroslav; Macková, Iveta; Kubíková, Blanka

2010-02-01

The crystal structure of tripotassium octafluoridotantalate, K(3)TaF(8), determined from laboratory powder diffraction data by the simulated annealing method and refined by total energy minimization in the solid state, is built from discrete potassium cations, fluoride anions and monocapped trigonal-prismatic [TaF(7)](2-) ions. All six atoms in the asymmetric unit are in special positions of the P6(3)mc space group: the Ta and one F atom in the 2b (3m) sites, the K and two F atoms in the 6c (m) sites, and one F atom in the 2a (3m) site. The structure consists of face-sharing K(6) octahedra with a fluoride anion at the center of each octahedron, forming chains of composition [FK(3)](2+) running along [001] with isolated [TaF(7)](2-) trigonal prisms in between. The structure of the title compound is different from the reported structure of Na(3)TaF(8) and represents a new structure type.

SU-F-T-82: Dosimetric Evaluation of a Shield Used for Hemi-Body Skin Electron Irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rivers, C; Singh, A; AlDahlawi, I

Purpose: We had several mycosis fungoides patients with a limited disease to about half of the skin surface. A custom-made plywood shield was used to protect the non-targeted skin region with our total skin electron irradiation (TSEI) technique. We report a dosimetric evaluation for our “hemi-body” skin electron irradiation technique. Methods: The technique is similar to our clinical total skin electron irradiation (TSEI), performed with a six-pair dual field (Stanford technique) at an extended source-to-skin distance (SSD) of 377 cm, with the addition of a plywood shield placed 50 cm from the patient. The shield is made of three layersmore » of standard 5/8″ thick plywood (total thickness of 4.75 cm) that are clamped securely on an adjustable-height stand. Gafchromic EBT3 films were used in assessing the shield’s transmission factor and the extend of the dose penumbra region. To verify the dose delivered for hemi-body skin radiation in a real patient treatment, in-vivo dosimetry using Gafchromic EBT3 films were performed. Film pieces were taped on the patient skin to measure the dose received during the first two fractions, placed on the forehead and upper body (shielded region); and also at the level of pelvic area, left thigh, and left ankle. Results: The shield transmission factor was found to be 10%, and the width of the penumbra (80-to-20% dose fall-off) was about 12 cm. In-vivo dosimetry of a real case confirmed the expected shielded area dose. Conclusion: Hemi-Body skin electron irradiation at an extended SSD is feasible with the addition of a plywood shield at a distance from patient skin. The penumbra dose region and the shield’s transmission factor should be evaluated prior to clinical use. We have treated several hemi-body skin patients with our custom-made plywood shield, the current patient measurements are representative of these for other patients as well.« less

Control of Cr6+ emissions from gas metal arc welding using a silica precursor as a shielding gas additive.

PubMed

Topham, Nathan; Wang, Jun; Kalivoda, Mark; Huang, Joyce; Yu, Kuei-Min; Hsu, Yu-Mei; Wu, Chang-Yu; Oh, Sewon; Cho, Kuk; Paulson, Kathleen

2012-03-01

Hexavalent chromium (Cr(6+)) emitted from welding poses serious health risks to workers exposed to welding fumes. In this study, tetramethylsilane (TMS) was added to shielding gas to control hazardous air pollutants produced during stainless steel welding. The silica precursor acted as an oxidation inhibitor when it decomposed in the high-temperature welding arc, limiting Cr(6+) formation. Additionally, a film of amorphous SiO(2) was deposited on fume particles to insulate them from oxidation. Experiments were conducted following the American Welding Society (AWS) method for fume generation and sampling in an AWS fume hood. The results showed that total shielding gas flow rate impacted the effectiveness of the TMS process. Increasing shielding gas flow rate led to increased reductions in Cr(6+) concentration when TMS was used. When 4.2% of a 30-lpm shielding gas flow was used as TMS carrier gas, Cr(6+) concentration in gas metal arc welding (GMAW) fumes was reduced to below the 2006 Occupational Safety and Health Administration standard (5 μg m(-3)) and the efficiency was >90%. The process also increased fume particle size from a mode size of 20 nm under baseline conditions to 180-300 nm when TMS was added in all shielding gas flow rates tested. SiO(2) particles formed in the process scavenged nanosized fume particles through intercoagulation. Transmission electron microscopy imagery provided visual evidence of an amorphous film of SiO(2) on some fume particles along with the presence of amorphous SiO(2) agglomerates. These results demonstrate the ability of vapor phase silica precursors to increase welding fume particle size and minimize chromium oxidation, thereby preventing the formation of hexavalent chromium.

Molecular orbital analysis of the inverse halogen dependence of nuclear magnetic shielding in LaX₃, X = F, Cl, Br, I.

PubMed

Moncho, Salvador; Autschbach, Jochen

2010-12-01

The NMR nuclear shielding tensors for the series LaX(3), with X = F, Cl, Br and I, have been computed using two-component relativistic density functional theory based on the zeroth-order regular approximation (ZORA). A detailed analysis of the inverse halogen dependence (IHD) of the La shielding was performed via decomposition of the shielding tensor elements into contributions from localized and delocalized molecular orbitals. Both spin-orbit and paramagnetic shielding terms are important, with the paramagnetic terms being dominant. Major contributions to the IHD can be attributed to the La-X bonding orbitals, as well as to trends associated with the La core and halogen lone pair orbitals, the latter being related to X-La π donation. An 'orbital rotation' model for the in-plane π acceptor f orbital of La helps to rationalize the significant magnitude of deshielding associated with the in-plane π donation. The IHD goes along with a large increase in the shielding tensor anisotropy as X becomes heavier, which can be associated with trends for the covalency of the La-X bonds, with a particularly effective transfer of spin-orbit coupling induced spin density from iodine to La in LaI(3). Copyright © 2010 John Wiley & Sons, Ltd.

The nematode homologue of Mediator complex subunit 28, F28F8.5, is a critical regulator of C. elegans development.

PubMed

Kostrouchová, Markéta; Kostrouch, David; Chughtai, Ahmed A; Kaššák, Filip; Novotný, Jan P; Kostrouchová, Veronika; Benda, Aleš; Krause, Michael W; Saudek, Vladimír; Kostrouchová, Marta; Kostrouch, Zdeněk

2017-01-01

The evolutionarily conserved Mediator complex is a critical player in regulating transcription. Comprised of approximately two dozen proteins, the Mediator integrates diverse regulatory signals through direct protein-protein interactions that, in turn, modulate the influence of Mediator on RNA Polymerase II activity. One Mediator subunit, MED28, is known to interact with cytoplasmic structural proteins, providing a potential direct link between cytoplasmic dynamics and the control of gene transcription. Although identified in many animals and plants, MED28 is not present in yeast; no bona fide MED28 has been described previously in Caenorhabditis elegans. Here, we identify bioinformatically F28F8.5, an uncharacterized predicted protein, as the nematode homologue of MED28. As in other Metazoa, F28F8.5 has dual nuclear and cytoplasmic localization and plays critical roles in the regulation of development. F28F8.5 is a vital gene and its null mutants have severely malformed gonads and do not reproduce. F28F8.5 interacts on the protein level with the Mediator subunits MDT-6 and MDT-30. Our results indicate that F28F8.5 is an orthologue of MED28 and suggest that the potential to link cytoplasmic and nuclear events is conserved between MED28 vertebrate and nematode orthologues.

Rate coefficients for the reaction of O(1D) with the atmospherically long-lived greenhouse gases NF3, SF3CF3, CHF3, C2F6, c-C3F8, n-C5F12, and n-C6F14

NASA Astrophysics Data System (ADS)

Baasandorj, M.; Hall, B. D.; Burkholder, J. B.

2012-09-01

The contribution of atmospherically persistent (long-lived) greenhouse gases to the radiative forcing of Earth has increased over the past several decades. The impact of highly fluorinated saturated compounds, in particular perfluorinated compounds, on climate change is a concern because of their long atmospheric lifetimes, which are primarily determined by stratospheric loss processes, as well as their strong absorption in the infrared "window" region. A potentially key stratospheric loss process for these compounds is their gas-phase reaction with electronically excited oxygen atoms, O(1D). Therefore, accurate reaction rate coefficient data is desired for input to climate change models. In this work, rate coefficients, k, were measured for the reaction of O(1D) with several key long-lived greenhouse gases, namely NF3, SF5CF3, CHF3 (HFC-23), C2F6, c-C4F8, n-C5F12, and n-C6F14. Room temperature rate coefficients for the total reaction, kTot, corresponding to loss of O(1D), and reactive channel, kR, corresponding to the loss of the reactant compound, were measured for NF3 and SF5CF3 using competitive reaction and relative rate methods, respectively. kR was measured for the CHF3 reaction and improved upper-limits were determined for the perfluorinated compounds included in this study. For NF3, kTot was determined to be (2.55 ± 0.38) × 10-11 cm3 molecule-1 s-1 and kR, which was measured using CF3Cl, N2O, CF2ClCF2Cl (CFC-114), and CF3CFCl2 (CFC-114a) as reference compounds, was determined to be (2.21 ± 0.33) × 10-11 cm3 molecule-1 s-1 corresponding to a reactive branching ratio of 0.87 ± 0.13. For SF5CF3, kTot = (3.24 ± 0.50) × 10-13 cm3 molecule-1 s-1 and kR < 5.8 × 10-14 cm3 molecule-1 s-1 were measured, where kR is a factor of three lower than the current recommendation of kTot for use in atmospheric modeling. For CHF3, kR was determined to be (2.35 ± 0.35) × 10-12 cm3 molecule-1 s-1, which corresponds to a reactive channel yield of 0.26 ± 0.04, and

SU-C-16A-04: Dosimetric Validation of a Partially-Shielded Gd-153 Brachytherapy Concept

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, X; Adams, Q; Flynn, R

Purpose: To demonstrate by measurement that using partially shielded Gd-153 sources for rotating-shield brachytherapy (RSBT) is feasible. RSBT is a potentially superior alternative to conventional high-dose-rate brachytherapy and provides the opportunity to dramatically improve tumor dose conformity for the treatment of, for example, prostate cancer. Methods: A custom-built, stainless steel encapsulated 150 mCi Gd-153 capsule with an outer length of 12.8 mm, outer diameter of 2.10 mm, active length of 9.98 mm, and active diameter of 1.53 mm was used. A partially shielded catheter was constructed with a 500 μm platinum shield and a 500 μm aluminum emission window, bothmore » with 180° azimuthal coverage. An acrylic phantom was constructed to measure the dose distributions from the shielded catheter in the transverse plane using Gafchromic EBT3 films. Film calibration curves were generated from 50, 70, and 100 kVp x-ray beams with NIST-traceable air kerma values to account for energy variation. Results: The transmission ratios of platinum to aluminum shielding at 1 cm off-axis are 7.5% and 7.6% for Monte Carlo (MCNP5) predicted and experimental results, respectively. The predicted/measured relative dose rates at 1 cm, 2 cm and 3 cm off-axis through the Al window were 100%/92.9%, 28.6%/27.0% and 13.8%/12.7%, respectively. Through the Pt shield, the predicted/measured relative dose rates were 7.5%/7.1%, 3.8%/3.0% and 2.4%/1.7%, respectively. Conclusion: Using partially-shielded Gd-153 sources for RSBT is a promising approach to improving brachytherapy dose distributions. The next step in making Gd-153 based RSBT a reality is developing a Gd-153 source that is small enough such that the source, shield, and catheter all fit within a 16 gauge needle, which has a 1.65 mm diameter. University of Iowa Research Foundation.« less

Sulfur hexafluoride (SF6) versus perfluoropropane (C3F8) tamponade and short term face-down position for macular hole repair: a randomized prospective study.

PubMed

Casini, Giamberto; Loiudice, Pasquale; De Cillà, Stefano; Radice, Paolo; Nardi, Marco

2016-01-01

To compare early visual and anatomical outcomes after either sulfur hexafluoride (SF 6 ) or perfluoropropane (C 3 F 8 ) tamponade for macular hole repair. 147 eyes affected by primary full-thickness macular hole underwent pars plana vitrectomy with dye assisted removal of the internal limiting membrane and gas tamponade. Prone position was prescribed for 48 h after surgery. All patients were divided into 3 groups depending on the size of the hole: small (<250 µm), medium (>250-<400 µm) or large (>400 µm). Eyes within the same group randomly received either SF 6 (70 eyes) or C 3 F 8 (77 eyes). A complete ophthalmic evaluation, including best corrected visual acuity and anatomic status of the macular holes, was conducted preoperatively, at 1 week and 1 month after surgery. Macular hole volume was calculated using optical coherence tomography scans. The Wilcoxon Signed Ranks Test, the Mann-Whitney Test, the Spearman's rank-order correlation coefficient and the study of variance for repeated measures were used for statistical analysis. Mean best-corrected visual acuity improved from 0.92 logMAR to 0.28 logMAR (P < 0.001). A reduction of the dimensions of macular holes was observed in all cases, with a total repair of 90 % (63/70 eyes) in the SF 6 group and 91 % in the C 3 F 8 group (70/77 eyes). There was a negative correlation between the initial minor diameter, the volume of the hole and the rate of anatomic success. Short-term anatomical and visual outcomes were similar in eyes treated with either SF 6 or C 3 F 8 , independently of the stage of the macular hole. The initial volume and the minor diameter of the hole may be considered as valid tools for predicting surgical success. Age and gender did not appear to have influenced the prognosis.

The nematode homologue of Mediator complex subunit 28, F28F8.5, is a critical regulator of C. elegans development

PubMed Central

Kostrouchová, Markéta; Kostrouch, David; Kaššák, Filip; Kostrouchová, Veronika; Benda, Aleš; Krause, Michael W.; Saudek, Vladimír; Kostrouchová, Marta

2017-01-01

The evolutionarily conserved Mediator complex is a critical player in regulating transcription. Comprised of approximately two dozen proteins, the Mediator integrates diverse regulatory signals through direct protein-protein interactions that, in turn, modulate the influence of Mediator on RNA Polymerase II activity. One Mediator subunit, MED28, is known to interact with cytoplasmic structural proteins, providing a potential direct link between cytoplasmic dynamics and the control of gene transcription. Although identified in many animals and plants, MED28 is not present in yeast; no bona fide MED28 has been described previously in Caenorhabditis elegans. Here, we identify bioinformatically F28F8.5, an uncharacterized predicted protein, as the nematode homologue of MED28. As in other Metazoa, F28F8.5 has dual nuclear and cytoplasmic localization and plays critical roles in the regulation of development. F28F8.5 is a vital gene and its null mutants have severely malformed gonads and do not reproduce. F28F8.5 interacts on the protein level with the Mediator subunits MDT-6 and MDT-30. Our results indicate that F28F8.5 is an orthologue of MED28 and suggest that the potential to link cytoplasmic and nuclear events is conserved between MED28 vertebrate and nematode orthologues. PMID:28603670

SU-F-I-71: Fetal Protection During Fluoroscopy: To Shield Or Not to Shield?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joshi, S; Vanderhoek, M

Purpose: Lead aprons are routinely used to shield the fetus from radiation during fluoroscopically guided interventions (FGI) involving pregnant patients. When placed in the primary beam, lead aprons often reduce image quality and increase fluoroscopic radiation output, which can adversely affect fetal dose. The purpose of this work is to identify an effective and practical method to reduce fetal dose without affecting image quality. Methods: A pregnant patient equivalent abdominal phantom is set on the table along with an image quality test object (CIRS model 903) representing patient anatomy of interest. An ion chamber is positioned at the x-ray beammore » entrance to the phantom, which is used to estimate the relative fetal dose. For three protective methods, image quality and fetal dose measurements are compared to baseline (no protection):1. Lead apron shielding the entire abdomen; 2. Lead apron shielding part of the abdomen, including the fetus; 3. Narrow collimation such that fetus is excluded from the primary beam. Results: With lead shielding the entire abdomen, the dose is reduced by 80% relative to baseline along with a drastic deterioration of image quality. With lead shielding only the fetus, the dose is reduced by 65% along with complete preservation of image quality, since the image quality test object is not shielded. However, narrow collimation results in 90% dose reduction and a slight improvement of image quality relative to baseline. Conclusion: The use of narrow collimation to protect the fetus during FGI is a simple and highly effective method that simultaneously reduces fetal dose and maintains sufficient image quality. Lead aprons are not as effective at fetal dose reduction, and if placed improperly, they can severely degrade image quality. Future work aims to investigate a wider variety of fluoroscopy systems to confirm these results across many different system geometries.« less

Biotransformation of ginsenosides F4 and Rg6 in zebrafish.

PubMed

Shen, Wen-Wen; Zhang, Hai-Xia; Qiu, Shou-Bei; Wei, Ying-Jie; Zhu, Fen-Xia; Wang, Jing; Wang, Dan-Dan; Jia, Xiao-Bin; Tang, Dao-Quan; Chen, Bin

2017-03-28

Ginsenosides F 4 and Rg 6 (GF 4 and GRg 6 ), two main active components of steamed notoginseng or red ginseng, are dehydrated disaccharide saponins. In this work, biotransformation of ginsenosides F 4 and Rg 6 in zebrafish was investigated by qualitatively identifying their metabolites and then proposing their possible metabolic pathways. The prediction of possible metabolism of ginsenosides F 4 and Rg 6 using zebrafish model which can effectively simulate existing mammals model was early and quickly performed. Metabolites of ginsenosides F 4 and Rg 6 after exposing to zebrafish for 24 h were identified by Ultraperformance Liquid Chromatography/Quadrupole-Time-of-Flight Mass Spectrometry. A total of 8 and 6 metabolites of ginsenosides F 4 and Rg 6 were identified in zebrafish, respectively. Of these, 7 and 5, including M1, M3-M5, M7-M9 and N1 (N5), N2, N4 (N9), N7-N8 were reported for the first time as far as we know. The mechanisms of their biotransformation involved were further deduced to be desugarization, glucuronidation, sulfation, dehydroxylation, loss of C-17 and/or C-23 residue pathways. It was concluded that loss of rhamnose at position C-6 and glucuronidation at position C-3 in zebrafish were considered as the main physiologic and metabolic processes of ginsenosides F 4 and ginsenosides Rg 6 , respectively.

F-8 DFBW on-board electronics

NASA Technical Reports Server (NTRS)

1971-01-01

. The DFBW research program is considered one of the most significant and most successful NASA aeronautical programs since the inception of the agency. F-8 aircraft were built originally for the U.S. Navy by LTV Aerospace of Dallas, Texas. The aircraft had a wingspan of 35 feet, 2 inches; was 54 feet, 6 inches long; and was powered by a Pratt & Whitney J57 turbojet engine.

Experimental Evaluation of the Thermal Performance of a Water Shield for a Surface Power Reactor

NASA Technical Reports Server (NTRS)

Pearson, J. Boise; Stewart, Eric T.; Reid, Robert S.

2007-01-01

A water based shielding system is being investigated for use on initial lunar surface power systems. The use of water may lower overall cost (as compared to development cost for other materials) and simplify operations in the setup and handling. The thermal hydraulic performance of the shield is of significant interest. The mechanism for transferring heat through the shield is natural convection. Natural convection in a representative lunar surface reactor shield design is evaluated at various power levels in the Water Shield Testbed (WST) at the NASA Marshall Space Flight Center. The experimental data from the WST is used to anchor a CFD model. Performance of a water shield on the lunar surface is then predicted by CFD models anchored to test data. The accompanying viewgraph presentation includes the following topics: 1) Testbed Configuration; 2) Core Heater Placement and Instrumentation; 3) Thermocouple Placement; 4) Core Thermocouple Placement; 5) Outer Tank Thermocouple Placement; 6) Integrated Testbed; 7) Methodology; 8) Experimental Results: Core Temperatures; 9) Experimental Results; Outer Tank Temperatures; 10) CFD Modeling; 11) CFD Model: Anchored to Experimental Results (1-g); 12) CFD MOdel: Prediction for 1/6-g; and 13) CFD Model: Comparison of 1-g to 1/6-g.

Rate coefficients for the reaction of O(1D) with the atmospherically long-lived greenhouse gases NF3, SF5CF3, CHF3, C2F6, c-C4F8, n-C5F12, and n-C6F14

NASA Astrophysics Data System (ADS)

Baasandorj, M.; Hall, B. D.; Burkholder, J. B.

2012-12-01

The contribution of atmospherically persistent (long-lived) greenhouse gases to the radiative forcing of Earth has increased over the past several decades. The impact of highly fluorinated, saturated compounds, in particular perfluorinated compounds, on climate change is a concern because of their long atmospheric lifetimes, which are primarily determined by stratospheric loss processes, as well as their strong absorption in the infrared "window" region. A potentially key stratospheric loss process for these compounds is their gas-phase reaction with electronically excited oxygen atoms, O(1D). Therefore, accurate reaction rate coefficient data is desired for input to climate change models. In this work, rate coefficients, k, were measured for the reaction of O(1D) with several key long-lived greenhouse gases, namely NF3, SF5CF3, CHF3 (HFC-23), C2F6, c-C4F8, n-C5F12, and n-C6F14. Room temperature rate coefficients for the total reaction, kTot, corresponding to loss of O(1D), and reactive channel, kR, corresponding to the loss of the reactant compound, were measured for NF3 and SF5CF3 using competitive reaction and relative rate methods, respectively. kR was measured for the CHF3 reaction and improved upper-limits were determined for the perfluorinated compounds included in this study. For NF3, kTot was determined to be (2.55 ± 0.38) × 10-11 cm3 molecule-1 s-1 and kR, which was measured using CF3Cl, N2O, CF2ClCF2Cl (CFC-114), and CF3CFCl2 (CFC-114a) as reference compounds, was determined to be (2.21 ± 0.33) × 10-11 cm3 molecule-1 s-1. For SF5CF3, kTot = (3.24 ± 0.50) × 10-13 cm3 molecule-1 s-1 and kR < 5.8 × 10×14 cm3 molecule-1 s-1 were measured, where kR is a factor of three lower than the current recommendation of kTot for use in atmospheric modeling. For CHF3 kR was determined to be (2.35 ± 0.35) × 10-12 cm3 molecule-1 s-1, which corresponds to a reactive channel yield of 0.26 ± 0.04, and resolves a large discrepancy among previously reported values

Measurements of occupational exposure for a technologist performing 18F FDG PET scans.

PubMed

Biran, Talma; Weininger, Jolie; Malchi, Shalom; Marciano, Rami; Chisin, Roland

2004-11-01

Radiation doses to one PET technologist performing 100 18F FDG (18F fluorodeoxyglucose) imaging procedures were measured in a clinical setting using two types of thermoluminescent dosimeter (TLD) badges, one finger-ring TLD and one electronic pocket dosimeter (EPD). 18F FDG was handled either with unshielded or with viewing window tungsten shielded syringes. The resulting doses using unshielded syringes were 13.8 +/- 0.8 microSv/370 MBq and 14.3 +/- 0.4 microSv/370 MBq, measured with TLD 100 and with TLD 700H/600H, respectively. For the same series of measurements, the doses obtained using shielded syringes were 10.7 +/- 0.4 microSv/370 MBq and 7.2 +/- 2.1 microSv/370 MBq with TLD700H/600H and with EPD, respectively. The dose to the right hand from shielded syringes was 69.3 +/- 5.5 microSv/370 MBq. All these values are within the ICRP recommended dose limits. Extrapolated to 725 examinations per year, the resulting effective dose measured with TLD would be 10 mSv with unshielded and 7.5 mSv with shielded syringes, respectively (25% dose reduction). The doses measured by TLD were consistently higher than those measured by EPD, suggesting that EPD measurements might underestimate occupational doses.

F-8 DFBW in flight

NASA Image and Video Library

1972-10-07

F-8 Digital Fly-By-Wire aircraft in flight. The computer-controlled flight systems pioneered by the F-8 DFBW created a revolution in aircraft design. The F-117A, X-29, X-31, and many other aircraft have relied on computers to make them flyable. Built with inherent instabilities to make them more maneuverable, they would be impossible for human pilots to fly if the computers failed or received incorrect data.

A comparison study of different RF shields for an 8-element transceive small animal array at 9.4T.

PubMed

Jin, Jin; Li, Yu; Liu, Feng; Weber, Ewald; Crozier, Stuart

2011-01-01

In this study, three types of radio-frequency shields are studied and compared in the context of ultra-high field small-animal magnetic resonance imaging. It has been demonstrated that the coil penetration depth and mutual coupling between the coils depend heavily on the type of shield employed. The results were used to guide the design of a 9.4T 8-element transceive small animal array, which provides high overall coil penetration.

F-8 Iron Bird Cockpit

NASA Technical Reports Server (NTRS)

1975-01-01

The F-8 DFBW (Digital-Fly-By-Wire) simulator used an 'Iron-Bird' for its cockpit. It was used from 1971 to 1986. The F-8 DFBW simulator was used in the development, testing, and validation of an all digital flight-control system installed in the F-8 aircraft that replaced the normal mechanical/hydraulic controls. Many military and commercial aircraft have digital flight control systems based on the technologies developed at NASA Dryden.

A New Microwave Shield Preparation for Super High Frequency Range: Occupational Approach to Radiation Protection.

PubMed

Zaroushani, Vida; Khavanin, Ali; Jonidi Jafari, Ahmad; Mortazavi, Seyed Bagher

2016-01-01

Widespread use of X-band frequency (a part of the super high frequency microwave) in the various workplaces would contribute to occupational exposure with potential of adverse health effects.  According to limited study on microwave shielding for the workplace, this study tried to prepare a new microwave shielding for this purpose. We used EI-403 epoxy thermosetting resin as a matrix and nickel oxide nanoparticle with the diameter of 15-35 nm as filler. The Epoxy/ Nickel oxide composites with 5, 7, 9 and 11 wt% were made in three different thicknesses (2, 4 and 6 mm). According to transmission / reflection method, shielding effectiveness (SE) in the X-band frequency range (8-12.5 GHz) was measured by scattering parameters directly given by the 2-port Vector Network Analyzer. The fabricated composites characterized by X-ray Diffraction and Field Emission Scanning Electron Microscope. The best average of shielding effectiveness in each thickness of fabricated composites obtained by 11%-2 mm, 7%-4 mm and 7%-6 mm composites with SE values of 46.80%, 66.72% and 64.52%, respectively. In addition, the 11%-6 mm, 5%-6 mm and 11%-4 mm-fabricated composites were able to attenuate extremely the incident microwave energy at 8.01, 8.51 and 8.53 GHz by SE of 84.14%, 83.57 and 81.30%, respectively. The 7%-4mm composite could be introduced as a suitable alternative microwave shield in radiation protection topics in order to its proper SE and other preferable properties such as low cost and weight, resistance to corrosion etc. It is necessary to develop and investigate the efficacy of the fabricated composites in the fields by future studies.

SU-F-P-53: RadShield: Semi-Automated Shielding Design for CT Using NCRP 147 and Isodose Curves

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeLorenzo, M; Rutel, I; Wu, D

Purpose: Computed tomography (CT) exam rooms are shielded more quickly and accurately compared to manual calculations using RadShield, a semi-automated diagnostic shielding software package. Last year, we presented RadShield’s approach to shielding radiographic and fluoroscopic rooms calculating air kerma rate and barrier thickness at many points on the floor plan and reporting the maximum values for each barrier. RadShield has now been expanded to include CT shielding design using not only NCRP 147 methodology but also by overlaying vendor provided isodose curves onto the floor plan. Methods: The floor plan image is imported onto the RadShield workspace to serve asmore » a template for drawing barriers, occupied regions and CT locations. SubGUIs are used to set design goals, occupancy factors, workload, and overlay isodose curve files. CTDI and DLP methods are solved following NCRP 147. RadShield’s isodose curve method employs radial scanning to extract data point sets to fit kerma to a generalized power law equation of the form K(r) = ar^b. RadShield’s semi-automated shielding recommendations were compared against a board certified medical physicist’s design using dose length product (DLP) and isodose curves. Results: The percentage error found between the physicist’s manual calculation and RadShield’s semi-automated calculation of lead barrier thickness was 3.42% and 21.17% for the DLP and isodose curve methods, respectively. The medical physicist’s selection of calculation points for recommending lead thickness was roughly the same as those found by RadShield for the DLP method but differed greatly using the isodose method. Conclusion: RadShield improves accuracy in calculating air-kerma rate and barrier thickness over manual calculations using isodose curves. Isodose curves were less intuitive and more prone to error for the physicist than inverse square methods. RadShield can now perform shielding design calculations for general scattering

Partial discharges and breakdown in C3F8

NASA Astrophysics Data System (ADS)

Koch, M.; Franck, C. M.

2014-10-01

Traditional search processes of gases or gas mixtures for replacing SF6 involve time consuming measurements of partial discharges and breakdown behaviour for several voltage waveforms and different field configurations. Recently a model for prediction of this behaviour for SF6 was described in literature. The model only requires basic properties of the gas such as the critical field strength and the effective ionization coefficient, which can be obtained by swarm parameter measurements, and thermodynamic properties, which can be calculated. In this paper, we show for the well-known and electronegative gas octafluoropropane (C3F8) that it is possible to transfer the model developed for SF6 to this gas to describe the breakdown behaviour of C3F8. Thus the model can be beneficial in the screening process of new insulation gases.

E2F8 as a Novel Therapeutic Target for Lung Cancer

PubMed Central

Park, Sin-Aye; Platt, James; Lee, Jong Woo; López-Giráldez, Francesc; Herbst, Roy S.

2015-01-01

Background: The E2F members have been divided into transcription activators (E2F1-E2F3) and repressors (E2F4-E2F8). E2F8 with E2F7 has been known to play an important physiologic role in embryonic development and cell cycle regulation by repressing E2F1. However, the function of E2F8 in cancer cells is unknown. Methods: E2F8 expression was assessed by immunoblotting or immunofluorescence staining in human lung cancer (LC) cells and tissues from LC patients (n = 45). Cell proliferation, colony formation, and invasion analysis were performed to evaluate the role of E2F8 in LC. Microarray analysis was used to determine the target genes of E2F8. The regulation of E2F8 on the expression of ubiquitin-like PHD and RING domain-containing 1 (UHRF1), one of E2F8 target genes, was determined using chromatin immunoprecipitation and promoter activity assays. Human LC xenograft models were used to determine the effects of inhibiting E2F8 by siRNAs (n = 7 per group) or antisense morpholino (n = 8 per group) on tumor growth. Survival was analyzed using the Kaplan-Meier method and group differences by the Student’s t test. All statistical tests were two-sided. Results: LC tumors overexpressed E2F8 compared with normal lung tissues. Depletion of E2F8 inhibited cell proliferation and tumor growth. E2F8 knockdown statistically significantly reduced the expression of UHRF1 (~60%-70%, P < .001), and the direct binding of E2F8 on the promoter of UHRF1 was identified. Kaplan-Meier analysis with a public database showed prognostic significance of aberrant E2F8 expression in LC (HR = 1.91 95% CI = 1.21 to 3.01 in chemo-naïve patients, P = .0047). Conclusions: We demonstrated that E2F8 is overexpressed in LC and is required for the growth of LC cells. These findings implicate E2F8 as a novel therapeutic target for LC treatment. PMID:26089541

F8U-3 aircraft

NASA Image and Video Library

1959-09-10

Crusader on runway. Navy aircraft number 6340. L59-6101 caption: The Navy's Vought XF8U-3 Supersonic Fighter was an entirely new design as compared to the earlier F8U Crusader series. This jet plane lost in competition with the McDonnell F4H, however, and was never put into production. Langley used the XF8U-3 in some of the first flight measurements of sonic boom intensity. Photograph published in Engineer in Charge A History of the Langley Aeronautical Laboratory, 1917-1958 by James R. Hansen. Page 507. Caption: Chance Vought F8U-3 airplane used in sonic boom investigation at Wallops, June-August 1959. Photograph published in A New Dimension Wallops Island Flight Test Range: The First Fifteen Years by Joseph Shortal. A NASA publication. Page 672.

Radioactive by-products of a self-shielded cyclotron and the liquid target system for F-18 routine production.

PubMed

Kambali, I; Suryanto, H; Parwanto

2016-06-01

Routine production of F-18 radionuclide using proton beams accelerated in a cyclotron could potentially generate residual radioisotopes in the cyclotron vicinity which eventually become major safety concerns over radiation exposure to the workers. In this investigation, a typical 11-MeV proton, self-shielded cyclotron has been assessed for its residual radiation sources in the cyclotron's shielding, tank/chamber, cave wall as well as target system. Using a portable gamma ray spectroscopy system, the radiation measurement in the cyclotron environment has been carried out. Experimental results indicate that relatively long-lived radioisotopes such as Mn-54, Zn-65 and Eu-152 are detected in the inner and outer surface of the cyclotron shielding respectively while Mn-54 spectrum is observed around the cyclotron chamber. Weak intensity of Eu-152 radioisotope is again spotted in the inner and outer surface of the cyclotron cave wall. Angular distribution measurement of the Eu-152 shows that the intensity slightly drops with increasing observation angle relative to the proton beam incoming angle. In the target system, gamma rays from Co-56, Mn-52, Co-60, Mn-54, Ag-110 m are identified. TALYS-calculated nuclear cross-section data are used to study the origins of the radioactive by-products.

Zn3Sb4O6F6: Hydrothermal synthesis, crystal structure and nonlinear optical properties

NASA Astrophysics Data System (ADS)

Ali, Sk Imran; Zhang, Weiguo; Halasyamani, P. Shiv; Johnsson, Mats

2017-12-01

Zn3Sb4O6F6 has been synthesized hydrothermally at 230 °C. The crystal structure was determined from single crystal X-ray diffraction data. It crystallizes in the cubic non-centrosymmetric space group I-43m with the unit cell parameter a = 8.1291(4) Å and is isostructural with M3Sb4O6F6 (M = Co, Ni). The new compound is the first oxofluoride containing Zn2+ and a p-element cation with a stereochemically active lone pair. The crystal structure is made up by [ZnO2F4] octahedra forming a network via corner sharing at F-atoms and [SbO3] trigonal pyramids that form [Sb4O6] cages that connect via the O-atoms to the Zn-atoms. Powder second-harmonic generation (SHG) measurements using 1064 nm radiation on Zn3Sb4O6F6 indicate an SHG intensity of approximately 40 × α-SiO2.

Synthesis and preclinical characterization of 1-(6'-deoxy-6'-[18F]fluoro-β-d-allofuranosyl)-2-nitroimidazole (β-6'-[18F]FAZAL) as a positron emission tomography radiotracer to assess tumor hypoxia.

PubMed

Wanek, Thomas; Kreis, Katharina; Križková, Petra; Schweifer, Anna; Denk, Christoph; Stanek, Johann; Mairinger, Severin; Filip, Thomas; Sauberer, Michael; Edelhofer, Patricia; Traxl, Alexander; Muchitsch, Viktoria E; Mereiter, Kurt; Hammerschmidt, Friedrich; Cass, Carol E; Damaraju, Vijaya L; Langer, Oliver; Kuntner, Claudia

2016-11-01

Positron emission tomography (PET) using fluorine-18 ( 18 F)-labeled 2-nitroimidazole radiotracers has proven useful for assessment of tumor oxygenation. However, the passive diffusion-driven cellular uptake of currently available radiotracers results in slow kinetics and low tumor-to-background ratios. With the aim to develop a compound that is actively transported into cells, 1-(6'-deoxy-6'-[ 18 F]fluoro-β-d-allofuranosyl)-2-nitroimidazole (β-[ 18 F]1), a putative nucleoside transporter substrate, was synthetized by nucleophilic [ 18 F]fluoride substitution of an acetyl protected labeling precursor with a tosylate leaving group (β-6) in a final radiochemical yield of 12±8% (n=10, based on [ 18 F]fluoride starting activity) in a total synthesis time of 60min with a specific activity at end of synthesis of 218±58GBq/μmol (n=10). Both radiolabeling precursor β-6 and unlabeled reference compound β-1 were prepared in multistep syntheses starting from 1,2:5,6-di-O-isopropylidene-α-d-allofuranose. In vitro experiments demonstrated an interaction of β-1 with SLC29A1 and SLC28A1/2/3 nucleoside transporter as well as hypoxia specific retention of β-[ 18 F]1 in tumor cell lines. In biodistribution studies in healthy mice β-[ 18 F]1 showed homogenous tissue distribution and excellent metabolic stability, which was unaffected by tissue oxygenation. PET studies in tumor bearing mice showed tumor-to-muscle ratios of 2.13±0.22 (n=4) at 2h after administration of β-[ 18 F]1. In ex vivo autoradiography experiments β-[ 18 F]1 distribution closely matched staining with the hypoxia marker pimonidazole. In conclusion, β-[ 18 F]1 shows potential as PET hypoxia radiotracer which merits further investigation. Copyright © 2016 Elsevier Ltd. All rights reserved.

E2F8 as a Novel Therapeutic Target for Lung Cancer.

PubMed

Park, Sin-Aye; Platt, James; Lee, Jong Woo; López-Giráldez, Francesc; Herbst, Roy S; Koo, Ja Seok

2015-09-01

The E2F members have been divided into transcription activators (E2F1-E2F3) and repressors (E2F4-E2F8). E2F8 with E2F7 has been known to play an important physiologic role in embryonic development and cell cycle regulation by repressing E2F1. However, the function of E2F8 in cancer cells is unknown. E2F8 expression was assessed by immunoblotting or immunofluorescence staining in human lung cancer (LC) cells and tissues from LC patients (n = 45). Cell proliferation, colony formation, and invasion analysis were performed to evaluate the role of E2F8 in LC. Microarray analysis was used to determine the target genes of E2F8. The regulation of E2F8 on the expression of ubiquitin-like PHD and RING domain-containing 1 (UHRF1), one of E2F8 target genes, was determined using chromatin immunoprecipitation and promoter activity assays. Human LC xenograft models were used to determine the effects of inhibiting E2F8 by siRNAs (n = 7 per group) or antisense morpholino (n = 8 per group) on tumor growth. Survival was analyzed using the Kaplan-Meier method and group differences by the Student's t test. All statistical tests were two-sided. LC tumors overexpressed E2F8 compared with normal lung tissues. Depletion of E2F8 inhibited cell proliferation and tumor growth. E2F8 knockdown statistically significantly reduced the expression of UHRF1 (~60%-70%, P < .001), and the direct binding of E2F8 on the promoter of UHRF1 was identified. Kaplan-Meier analysis with a public database showed prognostic significance of aberrant E2F8 expression in LC (HR = 1.91 95% CI = 1.21 to 3.01 in chemo-naïve patients, P = .0047). We demonstrated that E2F8 is overexpressed in LC and is required for the growth of LC cells. These findings implicate E2F8 as a novel therapeutic target for LC treatment. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

F-8 SCW in flight

NASA Technical Reports Server (NTRS)

1973-01-01

A Vought F-8A Crusader was selected by NASA as the testbed aircraft (designated TF-8A) to install an experimental Supercritical Wing in place of the conventional wing. The unique design of the Supercritical Wing (SCW) reduces the effect of shock waves on the upper surface near Mach 1, which in turn reduces drag. In this photograph a Vought F-8A Crusader is shown being used as a flying testbed for an experimental Supercritical Wing airfoil. The smooth fairing of the fiberglass glove with the wing is illustrated in this view. This is the configuration of the F-8 SCW aircraft late in the program. The SCW team fitted the fuselage with bulges fore and aft of the wings. This was similar to the proposed shape of a near-sonic airliner. Both the SCW airfoil and the bulged-fuselage design were optimal for cruise at Mach 0.98. Dr. Whitcomb (designer of the SCW) had previously spent about four years working on supersonic transport designs. He concluded that these were impractical due to their high operating costs. The high drag at speeds above Mach 1 resulted in greatly increased costs. Following the fuel-price rises caused by the October 1973 oil embargo, airlines lost interest in near-sonic transports. Rather, they wanted a design that would have lower fuel consumption. Dr. Whitcomb developed a modified supercritical-wing shape that provided higher lift-to-drag ratios at the same speeds. He did this by using thicker airfoil sections and a reduced wing sweepback. This resulted in an increased aspect ratio without an increase in wing weight. In the three decades since the F-8 SCW flew, the use of such airfoils has become common. The F-8 Supercritical Wing was a flight research project designed to test a new wing concept designed by Dr. Richard Whitcomb, chief of the Transonic Aerodynamics Branch, Langley Research Center, Hampton, Virginia. Compared to a conventional wing, the supercritical wing (SCW) is flatter on the top and rounder on the bottom with a downward curve at the

The phase transition of Pb8F14I2.

PubMed

Weil, Matthias

2017-01-01

The reversible phase transition of Pb 8 F 14 I 2 is of continuous type and takes place at about 107 °C as monitored by temperature-dependent single crystal and powder X-ray diffraction measurements, optical microscopy, and differential scanning calorimetry. The low-temperature ferroelastic phase crystallizes in the orthorhombic crystal system (23 °C, Bmmb , Z  = 2, a  = 6.0699(6) Å, b  = 6.0165(6) Å, c  = 25.077(2) Å, 1487 structure factors, 41 parameter, R ( F 2 ) = 0.0346, wR ( F 2 ) = 0.0771) and changes its symmetry to the tetragonal crystal system into the high-temperature paraelastic phase (130 °C, I 4/ mmm , Z  = 1, a  = 4.2667(12) Å, c  = 25.388(7) Å, 430 structure factors, 303 parameter, R ( F 2 ) = 0.0575, wR ( F 2 ) = 0.1564). Group-subgroup relationships between the two structures and a hypothetical intermediate structure are presented.

Development of a Body Shield for Small Animal PET System to Reduce Random and Scatter Coincidences

NASA Astrophysics Data System (ADS)

Wada, Yasuhiro; Yamamoto, Seiichi; Watanabe, Yasuyoshi

2015-02-01

For small animal positron emission tomography (PET) research using high radioactivity, such as dynamic studies, the resulting high random coincidence rate of the system degrades image quality. The random coincidence rate is increased not only by the gamma photons from inside the axial-field-of-view (axial-FOV) of the PET system but also by those from outside the axial-FOV. For brain imaging in small animal studies, significant interference is observed from gamma photons emitted from the body. Single gamma photons from the body enter the axial-FOV and increase the random and scatter coincidences. Shielding against the gamma photons from outside the axial-FOV would improve the image quality. For this purpose, we developed a body shield for a small animal PET system, the microPET Primate 4-ring system, and evaluated its performance. The body shield is made of 9-mm-thick lead and it surrounds most of a rat's body. We evaluated the effectiveness of the body shield using a head phantom and a body phantom with a radioactivity concentration ratio of 1:2 and a maximum total activity of approximately 250 MBq. The random coincidence rate was dramatically decreased to 1/10, and the noise equivalent count rate (NECR) was increased 6 times with an activity of 7 MBq in the head phantom. The true count rate was increased to 35% due to the decrease in system deadtime. The average scatter fraction was decreased to 1/2.5 with the body shield. Count rate measurements of rat were also conducted with an injection activity of approximately 25 MBq of [C-11]N,N-dimethyl-2-(2-amino-4-cyanophenylthio) benzylamine ([C-11]DASB) and approximately 70 and 310 MBq of 2-deoxy-2-(F-18)fluoro-D-glucose ([F-18]FDG). Using the body shield, [F-18]FDG images of rats were improved by increasing the amount of radioactivity injected. The body shield designed for small animal PET systems is a promising tool for improving image quality and quantitation accuracy in small animal molecular imaging research.

F-8 SCW on display stand

NASA Image and Video Library

1995-03-13

A Vought F-8A Crusader was selected by NASA as the testbed aircraft (designated TF-8A) to install an experimental Supercritical Wing (SCW) in place of the conventional wing. The unique design of the Supercritical Wing reduces the effect of shock waves on the upper surface near Mach 1, which in turn reduces drag. In the photograph the TF-8A Crusader with the Supercritical Wing is shown on static display in front of the NASA Dryden Flight Research Center, Edwards, California. The F-8 SCW aircraft, along with the F-8 Digital Fly-By-Wire aircraft were placed on display on May 27, 1992, at a conference marking the 20th anniversary of the start of the two programs.

An evaluation of NCRP report 151--radiation shielding design for radiotherapy facilities, and a feasibility study for 6 MV open-door treatments in an existing high-energy radiation therapy bunker

NASA Astrophysics Data System (ADS)

Kildea, John

This thesis describes a study of shielding design techniques used for radiation therapy facilities that employ megavoltage linear accelerators. Specifically, an evaluation of the shielding design formalism described in NCRP report 151 was undertaken and a feasibility study for open-door 6 MV radiation therapy treatments in existing 6 MV, 18 MV treatment rooms at the Montreal General Hospital (MGH) was conducted. To evaluate the shielding design formalism of NCRP 151, barrier-attenuated equivalent doses were measured for several of the treatment rooms at the MGH and compared with expectations from NCRP 151 calculations. It was found that, while the insight and recommendations of NCRP 151 are very valuable, its dose predictions are not always correct. As such, the NCRP 151 methodology is best used in conjunction with physical measurements. The feasibility study for 6 MV open-door treatments made use of the NCRP 151 formalism, together with physical measurements for realistic 6 MV workloads. The results suggest that, dosimetrically, 6 MV open door treatments are feasible. A conservative estimate for the increased dose at the door arising from such treatments is 0.1 mSv, with a 1/8 occupancy factor, as recommended in NCRP 151, included.

Atmospheric abundance and global emissions of perfluorocarbons CF4, C2F6 and C3F8 since 1800 inferred from ice core, firn, air archive and in situ measurements

NASA Astrophysics Data System (ADS)

Trudinger, Cathy M.; Fraser, Paul J.; Etheridge, David M.; Sturges, William T.; Vollmer, Martin K.; Rigby, Matt; Martinerie, Patricia; Mühle, Jens; Worton, David R.; Krummel, Paul B.; Steele, L. Paul; Miller, Benjamin R.; Laube, Johannes; Mani, Francis S.; Rayner, Peter J.; Harth, Christina M.; Witrant, Emmanuel; Blunier, Thomas; Schwander, Jakob; O'Doherty, Simon; Battle, Mark

2016-09-01

Perfluorocarbons (PFCs) are very potent and long-lived greenhouse gases in the atmosphere, released predominantly during aluminium production and semiconductor manufacture. They have been targeted for emission controls under the United Nations Framework Convention on Climate Change. Here we present the first continuous records of the atmospheric abundance of CF4 (PFC-14), C2F6 (PFC-116) and C3F8 (PFC-218) from 1800 to 2014. The records are derived from high-precision measurements of PFCs in air extracted from polar firn or ice at six sites (DE08, DE08-2, DSSW20K, EDML, NEEM and South Pole) and air archive tanks and atmospheric air sampled from both hemispheres. We take account of the age characteristics of the firn and ice core air samples and demonstrate excellent consistency between the ice core, firn and atmospheric measurements. We present an inversion for global emissions from 1900 to 2014. We also formulate the inversion to directly infer emission factors for PFC emissions due to aluminium production prior to the 1980s. We show that 19th century atmospheric levels, before significant anthropogenic influence, were stable at 34.1 ± 0.3 ppt for CF4 and below detection limits of 0.002 and 0.01 ppt for C2F6 and C3F8, respectively. We find a significant peak in CF4 and C2F6 emissions around 1940, most likely due to the high demand for aluminium during World War II, for example for construction of aircraft, but these emissions were nevertheless much lower than in recent years. The PFC emission factors for aluminium production in the early 20th century were significantly higher than today but have decreased since then due to improvements and better control of the smelting process. Mitigation efforts have led to decreases in emissions from peaks in 1980 (CF4) or early-to-mid-2000s (C2F6 and C3F8) despite the continued increase in global aluminium production; however, these decreases in emissions appear to have recently halted. We see a temporary reduction of around

Determining the relative strengths of aromatic and aliphatic C-H⋅⋅⋅X hydrogen bonds in imidazolium ionic liquids through measurement of H/D isotope effects on 19 F nuclear shielding.

PubMed

Bottini, Gualberto; Moyna, Guillermo

2018-02-01

The relative strengths of aromatic and aliphatic C-H⋅⋅⋅X hydrogen bonds in imidazolium ionic liquids were investigated through measurement of H/D isotope effects on the 19 F nuclear shielding of deuterated isotopologues of 1-n-butyl-3-methylimidazolium hexafluorophosphate and tetrafluoroborate ([C 4 mim]PF 6 and [C 4 mim]BF 4 ). Δ 19 F(H,D) values ranging from 9.7 to 49.7 ppb were observed for [C 4 mim]PF 6 isotopologues, while for the [C 4 mim]BF 4 series these went from 26.2 to 83.8 ppb. Our findings indicate that the interactions between the fluorinated anions and protons on the C-1' and C-1″ position of the N-alkyl sidechains are comparable to, and in some cases stronger than, those involving protons on the aromatic ring, underscoring the role that these weak interionic forces have on the local ordering of imidazolium salts in the liquid state. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Magnetic shielding investigation for a 6 MV in-line linac within the parallel configuration of a linac-MR system.

PubMed

Santos, D M; St Aubin, J; Fallone, B G; Steciw, S

2012-02-01

In our current linac-magnetic resonance (MR) design, a 6 MV in-line linac is placed along the central axis of the MR's magnet where the MR's fringe magnetic fields are parallel to the overall electron trajectories in the linac waveguide. Our previous study of this configuration comprising a linac-MR SAD of 100 cm and a 0.5 T superconducting (open, split) MR imager. It showed the presence of longitudinal magnetic fields of 0.011 T at the electron gun, which caused a reduction in target current to 84% of nominal. In this study, passive and active magnetic shielding was investigated to recover the linac output losses caused by magnetic deflections of electron trajectories in the linac within a parallel linac-MR configuration. Magnetic materials and complex shield structures were used in a 3D finite element method (FEM) magnetic field model, which emulated the fringe magnetic fields of the MR imagers. The effects of passive magnetic shielding was studied by surrounding the electron gun and its casing with a series of capped steel cylinders of various inner lengths (26.5-306.5 mm) and thicknesses (0.75-15 mm) in the presence of the fringe magnetic fields from a commercial MR imager. In addition, the effects of a shield of fixed length (146.5 mm) with varying thicknesses were studied against a series of larger homogeneous magnetic fields (0-0.2 T). The effects of active magnetic shielding were studied by adding current loops around the electron gun and its casing. The loop currents, separation, and location were optimized to minimize the 0.011 T longitudinal magnetic fields in the electron gun. The magnetic field solutions from the FEM model were added to a validated linac simulation, consisting of a 3D electron gun (using OPERA-3d/scala) and 3D waveguide (using comsol Multiphysics and PARMELA) simulations. PARMELA's target current and output phase-space were analyzed to study the linac's output performance within the magnetic shields. The FEM model above agreed within 1

Structural study of the ammonium octafluoroneptunate, [NH 4] 4NpF 8

DOE PAGES

Poineau, Frederic; Silva, Chinthaka M.; Yeamans, Charles B.; ...

2016-04-21

The [NH 4] 4NpF 8 salt was prepared from the solid-state reaction of NpO 2 with NH 4HF 2 and characterized by powder X-ray diffraction and X-ray absorption fine structure spectroscopy. The diffraction results confirm the compound to be isostructural to [NH 4] 4UF 8 with the following lattice parameter (a = 13.054(4) Å, b = 6.681(2) Å, c = 13.676(5) Å, ß = 121.14 Å). For the first time, a Neptunium fluoride complex has been characterized by XAFS spectroscopy. The energy position of the white line and inflection of the XANES spectra of [NH 4] 4NpF 8 are consistentmore » with the presence of Np(IV). Adjustment of the EXAFS spectra indicates that the coordination number (7.4±1.5) and the average Np-F distance (2.26(1) Å) are consistent with the presence of the NpF8 dodecahedron. The average Np-F distance is ~0.02 Å shorter than the U-F distance in [NH 4] 4UF 8 and is a result of the actinide contraction.« less

^2H(^18F,p)^19F Study at 6 MeV/u

NASA Astrophysics Data System (ADS)

Kozub, R. L.; Nesaraja, C. D.; Moazen, B. H.; Scott, J. P.; Bardayan, D. W.; Blackmon, J. C.; Gross, C. J.; Shapira, D.; Smith, M. S.; Batchelder, J. C.; Brune, C. R.; Champagne, A. E.; Sahin, L.; Cizewski, J. A.; Thomas, J. S.; Davinson, T.; Woods, P. J.; Greife, U.; Jewett, C.; Livesay, R. J.; Ma, Z.; Parker, P. D.

2003-04-01

The degree to which the (p,α) and (p,γ) reactions destroy ^18F at temperatures ˜1-4 x 10^8 K is important for understanding the synthesis of nuclei in nova explosions and for using ^18F as a monitor of nova mechanisms in gamma ray astronomy. The reactions are dominated by low-lying proton resonances near the ^18F+p threshold (E_x=6.411 MeV excitation energy in ^19Ne). To gain further information about these resonances, we have used the inverse ^18F(d,p)^19F neutron transfer reaction at the Holifield Radioactive Ion Beam Facility to selectively populate corresponding mirror states in ^19F. Proton angular distributions were measured for states in ^19F in the excitation energy range 0-9 MeV. Results and implications for the ^18F+p reactions and nuclear structure will be presented. ^1Supported by DOE. ^2ORNL is managed by UT-Battelle, LLC, for the USDOE.

Acoustic Shielding for a Model Scale Counter-rotation Open Rotor

NASA Technical Reports Server (NTRS)

Stephens, David B.; Edmane, Envia

2012-01-01

The noise shielding benefit of installing an open rotor above a simplified wing or tail is explored experimentally. The test results provide both a benchmark data set for validating shielding prediction tools and an opportunity for a system level evaluation of the noise reduction potential of propulsion noise shielding by an airframe component. A short barrier near the open rotor was found to provide up to 8.5 dB of attenuation at some directivity angles, with tonal sound particularly well shielded. Predictions from two simple shielding theories were found to overestimate the shielding benefit.

A comparison of time-optimal interception trajectories for the F-8 and F-15

NASA Technical Reports Server (NTRS)

Calise, Anthony J.; Pettengill, James B.

1990-01-01

The simulation results of a real time control algorithm for onboard computation of time-optimal intercept trajectories for the F-8 and F-15 aircraft are given. Due to the inherent aerodynamic and propulsion differences in the aircraft, there are major differences in their optimal trajectories. The significant difference in the two aircrafts are their flight envelopes. The F-8's optimal cruise velocity is thrust limited, while the F-15's optimal cruise velocity is at the intersection of the Mach and dynamic pressure constraint boundaries. This inherent difference necessitated the development of a proportional thrust controller for use as the F-15 approaches it's optimal cruise energy. Documented here is the application of singular perturbation theory to the trajectory optimization problem, along with a summary of the control algorithms. Numerical results for the two aircraft are compared to illustrate the performance of the minimum time algorithm, and to compute the resulting flight paths.

Shields-1, A SmallSat Radiation Shielding Technology Demonstration

NASA Technical Reports Server (NTRS)

Thomsen, D. Laurence, III; Kim, Wousik; Cutler, James W.

2015-01-01

The NASA Langley Research Center Shields CubeSat initiative is to develop a configurable platform that would allow lower cost access to Space for materials durability experiments, and to foster a pathway for both emerging and commercial-off-the-shelf (COTS) radiation shielding technologies to gain spaceflight heritage in a relevant environment. The Shields-1 will be Langleys' first CubeSat platform to carry out this mission. Radiation shielding tests on Shields-1 are planned for the expected severe radiation environment in a geotransfer orbit (GTO), where advertised commercial rideshare opportunities and CubeSat missions exist, such as Exploration Mission 1 (EM-1). To meet this objective, atomic number (Z) graded radiation shields (Zshields) have been developed. The Z-shield properties have been estimated, using the Space Environment Information System (SPENVIS) radiation shielding computational modeling, to have 30% increased shielding effectiveness of electrons, at half the thickness of a corresponding single layer of aluminum. The Shields-1 research payload will be made with the Z-graded radiation shields of varying thicknesses to create dose-depth curves to be compared with baseline materials. Additionally, Shields-1 demonstrates an engineered Z-grade radiation shielding vault protecting the systems' electronic boards. The radiation shielding materials' performances will be characterized using total ionizing dose sensors. Completion of these experiments is expected to raise the technology readiness levels (TRLs) of the tested atomic number (Z) graded materials. The most significant contribution of the Z-shields for the SmallSat community will be that it enables cost effective shielding for small satellite systems, with significant volume constraints, while increasing the operational lifetime of ionizing radiation sensitive components. These results are anticipated to increase the development of CubeSat hardware design for increased mission lifetimes, and enable

ZnO:Zn/6LiF scintillator-A low afterglow alternative to ZnS:Ag/6LiF for thermal neutron detection

NASA Astrophysics Data System (ADS)

Sykora, G. Jeff; Schooneveld, Erik M.; Rhodes, Nigel J.

2018-03-01

Current ZnS:Ag/6LiF based scintillation detectors are often count rate limited by the long lifetime afterglow in the scintillator. Despite this drawback, new instruments at neutron scattering facilities, like ISIS in the UK, would still like to use ZnS:Ag/6LiF detectors due to their low gamma sensitivity, high light output, simplicity of detector design and relatively inexpensive production. One particular advantage of ZnS:Ag/6LiF detectors is their ability to provide strong pulse shape discrimination between neutrons and gammas. Despite the advantages of these detectors, it is becoming clear that new and upgraded instruments will be limited by the count rate capability of ZnS:Ag/6LiF, so an alternative scintillator technology with equivalent simplicity is being sought. ZnO:Zn/6LiF is investigated here as a low afterglow alternative to ZnS:Ag/6LiF. Basic scintillation properties of ZnO:Zn are studied and are discussed. Pulse shape discrimination between neutrons and gammas is explored and taken advantage of through simple single photon counting methods. A further step toward a realistic detector for neutron scattering is also taken by fiber coupling the ZnO:Zn/6LiF to a PMT. In an initial study of this fiber coupled configuration, 60Co gamma sensitivity of ∼ 7 × 10-6 is shown and improvements in count rate capability of at least a factor of 6 over ZnS:Ag/6LiF based neutron detectors are demonstrated.

Dark Matter Limits From a 2L C3F8 Filled Bubble Chamber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robinson, Alan Edward

2015-12-01

The PICO-2L C3F8 bubble chamber search forWeakly Interacting Massive Particle (WIMP) dark matter was operated in the SNOLAB underground laboratory at the same location as the previous CF3I lled COUPP-4kg detector. Neutron calibrations using photoneutron sources in C3F8 and CF3I lled calibration bubble chambers were performed to verify the sensitivity of these target uids to dark matter scattering. This data was combined with similar measurements using a low-energy neutron beam at the University of Montreal and in situ calibrations of the PICO-2L and COUPP-4kg detectors. C3F8 provides much greater sensitivity to WIMP-proton scattering than CF3I in bubble chamber detectors. PICO-2Lmore » searched for dark matter recoils with energy thresholds below 10 keV. Radiopurity assays of detector materials were performed and the expected neutron recoil background was evaluated to be 1.6+0:3« less

Catabolism of 6-ketoprostaglandin F1alpha by the rat kidney cortex.

PubMed

Pace-Asciak, C R; Domazet, Z; Carrara, M

1977-05-25

Homogenates of the rat kidney cortex converted 5,8,9,11,12,14,15-hepta-tritiated 6-ketoprostaglandin F 1alpha into one major product identified by gas chromatography-mass spectrometry of the methoxime-methyl ester trimethylsilyl ether derivative as 6,15-diketo-9,11-dihydroxyprost-13-enoic acid. The sequence of derivatisation i.e. methoximation prior to methylation, was crucial as methylation of 15-keto catabolites of the E, F and 6-keto-F series affords degradation products. The corresponding 15-keto-13,14-dihydro catabolite was formed in much smaller quantities. Time course studies indicated that 6-keto-prostaglandin F1alpha was catabolised at a slower rate (about 2-5 fold) than prostaglandin F1alpha. The catabolic activity was blocked by NADH.

Three-phase heterostructures f-NiFe2O4/PANI/PI EMI shielding fabric with high Microwave Absorption Performance

NASA Astrophysics Data System (ADS)

Wang, Yu; Wang, Wei; Yu, Dan

2017-12-01

In this work, a three-phase heterostructures f-NiFe2O4/PANI/PI EMI shielding fabric with a layer by layer structure was designed and prepared to obtain excellent microwave attenuation performance. Firstly, PANI/PI fabric was prepared via in-situ deposition method. Then, the NiFe2O4 nanoparticles functionalized by oleic acid were uniformly dispersed in epoxy resin and coated on the top and bottom of PANI/PI fabric with 0.041 mm total thickness. The investigation of chemical structure and surface morphologies indicated the composite structure of f-NiFe2O4/PANI/PI fabric. Various parameters like magnetic property, reflection loss and attenuation constant were used to evaluate its microwave attenuation performance. The results demonstrated that the 30f-NiFe2O4/PANI/PI fabric had a highest attenuation effectiveness with the minimum reflection loss value of -42.5 dB (>90% attenuation) at 12.5 GHz and the effective absorption bandwidth was 3.4 GHz. The study of attenuation mechanism indicated that the dielectric loss from PANI, the magnetic loss caused by f-NiFe2O4 and the layer by layer structure effectively improved microwave attenuation performance of composite fabric. Furthermore, the favorable flexibility and dimensional stability of this resultant fabric would allow the composite fabric for a long time service under pressure or foldable conditions. In sum, the study clearly indicated that three-phase heterostructures f-NiFe2O4/PANI/PI fabric was a good candidate as electromagnetic shielding materials in many fields.

Reliability of Monte Carlo simulations in modeling neutron yields from a shielded fission source

NASA Astrophysics Data System (ADS)

McArthur, Matthew S.; Rees, Lawrence B.; Czirr, J. Bart

2016-08-01

Using the combination of a neutron-sensitive 6Li glass scintillator detector with a neutron-insensitive 7Li glass scintillator detector, we are able to make an accurate measurement of the capture rate of fission neutrons on 6Li. We used this detector with a 252Cf neutron source to measure the effects of both non-borated polyethylene and 5% borated polyethylene shielding on detection rates over a range of shielding thicknesses. Both of these measurements were compared with MCNP calculations to determine how well the calculations reproduced the measurements. When the source is highly shielded, the number of interactions experienced by each neutron prior to arriving at the detector is large, so it is important to compare Monte Carlo modeling with actual experimental measurements. MCNP reproduces the data fairly well, but it does generally underestimate detector efficiency both with and without polyethylene shielding. For non-borated polyethylene it underestimates the measured value by an average of 8%. This increases to an average of 11% for borated polyethylene.

Thermoelectric Properties of Poly(3-hexylthiophene) (P3HT) Doped with 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F 4TCNQ) by Vapor-Phase Infiltration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lim, Eunhee; Peterson, Kelly A.; Su, Gregory M.

Doping of thin films of semiconducting polymers provides control of their electrical conductivity and thermopower. The electrical conductivity of semiconducting polymers rises nonlinearly with the carrier concentration, and there is a lack of understanding of the detailed factors that lead to this behavior. Here, we report a study of the morphological effects of doping on the electrical conductivity of poly(3-hexylthiophene) (P3HT) thin films doped with small molecule 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F 4TCNQ). Resonant soft X-ray scattering shows that the morphology of films of P3HT is not strongly changed by infiltration of F 4TCNQ from the vapor phase. We show that the localmore » ordering of P3HT, the texture and form factor of crystallites, and the long-range connectivity of crystalline domains contribute to the electrical conductivity in thin films. The thermopower of films of P3HT doped with F 4TCNQ from the vapor phase is not strongly enhanced relative to films doped from solution, but the electrical conductivity is significantly higher, improving the thermoelectric power factor.« less

Thermoelectric Properties of Poly(3-hexylthiophene) (P3HT) Doped with 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F 4TCNQ) by Vapor-Phase Infiltration

DOE PAGES

Lim, Eunhee; Peterson, Kelly A.; Su, Gregory M.; ...

2018-01-29

Doping of thin films of semiconducting polymers provides control of their electrical conductivity and thermopower. The electrical conductivity of semiconducting polymers rises nonlinearly with the carrier concentration, and there is a lack of understanding of the detailed factors that lead to this behavior. Here, we report a study of the morphological effects of doping on the electrical conductivity of poly(3-hexylthiophene) (P3HT) thin films doped with small molecule 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F 4TCNQ). Resonant soft X-ray scattering shows that the morphology of films of P3HT is not strongly changed by infiltration of F 4TCNQ from the vapor phase. We show that the localmore » ordering of P3HT, the texture and form factor of crystallites, and the long-range connectivity of crystalline domains contribute to the electrical conductivity in thin films. The thermopower of films of P3HT doped with F 4TCNQ from the vapor phase is not strongly enhanced relative to films doped from solution, but the electrical conductivity is significantly higher, improving the thermoelectric power factor.« less

Impact of a flattening filter free linear accelerator on structural shielding design.

PubMed

Jank, Julia; Kragl, Gabriele; Georg, Dietmar

2014-03-01

The present study aimed to assess the effects of a flattening filter free medical accelerator on structural shielding demands of a treatment vault of a medical linear accelerator. We tried to answer the question, to what extent the required thickness of the shielding barriers can be reduced if instead of the standard flattened photon beams unflattened ones are used. We chose both an experimental as well as a theoretical approach. On the one hand we measured photon dose rates at protected places outside the treatment room and compared the obtained results for flattened and unflattened beams. On the other hand we complied with international guidelines for adequate treatment vault design and calculated the shielding barriers according to the therein given specifications. Measurements were performed with an Elekta Precise™ linac providing nominal photon energies of 6 and 10 MV. This machine underwent already earlier some modifications in order to be able to operate both with and without a flattening filter. Photon dose rates were measured with a LB133-1 dose rate meter manufactured by Berthold. To calculate the thickness of shielding barriers we referred to the Austrian standard ÖNORM S 5216 and to the US American NCRP Report No. 151. We determined a substantial photon dose rate reduction for all measurement points and photon energies. For unflattened 6 MV beams a reduction factor ranging from 1.4 to 1.8 was identified. The corresponding values for unflattened 10 MV beams were 2.1 and 3.2. The performed shielding calculations indicated the same tendency: For all relevant radiation components we found a reduction in shielding thickness when unflattened beams were used. The required thickness of primary barriers was reduced up to 8.0%, the thickness of secondary barriers up to 11.4%, respectively. For an adequate dimensioning of treatment vault shielding barriers it is by no means irrelevant if the accommodated linac operates with or without a flattening filter. The

SU-F-E-13: Design and Fabrication of Gynacological Brachytherapy Shielding & Non Shielding Applicators Using Indigenously Developed 3D Printing Machine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shanmugam, S

Purpose: In this innovative work we have developed Gynecological Brachytherapy shielding & Non Shielding Applicators and compared with the commercially available applicators by using the indigenously developed 3D Printing machine. Methods: We have successfully indigenously developed the 3D printing machine. Which contain the 3 dimensional motion platform, Heater unit, base plate, ect… To fabricate the Gynecological Brachytherapy shielding & non shielding applicators the 3D design were developed in the computer as virtual design. This virtual design is made in a CAD computer file using a 3D modeling program. Separate programme for the shielding & non shielding applicators. We have alsomore » provided the extra catheter insert provision in the applicator for the multiple catheter. The DICOM file of the applicator were then converted to stereo Lithography file for the 3D printer. The shielding & Non Shielding Applicators were printed on a indigenously developed 3D printer material. The same dimensions were used to develop the applicators in the acrylic material also for the comparative study. A CT scan was performed to establish an infill-density calibration curve as well as characterize the quality of the print such as uniformity and the infill pattern. To commission the process, basic CT and dose properties of the printing materials were measured in photon beams and compared against water and soft tissue. Applicator were then scanned to confirm the placement of multiple catheter position. Finally dose distributions with rescanned CTs were compared with those computer-generated applicators. Results: The doses measured from the ion Chamber and X-Omat film test were within 2%. The shielded applicator reduce the rectal dose comparatively with the non shielded applicator. Conclusion: As of submission 3 unique cylinders have been designed, printed, and tested dosimetrically. A standardizable workflow for commissioning custom 3D printed applicators was codified and

Comparison of Linear and Hyperbranched Polyether Lipids for Liposome Shielding by 18F-Radiolabeling and Positron Emission Tomography.

PubMed

Wagener, Karolin; Worm, Matthias; Pektor, Stefanie; Schinnerer, Meike; Thiermann, Raphael; Miederer, Matthias; Frey, Holger; Rösch, Frank

2018-04-27

Multifunctional and highly biocompatible polyether structures play a key role in shielding liposomes from degradation in the bloodstream, providing also multiple functional groups for further attachment of targeting moieties. In this work hyperbranched polyglycerol ( hbPG) bearing lipids with long alkyl chain anchor are evaluated with respect to steric stabilization of liposomes. The branched polyether lipids possess a hydrophobic bis(hexadecyl)glycerol membrane anchor for the liposomal membrane. hbPG was chosen as a multifunctional alternative to PEG, enabling the eventual linkage of multiple targeting vectors. Different hbPG lipids ( M n = 2900 and 5200 g mol -1 ) were examined. A linear bis(hexadecyl)glycerol-PEG lipid ( M n = 3000 g mol -1 ) was investigated as well, comparing hbPG and PEG with respect to shielding properties. Radiolabeling of the polymers was carried out using 1-azido-2-(2-(2-[ 18 F]fluoroethoxy)ethoxy)ethane ([ 18 F]F-TEG-N) 3 via copper-catalyzed alkyne-azide cycloaddition with excellent radiochemical yields exceeding 95%. Liposomes were prepared by the thin-film hydration method followed by repeated extrusion. Use of a custom automatic extrusion device gave access to reproducible sizes of the liposomes (hydrodynamic radius of 60-94 nm). The in vivo fate of the bis(hexadecyl)glycerol polyethers and their corresponding assembled liposome structures were evaluated via noninvasive small animal positron emission tomography (PET) imaging and biodistribution studies (1 h after injection and 4 h after injection) in mice. Whereas the main uptake of the nonliposomal polyether lipids was observed in the kidneys and in the bladder after 1 h due to rapid renal clearance, in contrast, the corresponding liposomes showed uptake in the blood pool as well as in organs with good blood supply, that is, heart and lung over the whole observation period of 4 h. The in vivo behavior of all three liposomal formulations was comparable, albeit with remarkable

Crystal Structure of 8β-Hydroxyeremophil-7(11)-ene-12,8α(4β,6α)-diolide

NASA Astrophysics Data System (ADS)

Xue, Hui-qing; Xue, Hui-feng; Wu, Biao; Wang, Han-qing; Xin, Xue-lei; Wu, Shui-xian

2006-12-01

8β-Hydroxyeremophil-7(11)-ene-12,8α(4β,6α)-diolide was isolated from the Ligularia intermedia and characterized by MS, multi NMR and X-ray single crystal diffraction. Its crystal structure was determined as in a orthorhombic type, with space group P212121 with a=6.8519(5), b=10.7191(8), c=18.5942(14) Å, V =1365.67(18) Å3, Z=4, and the calculated density is 1.354 mg/m3. F(000)=592, µ=0.101 mm-1.

Tunable photoluminescence properties of Ca{sub 8}NaLa(PO{sub 4}){sub 6}F{sub 2}:Eu{sup 2+},Mn{sup 2+} phosphor under UV excitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Fen; Lan, Tong; Tang, Wanjun, E-mail: tangmailbox@126.com

2015-04-15

Highlights: • Ca{sub 8}NaLa(PO{sub 4}){sub 6}F{sub 2}:Eu{sup 2+},Mn{sup 2+} was prepared by a combustion-assisted synthesis method. • The phosphor presents blue and yellow double color emissions. • Efficient energy transfer from Eu{sup 2+} to Mn{sup 2+} in this phosphor is observed obviously. • White emitting was realized in Ca{sub 8}NaGd(PO{sub 4}){sub 6}F{sub 2}:0.10Eu{sup 2+},0.32Mn{sup 2+},0.10B phosphor. - Abstract: A series of Eu{sup 2+} and Mn{sup 2+} coactivated Ca{sub 8}NaLa(PO{sub 4}){sub 6}F{sub 2} (CNLF) phosphors have been synthesized by a combustion-assisted synthesis method. The investigation revealed that Ca{sub 8}NaLa(PO{sub 4}){sub 6}F{sub 2} crystallized in a hexagonal crystal system with the spacemore » group P6{sub 3}/m (176). The Eu{sup 2+} activated phosphors can be efficiently excited in the range of 270–400 nm and give intense blue emission peaking at 451 nm. By codoping the Eu{sup 2+} and Mn{sup 2+} ions into the CNLF host and singly varying the doping content of the Mn{sup 2+} ion, tunable colors from blue to white and eventually to yellow are obtained in CNLF:Eu{sup 2+},Mn{sup 2+} phosphors under the irradiation of 330 nm. The energy transfer from Eu{sup 2+} to Mn{sup 2+} in CNLF:Eu{sup 2+},Mn{sup 2+} has been demonstrated to be a resonant type via a dipole–dipole mechanism and the critical distance of energy transfer from Eu{sup 2+} to Mn{sup 2+} was estimated to be about 11.9 Å. The investigation indicates that the obtained samples might have potential application in white LEDs.« less

Commissioning of a grid-based Boltzmann solver for cervical cancer brachytherapy treatment planning with shielded colpostats.

PubMed

Mikell, Justin K; Klopp, Ann H; Price, Michael; Mourtada, Firas

2013-01-01

We sought to commission a gynecologic shielded colpostat analytic model provided from a treatment planning system (TPS) library. We have reported retrospectively the dosimetric impact of this applicator model in a cohort of patients. A commercial TPS with a grid-based Boltzmann solver (GBBS) was commissioned for (192)Ir high-dose-rate (HDR) brachytherapy for cervical cancer with stainless steel-shielded colpostats. Verification of the colpostat analytic model was verified using a radiograph and vendor schematics. MCNPX v2.6 Monte Carlo simulations were performed to compare dose distributions around the applicator in water with the TPS GBBS dose predictions. Retrospectively, the dosimetric impact was assessed over 24 cervical cancer patients' HDR plans. Applicator (TPS ID #AL13122005) shield dimensions were within 0.4 mm of the independent shield dimensions verification. GBBS profiles in planes bisecting the cap around the applicator agreed with Monte Carlo simulations within 2% at most locations; differing screw representations resulted in differences of up to 9%. For the retrospective study, the GBBS doses differed from TG-43 as follows (mean value ± standard deviation [min, max]): International Commission on Radiation units [ICRU]rectum (-8.4 ± 2.5% [-14.1, -4.1%]), ICRUbladder (-7.2 ± 3.6% [-15.7, -2.1%]), D2cc-rectum (-6.2 ± 2.6% [-11.9, -0.8%]), D2cc-sigmoid (-5.6 ± 2.6% [-9.3, -2.0%]), and D2cc-bladder (-3.4 ± 1.9% [-7.2, -1.1%]). As brachytherapy TPSs implement advanced model-based dose calculations, the analytic applicator models stored in TPSs should be independently validated before clinical use. For this cohort, clinically meaningful differences (>5%) from TG-43 were observed. Accurate dosimetric modeling of shielded applicators may help to refine organ toxicity studies. Copyright © 2013 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

Optically pumped cerium-doped LiSrAlF.sub.6 and LiCaAlF.sub.6

DOEpatents

Marshall, Christopher D.; Payne, Stephen A.; Krupke, William F.

1996-01-01

Ce.sup.3+ -doped LiSrAlF.sub.6 crystals are pumped by ultraviolet light which is polarized along the c axis of the crystals to effectively energize the laser system. In one embodiment, the polarized fourth harmonic light output from a conventional Nd:YAG laser operating at 266 nm is arranged to pump Ce:LiSrAlF.sub.6 with the pump light polarized along the c axis of the crystal. The Ce:LiSrAlF.sub.6 crystal may be placed in a laser cavity for generating tunable coherent ultraviolet radiation in the range of 280-320 nm. Additionally, Ce-doped crystals possessing the LiSrAlF.sub.6 type of chemical formula, e.g. Ce-doped LiCaAlF.sub.6 and LiSrGaF.sub.6, can be used. Alternative pump sources include an ultraviolet-capable krypton or argon laser, or ultraviolet emitting flashlamps. The polarization of the pump light will impact operation. The laser system will operate efficiently when light in the 280-320 nm gain region is injected or recirculated in the system such that the beam is also polarized along the c axis of the crystal. The Ce:LiSrAlF.sub.6 laser system can be configured to generate ultrashort pulses, and it may be used to pump other devices, such as an optical parametric oscillator.

Investigation of the strength of shielded and unshielded underwater electrical cables

NASA Astrophysics Data System (ADS)

Glowe, D. E.; Arnett, S. L.

1981-09-01

The mechanical properties of shielded and unshielded submarine cables (MIL-C-915/8E) were investigated to determine the effect of shielding on cable life, performance, and reliability. Ten cables (five shielded and five unshielded) were selected for laboratory evaluation. A mission profile was developed to establish the mechanical stress limits that cables must endure in service and a test sequence designed to measure tensile strength, flexural abrasion endurance, crush resistance, creep under static tension, and performance in a hull-stuffing tube. The results of this program showed that: (1) DSS-2 cable does not have adequate tensile strength and should have a strength member added. DSS-3 and larger cables have adequate tensile strength with or without the shield; (2) Unshielded DSS-3 type cable does not perform satisfactorily in hull-stuffing tubes; (3) Shielding is not required to meet mission profile specifications for cable crush or flexural abrasion resistance; (4) Construction parameters other than shielding can significantly affect mechanical performance of cable; (5) Unshielded cable construction can result in increased reliability since it permits a thicker single-jacket construction; and (6) Unshielded cable construction can reduce the cost of cable by 8 to 20 percent.

SU-E-T-273: Radiation Shielding for a Fixed Horizontal-Beam Linac in a Shipping Container and a Conventional Treatment Vault

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsieh, M; Balter, P; Beadle, B

Purpose: A fixed horizontal-beam linac, where the patient is treated in a seated position, could lower the overall costs of the treatment unit and room shielding substantially. This design also allows the treatment room and control area to be contained within a reduced space, such as a shipping container. The main application is the introduction of low-cost, high-quality radiation therapy to low- and middle-income regions. Here we consider shielding for upright treatments with a fixed-6MV-beam linac in a shipping container and a conventional treatment vault. Methods: Shielding calculations were done for two treatment room layouts using calculation methods in NCRPmore » Report 151: (1) a shipping container (6m × 2.4m with the remaining space occupied by the console area), and (2) the treatment vault in NCRP 151 (7.8m by 5.4m by 3.4m). The shipping container has a fixed gantry that points in one direction at all times. For the treatment vault, various beam directions were evaluated. Results: The shipping container requires a primary barrier of 168cm concrete (4.5 TVL), surrounded by a secondary barrier of 3.6 TVL. The other walls require between 2.8–3.3 TVL. Multiple shielding calculations were done along the side wall. The results show that patient scatter increases in the forward direction and decreases dramatically in the backward direction. Leakage scatter also varies along the wall, depending largely on the distance between the gantry and the wall. For the treatment room, fixed-beam requires a slightly thicker primary barrier than the conventional linac (0.6 TVL), although this barrier is only needed in the center of one wall. The secondary barrier is different only by 0–0.2 TVL. Conclusion: This work shows that (1) the shipping container option is achievable, using indigenous materials for shielding and (2) upright treatments can be performed in a conventional treatment room with minimal additional shielding. Varian Medical Systems.« less

F-8 DFBW on-board electronics

NASA Image and Video Library

1971-07-18

The Apollo hardware jammed into the F-8C. The computer is partially visible in the avionics bay at the top of the fuselage behind the cockpit. Note the display and keyboard unit in the gun bay. To carry the computers and other equipment, the F-8 DFBW team removed the aircraft's guns and ammunition boxes.

Nevadaite, (Cu2+, Al, V3+)6 [Al8 (PO4)8 F8] (OH 2 (H2O)22, a new phosphate mineral species from the Gold Quarry mine, Carlin, Eureka County, Nevada: description and crystal structure

USGS Publications Warehouse

Cooper, M.A.; Hawthorne, F.C.; Roberts, Andrew C.; Foord, E.E.; Erd, Richard C.; Evans, H.T.; Jensen, M.C.

2004-01-01

Nevadaite, (Cu2+, ???, Al, V3+)6 (PO4)8 F8 (OH)2 (H2O)22, is a new supergene mineral species from the Gold Quarry mine, near Carlin, Eureka County, Nevada, U.S.A. Nevadaite forms radiating clusters to 1 mm of prismatic crystals, locally covering surfaces more that 2 cm across; individual crystals are elongate on [001] with a length:width ratio of > 10:1 and a maximum diameter of ???30 ??m. It also occurs as spherules and druses associated with colorless to purple-black fluellite, colorless wavellite, strengitevariscite, acicular maroon-to-red hewettite, and rare anatase, kazakhstanite, tinticite, leucophosphite, torbernite and tyuyamunite. Nevadaite is pale green to turquoise blue with a pale powder-blue streak and a vitreous luster; it does not fluoresce under ultra-violet light. It has no cleavage, a Mohs hardness of ???3, is brittle with a conchoidal fracture, and has measured and calculated densities of 2.54 and 2.55 g/cm3, respectively. Nevadaite is biaxial negative, with ?? 1.540, ?? 1.548, ?? 1.553, 2V(obs.) = 76??, 2V(calc.) = 76??, pleochroic with X pale greenish blue, Y very pale greenish blue, Z blue, and with absorption Z ??? X > Y and orientation X = c, Y = a, Z = b. Nevadaite is orthorhombic, space group P21mn, a 12.123(2), b 18.999(2), c 4.961(1) A?? , V 1142.8(2) A??3, Z = 1, a:b:c = 0.6391:1:0.2611. The strongest seven lines in the X-ray powder-diffraction pattern [d in A??(I)(hkl)] are: 6.077(10)(200), 5.618(9)(130), 9.535(8)(020), 2.983(6)(241), 3.430(4)(041), 2.661(4)(061 , and 1.844(4)(352). A chemical analysis with an electron microprobe gave P2O5 32.54, Al2O3 27.07, V2O3 4.24, Fe2O3 0.07, CuO 9.24, ZnO 0.11, F 9.22, H2O (calc.) 23.48, OH ??? F -3.88, sum 102.09 wt.%; the valence states of V and Fe, and the amount of H2O, were determined by crystal-structure analysis. The resulting empirical formula on the basis of 63.65 anions (including 21.65 H2O pfu) is (CU2+2.00 Zn0.02 V3+0.98 Fe3+0.01 Al1.15)??4.16 Al8 P7.90 O32 [F8.37 (OH 1.63]??10 (H2O

New organic superconductors beta-(BDA-TTP)2X [BDA-TTP + 2,5-bis(1,3-dithian-2ylidene)-1,3,4,6-tetrathiapentalene; X(-) = SbF6(-), AsF6(-), and PF6(-)].

PubMed

Yamada, J; Watanabe, M; Akutsu, H; Nakatsuji, S; Nishikawa, H; Ikemoto, I; Kikuchi, K

2001-05-09

The synthesis, electrochemical properties, and molecular structure of a new pi-electron donor, 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene (BDA-TTP), is described. In contrast to the hitherto-known tetrachalcogenafulvalene pi-donors providing organic superconductors, this donor contains only the bis-fused 1,3-dithiole-2-ylidene unit as a pi-electron system, yet produces a series of ambient-pressure superconductors beta-(BDA-TTP)2X [X = SbF6 (magnetic T(c) = 6.9 K, resistive T(c) = 7.5 K), AsF6 (magnetic T(c) = 5.9 K, resistive T(c) = 5.8 K), and PF6 (magnetic T(c) = 5.9 K)], which are isostructural. The values of the intermolecular overlap integrals calculated on the donor layers of these superconductors suggest a two-dimensional (2D) electronic structure with loose donor packing. Tight-binding band calculations also indicate that these superconductors have the 2D band dispersion relations and closed Fermi surfaces.

NMR shielding and spin–rotation constants of {sup 175}LuX (X = {sup 19}F, {sup 35}Cl, {sup 79}Br, {sup 127}I) molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Demissie, Taye B.

2015-12-31

This presentation demonstrates the relativistic effects on the spin-rotation constants, absolute nuclear magnetic resonance (NMR) shielding constants and shielding spans of {sup 175}LuX (X = {sup 19}F, {sup 35}Cl, {sup 79}Br, {sup 127}I) molecules. The results are obtained from calculations performed using density functional theory (non-relativistic and four-component relativistic) and coupled-cluster calculations. The spin-rotation constants are compared with available experimental values. In most of the molecules studied, relativistic effects make an order of magnitude difference on the NMR absolute shielding constants.

Optically pumped cerium-doped LiSrAlF{sub 6} and LiCaAlF{sub 6}

DOEpatents

Marshall, C.D.; Payne, S.A.; Krupke, W.F.

1996-05-14

Ce{sup 3+}-doped LiSrAlF{sub 6} crystals are pumped by ultraviolet light which is polarized along the c axis of the crystals to effectively energize the laser system. In one embodiment, the polarized fourth harmonic light output from a conventional Nd:YAG laser operating at 266 nm is arranged to pump Ce:LiSrAlF{sub 6} with the pump light polarized along the c axis of the crystal. The Ce:LiSrAlF{sub 6} crystal may be placed in a laser cavity for generating tunable coherent ultraviolet radiation in the range of 280-320 nm. Additionally, Ce-doped crystals possessing the LiSrAlF{sub 6} type of chemical formula, e.g. Ce-doped LiCaAlF{sub 6} and LiSrGaF{sub 6}, can be used. Alternative pump sources include an ultraviolet-capable krypton or argon laser, or ultraviolet emitting flashlamps. The polarization of the pump light will impact operation. The laser system will operate efficiently when light in the 280-320 nm gain region is injected or recirculated in the system such that the beam is also polarized along the c axis of the crystal. The Ce:LiSrAlF{sub 6} laser system can be configured to generate ultrashort pulses, and it may be used to pump other devices, such as an optical parametric oscillator. 10 figs.

A phase II study of radioimmunotherapy with intraventricular 131 I-3F8 for medulloblastoma.

PubMed

Kramer, Kim; Pandit-Taskar, Neeta; Humm, John L; Zanzonico, Pat B; Haque, Sofia; Dunkel, Ira J; Wolden, Suzanne L; Donzelli, Maria; Goldman, Debra A; Lewis, Jason S; Lyashchenko, Serge K; Khakoo, Yasmin; Carrasquillo, Jorge A; Souweidane, Mark M; Greenfield, Jeffrey P; Lyden, David; De Braganca, Kevin D; Gilheeney, Stephen W; Larson, Steven M; Cheung, Nai-Kong V

2018-01-01

High-risk and recurrent medulloblastoma (MB) is associated with significant mortality. The murine monoclonal antibody 3F8 targets the cell-surface disialoganglioside GD2 on MB. We tested the efficacy, toxicity, and dosimetry of compartmental radioimmunotherapy (cRIT) with intraventricular 131 I-labeled 3F8 in patients with MB on a phase II clinical trial. Patients with histopathologically confirmed high-risk or recurrent MB were eligible for cRIT. After determining adequate cerebrospinal fluid (CSF) flow, patients received 2 mCi (where Ci is Curie) 124 I-3F8 or 131 I-3F8 with nuclear imaging for dosimetry, followed by up to four therapeutic (10 mCi/dose) 131 I-3F8 injections. Dosimetry estimates were based on serial CSF and blood samplings over 48 hr plus region-of-interest analyses on serial imaging scans. Disease evaluation included pre- and posttherapy brain/spine magnetic resonance imaging approximately every 3 months for the first year after treatment, and every 6-12 months thereafter. Forty-three patients received a total of 167 injections; 42 patients were evaluable for outcome. No treatment-related deaths occurred. Toxicities related to drug administration included acute bradycardia with somnolence, headache, fatigue, and CSF pleocytosis consistent with chemical meningitis and dystonic reaction. Total CSF absorbed dose was 1,453 cGy (where Gy is Gray; 350.0-2,784). Median overall survival from first dose of cRIT was 24.9 months (95% confidence interval [CI]:16.3-55.8). Patients treated in radiographic and cytologic remission were at a lower risk of death compared to patients with radiographically measurable disease (hazard ratio: 0.40, 95% CI: 0.18-0.88, P = 0.024). cRIT with 131 I-3F8 is safe, has favorable dosimetry to CSF, and when added to salvage therapy using conventional modalities, may have clinical utility in maintaining remission in high-risk or recurrent MB. © 2017 Wiley Periodicals, Inc.

Dosimetric evaluation of lead and tungsten eye shields in electron beam treatment.

PubMed

Shiu, A S; Tung, S S; Gastorf, R J; Hogstrom, K R; Morrison, W H; Peters, L J

1996-06-01

The purpose of this study is to report that commercially available eye shields (designed for orthovoltage x-rays) are inadequate to protect the ocular structures from penetrating electrons for electron beam energies equal to or greater than 6 MeV. Therefore, a prototype medium size tungsten eye shield was designed and fabricated. The advantages of the tungsten eye shield over lead are discussed. Electron beams (6-9 MeV) are often used to irradiate eyelid tumors to curative doses. Eye shields can be placed under the eyelids to protect the globe. Film and thermoluminescent dosimeters (TLDs) were used within a specially constructed polystyrene eye phantom to determine the effectiveness of various commercially available internal eye shields (designed for orthovoltage x-rays). The same procedures were used to evaluate a prototype medium size tungsten eye shield (2.8 mm thick), which was designed and fabricated for protection of the globe from penetrating electrons for electron beam energy equal to 9 MeV. A mini-TLD was used to measure the dose enhancement due to electrons backscattered off the tungsten eye shield, both with or without a dental acrylic coating that is required to reduce discomfort, permit sterilization of the shield, and reduce the dose contribution from backscattered electrons. Transmission of a 6 MeV electron beam through a 1.7 mm thick lead eye shield was found to be 50% on the surface (cornea) of the phantom and 27% at a depth of 6 mm (lens). The thickness of lead required to stop 6-9 MeV electron beams is impractical. In place of lead, a prototype medium size tungsten eye shield was made. For 6 to 9 MeV electrons, the doses measured on the surface (cornea) and at 6 mm (lens) and 21 mm (retina) depths were all less than 5% of the maximum dose of the open field (4 x 4 cm). Electrons backscattered off a tungsten eye shield without acrylic coating increased the lid dose from 85 to 123% at 6 MeV and 87 to 119% at 9 MeV. For the tungsten eye shield coated

A randomised crossover comparison of mouth-to-face-shield ventilation and mouth-to-pocket-mask ventilation by surf lifeguards in a manikin.

PubMed

Adelborg, K; Bjørnshave, K; Mortensen, M B; Espeseth, E; Wolff, A; Løfgren, B

2014-07-01

Thirty surf lifeguards (mean (SD) age: 25.1 (4.8) years; 21 male, 9 female) were randomly assigned to perform 2 × 3 min of cardiopulmonary resuscitation on a manikin using mouth-to-face-shield ventilation (AMBU LifeKey) and mouth-to-pocket-mask ventilation (Laerdal Pocket Mask). Interruptions in chest compressions, effective ventilation (visible chest rise) ratio, tidal volume and inspiratory time were recorded. Interruptions in chest compressions per cycle were increased with mouth-to-face-shield ventilation (mean (SD) 8.6 (1.7) s) compared with mouth-to-pocket-mask ventilation (6.9 (1.2) s, p < 0.0001). The proportion of effective ventilations was less using mouth-to-face-shield ventilation (199/242 (82%)) compared with mouth-to-pocket-mask ventilation (239/240 (100%), p = 0.0002). Tidal volume was lower using mouth-to-face-shield ventilation (mean (SD) 0.36 (0.20) l) compared with mouth-to-pocket-mask ventilation (0.45 (0.20) l, p = 0.006). No differences in inspiratory times were observed between mouth-to-face-shield ventilation and mouth-to-pocket-mask ventilation. In conclusion, mouth-to-face-shield ventilation increases interruptions in chest compressions, reduces the proportion of effective ventilations and decreases delivered tidal volumes compared with mouth-to-pocket-mask ventilation. © 2014 The Association of Anaesthetists of Great Britain and Ireland.

Adimensional theory of shielding in ultracold collisions of dipolar rotors

NASA Astrophysics Data System (ADS)

González-Martínez, Maykel L.; Bohn, John L.; Quéméner, Goulven

2017-09-01

We investigate the electric field shielding of ultracold collisions of dipolar rotors, initially in their first rotational excited state, using an adimensional approach. We establish a map of good and bad candidates for efficient evaporative cooling based on this shielding mechanism, by presenting the ratio of elastic over quenching processes as a function of a rescaled rotational constant B ˜=B /sE3 and a rescaled electric field F ˜=d F /B . B ,d ,F ,andsE 3 are respectively the rotational constant, the full electric dipole moment of the molecules, the applied electric field, and a characteristic dipole-dipole energy. We identify two groups of bi-alkali-metal dipolar molecules. The first group, including RbCs, NaK, KCs, LiK, NaRb, LiRb, NaCs, and LiCs, is favorable with a ratio over 1000 at collision energies equal to (or even higher than) their characteristic dipolar energy. The second group, including LiNa and KRb, is not favorable. More generally, for molecules well described by Hund's case b, our adimensional study provides the conditions of efficient evaporative cooling. The range of appropriate rescaled rotational constant and rescaled field is approximately B ˜≥108 and 3.25 ≤F ˜≤3.8 , with a maximum ratio reached for F ˜≃3.4 for a given B ˜. We also discuss the importance of the electronic van der Waals interaction on the adimensional character of our study.

In situ genetic correction of F8 intron 22 inversion in hemophilia A patient-specific iPSCs

PubMed Central

Wu, Yong; Hu, Zhiqing; Li, Zhuo; Pang, Jialun; Feng, Mai; Hu, Xuyun; Wang, Xiaolin; Lin-Peng, Siyuan; Liu, Bo; Chen, Fangping; Wu, Lingqian; Liang, Desheng

2016-01-01

Nearly half of severe Hemophilia A (HA) cases are caused by F8 intron 22 inversion (Inv22). This 0.6-Mb inversion splits the 186-kb F8 into two parts with opposite transcription directions. The inverted 5′ part (141 kb) preserves the first 22 exons that are driven by the intrinsic F8 promoter, leading to a truncated F8 transcript due to the lack of the last 627 bp coding sequence of exons 23–26. Here we describe an in situ genetic correction of Inv22 in patient-specific induced pluripotent stem cells (iPSCs). By using TALENs, the 627 bp sequence plus a polyA signal was precisely targeted at the junction of exon 22 and intron 22 via homologous recombination (HR) with high targeting efficiencies of 62.5% and 52.9%. The gene-corrected iPSCs retained a normal karyotype following removal of drug selection cassette using a Cre-LoxP system. Importantly, both F8 transcription and FVIII secretion were rescued in the candidate cell types for HA gene therapy including endothelial cells (ECs) and mesenchymal stem cells (MSCs) derived from the gene-corrected iPSCs. This is the first report of an efficient in situ genetic correction of the large inversion mutation using a strategy of targeted gene addition. PMID:26743572

In situ genetic correction of F8 intron 22 inversion in hemophilia A patient-specific iPSCs.

PubMed

Wu, Yong; Hu, Zhiqing; Li, Zhuo; Pang, Jialun; Feng, Mai; Hu, Xuyun; Wang, Xiaolin; Lin-Peng, Siyuan; Liu, Bo; Chen, Fangping; Wu, Lingqian; Liang, Desheng

2016-01-08

Nearly half of severe Hemophilia A (HA) cases are caused by F8 intron 22 inversion (Inv22). This 0.6-Mb inversion splits the 186-kb F8 into two parts with opposite transcription directions. The inverted 5' part (141 kb) preserves the first 22 exons that are driven by the intrinsic F8 promoter, leading to a truncated F8 transcript due to the lack of the last 627 bp coding sequence of exons 23-26. Here we describe an in situ genetic correction of Inv22 in patient-specific induced pluripotent stem cells (iPSCs). By using TALENs, the 627 bp sequence plus a polyA signal was precisely targeted at the junction of exon 22 and intron 22 via homologous recombination (HR) with high targeting efficiencies of 62.5% and 52.9%. The gene-corrected iPSCs retained a normal karyotype following removal of drug selection cassette using a Cre-LoxP system. Importantly, both F8 transcription and FVIII secretion were rescued in the candidate cell types for HA gene therapy including endothelial cells (ECs) and mesenchymal stem cells (MSCs) derived from the gene-corrected iPSCs. This is the first report of an efficient in situ genetic correction of the large inversion mutation using a strategy of targeted gene addition.

Plasma 8-iso-Prostaglandin F2α concentrations and outcomes after acute intracerebral hemorrhage.

PubMed

Du, Quan; Yu, Wen-Hua; Dong, Xiao-Qiao; Yang, Ding-Bo; Shen, Yong-Feng; Wang, Hao; Jiang, Li; Du, Yuan-Feng; Zhang, Zu-Yong; Zhu, Qiang; Che, Zhi-Hao; Liu, Qun-Jie

2014-11-01

Higher plasma 8-iso-Prostaglandin F2α concentrations have been associated with poor outcome of severe traumatic brain injury. We further investigated the relationships between plasma 8-iso-Prostaglandin F2α concentrations and clinical outcomes in patients with acute intracerebral hemorrhage. Plasma 8-iso-Prostaglandin F2α concentrations of 128 consecutive patients and 128 sex- and gender-matched healthy subjects were measured by enzyme-linked immunosorbent assay. We assessed their relationships with disease severity and clinical outcomes including 1-week mortality, 6-month mortality and unfavorable outcome (modified Rankin Scale score>2). Plasma 8-iso-Prostaglandin F2α concentrations were substantially higher in patients than in healthy controls. Plasma 8-iso-Prostaglandin F2α concentrations were positively associated with National Institutes of Health Stroke Scale (NIHSS) scores and hematoma volume using a multivariate linear regression. It emerged as an independent predictor for clinical outcomes of patients using a forward stepwise logistic regression. ROC curves identified the predictive values of plasma 8-iso-Prostaglandin F2α concentrations, and found its predictive value was similar to NIHSS scores and hematoma volumes. However, it just numerically added the predictive values of NIHSS score and hematoma volume. Increased plasma 8-iso-Prostaglandin F2α concentrations are associated with disease severity and clinical outcome after acute intracerebral hemorrhage. Copyright © 2014 Elsevier B.V. All rights reserved.

In-Plane Shielding for CT: Effect of Off-Centering, Automatic Exposure Control and Shield-to-Surface Distance

PubMed Central

Dang, Pragya; Singh, Sarabjeet; Saini, Sanjay; Shepard, Jo-Anne O.

2009-01-01

Objective To assess effects of off-centering, automatic exposure control, and padding on attenuation values, noise, and radiation dose when using in-plane bismuth-based shields for CT scanning. Materials and Methods A 30 cm anthropomorphic chest phantom was scanned on a 64-multidetector CT, with the center of the phantom aligned to the gantry isocenter. Scanning was repeated after placing a bismuth breast shield on the anterior surface with no gap and with 1, 2, and 6 cm of padding between the shield and the phantom surface. The "shielded" phantom was also scanned with combined modulation and off-centering of the phantom at 2 cm, 4 cm and 6 cm below the gantry isocenter. CT numbers, noise, and surface radiation dose were measured. The data were analyzed using an analysis of variance. Results The in-plane shield was not associated with any significant increment for the surface dose or CT dose index volume, which was achieved by comparing the radiation dose measured by combined modulation technique to the fixed mAs (p > 0.05). Irrespective of the gap or the surface CT numbers, surface noise increased to a larger extent compared to Hounsfield unit (HU) (0-6 cm, 26-55%) and noise (0-6 cm, 30-40%) in the center. With off-centering, in-plane shielding devices are associated with less dose savings, although dose reduction was still higher than in the absence of shielding (0 cm off-center, 90% dose reduction; 2 cm, 61%) (p < 0.0001). Streak artifacts were noted at 0 cm and 1 cm gaps but not at 2 cm and 6 cm gaps of shielding to the surface distances. Conclusion In-plane shields are associated with greater image noise, artifactually increased attenuation values, and streak artifacts. However, shields reduce radiation dose regardless of the extent of off-centering. Automatic exposure control did not increase radiation dose when using a shield. PMID:19270862

[Trial manufacture of a plunger shield for a disposable plastic syringe].

PubMed

Murakami, Shigeki; Emoto, Takashi; Mori, Hiroshige; Fujita, Katsuhisa; Kubo, Naoki

2008-08-20

A syringe-type radiopharmaceutical being supplied by a manufacturer has a syringe shield and a plunger shield, whereas an in-hospital labeling radiopharmaceutical is administered by a disposable plastic syringe without the plunger shield. In cooperation with Nihon Medi-Physics Co. Ltd., we have produced a new experimental plunger shield for the disposable plastic syringe. In order to evaluate this shielding effect, we compared the leaked radiation doses of our plunger shield with those of the syringe-type radiopharmaceutical (Medi shield type). Our plunger shield has a lead plate of 21 mm in diameter and 3 mm thick. This shield is equipped with the plunger-end of a disposal plastic syringe. We sealed 99mTc solution into a plastic syringe (Terumo Co.) of 5 ml with our plunger shield and Medi shield type of 2 ml. We measured leaked radiation doses around syringes using fluorescent glass dosimeters (Dose Ace). The number of measure points was 18. The measured doses were converted to 70 microm dose equivalent at 740 MBq of radioactivity. The results of our plunger shield and the Medi shield type were as follows: 4-13 microSv/h and 3-14 microSv/h at shielding areas, 3-545 microSv/h and 6-97 microSv/h at non-shielding areas, 42-116 microSv/h and 88-165 microSv/h in the vicinity of the syringe shield, and 1071 microSv/h and 1243 microSv/h at the front of the needle. For dose rates of shielding areas around the syringe, the shielding effects were approximately the same as those of the Medi shield type. In conclusion, our plunger shield may be useful for reducing finger exposure during the injection of an in-hospital labeled radiopharmaceutical.

Synthesis and characterization of p-type conductivity dopant 2-(3-(adamantan-1-yl)propyl)-3,5,6-trifluoro-7,7,8,8-tetracyanoquinodimethane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rainbolt, James E.; Koech, Phillip K.; Polikarpov, Evgueni

2013-01-22

We report the synthesis and characterization of 2-(3-(adamantan-1-yl)propyl)-3,5,6-trifluoro-7,7,8,8-tetracyanoquinodimethane (F3TCNQ-Ad1), a substituted analog of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), designed for p-type conductivity doping. The dopant is designed as a model for substituted alternatives to F4TCNQ that maintain similar electronic properties with the goal of engineering dopants with superior fabrication characteristics over F4TCNQ. We describe the design strategy for F3TCNQ-Ad1 based on molecular modeling predictions that substitution of a single fluorine atom of F4TCNQ has little effect on the electronic properties of the molecule. Photophysical and electrochemical characterization reveal that the adamantyl substituent in F3TCNQ-Ad1 does not significantly alter the electronic properties of themore » substituted dopant relative to F4TCNQ. Unfortunately, F3TCNQ-Ad1 degrades under standard sublimation conditions, preventing sublimation deposition processing. Instead, hole-only devices were made via solution-processing of the p-doped films with the structure glass/ITO/2.3 x103Å PVK:(MTDATA:dopant)/2.0x102Å Au/1.0x103Å Al, where dopant is either F4TCNQ or F3TCNQ-Ad1. We demonstrate that F3TCNQ-Ad1 increased the conductivity of the films by at least 1,000 times compared to an undoped device.« less

F-8 oblique wing structural feasibility study

NASA Technical Reports Server (NTRS)

Koltko, E.; Katz, A.; Bell, M. A.; Smith, W. D.; Lauridia, R.; Overstreet, C. T.; Klapprott, C.; Orr, T. F.; Jobe, C. L.; Wyatt, F. G.

1975-01-01

The feasibility of fitting a rotating oblique wing on an F-8 aircraft to produce a full scale manned prototype capable of operating in the transonic and supersonic speed range was investigated. The strength, aeroelasticity, and fatigue life of such a prototype are analyzed. Concepts are developed for a new wing, a pivot, a skewing mechanism, control systems that operate through the pivot, and a wing support assembly that attaches in the F-8 wing cavity. The modification of the two-place NTF-8A aircraft to the oblique wing configuration is discussed.

The OD/OH Isotope Ratio in Comets 8P/Tuttle and C/2012 F6 (Lemmon)

NASA Astrophysics Data System (ADS)

Rousselot, Philippe; Jehin, Emmanuel; Hutsemekers, Damien; Manfroid, Jean; Decock, Alice; Bockelee-Morvan, Dominique

2016-10-01

The determination of isotopic ratios in solar system objects is an important source of information about their origin, especially for comets. Among these ratios the D/H is of particular importance because of its sensitivity to fractionation processes and physical environment, and the abundance of hydrogen in the solar system. The main molecule used to derive this ratio in comets is water. So far, apart water, only HCN has permitted to derive D/H ratio and not only upper limits.Most of the existing determinations of D/H in water molecules have been obtained by spectroscopic observations of water lines in the sub-mm or near infrared range [1,2]. So far only one measurement has been based on OD/OH emission lines radicals in the near-UV [3] and another one on the Lyman-alpha D emission [4]. In situ measurements have also been obtained in comets 1P/Halley and 67P/Churyumov-Gerasimenko using mass spectrometer [5,6,7,8].In this work we have used the OH and OD ultraviolet bands at 310 nm observed with the ESO 8-m Very Large Telescope feeding the Ultraviolet-Visual Echelle Spectrograph (UVES) for measuring the D/H ratio in comets 8P/Tuttle and C/2012 F6 (Lemmon). The OH and OD being the photodissociation products of H2O and HDO such observations allow to derive D/H ratio for water molecules. This work constitutes an independant determination of the D/H ratios already published for these comets and based on observations performed in the sub-mm and near infrared range of H2O and HDO lines. We present our modeling, data analysis and numerical values obtained for this ratio.[1] D. Bockelée-Morvan et al., 2015, SSR 197, 47-83 [2] N. Biver et al., 2016, A&A 589, id A78, 11p [3] D. Hutsemékers et al., 2008, A&A 490, L31 [4] H.A. Weaver et al., 2008, LPI Contributions 1405, 8216 [5] H. Balsiger, K. Altwegg, J. Geiss, 1995, JGR 100, 5827 [6] P. Eberhardt et al., 1995, A&A 302, 301 [7] R.H. Brown et al., 2012, PSS 60, 166 [8] K. Alwegg et al., 2015, Science 347, article id. 1261952

1.8 billion years of fluid-crust interaction: A zircon oxygen isotope record for the lower crust, western Churchill Province, Canadian Shield

NASA Astrophysics Data System (ADS)

Petts, Duane C.; Moser, Desmond E.; Longstaffe, Frederick J.; Davis, William J.; Stern, Richard A.

2014-04-01

The western Churchill Province of the Canadian Shield experienced a prolonged and complex formation history (ca. 4.04 to 1.70 Ga), with evidence for multiple episodes of orogenesis and regional magmatic activity. Here we report on the oxygen isotopic compositions of garnet and zircon recovered from lower crustal xenoliths, which have U-Pb ages between ca. 3.5 and 1.7 Ga. Overall, zircon from four metabasite xenoliths from the Rankin Inlet sample suite have δ18O values ranging from + 5.5 to + 8.6‰. Zircon from three metatonalite/anorthosite xenoliths and five metabasite xenoliths from the Repulse Bay sample suite have δ18O values of + 5.6 to + 8.3‰. High δ18O values (> + 6.0‰) for the oldest igneous zircon cores (ca. 3.5 Ga and 3.0-2.6 Ga) indicate that their metatonalite/anorthosite protolith magmas were generated from, or had assimilated, supracrustal rocks that interacted previously with surface-derived fluids. Igneous zircon cores (ca. 2.9-2.6 Ga) from one metabasite xenolith have δ18O values of + 5.6 to + 6.4‰, which suggests a formation from a mantle-derived basaltic/gabbroic magma. Metamorphic zircon cores (ca. 2.0-1.9 Ga) from one metabasite xenolith commonly have δ18O values between + 6.0 and + 6.3‰, which is indicative of a basalt/gabbro protolith and localized reworking of the lower crust caused by regional-scale plate convergence. The wide range of δ18O values (+ 5.5 to + 8.3‰) for ca. 1.75-1.70 Ga metamorphic zircon rims (identified in all xenoliths) indicates regional transient heating and reworking of mantle- and supracrustal-derived crust, induced by magmatic underplating along the crust-mantle boundary.

Hard X-ray photoemission study of the Fabre salts (TMTTF)2X (X = SbF6 and PF6)

NASA Astrophysics Data System (ADS)

Medjanik, Katerina; de Souza, Mariano; Kutnyakhov, Dmytro; Gloskovskii, Andrei; Müller, Jens; Lang, Michael; Pouget, Jean-Paul; Foury-Leylekian, Pascale; Moradpour, Alec; Elmers, Hans-Joachim; Schönhense, Gerd

2014-11-01

Core-level photoemission spectra of the Fabre salts with X = SbF6 and PF6 were taken using hard X-rays from PETRA III, Hamburg. In these salts TMTTF layers show a significant stack dimerization with a charge transfer of 1 e per dimer to the anion SbF6 or PF6. At room temperature and slightly below the core-level spectra exhibit single lines, characteristic for a well-screened metallic state. At reduced temperatures progressive charge localization sets in, followed by a 2nd order phase transition into a charge-ordered ground state. In both salts groups of new core-level signals occur, shifted towards lower kinetic energies. This is indicative of a reduced transverse-conductivity across the anion layers, visible as layer-dependent charge depletion for both samples. The surface potential was traced via shifts of core-level signals of an adsorbate. A well-defined potential could be established by a conducting cap layer of 5 nm aluminum which appears "transparent" due to the large probing depth of HAXPES (8-10 nm). At the transition into the charge-ordered phase the fluorine 1 s line of (TMTTF)2SbF6 shifts by 2.8 eV to higher binding energy. This is a spectroscopic fingerprint of the loss of inversion symmetry accompanied by a cooperative shift of the SbF6 anions towards the more positively charged TMTTF donors. This shift does not occur for the X = PF6 compound, most likely due to smaller charge disproportion or due to the presence of charge disorder.

F-doped VO2 nanoparticles for thermochromic energy-saving foils with modified color and enhanced solar-heat shielding ability.

PubMed

Dai, Lei; Chen, Shi; Liu, Jianjun; Gao, Yanfeng; Zhou, Jiadong; Chen, Zhang; Cao, Chuanxiang; Luo, Hongjie; Kanehira, Minoru

2013-07-28

F-doped VO2 (M1) nanoparticles were prepared via one-pot hydrothermal synthesis. The F-doping can minimise the size of the VO2 (M1) nanoparticles, induce a homogeneous size distribution and effectively decrease the phase transition temperature to 35 °C at 2.93% F in VO2. VO2 smart glass foils obtained by casting these nanoparticles exhibit excellent thermochromism in the near-infrared region, which suggests that these foils can be used for energy-efficient glass. Compared to a pure VO2 foil, the 2.93% F-doped VO2 foil exhibits an increased solar-heat shielding ability (35.1%) and a modified comfortable colour, while still retaining an excellent solar modulation ability (10.7%) and an appropriate visible transmittance (48.7%). The F-doped VO2 foils are the first to simultaneously meet the requirements of a reduced phase transition temperature, diluted colour and excellent thermochromic properties, and these properties make the further improved F-doped VO2 foils suitable for commercial applications in energy efficient glass.

Electric Field and Current Density Performance Analysis of Sf6, C4f8 and CO2 Gases As An Insulation

NASA Astrophysics Data System (ADS)

Mazli, Ahmad Danial Ahmad; Jamail, Nor Akmal Mohd; Azlin Othman, Nordiana

2017-08-01

SF6 gases are not only widely used as an insulating component in electric power industry but also as an arc extinguishing performance in high voltage (HV) gas-insulated circuit breaker (GCB). SF6 gases is generally used in the production of semiconductor materials and devices. Though these gasses is widely used in many application, the presences of temperature hotspot in the insulations may affect the insulation characteristics particularly electric field and current density. Therefore, it is important to determine the relationship between electric field and current density of gasses used in the insulator in the presence of hotspot. In this paper, three types of gases in particular Sulphur Hexafluoride (SF6), Octafluorocylobutane (C4F8), and Carbon Dioxide (CO2) was used in the insulator for gas insulation with the presence of two hotspots. These two hotspost were detected by referring the rising temperature in the insulator which are 1000 and 2000 Kelvin temperature for hotspot 1 and hotspot 2, respectively. From the simulation results, it can be concluded that Sulphur Hexafluoride (SF6) is the best choice for gas insulation since it had the lowest current density and electric field compared to Octafluorocylobutane (C4F8), and Carbon Dioxide (CO2). It is observed that the maximum current density and electric field for SF6 during normal condition are 358.94 × 103 V/m and 0.643 × 109 A/m2, respectively. Meanwhile, during temperature rising at hotspot 1 and hotspot 2, SF6 also had lowest current density and electric field compared to the other gasses where the results for Emax and Jmax at hotspot 1 are 322.34 × 103 V/m and 1.934 × 109 A/m2, respectively; While, Emax and Jmax at hotspot 2 are 259.77× 103 V/m and 2.824 × 109 A/m2. The results of this analysis can be used to find the best choices of gas that can be used in the insulator.

Treatment vault shielding for a flattening filter-free medical linear accelerator

NASA Astrophysics Data System (ADS)

Kry, Stephen F.; Howell, Rebecca M.; Polf, Jerimy; Mohan, Radhe; Vassiliev, Oleg N.

2009-03-01

The requirements for shielding a treatment vault with a Varian Clinac 2100 medical linear accelerator operated both with and without the flattening filter were assessed. Basic shielding parameters, such as primary beam tenth-value layers (TVLs), patient scatter fractions, and wall scatter fractions, were calculated using Monte Carlo simulations of 6, 10 and 18 MV beams. Relative integral target current requirements were determined from treatment planning studies of several disease sites with, and without, the flattening filter. The flattened beam shielding data were compared to data published in NCRP Report No. 151, and the unflattened beam shielding data were presented relative to the NCRP data. Finally, the shielding requirements for a typical treatment vault were determined for a single-energy (6 MV) linac and a dual-energy (6 MV/18 MV) linac. With the exception of large-angle patient scatter fractions and wall scatter fractions, the vault shielding parameters were reduced when the flattening filter was removed. Much of this reduction was consistent with the reduced average energy of the FFF beams. Primary beam TVLs were reduced by 12%, on average, and small-angle scatter fractions were reduced by up to 30%. Head leakage was markedly reduced because less integral target current was required to deliver the target dose. For the treatment vault examined in the current study, removal of the flattening filter reduced the required thickness of the primary and secondary barriers by 10-20%, corresponding to 18 m3 less concrete to shield the single-energy linac and 36 m3 less concrete to shield the dual-energy linac. Thus, a shielding advantage was found when the linac was operated without the flattening filter. This translates into a reduction in occupational exposure and/or the cost and space of shielding.

Treatment vault shielding for a flattening filter-free medical linear accelerator.

PubMed

Kry, Stephen F; Howell, Rebecca M; Polf, Jerimy; Mohan, Radhe; Vassiliev, Oleg N

2009-03-07

The requirements for shielding a treatment vault with a Varian Clinac 2100 medical linear accelerator operated both with and without the flattening filter were assessed. Basic shielding parameters, such as primary beam tenth-value layers (TVLs), patient scatter fractions, and wall scatter fractions, were calculated using Monte Carlo simulations of 6, 10 and 18 MV beams. Relative integral target current requirements were determined from treatment planning studies of several disease sites with, and without, the flattening filter. The flattened beam shielding data were compared to data published in NCRP Report No. 151, and the unflattened beam shielding data were presented relative to the NCRP data. Finally, the shielding requirements for a typical treatment vault were determined for a single-energy (6 MV) linac and a dual-energy (6 MV/18 MV) linac. With the exception of large-angle patient scatter fractions and wall scatter fractions, the vault shielding parameters were reduced when the flattening filter was removed. Much of this reduction was consistent with the reduced average energy of the FFF beams. Primary beam TVLs were reduced by 12%, on average, and small-angle scatter fractions were reduced by up to 30%. Head leakage was markedly reduced because less integral target current was required to deliver the target dose. For the treatment vault examined in the current study, removal of the flattening filter reduced the required thickness of the primary and secondary barriers by 10-20%, corresponding to 18 m(3) less concrete to shield the single-energy linac and 36 m(3) less concrete to shield the dual-energy linac. Thus, a shielding advantage was found when the linac was operated without the flattening filter. This translates into a reduction in occupational exposure and/or the cost and space of shielding.

Comparative Study of Multiplet Structures of Mn4+ in K2SiF6, K2GeF6, and K2TiF6 Based on First-Principles Configuration-Interaction Calculations

NASA Astrophysics Data System (ADS)

Novita, Mega; Ogasawara, Kazuyoshi

2012-02-01

We performed first-principles configuration-interaction calculations of multiplet energies for Mn4+ in K2SiF6, K2GeF6, and K2TiF6 crystals. The results indicate that corrections based on a single-electron calculation are effective for the prediction of 4A2 → 4T2 and 4A2 → 4T1a transition energies, while such corrections are not necessary for the prediction of the 4A2 → 2E transition energy. The cluster size dependence of the multiplet energies is small. However, the 4A2 → 2E transition energy is slightly improved by using larger clusters including K ions. The theoretical multiplet energies are improved further by considering the lattice relaxation effect. As a result, the characteristic multiplet energy shifts depending on the host crystal are well reproduced without using any empirical parameters. Although K2GeF6 and K2TiF6 have lower symmetry than K2SiF6, the results indicate that the variation of the multiplet energy is mainly determined by the Mn-F bond length.

Reconstructive phase transition in (NH4)3TiF7 accompanied by the ordering of TiF6 octahedra.

PubMed

Molokeev, Maxim; Misjul, S V; Flerov, I N; Laptash, N M

2014-12-01

An unusual phase transition P4/mnc → Pa\\bar 3 has been detected after cooling the (NH4)3TiF7 compound. Some TiF6 octahedra, which are disordered in the room-temperature tetragonal structure, become ordered in the low-temperature cubic phase due to the disappearance of the fourfold axis. Other TiF6 octahedra undergo large rotations resulting in huge displacements of the F atoms by 1.5-1.8 Å that implies a reconstructive phase transition. It was supposed that phases P4/mbm and Pm\\bar 3m could be a high-temperature phase and a parent phase, respectively, in (NH4)3TiF7. Therefore, the sequence of phase transitions can be written as Pm\\bar 3m → P4/mbm → P4/mnc → Pa\\bar 3. The interrelation between (NH4)3TiF7, (NH4)3GeF7 and (NH4)3PbF7 is found, which allows us to suppose phase transitions in relative compounds.

Rietveld refinement and ionic conductivity of Ca{sub 8.4}Bi{sub 1.6}(PO{sub 4}){sub 6}O{sub 1.8}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tmar Trabelsi, I., E-mail: ilhem_tmar@yahoo.fr; Madani, A.; Mercier, A.M.

2013-01-15

The structure of Ca{sub 8.4}Bi{sub 1.6}(PO{sub 4}){sub 6}O{sub 1.8}, isostructural with Fluoroapatite, was determined by X-ray powder diffraction methods. The results of Rietveld refinement revealed that the formula of this compound is [Ca{sub 4}]{sup 4f}[Ca{sub 4.4}Bi{sub 1.6}]{sup 6h}(PO{sub 4}){sub 6}[O{sub 1.8}]{sup 2a}, space group P63/m (a=9.468 (3) A, c=6.957 (3) A). A total substitution of Bi{sup 3+} ions in the (6h) sites was related particularly to the high polarizability of the Bi{sup 3+} ion compared to Ca{sup 2+}. The observed frequencies in the Raman and infrared spectra were explained and discussed on the basis of unit-cell group analyses and inmore » comparison with Fluoroapatite and other oxyapatites. The ionic conductivity over a wide range of temperature was investigated according to the complex impedance method. The highest overall conductivity values were found at {sigma}{sub 700 Degree-Sign C} =5.03 Multiplication-Sign 10{sup -7} S cm{sup -1} and E{sub a}=0.50 eV. - Graphical abstract: The final Rietveld refinement plot of the Ca{sub 8.4}Bi{sub 1.6} (PO{sub 4}){sub 6}O{sub 1.8}. Highlights: Black-Right-Pointing-Pointer The Rietveld refinement revealed that the formula of this compound is Ca{sub 8.4}Bi{sub 1.6}(PO{sub 4}){sub 6}O{sub 1.8}. Black-Right-Pointing-Pointer Vibrational spectroscopy supports the high symmetry P63/m space group for this apatite. Black-Right-Pointing-Pointer This apatite contained channels where oxygen ions were located in 2a sites. Black-Right-Pointing-Pointer The possibility of anionic conduction along these channels was considered.« less

A high-performance magnetic shield with large length-to-diameter ratio.

PubMed

Dickerson, Susannah; Hogan, Jason M; Johnson, David M S; Kovachy, Tim; Sugarbaker, Alex; Chiow, Sheng-wey; Kasevich, Mark A

2012-06-01

We have demonstrated a 100-fold improvement in the magnetic field uniformity on the axis of a large aspect ratio, cylindrical, mumetal magnetic shield by reducing discontinuities in the material of the shield through the welding and re-annealing of a segmented shield. The three-layer shield reduces Earth's magnetic field along an 8 m region to 420 μG (rms) in the axial direction, and 460 and 730 μG (rms) in the two transverse directions. Each cylindrical shield is a continuous welded tube which has been annealed after manufacture and degaussed in the apparatus. We present both experiments and finite element analysis that show the importance of uniform shield material for large aspect ratio shields, favoring a welded design over a segmented design. In addition, we present finite element results demonstrating the smoothing of spatial variations in the applied magnetic field by cylindrical magnetic shields. Such homogenization is a potentially useful feature for precision atom interferometric measurements.

Detection of shielded nuclear material in a cargo container

NASA Astrophysics Data System (ADS)

Jones, James L.; Norman, Daren R.; Haskell, Kevin J.; Sterbentz, James W.; Yoon, Woo Y.; Watson, Scott M.; Johnson, James T.; Zabriskie, John M.; Bennett, Brion D.; Watson, Richard W.; Moss, Cavin E.; Frank Harmon, J.

2006-06-01

The Idaho National Laboratory, along with Los Alamos National Laboratory and the Idaho State University's Idaho Accelerator Center, are developing electron accelerator-based, photonuclear inspection technologies for the detection of shielded nuclear material within air-, rail-, and especially, maritime-cargo transportation containers. This paper describes a developing prototypical cargo container inspection system utilizing the Pulsed Photonuclear Assessment (PPA) technology, incorporates interchangeable, well-defined, contraband shielding structures (i.e., "calibration" pallets) providing realistic detection data for induced radiation signatures from smuggled nuclear material, and provides various shielded nuclear material detection results. Using a 4.8-kg quantity of depleted uranium, neutron and gamma-ray detection responses are presented for well-defined shielded and unshielded configurations evaluated in a selected cargo container inspection configuration.

Aircraft Radiation Shield Experiments--Preflight Laboratory Testing

NASA Technical Reports Server (NTRS)

Singleterry, Robert C., Jr.; Shinn, Judy L.; Wilson, John W.; Maiden, Donald L.; Thibeault, Sheila A.; Badavi, Francis F.; Conroy, Thomas; Braby, Leslie

1999-01-01

In the past, measurements onboard a research Boeing 57F (RB57-F) aircraft have demonstrated that the neutron environment within the aircraft structure is greater than that in the local external environment. Recent studies onboard Boeing 737 commercial flights have demonstrated cabin variations in radiation exposure up to 30 percent. These prior results were the basis of the present study to quantify the potential effects of aircraft construction materials on the internal exposures of the crew and passengers. The present study constitutes preflight measurements using an unmoderated Cf-252 fission neutron source to quantify the effects of three current and potential aircraft materials (aluminum, titanium, and graphite-epoxy composite) on the fast neutron flux. Conclusions about the effectiveness of the three selected materials for radiation shielding must wait until testing in the atmosphere is complete; however, it is clear that for shielding low-energy neutrons, the composite material is an improved shielding material over aluminum or titanium.

TH-CD-201-02: A Monte Carlo Investigation of a Novel Detector Arrangement for the Energy Spectrum Measurement of a 6MV Linear Accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taneja, S; Bartol, L; Culberson, W

2016-06-15

Purpose: Direct measurement of the energy spectrum of a 6MV linear accelerator has not been successful due to the high fluence rate, high energy nature of these photon beams. Previous work used a Compton Scattering (CS) spectrometry setup with a shielded spectrometer for spectrum measurements. Despite substantial lead shielding, excessive pulse pile-up was seen. MCNP6 transport code was used to investigate the feasibility and effectiveness of performing measurements using a novel detector setup. Methods: Simulations were performed with a shielded high-purity germanium (HPGe) semiconductor detector placed in the accelerator vault’s maze, with a 2 cm diameter collimator through a 92more » cm thick concrete wall. The detector was positioned 660 cm from a scattering rod (placed at isocenter) at an angle of 45° relative to the central axis. This setup was compared with the shielded detector positioned in the room, 200 cm from the scattering rod at the same CS angle. Simulations were used to determine fluence contributions from three sources: (1) CS photons traveling through the collimator aperture, the intended signal, (2) CS scatter photons penetrating the detector shield, and (3) room-scattered photons penetrating the detector shield. Variance reduction techniques including weight windows, DXTRAN spheres, forced collisions, and energy cutoffs were used. Results: Simulations showed that the number of pulses per starting particle from an F8 detector tally for the intended signal decreased by a factor of 10{sup 2} when moving the detector out of the vault. This reduction in signal was amplified for the unwanted scatter signal which decreased by up to a factor of 10{sup 9}. Conclusion: This work used MCNP6 to show that using a vault wall to shield unwanted scatter and increasing isocenter-to-detector distance reduces unwanted fluence to the detector. This study aimed to provide motivation for future experimental work using the proposed setup.« less

NMR shielding calculations across the periodic table: diamagnetic uranium compounds. 2. Ligand and metal NMR.

PubMed

Schreckenbach, Georg

2002-12-16

In this and a previous article (J. Phys. Chem. A 2000, 104, 8244), the range of application for relativistic density functional theory (DFT) is extended to the calculation of nuclear magnetic resonance (NMR) shieldings and chemical shifts in diamagnetic actinide compounds. Two relativistic DFT methods are used, ZORA ("zeroth-order regular approximation") and the quasirelativistic (QR) method. In the given second paper, NMR shieldings and chemical shifts are calculated and discussed for a wide range of compounds. The molecules studied comprise uranyl complexes, [UO(2)L(n)](+/-)(q); UF(6); inorganic UF(6) derivatives, UF(6-n)Cl(n), n = 0-6; and organometallic UF(6) derivatives, UF(6-n)(OCH(3))(n), n = 0-5. Uranyl complexes include [UO(2)F(4)](2-), [UO(2)Cl(4)](2-), [UO(2)(OH)(4)](2-), [UO(2)(CO(3))(3)](4-), and [UO(2)(H(2)O)(5)](2+). For the ligand NMR, moderate (e.g., (19)F NMR chemical shifts in UF(6-n)Cl(n)) to excellent agreement [e.g., (19)F chemical shift tensor in UF(6) or (1)H NMR in UF(6-n)(OCH(3))(n)] has been found between theory and experiment. The methods have been used to calculate the experimentally unknown (235)U NMR chemical shifts. A large chemical shift range of at least 21,000 ppm has been predicted for the (235)U nucleus. ZORA spin-orbit appears to be the most accurate method for predicting actinide metal chemical shifts. Trends in the (235)U NMR chemical shifts of UF(6-n)L(n) molecules are analyzed and explained in terms of the calculated electronic structure. It is argued that the energy separation and interaction between occupied and virtual orbitals with f-character are the determining factors.

125Te NMR shielding and optoelectronic spectra in XTe3O8 (X = Ti, Zr, Sn and Hf) compounds: Ab initio calculations

NASA Astrophysics Data System (ADS)

Bashi, M.; Rahnamaye Aliabad, H. A.; Mowlavi, A. A.; Ahmad, Iftikhar

2017-11-01

We have calculated the NMR shielding, structural properties and optoelectronic spectra of XTe3O8 (X = Ti, Zr, Sn and Hf) compounds. The full potential linearized augmented plane wave (FP-LAPW) method and the modified Becke-Johnson (mBJ) are used by density functional theory schemes. The calculated shielding and measured shifts are arranged in a straight line and the tensors of magnetic shielding have a low symmetry and the shielding along the x direction is greater than the y and z directions. Obtained results show that the X ions have the most important influence on the 125Te chemical shift. Calculated chemical shielding components (σii) decrease from Ti to Sn then increases from Sn to Hf so that these behaviors are vice versa for 125Te isotropic chemical shift (δiso). Density of states spectra show that the X-p and d states play key role in the optical and NMR calculations. Optical results illustrate that there is a direct relation between the chemical shielding components for Te atom and the static dielectric function, refractive index and Plasmon energies.

Detection of Shielded Nuclear Material in a Cargo Container

DOE Office of Scientific and Technical Information (OSTI.GOV)

J. L. Jones; D. R. Norman; K. J. Haskell

The Idaho National Laboratory, along with Los Alamos National Laboratory and the Idaho State University’s Idaho Accelerator Center, are developing electron accelerator-based, photonuclear inspection technologies for the detection of shielded nuclear material within air-, rail-, and especially, maritime-cargo transportation containers. This paper describes a developing prototypical cargo container inspection system utilizing the Pulsed Photonuclear Assessment (PPA) technology, incorporates interchangeable, well-defined, contraband shielding structures (i.e., "calibration" pallets) providing realistic detection data for induced radiation signatures from smuggled nuclear material, and provides various shielded nuclear material detection results. Using a 4.8-kg quantity of depleted uranium, neutron and gamma-ray detection responses are presentedmore » for well-defined shielded and unshielded configurations evaluated in a selected cargo container inspection configuration. © 2001 Elsevier Science. All rights reserved« less

Plasma oscillations in a 6-kW magnetically shielded Hall thruster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jorns, Benjamin A., E-mail: benjamin.a.jorns@jpl.nasa.gov; Hofer, Richard R.

2014-05-15

Plasma oscillations from 0–100 kHz in a 6-kW magnetically shielded Hall thruster are experimentally characterized with a high-speed, optical camera. Two modes are identified at 7–12 kHz and 70–90 kHz. The low frequency mode is found to be azimuthally uniform across the thruster face, while the high frequency oscillation is peaked close to the centerline-mounted cathode with an m = 1 azimuthal dependence. An analysis of these results in the context of wave-based theory suggests that the low frequency wave is the breathing mode oscillation, while the higher frequency mode is gradient-driven. The effect of these oscillations on thruster operation is examined through an analysismore » of thruster discharge current and a comparison with published observations from an unshielded variant of the thruster. Most notably, it is found that although the oscillation spectra of the two thrusters are different, they exhibit nearly identical steady-state behavior.« less

Structure cristalline de NaLiYb/sub 2/F/sub 8/: composes isotypes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dib, A.; Gorius, M.F.; Aleonard, S.

1986-11-15

NaLiYb/sub 2/F/sub 8/ crystallizes in the monoclinic system, space group C2/c, with a = 10.3516(9), b = 8.2069(9), c = 6,9674(7) A, ..beta.. = 90/sup 0/, Z = 4. The crystal structure has been solved from single crystal diffractometer measurements (AgK..cap alpha.. radiation) using Patterson and Fourier syntheses and refined by a least-squares method. The final R value is 0.021 for 1756 independent observed reflections. Two YbF/sub 8/ polyhedra share one of their edges to form Yb/sub 2/F/sub 14/ groups which are three-dimensionally linked and create cavities in which Na and Li are located. Yb/sub 2/F/sub 14/ groups share twomore » of their edges with these of one NaF/sub 7/ (or NaF/sub 9/ polyhedron to form Y/sub 2/NaF/sub 20/ blocks. As well, the structure may be described by the packing of planes formed by these two-dimensionally linked blocks. The description of this structure is compared with that ascribed to NaLiY/sub 2/F/sub 8/, which has been described in the monoclinic system, space group P2/sub 1//m, with a' = (a + b)/2, b' = c,c' = (b - a)/2, Z = 2. It is shown that positions of the atoms confer pseudoorthorhombic symmetry on the cell. Lattice parameters of isotypic compounds are given in the pseudoorthorhombic lattice and they are compared with those recently published with the structure described in the monoclinic system, space group P2/sub 1//m.« less

WE-G-17A-09: Novel Magnetic Shielding Design for Inline and Perpendicular Integrated 6 MV Linac and 1.0 T MRI Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, X; Ma, B; Kuang, Y

2014-06-15

Purpose: The influence of fringe magnetic fields delivered by magnetic resonance imaging (MRI) on the beam generation and transportation in Linac is still a major challenge for the integration of linear accelerator and MRI (Linac-MRI). In this study, we investigated an optimal magnetic shielding design for Linac-MRI and further characterized the beam trajectory in electron gun. Methods: Both inline and perpendicular configurations were analyzed in this study. The configurations, comprising a Linac-MRI with a 100cm SAD and an open 1.0 T superconductive magnet, were simulated by the 3D finite element method (FEM). The steel shielding around the Linac was includedmore » in the 3D model, the thickness of which was varied from 1mm to 20mm, and magnetic field maps were acquired with and without additional shielding. The treatment beam trajectory in electron gun was evaluated using OPERA 3d SCALA with and without shielding cases. Results: When Linac was not shielded, the uniformity of diameter sphere volume (DSV) (30cm) was about 5 parts per million (ppm) and the fringe magnetic fields in electron gun were more than 0.3 T. With shielding, the magnetic fields in electron gun were reduced to less than 0.01 T. For the inline configuration, the radial magnetic fields in the Linac were about 0.02T. A cylinder steel shield used (5mm thick) altered the uniformity of DSV to 1000 ppm. For the perpendicular configuration, the Linac transverse magnetic fields were more than 0.3T, which altered the beam trajectory significantly. A 8mm-thick cylinder steel shield surrounding the Linac was used to compensate the output losses of Linac, which shifted the magnetic fields' uniformity of DSV to 400 ppm. Conclusion: For both configurations, the Linac shielding was used to ensure normal operation of the Linac. The effect of magnetic fields on the uniformity of DSV could be modulated by the shimming technique of the MRI magnet. NIH/NIGMS grant U54 GM104944, Lincy Endowed Assistant

21 CFR 886.4750 - Ophthalmic eye shield.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Ophthalmic eye shield. 886.4750 Section 886.4750...) MEDICAL DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4750 Ophthalmic eye shield. (a) Identification. An ophthalmic eye shield is a device that consists of a plastic or aluminum eye covering intended to...

21 CFR 886.4750 - Ophthalmic eye shield.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ophthalmic eye shield. 886.4750 Section 886.4750...) MEDICAL DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4750 Ophthalmic eye shield. (a) Identification. An ophthalmic eye shield is a device that consists of a plastic or aluminum eye covering intended to...

Crystal growth of argyrodite-type phases Cu 8-xGeS 6-xI x and Cu 8-xGeSe 6-xI x (0⩽ x⩽0.8)

NASA Astrophysics Data System (ADS)

Tomm, Yvonne; Schorr, Susan; Fiechter, Sebastian

2008-04-01

The growth of single crystalline argyrodites of type Cu 8-xGeX 6-xY x ( X=S, Se; Y=I) is reported. These materials undergo solid-solid phase transitions at temperatures ranging from 30 to 90 °C. In the high temperature phase, Cu 8GeS 6 crystallizes in the cubic space group F4¯3m. In the low temperature phase, the compound is present in the orthorhombic space group Pmn2 1. Cu 8GeSe 6 appears exclusively in the hexagonal space groups P6 3mc or P6 3cm, respectively. Single crystals of these argyrodites were obtained by chemical vapor transport in a temperature gradient Δ T=980-950 and Δ T=700-620 °C for sulfides and selenides, respectively. As a result of the growth process, the high temperature phase remains stable even at ambient temperature by incorporation of the transport agent iodine during the growth process. As determined by energy dispersive X-ray analysis (EDAX), the composition of the sulfide crystals grown ranges from Cu 8GeS 6 to Cu 7.16GeS 5.16I 0.84. The selenide crystallizes as Cu 7.69GeSe 5.69I 0.31. In contrast, the solid state reaction of the elements Cu, Ge and X produces a material in the low temperature modification with an ideal composition of Cu 8GeX 6.

LPT. Shield test facility (TAN645 and 646). Calibration lab shield ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

LPT. Shield test facility (TAN-645 and -646). Calibration lab shield door. Ralph M. Parsons 1229-17 ANP/GE-6-645-MS-1. April 1957. Approved by INEEL Classification Office for public release. INEEL index code no. 037-0645-40-693-107369 - Idaho National Engineering Laboratory, Test Area North, Scoville, Butte County, ID

A DFT investigation on geometry and chemical bonding of isoelectronic Si8N6V-, Si8N6Cr, and Si8N6Mn+ clusters

NASA Astrophysics Data System (ADS)

Tam, Nguyen Minh; Pham, Hung Tan; Cuong, Ngo Tuan; Tung, Nguyen Thanh

2017-10-01

The geometric feature and chemical bonding of isoelectronic systems Si8N6Mq (M = V, Cr, Mn and q = -1, 0, 1, respectively) are investigated by means of density-functional-theory calculations. The encapsulated form is found for all ground-state structures, where the metal atom locates at the central site of the hollow Si8N6 cage. The Si8N6 cage is established by adding two Si atoms to a distorted Si6N6 prism, which is a combination of Si4N2 and Si2N4 strings. Chemical bonding of Si8N6Mq systems is explored by using the electron localization indicator and theory of atom in molecule, revealing the vital role of metal center in stabilizing the clusters.

Pretinning Nickel-Plated Wire Shields

NASA Technical Reports Server (NTRS)

Igawa, J. A.

1985-01-01

Nickel-plated copper shielding for wires pretinned for subsequent soldering with help of activated rosin flux. Shield cut at point 0.25 to 0.375 in. (6 to 10 mm) from cut end of outer jacket. Loosened end of shield straightened and pulled toward cut end. Insulation of inner wires kept intact during pretinning.

F8 and F9 mutations in US haemophilia patients: correlation with history of inhibitor and race/ethnicity.

PubMed

Miller, C H; Benson, J; Ellingsen, D; Driggers, J; Payne, A; Kelly, F M; Soucie, J M; Craig Hooper, W

2012-05-01

Both genetic and treatment-related risk factors contribute to the development of inhibitors in haemophilia. An inhibitor surveillance system piloted at 12 US sites has the goal of assessing risk factors through prospective data collection. This report examines the relationship of genotype and race/ethnicity to history of inhibitor in a large cohort of US haemophilia patients. Mutation analysis was performed on 676 haemophilia A (HA) and 153 haemophilia B (HB) patients by sequencing, Multiplex Ligation-dependent Probe Amplification, and PCR for inversions in F8 introns 22 (inv22) and 1 (inv1). Two HB patients with deletions had history of inhibitor. In severe HA, frequency of history of inhibitor was: large deletion 57.1%, splice site 35.7%, inv22 26.8%, nonsense 24.5%, frameshift 12.9%, inv1 11.1% and missense 9.5%. In HA, 19.6% of 321 White non-Hispanics (Whites), 37.1% of 35 Black non-Hispanics (Blacks) and 46.9% of 32 Hispanics had history of inhibitor (P = 0.0003). Mutation types and novel mutation rates were similar across ethnicities. When F8 haplotypes were constructed, Whites and Hispanics showed only H1 and H2. Within H1, history of inhibitor was 12.4% in Whites, 40.0% in Blacks (P = 0.009) and 32.4% in Hispanics (P = 0.002). Inhibitor frequency is confirmed to vary by mutation type and race in a large US population. White patients with history of inhibitor did not exhibit rare F8 haplotypes. F8 gene analysis did not reveal a cause for the higher inhibitor frequencies in Black and Hispanic patients. © 2011 Blackwell Publishing Ltd.

An unusual 2p-3d-4f heterometallic coordination polymer featuring Ln8Na and Cu8I clusters as nodes

NASA Astrophysics Data System (ADS)

Zhao, Mingjuan; Chen, Shimin; Huang, Yutian; Dan, Youmeng

2017-01-01

A new cluster-based three-dimensional 2p-3d-4f heterometallic framework {[Ho8Na(OH)6Cu16I2(CPT)24](NO3)9(H2O)6(CH3CN)18}n (1, HCPT = 4-(4-carboxyphenyl)-1,2,4 triazole) has been prepared under solvothermal condition by using a custom-designed bifunctional organic ligand. The single-crystal structure analysis reveals that this framework features novel Ln8Na and Cu8I clusters as nodes, these nodes are further connected by the CPT ligands to give rise to a (6,14)-connected network. The magnetic property of this framework has also been investigated.

Thermal fatigue tests of a radiative heat shield panel for a hypersonic transport

NASA Technical Reports Server (NTRS)

Webb, Granville L.; Clark, Ronald K.; Sharpe, Ellsworth L.

1985-01-01

A pair of corrugation stiffened, beaded skin Rene 41 heat shield panels were exposed to 20,000 thermal cycles between room temperature and 1450 F to evaluate the thermal fatigue response of Rene 41 metallic heat shields for hypersonic cruise aircraft applications. At the conclusion of the tests, the panels retained substantial structural integrity; however, there were cracks and excessive wear in the vicinity of fastener holes and there was an 80-percent loss in ductility of the skin. Shrinkage of the panel which caused the cracks and wear must be considered in design of panels for Thermal Protection Systems (TPS) applications.

An almost completely shielded microelectrode.

PubMed

Sachs, F; McGarrigle, R

1980-12-01

We present a new method of shielding microelectrodes to within 20 micron of the tip. Stray capacity is reduced to less than 50 fF. Ordinary microelectrodes are covered with silver in a vacuum evaporator. Silver is removed from the tip by contact with a ball of mercury. The microelectrode is then insulated with a glass barrel which is sealed by dipping the tip in diluted polystyrene in amyl acetate, or by dipping the electrode in melted wax. The latter method is quick, easy and reliable.

MARIUS HILLS REGION, MOON: Stratigraphy of low shields and mare basalts

NASA Astrophysics Data System (ADS)

Gebhart, Jennifer; Hiesinger, Harry; van der Bogert, Carolyn; Hendrik Pasckert, Jan; Weinauer, Julia; Lawrence, Samuel; Stopar, Julie; Robinson, Mark

2016-04-01

The Marius Hills region consists of more than 250 individual basaltic low shields (usually referred to as "domes") and cones, located on a broad topographic rise. The bases of numerous low shields have slope angles of ~2-3° whereas the upper portions have slopes of ~6-7° [1], interpreted to reflect changes in composition over time [1]. However, the absence of spectral differences between the two dome morphologies and the surrounding mare basalts suggests that the observed morphologies are more plausibly explained by changes in effusion rates, temperature (viscosity), and/or crystallization over time [e.g., 2]. Previous studies indicate that volcanism in this region occurred in the Upper Imbrian (3.2-3.8 Ga) [3], although several other authors reported ages ranging from the Imbrian (~3.3 Ga) to the Eratosthenian (~2.5 Ga) [e.g., 1,2,4]. [2,5] reported that all low shields are embayed by younger mare units, indicating that they formed during an older stage of volcanic activity. Mare basalts surrounding the Marius Hills exhibit absolute model ages of 1.2-3.7 Ga [6]. We used 36 LRO NAC images to perform crater size-frequency distribution (CSFD) measurements. The images were calibrated and map-projected with ISIS 3 and imported into ArcGIS. Within ArcGIS, we used CraterTools [7] to perform our CSFD measurements. The crater size-frequency distributions were then plotted with CraterStats [8], using the production and chronology functions of [9]. We conducted CSFD measurements for 50 Marius Hills low shields. Our count area sizes ranged from 1.06 x 101 to 8.75 x 101 km2; those for adjacent basalts varied between 6.17 x 100 and 8.01 x 101 km2. We determined absolute model ages (AMAs) of 1.03 to 3.65 Ga for the low shields and did not find a spatial correlation of ages versus their locations. CSFD measurements for 27 adjacent basalts show AMAs of 1.20-3.69 Ga. Of those basalts, 24 exhibit AMAs of 3-3.5 Ga; there is no correlation of AMAs and the geographic position of the

Advanced Multifunctional MMOD Shield: Radiation Shielding Assessment

NASA Technical Reports Server (NTRS)

Rojdev, Kristina; Christiansen, Eric

2013-01-01

As NASA is looking to explore further into deep space, multifunctional materials are a necessity for decreasing complexity and mass. One area where multifunctional materials could be extremely beneficial is in the micrometeoroid orbital debris (MMOD) shield. A typical MMOD shield on the International Space Station (ISS) is a stuffed whipple shield consisting of multiple layers. One of those layers is the thermal blanket, or multi-layer insulation (MLI). Increasing the MMOD effectiveness of MLI blankets, while still preserving their thermal capabilities, could allow for a less massive MMOD shield. Thus, a study was conducted to evaluate a concept MLI blanket for an MMOD shield. In conjunction, this MLI blanket and the subsequent MMOD shield was also evaluated for its radiation shielding effectiveness towards protecting crew. The overall MMOD shielding system using the concept MLI blanket proved to only have a marginal increase in the radiation mitigating properties. Therefore, subsequent analysis was performed on various conceptual MMOD shields to determine the combination of materials that may prove superior for radiation mitigating purposes. The following paper outlines the evaluations performed and discusses the results and conclusions of this evaluation for radiation shielding effectiveness.

Thyroid Dose During Neurointerventional Procedures: Does Lead Shielding Reduce the Dose?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shortt, C. P.; Fanning, N. F.; Malone, L.

2007-09-15

Purpose. To assess radiation dose to the thyroid in patients undergoing neurointerventional procedures and to evaluate dose reduction to the thyroid by lead shielding. Methods and Materials. A randomized patient study was undertaken to evaluate the dose reduction by thyroid lead shields and assess their practicality in a clinical setting. Sixty-five patients attending for endovascular treatment of arteriovenous malformations (AVMs) and aneurysms were randomized into one of 2 groups a) No Thyroid Shield and b) Thyroid Lead Shield. Two thermoluminescent dosimeters (TLDs) were placed over the thyroid gland (1 on each side) at constant positions on each patient in bothmore » groups. A thyroid lead shield (Pb eq. 0.5 mm) was placed around the neck of patients in the thyroid lead shield group after the neurointerventional radiologist had obtained satisfactory working access above the neck. The total dose-area-product (DAP) value, number and type of digital subtraction angiography (DSA) runs and fluoroscopy time were recorded for all patients. Results. Of the 72 patients who initially attended for neurointerventional procedures, 7 were excluded due to failure to consent or because of procedures involving access to the external carotid circulation. Of the remaining 65 who were randomized, a further 9 were excluded due to; procedureabandonment, unfeasible shield placement or shield interference with the procedure. Patient demographics included mean age of 47.9 yrs (15-74), F:M=1.4:1. Mean fluoroscopy time was 25.9 min. Mean DAP value was 13,134.8 cGy.cm{sup 2} and mean number of DSA runs was 13.4. The mean relative thyroid doses were significantly different (p< 0.001) between the unshielded (7.23 mSv/cGy2 x 105) and shielded groups (3.77 mSv/cGy2 x 105). A mean thyroid dose reduction of 48% was seen in the shielded group versus the unshielded group. Conclusion. Considerable doses to the thyroid are incurred during neurointerventional procedures, highlighting the need for

Syntheses, crystal structures and Raman spectra of Ba(BF{sub 4})(PF{sub 6}), Ba(BF{sub 4})(AsF{sub 6}) and Ba{sub 2}(BF{sub 4}){sub 2}(AsF{sub 6})(H{sub 3}F{sub 4}); the first examples of metal salts containing simultaneously tetrahedral BF{sub 4}{sup -} and octahedral AF{sub 6}{sup -} anions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lozinsek, Matic; Bunic, Tina; Goreshnik, Evgeny, E-mail: evgeny.goreshnik@ijs.s

2009-10-15

In the system BaF{sub 2}/BF{sub 3}/PF{sub 5}/anhydrous hydrogen fluoride (aHF) a compound Ba(BF{sub 4})(PF{sub 6}) was isolated and characterized by Raman spectroscopy and X-ray diffraction on the single crystal. Ba(BF{sub 4})(PF{sub 6}) crystallizes in a hexagonal P6-bar2m space group with a=10.2251(4) A, c=6.1535(4) A, V=557.17(5) A{sup 3} at 200 K, and Z=3. Both crystallographically independent Ba atoms possess coordination polyhedra in the shape of tri-capped trigonal prisms, which include F atoms from BF{sub 4}{sup -} and PF{sub 6}{sup -} anions. In the analogous system with AsF{sub 5} instead of PF{sub 5} the compound Ba(BF{sub 4})(AsF{sub 6}) was isolated and characterized.more » It crystallizes in an orthorhombic Pnma space group with a=10.415(2) A, b=6.325(3) A, c=11.8297(17) A, V=779.3(4) A{sup 3} at 200 K, and Z=4. The coordination around Ba atom is in the shape of slightly distorted tri-capped trigonal prism which includes five F atoms from AsF{sub 6}{sup -} and four F atoms from BF{sub 4}{sup -} anions. When the system BaF{sub 2}/BF{sub 3}/AsF{sub 5}/aHF is made basic with an extra addition of BaF{sub 2}, the compound Ba{sub 2}(BF{sub 4}){sub 2}(AsF{sub 6})(H{sub 3}F{sub 4}) was obtained. It crystallizes in a hexagonal P6{sub 3}/mmc space group with a=6.8709(9) A, c=17.327(8) A, V=708.4(4) A{sup 3} at 200 K, and Z=2. The barium environment in the shape of tetra-capped distorted trigonal prism involves 10 F atoms from four BF{sub 4}{sup -}, three AsF{sub 6}{sup -} and three H{sub 3}F{sub 4}{sup -} anions. All F atoms, except the central atom in H{sub 3}F{sub 4} moiety, act as mu{sub 2}-bridges yielding a complex 3-D structural network. - Graphical abstract: The first three compounds, containing simultaneously tetrahedral BF{sub 4}{sup -} and octahedral AF{sub 6}{sup -} (A=P, As) anions have been synthesized and characterized by Raman spectroscopy and X-ray single crystal diffraction. In the system BaF{sub 2}/BF{sub 3}/PF{sub 5}/anhydrous hydrogen

12 CFR 563f.6 - General exemption.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 12 Banks and Banking 5 2010-01-01 2010-01-01 false General exemption. 563f.6 Section 563f.6 Banks and Banking OFFICE OF THRIFT SUPERVISION, DEPARTMENT OF THE TREASURY MANAGEMENT OFFICIAL INTERLOCKS... controlled or managed by persons who are members of a minority group, or women; (3) Is a depository...

Absolute frequency of cesium 6S-8S 822 nm two-photon transition by a high-resolution scheme.

PubMed

Wu, Chien-Ming; Liu, Tze-Wei; Wu, Ming-Hsuan; Lee, Ray-Kuang; Cheng, Wang-Yau

2013-08-15

We present an alternative scheme for determining the frequencies of cesium (Cs) atom 6S-8S Doppler-free transitions. With the use of a single electro-optical crystal, we simultaneously narrow the laser linewidth, lock the laser frequency, and resolve a narrow spectrum point by point. The error budget for this scheme is presented, and we prove that the transition frequency obtained from the Cs cell at room temperature and with one-layer μ-metal shielding is already very near that for the condition of zero collision and zero magnetic field. We point out that a sophisticated linewidth measurement could be a good guidance for choosing a suitable Cs cell for better frequency accuracy.

Effects of feedstock availability on the negative ion behavior in a C{sub 4}F{sub 8} inductively coupled plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Shu-Xia; Research group PLASMANT, Dept. Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp; Gao, Fei

2015-07-21

In this paper, the negative ion behavior in a C{sub 4}F{sub 8} inductively coupled plasma (ICP) is investigated using a hybrid model. The model predicts a non-monotonic variation of the total negative ion density with power at low pressure (10–30 mTorr), and this trend agrees well with experiments that were carried out in many fluorocarbon (fc) ICP sources, like C{sub 2}F{sub 6}, CHF{sub 3}, and C{sub 4}F{sub 8}. This behavior is explained by the availability of feedstock C{sub 4}F{sub 8} gas as a source of the negative ions, as well as by the presence of low energy electrons due tomore » vibrational excitation at low power. The maximum of the negative ion density shifts to low power values upon decreasing pressure, because of the more pronounced depletion of C{sub 4}F{sub 8} molecules, and at high pressure (∼50 mTorr), the anion density continuously increases with power, which is similar to fc CCP sources. Furthermore, the negative ion composition is identified in this paper. Our work demonstrates that for a clear understanding of the negative ion behavior in radio frequency C{sub 4}F{sub 8} plasma sources, one needs to take into account many factors, like the attachment characteristics, the anion composition, the spatial profiles, and the reactor configuration. Finally, a detailed comparison of our simulation results with experiments is conducted.« less

Optical properties of BaY2F8:Ce3+

NASA Astrophysics Data System (ADS)

Fabeni, P.; di Martino, D.; Nikl, M.; Pazzi, G. P.; Sani, E.; Toncelli, A.; Tonelli, M.; Vedda, A.

2005-01-01

The optical properties of Ce3+-doped BaY2F8 crystals were investigated under selective laser excitation and X-ray irradiation. In both cases, the emission spectrum is dominated by the characteristic doublet transition from the lowest energy level of the 5d configuration to the spin-orbit split 2F ground state of Ce3+. Excitation bands at 4.1, 5.0, 5.9 and 6.2 eV, due to transitions between 4f and split 5d levels were observed. The emission time decay was satisfactorily analyzed by a single exponential component, characterized by a decay time of approximately 28 ns at 10 K and slightly increasing with temperature. A monotonic temperature quenching of the photo-luminescence intensity was observed; on the other hand, the temperature dependence of radio-luminescence intensity is modulated by the presence of shallow traps competing with Ce3+ ions in carrier trapping during irradiation.

The F8H Glycosyltransferase is a Functional Paralog of FRA8 Involved in Glucuronoxylan Biosynthesis in Arabidopsis

EPA Science Inventory

The FRAGILE FIBER8 gene was previously shown to be required for the biosynthesis of the reducing end tetrasaccharide sequence of glucuronoxylan (GX) in Arabidopsis thaliana. Here, we demonstrate that F8H, a close homolog of FRA8, is a functional ortholog of FRA8 involved in GX bi...

Absolute NMR shielding scales and nuclear spin–rotation constants in {sup 175}LuX and {sup 197}AuX (X = {sup 19}F, {sup 35}Cl, {sup 79}Br and {sup 127}I)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Demissie, Taye B., E-mail: taye.b.demissie@uit.no; Komorovsky, Stanislav; Repisky, Michal

2015-10-28

We present nuclear spin–rotation constants, absolute nuclear magnetic resonance (NMR) shielding constants, and shielding spans of all the nuclei in {sup 175}LuX and {sup 197}AuX (X = {sup 19}F, {sup 35}Cl, {sup 79}Br, {sup 127}I), calculated using coupled-cluster singles-and-doubles with a perturbative triples (CCSD(T)) correction theory, four-component relativistic density functional theory (relativistic DFT), and non-relativistic DFT. The total nuclear spin–rotation constants determined by adding the relativistic corrections obtained from DFT calculations to the CCSD(T) values are in general in agreement with available experimental data, indicating that the computational approach followed in this study allows us to predict reliable results formore » the unknown spin–rotation constants in these molecules. The total NMR absolute shielding constants are determined for all the nuclei following the same approach as that applied for the nuclear spin–rotation constants. In most of the molecules, relativistic effects significantly change the computed shielding constants, demonstrating that straightforward application of the non-relativistic formula relating the electronic contribution to the nuclear spin–rotation constants and the paramagnetic contribution to the shielding constants does not yield correct results. We also analyze the origin of the unusually large absolute shielding constant and its relativistic correction of gold in AuF compared to the other gold monohalides.« less

6. Photocopy of drawing. (This drawing is an 8' x ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

6. Photocopy of drawing. (This drawing is an 8' x 10' enlargement from a 4' x 5' negative; 1942 drawing titled 'Mobilization Buildings, Hospital Mess, Types HM-336-A, B, C, D, E, F, & G, Electrical,' Plan 800-3136, located at Directorate of Engineering and Housing, Fort McPherson.) - Fort McPherson, World War II Station Hospital, Mess Hall, Anderson Way & Howe Street, Atlanta, Fulton County, GA

Dryden F-8 Research Aircraft Fleet 1973 in flight, DFBW and SCW

NASA Technical Reports Server (NTRS)

1973-01-01

. Digital-fly-by-wire is more efficient because it is lighter and takes up less space than the hydraulic systems it replaced. This either reduces the fuel required to fly or increases the number of passengers or pounds of cargo the aircraft can carry. Digital fly-by-wire is currently used in a variety of aircraft ranging from F/A-18 fighters to the Boeing 777. The DFBW research program is considered one of the most significant and most successful NASA aeronautical programs since the inception of the agency. F-8 aircraft were built originally for the U.S. Navy by LTV Aerospace of Dallas, Texas. The aircraft had a wingspan of 35 feet, 2 inches; was 54 feet, 6 inches long; and was powered by a Pratt & Whitney J57 turbojet engine. The F-8 Supercritical Wing was a flight research project designed to test a new wing concept designed by Dr. Richard Whitcomb, chief of the Transonic Aerodynamics Branch, Langley Research Center, Hampton, Virginia. Compared to a conventional wing, the supercritical wing (SCW) is flatter on the top and rounder on the bottom with a downward curve at the trailing edge. The Supercritical Wing was designed to delay the formation of and reduce the shock wave over the wing just below and above the speed of sound (transonic region of flight). Delaying the shock wave at these speeds results in less drag. Results of the NASA flight research at the Flight Research Center, Edwards, California, (later renamed the Dryden Flight Research Center) demonstrated that aircraft using the supercritical wing concept would have increased cruising speed, improved fuel efficiency, and greater flight range than those using conventional wings. As a result, supercritical wings are now commonplace on virtually every modern subsonic commercial transport. Results of the NASA project showed the SCW had increased the transonic efficiency of the F-8 as much as 15 percent and proved that passenger transports with supercritical wings, versus conventional wings, could save $78 million (in

A pericentric inversion of chromosome X disrupting F8 and resulting in haemophilia A.

PubMed

Xin, Yu; Zhou, Jingyi; Ding, Qiulan; Chen, Changming; Wu, Xi; Wang, Xuefeng; Wang, Hongli; Jiang, Xiaofeng

2017-08-01

The frequency of X chromosome pericentric inversion is much less than that of autosome chromosome. We hereby characterise a pericentric inversion of X chromosome associated with severe factor VIII (FVIII) deficiency in a sporadic haemophilia A (HA) pedigree. PCR primer walking and genome walking strategies were adopted to identify the exact breakpoints of the inversion. Copy number variations (CNVs) of the F8 and the whole chromosomes were detected by AccuCopy and Affymetrix CytoScan High Definition (HD) assays, respectively. A karyotype analysis was performed by cytogenetic G banding technique. We identified a previously undescribed type of pericentric inversion of the X chromosome [inv(X)(p11.21q28)] in the proband with FVIII:C <1%. One breakpoint was located in the intron 7 of the F 8, which disrupted the transcription of the F8, and the other located in the upstream of the PFKFB1 of the X chromosome. The inversion segment was approximately 64.4% of the total chromosomal length. The karyotype analysis of the X chromosome confirmed the pericentric inversion of the X chromosome in the proband and his mother. A haplotype analysis traced the inversion to his maternal grandfather, who was not a somatic mosaic of the inversion. This finding indicated that the causative mutation may originate from his germ cells or a rare possibility of germ-cell mosaicism. The characterisation of pericentric inversion involving F8 extended the molecular mechanisms causing HA. The pericentric inversion rearrangement involves F8 by non-homologous end joining is responsible for pathogensis of severe HA. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Routine 18F- production with 180 μA to 200 μA target beam current on a GE PETtrace 800 cyclotron

NASA Astrophysics Data System (ADS)

Eberl, S.; Eriksson, T.; Svedberg, O.; Norling, J.; Henderson, D.; Lam, P.; Bourdier, T.; Fulham, M.

2012-12-01

Through upgrades and enhancements, which are now standard on current PETtrace 800 cyclotrons, a GE PETtrace cyclotron installed in 2002 has demonstrated reliable routine [18F]FDG production at total target beam currents of 180 μA without detriment to saturation and [18F]FDG yields. Routine production at 200 μA has been achieved and its evaluation is continuing. Self-shielded target using W/Cu alloy for the target body afforded a reduction in dose rate from the Havar foils by a factor of ˜ 8-10, reducing dose from the targets and need for removing targets during maintenance. The main activation product in the shield is 187W (T1/2 24 h). The 60Co ((T1/2 5.3 y) activation is about 250 times less at 24 h post EOB and is not considered a major issue despite its long half-life.

76 FR 19466 - Wellpoint, Inc. D/B/A/Anthem Blue Cross & Blue Shield, et al.; Amended Certification Regarding...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-07

.../B/A/Anthem Blue Cross & Blue Shield, et al.; Amended Certification Regarding Eligibility To Apply for Worker Adjustment Assistance TA-W-74,895 Wellpoint, Inc. D/B/A/Anthem Blue Cross & Blue Shield... Enterprise Provider Data Management Team North Haven, Connecticut TA-W-74,895F Wellpoint, Inc. D/B/A/Blue...

Application of a dummy eye shield for electron treatment planning

PubMed Central

Kang, Sei-Kwon; Park, Soah; Hwang, Taejin; Cheong, Kwang-Ho; Han, Taejin; Kim, Haeyoung; Lee, Me-Yeon; Kim, Kyoung Ju; Oh, Do Hoon; Bae, Hoonsik

2013-01-01

Metallic eye shields have been widely used for near-eye treatments to protect critical regions, but have never been incorporated into treatment plans because of the unwanted appearance of the metal artifacts on CT images. The purpose of this work was to test the use of an acrylic dummy eye shield as a substitute for a metallic eye shield during CT scans. An acrylic dummy shield of the same size as the tungsten eye shield was machined and CT scanned. The BEAMnrc and the DOSXYZnrc were used for the Monte Carlo (MC) simulation, with the appropriate material information and density for the aluminum cover, steel knob and tungsten body of the eye shield. The Pinnacle adopting the Hogstrom electron pencil-beam algorithm was used for the one-port 6-MeV beam plan after delineation and density override of the metallic parts. The results were confirmed with the metal oxide semiconductor field effect transistor (MOSFET) detectors and the Gafchromic EBT2 film measurements. For both the maximum eyelid dose over the shield and the maximum dose under the shield, the MC results agreed with the EBT2 measurements within 1.7%. For the Pinnacle plan, the maximum dose under the shield agreed with the MC within 0.3%; however, the eyelid dose differed by –19.3%. The adoption of the acrylic dummy eye shield was successful for the treatment plan. However, the Pinnacle pencil-beam algorithm was not sufficient to predict the eyelid dose on the tungsten shield, and more accurate algorithms like MC should be considered for a treatment plan. PMID:22915776

Demonstration of suppressed phonon tunneling losses in phononic bandgap shielded membrane resonators for high-Q optomechanics.

PubMed

Tsaturyan, Yeghishe; Barg, Andreas; Simonsen, Anders; Villanueva, Luis Guillermo; Schmid, Silvan; Schliesser, Albert; Polzik, Eugene S

2014-03-24

Dielectric membranes with exceptional mechanical and optical properties present one of the most promising platforms in quantum opto-mechanics. The performance of stressed silicon nitride nanomembranes as mechanical resonators notoriously depends on how their frame is clamped to the sample mount, which in practice usually necessitates delicate, and difficult-to-reproduce mounting solutions. Here, we demonstrate that a phononic bandgap shield integrated in the membrane's silicon frame eliminates this dependence, by suppressing dissipation through phonon tunneling. We dry-etch the membrane's frame so that it assumes the form of a cm-sized bridge featuring a 1-dimensional periodic pattern, whose phononic density of states is tailored to exhibit one, or several, full band gaps around the membrane's high-Q modes in the MHz-range. We quantify the effectiveness of this phononic bandgap shield by optical interferometry measuring both the suppressed transmission of vibrations, as well as the influence of frame clamping conditions on the membrane modes. We find suppressions up to 40 dB and, for three different realized phononic structures, consistently observe significant suppression of the dependence of the membrane's modes on sample clamping-if the mode's frequency lies in the bandgap. As a result, we achieve membrane mode quality factors of 5 × 10(6) with samples that are tightly bolted to the 8 K-cold finger of a cryostat. Q × f -products of 6 × 10(12) Hz at 300 K and 14 × 10(12) Hz at 8 K are observed, satisfying one of the main requirements for optical cooling of mechanical vibrations to their quantum ground-state.

E2F8 is essential for polyploidization in mammalian cells.

PubMed

Pandit, Shusil K; Westendorp, Bart; Nantasanti, Sathidpak; van Liere, Elsbeth; Tooten, Peter C J; Cornelissen, Peter W A; Toussaint, Mathilda J M; Lamers, Wouter H; de Bruin, Alain

2012-11-01

Polyploidization is observed in all mammalian species and is a characteristic feature of hepatocytes, but its molecular mechanism and biological significance are unknown. Hepatocyte polyploidization in rodents occurs through incomplete cytokinesis, starts after weaning and increases with age. Here, we show in mice that atypical E2F8 is induced after weaning and required for hepatocyte binucleation and polyploidization. A deficiency in E2f8 led to an increase in the expression level of E2F target genes promoting cytokinesis and thereby preventing polyploidization. In contrast, loss of E2f1 enhanced polyploidization and suppressed the polyploidization defect of hepatocytes deficient for atypical E2Fs. In addition, E2F8 and E2F1 were found on the same subset of target promoters. Contrary to the long-standing hypothesis that polyploidization indicates terminal differentiation and senescence, we show that prevention of polyploidization through inactivation of atypical E2Fs has, surprisingly, no impact on liver differentiation, zonation, metabolism and regeneration. Together, these results identify E2F8 as a repressor and E2F1 as an activator of a transcriptional network controlling polyploidization in mammalian cells.

Argon-shielded hot pressing of titanium alloy (Ti6Al4V) powders.

PubMed

Gronostajski, Zbigniew; Bandoła, P; Skubiszewski, T

2010-01-01

The paper presents the method of the argon - shielded hot pressing of titanium alloy (Ti6A14V) powder (used in medical industry). The powders produced in the GA (gas atomization) process and in the HDH (hydride - dehydride) process were used in the experiments. A pressing process was conducted at a temperature of 800-850 degrees C for different lengths of time. An unoxidized sintered material, nearly as dense as a solid material and having a lamellar structure (alpha+beta), was obtained from the titanium alloy powder produced in the HDH process.

Experiment K-6-24, K-6-25, K-6-26. Radiation dosimetry and spectrometry

NASA Technical Reports Server (NTRS)

Benton, E. V.; Frank, A.; Benton, E. R.; Dudkin, V.; Marennyi, A.

1990-01-01

Radiation experiments flown by the University of San Francisco on the Cosmos 1887 spacecraft were designed to measure the depth dependence of both total dose and heavy particle flux, dose and dose equivalent, down to very thin shielding. Three experiments were flown and were located both inside and outside the Cosmos 1887 spacecraft. Tissue absorbed dose rates of 264 to 0.028 rad d(-1) under shielding of 0.013 to 3.4 g/sq cm of (7)LiF were found outside the spacecraft and 0.025 rad d(-1) inside. Heavy particle fluxes of 3.43 to 1.03 x 10 to the minus 3rd power cm -2 sub s -1 sub sr -1 under shielding of 0.195 to 1.33 g/sq cm plastic were found outside the spacecraft and 4.25 times 10 to the minus 4th power cm -2 sub s -1 sub sr -1 inside (LET infinity H2O greater than or equal to 4 keV/micron m). The corresponding heavy particle dose equivalent rates outside the spacecraft were 30.8 to 19.8 mrem d(-1) and 11.4 mrem d(-1) inside. The large dose and particle fluxes found at small shielding thicknesses emphasize the importance of these and future measurements at low shielding, for predicting radiation effects on space materials and experiments where shielding is minimal and on astronauts during EVA. The Cosmos 1887 mission contained a variety of international radiobiological investigations to which the measurements apply. The high inclination orbit (62 degrees) of this mission provided a radiation environment which is seldom available to U.S. investigators. The radiation measurements will be compared with those of other research groups and also with those performed on the Shuttle, and will be used to refine computer models employed to calculate radiation exposures on other spacecraft, including the Space Station.

SiO2 and CaF2 Behavior During Shielded Metal Arc Welding and Their Effect on Slag Detachability of the CaO-CaF2-SiO2 Type ENiCrFe-7-Covered Electrode

NASA Astrophysics Data System (ADS)

Wang, Huang; Qin, Renyao; He, Guo

2016-09-01

The metallurgical behavior during shielded metal arc welding (SMAW) and the slag detachability of the CaO-CaF2-SiO2 type ENiCrFe-7-covered electrodes was investigated. The results indicated that the slag detachability could be improved as the SiO2 in the flux coatings decreased. When the SiO2 in the flux coating was 10.9 pct, about 28.3 pct CaF2 resulted in the best slag detachability. The CaF2 and SiO2 in the flux coating interacted during SMAW to form gaseous SiF4 to be evacuated. In the reactions, one SiO2 consumed two CaF2, leading to the reduction of the ratio of CaF2/SiO2. After comparing the slag compositions, the best slag detachability was obtained at CaO:CaF2:SiO2 = 1.7:1.8:1, but the worst slag detachability appeared at CaO:CaF2:SiO2 = 1.3:0.9:1. The XRD analysis revealed that the oxides and fluorides in the slags preferred to gather together to form cuspidine and other complex phases. If the CaF2 was dominant in the slags, they intended to form homogenous porous microstructures that were relatively strong and would most likely detach from the weld metal in blocks, exhibiting good slag detachability. If the cuspidine phase was dominant, the slags exhibited a `rock strata'-like microstructure in the intergranular area. Such microstructure was very fragile and could be broken into fine powders that were easily embedded in the weld ripples, leading to slag adhesions. This work provides the researcher with a wealth of information and data, which will also be beneficial to the welding material producers and users.

17 CFR 270.8f-1 - Deregistration of certain registered investment companies.

Code of Federal Regulations, 2010 CFR

2010-04-01

... registered investment companies. 270.8f-1 Section 270.8f-1 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION (CONTINUED) RULES AND REGULATIONS, INVESTMENT COMPANY ACT OF 1940 § 270.8f-1 Deregistration of certain registered investment companies. A registered investment company that seeks a...

Evaluation of shielding parameters for heavy metal fluoride based tellurite-rich glasses for gamma ray shielding applications

NASA Astrophysics Data System (ADS)

Sayyed, M. I.; Lakshminarayana, G.; Kityk, I. V.; Mahdi, M. A.

2017-10-01

In this work, we have evaluated the γ-ray shielding parameters such as mass attenuation coefficient (μ/ρ), effective atomic number (Zeff), half value layer (HVL), mean free path (MFP) and exposure buildup factors (EBF) for heavy metal fluoride (PbF2) based tellurite-rich glasses. In addition, neutron total macroscopic cross sections (∑R) for these glasses were also calculated. The maximum value for μ/ρ, Zeff and ∑R was found for heavy metal (Bi2O3) oxide introduced glass. The results of the selected glasses have been compared, in terms of MFP with different glass systems. The shielding effectiveness of the selected glasses is found comparable or better than of common ones, which indicates that these glasses with suitable oxides could be developed for gamma ray shielding applications.

Double-layer neutron shield design as neutron shielding application

NASA Astrophysics Data System (ADS)

Sariyer, Demet; Küçer, Rahmi

2018-02-01

The shield design in particle accelerators and other high energy facilities are mainly connected to the high-energy neutrons. The deep penetration of neutrons through massive shield has become a very serious problem. For shielding to be efficient, most of these neutrons should be confined to the shielding volume. If the interior space will become limited, the sufficient thickness of multilayer shield must be used. Concrete and iron are widely used as a multilayer shield material. Two layers shield material was selected to guarantee radiation safety outside of the shield against neutrons generated in the interaction of the different proton energies. One of them was one meter of concrete, the other was iron-contained material (FeB, Fe2B and stainless-steel) to be determined shield thicknesses. FLUKA Monte Carlo code was used for shield design geometry and required neutron dose distributions. The resulting two layered shields are shown better performance than single used concrete, thus the shield design could leave more space in the interior shielded areas.

Depleted uranium hexafluoride: The source material for advanced shielding systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quapp, W.J.; Lessing, P.A.; Cooley, C.R.

1997-02-01

The U.S. Department of Energy (DOE) has a management challenge and financial liability problem in the form of 50,000 cylinders containing 555,000 metric tons of depleted uranium hexafluoride (UF{sub 6}) that are stored at the gaseous diffusion plants. DOE is evaluating several options for the disposition of this UF{sub 6}, including continued storage, disposal, and recycle into a product. Based on studies conducted to date, the most feasible recycle option for the depleted uranium is shielding in low-level waste, spent nuclear fuel, or vitrified high-level waste containers. Estimates for the cost of disposal, using existing technologies, range between $3.8 andmore » $11.3 billion depending on factors such as the disposal site and the applicability of the Resource Conservation and Recovery Act (RCRA). Advanced technologies can reduce these costs, but UF{sub 6} disposal still represents large future costs. This paper describes an application for depleted uranium in which depleted uranium hexafluoride is converted into an oxide and then into a heavy aggregate. The heavy uranium aggregate is combined with conventional concrete materials to form an ultra high density concrete, DUCRETE, weighing more than 400 lb/ft{sup 3}. DUCRETE can be used as shielding in spent nuclear fuel/high-level waste casks at a cost comparable to the lower of the disposal cost estimates. Consequently, the case can be made that DUCRETE shielded casks are an alternative to disposal. In this case, a beneficial long term solution is attained for much less than the combined cost of independently providing shielded casks and disposing of the depleted uranium. Furthermore, if disposal is avoided, the political problems associated with selection of a disposal location are also avoided. Other studies have also shown cost benefits for low level waste shielded disposal containers.« less

24 CFR 8.6 - Communications.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 24 Housing and Urban Development 1 2011-04-01 2011-04-01 false Communications. 8.6 Section 8.6... URBAN DEVELOPMENT General Provisions § 8.6 Communications. (a) The recipient shall take appropriate steps to ensure effective communication with applicants, beneficiaries, and members of the public. (1...

24 CFR 8.6 - Communications.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 24 Housing and Urban Development 1 2012-04-01 2012-04-01 false Communications. 8.6 Section 8.6... URBAN DEVELOPMENT General Provisions § 8.6 Communications. (a) The recipient shall take appropriate steps to ensure effective communication with applicants, beneficiaries, and members of the public. (1...

24 CFR 8.6 - Communications.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 24 Housing and Urban Development 1 2010-04-01 2010-04-01 false Communications. 8.6 Section 8.6... URBAN DEVELOPMENT General Provisions § 8.6 Communications. (a) The recipient shall take appropriate steps to ensure effective communication with applicants, beneficiaries, and members of the public. (1...

Evaluation of stratospheric age of air from CF4, C2F6, C3F8, CHF3, HFC-125, HFC-227ea and SF6; implications for the calculations of halocarbon lifetimes, fractional release factors and ozone depletion potentials

NASA Astrophysics Data System (ADS)

Leedham Elvidge, Emma; Bönisch, Harald; Brenninkmeijer, Carl A. M.; Engel, Andreas; Fraser, Paul J.; Gallacher, Eileen; Langenfelds, Ray; Mühle, Jens; Oram, David E.; Ray, Eric A.; Ridley, Anna R.; Röckmann, Thomas; Sturges, William T.; Weiss, Ray F.; Laube, Johannes C.

2018-03-01

In a changing climate, potential stratospheric circulation changes require long-term monitoring. Stratospheric trace gas measurements are often used as a proxy for stratospheric circulation changes via the mean age of air values derived from them. In this study, we investigated five potential age of air tracers - the perfluorocarbons CF4, C2F6 and C3F8 and the hydrofluorocarbons CHF3 (HFC-23) and HFC-125 - and compare them to the traditional tracer SF6 and a (relatively) shorter-lived species, HFC-227ea. A detailed uncertainty analysis was performed on mean ages derived from these new tracers to allow us to confidently compare their efficacy as age tracers to the existing tracer, SF6. Our results showed that uncertainties associated with the mean age derived from these new age tracers are similar to those derived from SF6, suggesting that these alternative compounds are suitable in this respect for use as age tracers. Independent verification of the suitability of these age tracers is provided by a comparison between samples analysed at the University of East Anglia and the Scripps Institution of Oceanography. All five tracers give younger mean ages than SF6, a discrepancy that increases with increasing mean age. Our findings qualitatively support recent work that suggests that the stratospheric lifetime of SF6 is significantly less than the previous estimate of 3200 years. The impact of these younger mean ages on three policy-relevant parameters - stratospheric lifetimes, fractional release factors (FRFs) and ozone depletion potentials - is investigated in combination with a recently improved methodology to calculate FRFs. Updates to previous estimations for these parameters are provided.

Shield Design for Lunar Surface Applications

NASA Astrophysics Data System (ADS)

Johnson, Gregory A.

2006-01-01

A shielding concept for lunar surface applications of nuclear power is presented herein. The reactor, primary shield, reactor equipment and power generation module are placed in a cavity in the lunar surface. Support structure and heat rejection radiator panels are on the surface, outside the cavity. The reactor power of 1,320 kWt was sized to deliver 50 kWe from a thermoelectric power conversion subsystem. The dose rate on the surface is less than 0.6 mRem/hr at 100 meters from the reactor. Unoptimized shield mass is 1,020 kg which is much lighter than a comparable 4π shield weighing in at 17,000 kg.

EMI shielding performance of lead hexaferrite/polyaniline composite in 8-18 GHz frequency range

NASA Astrophysics Data System (ADS)

Choudhary, Harish Kumar; Pawar, Shital Patangrao; Bose, Suryasarathi; Sahoo, Balaram

2018-05-01

EMI shielding properties of nanocomposite containing lead hexaferrite (PFO) and polyaniline (PANI), a conducting polymer, was studied in X and Ku band frequencies. The nanocomposite shows enhanced EMI shielding properties than that of the pure PANI. Incorporation of PFO particles in the PANI enhances the total shielding effectiveness (SET) up to -24 dB at 18 GHz. This means that these nanocomposites can shield ˜99 % of the incoming EM radiation. The PFO/PANI shows much higher attenuation constant values over the measured frequency range. By adding the PFO in the PANI we have created more interfaces between Wax-PFO, Wax-PANI, PANI-PFO and PFO-PANI. These enhanced interfaces lead to Maxwell-Wagner polarization which results in a higher dielectric loss than only PANI.

Radioluminescence as a function of temperature and low temperature thermoluminescence of BaY2F8:Ce and BaY2F8:Nd crystals

NASA Astrophysics Data System (ADS)

Kowalski, Z.; Kaczmarek, S. M.; Brylew, K.; Drozdowski, W.

2016-09-01

Radioluminescence spectra at temperatures ranging from 10 to 320 K and low temperature thermoluminescence glow curves of BaY2F8:Ce and BaY2F8:Nd scintillator crystals have been investigated. In both materials the intensities of the excitonic and the activator ion's emission at X-ray excitation vary with temperature, anticorrelating with each other, which provides valuable information on the host-to-ion energy transfer. Detailed thermoluminescence studies, in turn, prove the existence of charge traps, which introduce quasi-continuous distributions of energy levels into the bandgap.

Multiplate Radiation Shields: Investigating Radiational Heating Errors

NASA Astrophysics Data System (ADS)

Richardson, Scott James

1995-01-01

Multiplate radiation shield errors are examined using the following techniques: (1) analytic heat transfer analysis, (2) optical ray tracing, (3) numerical fluid flow modeling, (4) laboratory testing, (5) wind tunnel testing, and (6) field testing. Guidelines for reducing radiational heating errors are given that are based on knowledge of the temperature sensor to be used, with the shield being chosen to match the sensor design. Small, reflective sensors that are exposed directly to the air stream (not inside a filter as is the case for many temperature and relative humidity probes) should be housed in a shield that provides ample mechanical and rain protection while impeding the air flow as little as possible; protection from radiation sources is of secondary importance. If a sensor does not meet the above criteria (i.e., is large or absorbing), then a standard Gill shield performs reasonably well. A new class of shields, called part-time aspirated multiplate radiation shields, are introduced. This type of shield consists of a multiplate design usually operated in a passive manner but equipped with a fan-forced aspiration capability to be used when necessary (e.g., low wind speed). The fans used here are 12 V DC that can be operated with a small dedicated solar panel. This feature allows the fan to operate when global solar radiation is high, which is when the largest radiational heating errors usually occur. A prototype shield was constructed and field tested and an example is given in which radiational heating errors were reduced from 2 ^circC to 1.2 ^circC. The fan was run continuously to investigate night-time low wind speed errors and the prototype shield reduced errors from 1.6 ^ circC to 0.3 ^circC. Part-time aspirated shields are an inexpensive alternative to fully aspirated shields and represent a good compromise between cost, power consumption, reliability (because they should be no worse than a standard multiplate shield if the fan fails), and accuracy

Electrical conductivity and electromagnetic interference shielding of epoxy nanocomposite foams containing functionalized multi-wall carbon nanotubes

NASA Astrophysics Data System (ADS)

Li, Jiantong; Zhang, Guangcheng; Zhang, Hongming; Fan, Xun; Zhou, Lisheng; Shang, Zhengyang; Shi, Xuetao

2018-01-01

Epoxy/functionalized multi-wall carbon nanotube (EP/F-MWCNT) microcellular foams were fabricated through a supercritical CO2 (scCO2) foaming method. MWCNTs with carboxylation treatment were disentangled by using alpha-zirconium phosphate (ZrP) assisting dispersion method and functionalized with sulfanilamide. The F-MWCNTs were redispersed in acetone for mixing with epoxy resins to prepare nanocomposites. It was found that the dispersion of MWCNTs could be improved, thus heterogeneous nucleation effect of F-MWCNTs took place effectively during the foaming process, resulting in the formation of microcellular structure with larger cell density and smaller cell size. The volume conductivity and electromagnetic interference shielding performance of foamed EP/F-MWCNT nanocomposites were studied. When the F-MWCNT addition was 5 wt%, the conductivity of the foamed EP/F-MWCNT nanocomposites was 3.02 × 10-4 S/cm and the EMI shielding effectiveness (SE) reached 20.5 dB, significantly higher than the corresponding results of nanocomposite counterparts, indicating that introducing microcellular structure in EP/F-MWCNT nanocomposites would beneficial to improve their electrical conductivity and electromagnetic interference shielding performance.

21 CFR 892.6500 - Personnel protective shield.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Personnel protective shield. 892.6500 Section 892.6500 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES RADIOLOGY DEVICES Miscellaneous Devices § 892.6500 Personnel protective shield. (a...

Convair XF-102 Model in the 8- by 6-Foot Supersonic Wind Tunnel

NASA Image and Video Library

1953-08-21

A .10-scale model of Convair’s XF-102 in the 8- by 6-Foot Supersonic Wind Tunnel at the National Advisory Committee for Aeronautics (NACA) Lewis Flight Propulsion Laboratory for jet exit studies. The XF-102 was a prototype of the F-102 Delta Dagger. The F-102 served as an interceptor against long range bombers from the Soviet Union. The aircraft was powered by a Pratt and Whitney J57 turbojet. The first prototype crashed two weeks after is first flight on October 24, 1953, just months after this photograph. Engineers then incorporated the fixed-wing design to reduce drag at supersonic speeds. The production model F-102 became the first delta-wing supersonic aircraft in operation. The 8- by 6-Foot Supersonic Wind Tunnel is used to study propulsion systems, including inlets and exit nozzles, combustion fuel injectors, flame holders, exit nozzles, and controls on ramjet and turbojet engines. Flexible sidewalls alter the tunnel’s nozzle shape to vary the Mach number during operation. A seven-stage axial compressor, driven by three electric motors that yield a total of 87,000 horsepower, generates air speeds from Mach 0.36 to 2.0.

Inhibition effects of flavonoids on 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline and 2-amino-3,7,8-trimethylimidazo[4,5-f]quinoxaline formation and alkoxy radical scavenging capabilities of flavonoids in a model system.

PubMed

Shao, Zeping; Han, Zhonghui; Zhang, Jinhui; Zhang, Yan; Wang, Shuo

2018-06-01

Heterocyclic aromatic amines (HAAs) have been considered as carcinogenic and mutagenic chemicals generated during thermal processing of protein-rich foods that can be inhibited by some flavonoids. Free radical scavenging is a major characteristic of flavonoids. The half-maximal inhibitory concentration (IC 50 ) values of nine flavonoids were determined by evaluating their capacity to inhibit 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-3,7,8-trimethylimidazo[4,5-f]quinoxaline (7,8-DiMeIQx) formation in a model system. The results of the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) test validated that MeIQx and 7,8-DiMeIQx formed via a free radical pathway. Electron spin resonance (ESR) spectroscopic analysis with spin trapping (α-(4-pyridyl N-oxide)-N-tert-butylnitrone (POBN) spin adduct, a N  = 15.2 G and a H  = 2.7 G) revealed that an alkoxy radical was the generated intermediate. The scavenging capacities of the nine flavonoids on alkoxy radicals were then evaluated based on the ESR spectra of the POBN spin adducts. The weak correlation between the alkoxy radical scavenging capacities and IC 50 of the flavonoids suggested that their inhibitory activity against MeIQx and 7,8-DiMeIQx formation operates by a more complex mechanism than simply scavenging alkoxy radicals. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Ford Motor Company NDE facility shielding design.

PubMed

Metzger, Robert L; Van Riper, Kenneth A; Jones, Martin H

2005-01-01

Ford Motor Company proposed the construction of a large non-destructive evaluation laboratory for radiography of automotive power train components. The authors were commissioned to design the shielding and to survey the completed facility for compliance with radiation doses for occupationally and non-occupationally exposed personnel. The two X-ray sources are Varian Linatron 3000 accelerators operating at 9-11 MV. One performs computed tomography of automotive transmissions, while the other does real-time radiography of operating engines and transmissions. The shield thickness for the primary barrier and all secondary barriers were determined by point-kernel techniques. Point-kernel techniques did not work well for skyshine calculations and locations where multiple sources (e.g. tube head leakage and various scatter fields) impacted doses. Shielding for these areas was determined using transport calculations. A number of MCNP [Briesmeister, J. F. MCNPCA general Monte Carlo N-particle transport code version 4B. Los Alamos National Laboratory Manual (1997)] calculations focused on skyshine estimates and the office areas. Measurements on the operational facility confirmed the shielding calculations.

Apollo display and keyboard unit (DSKY) used on F-8 DFBW

NASA Technical Reports Server (NTRS)

1996-01-01

adjustments than a human pilot can. For airliners, computerized control ensures a smoother ride than a human pilot alone can provide. Digital-fly-by-wire is more efficient because it is lighter and takes up less space than the hydraulic systems it replaced. This either reduces the fuel required to fly or increases the number of passengers or pounds of cargo the aircraft can carry. Digital fly-by-wire is currently used in a variety of aircraft ranging from F/A-18 fighters to the Boeing 777. The DFBW research program is considered one of the most significant and most successful NASA aeronautical programs since the inception of the agency. F-8 aircraft were built originally for the U.S. Navy by LTV Aerospace of Dallas, Texas. The aircraft had a wingspan of 35 feet, 2 inches; was 54 feet, 6 inches long; and was powered by a Pratt & Whitney J57 turbojet engine.

26 CFR 5c.168(f)(8)-4 - Minimum investment of lessor.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 26 Internal Revenue 14 2010-04-01 2010-04-01 false Minimum investment of lessor. 5c.168(f)(8)-4....168(f)(8)-4 Minimum investment of lessor. (a) Minimum investment. Under section 168(f)(8)(B)(ii), an... has a minimum at risk investment which, at the time the property is placed in service under the lease...

26 CFR 5c.168(f)(8)-4 - Minimum investment of lessor.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 26 Internal Revenue 14 2011-04-01 2010-04-01 true Minimum investment of lessor. 5c.168(f)(8)-4....168(f)(8)-4 Minimum investment of lessor. (a) Minimum investment. Under section 168(f)(8)(B)(ii), an... has a minimum at risk investment which, at the time the property is placed in service under the lease...

Source terms, shielding calculations and soil activation for a medical cyclotron.

PubMed

Konheiser, J; Naumann, B; Ferrari, A; Brachem, C; Müller, S E

2016-12-01

Calculations of the shielding and estimates of soil activation for a medical cyclotron are presented in this work. Based on the neutron source term from the 18 O(p,n) 18 F reaction produced by a 28 MeV proton beam, neutron and gamma dose rates outside the building were estimated with the Monte Carlo code MCNP6 (Goorley et al 2012 Nucl. Technol. 180 298-315). The neutron source term was calculated with the MCNP6 code and FLUKA (Ferrari et al 2005 INFN/TC_05/11, SLAC-R-773) code as well as with supplied data by the manufacturer. MCNP and FLUKA calculations yielded comparable results, while the neutron yield obtained using the manufacturer-supplied information is about a factor of 5 smaller. The difference is attributed to the missing channels in the manufacturer-supplied neutron source terms which considers only the 18 O(p,n) 18 F reaction, whereas the MCNP and FLUKA calculations include additional neutron reaction channels. Soil activation was performed using the FLUKA code. The estimated dose rate based on MCNP6 calculations in the public area is about 0.035 µSv h -1 and thus significantly below the reference value of 0.5 µSv h -1 (2011 Strahlenschutzverordnung, 9 Auflage vom 01.11.2011, Bundesanzeiger Verlag). After 5 years of continuous beam operation and a subsequent decay time of 30 d, the activity concentration of the soil is about 0.34 Bq g -1 .

Synthesis and fluorescence emission properties of 1,3,6,8-tetraarylpyrenes

NASA Astrophysics Data System (ADS)

Hu, Jian-Yong; Feng, Xing; Tomiyasu, Hirotsugu; Seto, Nobuyuki; Rayhan, Ummey; Elsegood, Mark R. J.; Redshaw, Carl; Yamato, Takehiko

2013-09-01

Three types of stable pyrene-based highly fluorescence (blue) compounds, 1-, 1,6-bis, 1,8-bis and 1,3,6,8-tetrakis(7-tert-butylpyrenyl)pyrenes and 1,3,6,8-tetrakis[9,9-bis(3-methylbutyl)-9H-fluoren-2-yl]pyrene, were successfully synthesized via a Pd/Cu-catalysed Suzuki cross-coupling reaction of the corresponding bromopyrenes with 7-tert-butyl-1-pyrenylboronic ester or 2-[9,9-bis(3-methylbutyl)-9H-fluoren-2-yl]-4,4,5,5-tetramethyl[1,3,2]dioxaborolane, respectively. All compounds have good solubility in common organic solvents and high thermal stability with melting points up to 270 °C; the exceptions are the isomeric 1,6-bis-, and 1,8-bispyrenyl-substituted pyrenes. All products show high extinction coefficients of absorption (λmax ≈ 349-396 nm) and high quantum yields (λmax ≈ 432-465 nm; Φf ≈ 0.75-0.99) in dichloromethane solution, and emit strong fluorescence in the visible region ranging from deep-blue to pure-blue on increasing the number of substituents. This data suggests that such systems have promise as blue emitters in organic light-emitting device (OLED) applications (OLED = organic light emitting diode). Crystal structures were determined for 1,3,6,8-tetrakis [9,9-bis(3-methylbutyl)-9H-fluoren-2-yl] pyrene and 1,3,6,8-tetrakis(4-methoxyphenyl)pyrene.

Copper Causes Regiospecific Formation of C4F8-Containing Six-Membered Rings and their Defluorination/Aromatization to C4F4-Containing Rings in Triphenylene/1,4-C4F8I2 Reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rippy, Kerry C.; Bukovsky, Eric V.; Clikeman, Tyler T.

The presence of Cu in reactions of triphenylene (TRPH) and 1,4-C4F8I2 at 360 °C led to regiospecific substitution of TRPH ortho C(β) atoms to form C4F8-containing rings, completely suppressing substitution on C(α) atoms. In addition, Cu caused selective reductive-defluorination/aromatization (RD/A) to form C4F4- containing aromatic rings. Without Cu, the reactions of TRPH and 1,4- C4F8I2 were not regiospecific and no RD/A was observed. These results, supported by DFT calculations, are the first examples of Cupromoted (i) regiospecific perfluoroannulation, (ii) preparative C–F activation, and (iii) RD/A. HPLC-purified products were characterized by X-ray diffraction, low-temperature PES, and 1H/19F NMR.

Comparative assessment of 6-[18 F]fluoro-L-m-tyrosine and 6-[18 F]fluoro-L-dopa to evaluate dopaminergic presynaptic integrity in a Parkinson's disease rat model.

PubMed

Becker, Guillaume; Bahri, Mohamed Ali; Michel, Anne; Hustadt, Fabian; Garraux, Gaëtan; Luxen, André; Lemaire, Christian; Plenevaux, Alain

2017-05-01

Because of the progressive loss of nigro-striatal dopaminergic terminals in Parkinson's disease (PD), in vivo quantitative imaging of dopamine (DA) containing neurons in animal models of PD is of critical importance in the preclinical evaluation of highly awaited disease-modifying therapies. Among existing methods, the high sensitivity of positron emission tomography (PET) is attractive to achieve that goal. The aim of this study was to perform a quantitative comparison of brain images obtained in 6-hydroxydopamine (6-OHDA) lesioned rats using two dopaminergic PET radiotracers, namely [ 18 F]fluoro-3,4-dihydroxyphenyl-L-alanine ([ 18 F]FDOPA) and 6-[ 18 F]fluoro-L-m-tyrosine ([ 18 F]FMT). Because the imaging signal is theoretically less contaminated by metabolites, we hypothesized that the latter would show stronger relationship with behavioural and post-mortem measures of striatal dopaminergic deficiency. We used a within-subject design to measure striatal [ 18 F]FMT and [ 18 F]FDOPA uptake in eight partially lesioned, eight fully lesioned and ten sham-treated rats. Animals were pretreated with an L-aromatic amino acid decarboxylase inhibitor. A catechol-O-methyl transferase inhibitor was also given before [ 18 F]FDOPA PET. Quantitative estimates of striatal uptake were computed using conventional graphical Patlak method. Striatal dopaminergic deficiencies were measured with apomorphine-induced rotations and post-mortem striatal DA content. We observed a strong relationship between [ 18 F]FMT and [ 18 F]FDOPA estimates of decreased uptake in the denervated striatum using the tissue-derived uptake rate constant K c . However, only [ 18 F]FMT K c succeeded to discriminate between the partial and the full 6-OHDA lesion and correlated well with the post-mortem striatal DA content. This study indicates that the [ 18 F]FMT could be more sensitive, with respect of [ 18 F]FDOPA, to investigate DA terminals loss in 6-OHDA rats, and open the way to in vivo L

Technical Note: On EM reconstruction of a multi channel shielded applicator for cervical cancer brachytherapy: A feasibility study.

PubMed

Tho, Daline; Racine, Emmanuel; Easton, Harry; Song, William Y; Beaulieu, Luc

2018-04-01

Electromagnetic tracking (EMT) is a promising technology for automated catheter and applicator reconstructions in brachytherapy. In this work, a proof-of-concept is presented for reconstruction of the individual channels of a new shielded tandem (140 mm long shield) dedicated to intensity-modulated brachytherapy. All six channels of a straight prototype were reconstructed using an electromagnetic (EM) system from Aurora (NDI, Waterloo, ON, Canada). The influence of the shield on the EMT system was characterized by taking measurements at nine different positions with and without the shielded part of the applicator next to the probe. A Student t-test was used to analyze the data. For registration purposes, the center-to-center distance (4 mm) was taken from the computed-assisted design (CAD) structure. The computed interchannel distances from the three opposite pairs were 4.33 ± 0.40 mm, 4.14 ± 0.35 mm, and 3.88 ± 0.26 mm. All interchannel distances were within the geometrical tolerance in the shielded portion of the applicator (±0.6 mm) and account for the fact that the sensor (0.8 mm diameter) was smaller than the channel diameter. According to the paired Student t-test, the data given by the EM system with and without the shielded applicator tip are not significantly different. This study shows that the reconstruction of channel path is possible within the mechanical accuracy of the applicator. © 2018 American Association of Physicists in Medicine.

EXPERIMENTAL EVALUATION OF THE THERMAL PERFORMANCE OF A WATER SHIELD FOR A SURFACE POWER REACTOR

DOE Office of Scientific and Technical Information (OSTI.GOV)

REID, ROBERT S.; PEARSON, J. BOSIE; STEWART, ERIC T.

2007-01-16

Water based reactor shielding is being investigated for use on initial lunar surface power systems. A water shield may lower overall cost (as compared to development cost for other materials) and simplify operations in the setup and handling. The thermal hydraulic performance of the shield is of significant interest. The mechanism for transferring heat through the shield is natural convection. Natural convection in a 100 kWt lunar surface reactor shield design is evaluated with 2 kW power input to the water in the Water Shield Testbed (WST) at the NASA Marshall Space Flight Center. The experimental data from the WSTmore » is used to validate a CFD model. Performance of the water shield on the lunar surface is then predicted with a CFD model anchored to test data. The experiment had a maximum water temperature of 75 C. The CFD model with 1/6-g predicts a maximum water temperature of 88 C with the same heat load and external boundary conditions. This difference in maximum temperature does not greatly affect the structural design of the shield, and demonstrates that it may be possible to use water for a lunar reactor shield.« less

Measurement of the transient shielding effectiveness of shielding cabinets

NASA Astrophysics Data System (ADS)

Herlemann, H.; Koch, M.

2008-05-01

Recently, new definitions of shielding effectiveness (SE) for high-frequency and transient electromagnetic fields were introduced by Klinkenbusch (2005). Analytical results were shown for closed as well as for non closed cylindrical shields. In the present work, the shielding performance of different shielding cabinets is investigated by means of numerical simulations and measurements inside a fully anechoic chamber and a GTEM-cell. For the GTEM-cell-measurements, a downscaled model of the shielding cabinet is used. For the simulations, the numerical tools CONCEPT II and COMSOL MULTIPHYSICS were available. The numerical results agree well with the measurements. They can be used to interpret the behaviour of the shielding effectiveness of enclosures as function of frequency. From the measurement of the electric and magnetic fields with and without the enclosure in place, the electric and magnetic shielding effectiveness as well as the transient shielding effectiveness of the enclosure are calculated. The transient SE of four different shielding cabinets is determined and discussed.

Directionally solidified Eu doped CaF2/Li3AlF6 eutectic scintillator for neutron detection

NASA Astrophysics Data System (ADS)

Kamada, Kei; Hishinuma, Kousuke; Kurosawa, Shunsuke; Shoji, Yasuhiro; Pejchal, Jan; Ohashi, Yuji; Yokota, Yuui; Yoshikawa, Akira

2015-12-01

Eu doped CaF2/Li3AlF6 eutectics were grown by μ-PD method. The directionally solidified eutectic with well-aligned 600 nm diameter Eu:CaF2 scintillator fibers surrounded with Li3AlF6 was prepared. The grown eutectics showed an emission peak at 422 nm ascribed to Eu2+ 4f-5d transition from Eu:CaF2 scintillation fiber. Li concentration in the Eu:CaF2-Li3AlF6 eutectic is around 0.038 mol/cm3,which is two times higher than that of LiCaAlF6 single crystal (0.016 mol/cm3). The light yield of Eu:CaF2-Li3AlF6 eutectic was around 7000 ph/neutron. The decay time was about 550 ns (89%) and 1450 ns (11%).

32 CFR 147.8 - Guideline F-Financial considerations.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 32 National Defense 1 2013-07-01 2013-07-01 false Guideline F-Financial considerations. 147.8 Section 147.8 National Defense Department of Defense OFFICE OF THE SECRETARY OF DEFENSE PERSONNEL... raise a security concern and may be disqualifying include: (1) A history of not meeting financial...

32 CFR 147.8 - Guideline F-Financial considerations.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 32 National Defense 1 2010-07-01 2010-07-01 false Guideline F-Financial considerations. 147.8 Section 147.8 National Defense Department of Defense OFFICE OF THE SECRETARY OF DEFENSE PERSONNEL... raise a security concern and may be disqualifying include: (1) A history of not meeting financial...

32 CFR 147.8 - Guideline F-Financial considerations.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 32 National Defense 1 2014-07-01 2014-07-01 false Guideline F-Financial considerations. 147.8 Section 147.8 National Defense Department of Defense OFFICE OF THE SECRETARY OF DEFENSE PERSONNEL... raise a security concern and may be disqualifying include: (1) A history of not meeting financial...

32 CFR 147.8 - Guideline F-Financial considerations.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 32 National Defense 1 2011-07-01 2011-07-01 false Guideline F-Financial considerations. 147.8 Section 147.8 National Defense Department of Defense OFFICE OF THE SECRETARY OF DEFENSE PERSONNEL... raise a security concern and may be disqualifying include: (1) A history of not meeting financial...

32 CFR 147.8 - Guideline F-Financial considerations.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 32 National Defense 1 2012-07-01 2012-07-01 false Guideline F-Financial considerations. 147.8 Section 147.8 National Defense Department of Defense OFFICE OF THE SECRETARY OF DEFENSE PERSONNEL... raise a security concern and may be disqualifying include: (1) A history of not meeting financial...

Passive magnetic shielding in MRI-Linac systems.

PubMed

Whelan, Brendan; Kolling, Stefan; Oborn, Brad M; Keall, Paul

2018-03-26

Passive magnetic shielding refers to the use of ferromagnetic materials to redirect magnetic field lines away from vulnerable regions. An application of particular interest to the medical physics community is shielding in MRI systems, especially integrated MRI-linear accelerator (MRI-Linac) systems. In these systems, the goal is not only to minimize the magnetic field in some volume, but also to minimize the impact of the shield on the magnetic fields within the imaging volume of the MRI scanner. In this work, finite element modelling was used to assess the shielding of a side coupled 6 MV linac and resultant heterogeneity induced within the 30 cm diameter of spherical volume (DSV) of a novel 1 Tesla split bore MRI magnet. A number of different shield parameters were investigated; distance between shield and magnet, shield shape, shield thickness, shield length, openings in the shield, number of concentric layers, spacing between each layer, and shield material. Both the in-line and perpendicular MRI-Linac configurations were studied. By modifying the shield shape around the linac from the starting design of an open ended cylinder, the shielding effect was boosted by approximately 70% whilst the impact on the magnet was simultaneously reduced by approximately 10%. Openings in the shield for the RF port and beam exit were substantial sources of field leakage; however it was demonstrated that shielding could be added around these openings to compensate for this leakage. Layering multiple concentric shield shells was highly effective in the perpendicular configuration, but less so for the in-line configuration. Cautious use of high permeability materials such as Mu-metal can greatly increase the shielding performance in some scenarios. In the perpendicular configuration, magnetic shielding was more effective and the impact on the magnet lower compared with the in-line configuration.

Passive magnetic shielding in MRI-Linac systems

NASA Astrophysics Data System (ADS)

Whelan, Brendan; Kolling, Stefan; Oborn, Brad M.; Keall, Paul

2018-04-01

Passive magnetic shielding refers to the use of ferromagnetic materials to redirect magnetic field lines away from vulnerable regions. An application of particular interest to the medical physics community is shielding in MRI systems, especially integrated MRI-linear accelerator (MRI-Linac) systems. In these systems, the goal is not only to minimize the magnetic field in some volume, but also to minimize the impact of the shield on the magnetic fields within the imaging volume of the MRI scanner. In this work, finite element modelling was used to assess the shielding of a side coupled 6 MV linac and resultant heterogeneity induced within the 30 cm diameter of spherical volume (DSV) of a novel 1 Tesla split bore MRI magnet. A number of different shield parameters were investigated; distance between shield and magnet, shield shape, shield thickness, shield length, openings in the shield, number of concentric layers, spacing between each layer, and shield material. Both the in-line and perpendicular MRI-Linac configurations were studied. By modifying the shield shape around the linac from the starting design of an open ended cylinder, the shielding effect was boosted by approximately 70% whilst the impact on the magnet was simultaneously reduced by approximately 10%. Openings in the shield for the RF port and beam exit were substantial sources of field leakage; however it was demonstrated that shielding could be added around these openings to compensate for this leakage. Layering multiple concentric shield shells was highly effective in the perpendicular configuration, but less so for the in-line configuration. Cautious use of high permeability materials such as Mu-metal can greatly increase the shielding performance in some scenarios. In the perpendicular configuration, magnetic shielding was more effective and the impact on the magnet lower compared with the in-line configuration.

Optimizing ZnS/6LiF scintillators for wavelength-shifting-fiber neutron detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crow, Lowell; Funk, Loren L; Hannan, Bruce W

2016-01-01

In this paper we compare the performance of grooved and flat ZnS/6LiF scintillators in a wavelength shifting-fiber (WLSF) detector. Flat ZnS/6LiF scintillators with the thickness L=0.2-0.8 mm were characterized using photon counting and pulse-height analysis and compared to a grooved scintillator of approximately 0.8 mm thick. While a grooved scintillator considerably increases the apparent thickness of the scintillator to neutrons for a given coating thickness, we find that the flat scintillators perform better than the grooved scintillators in terms of both light yield and neutron detection efficiency. The flat 0.8-mm-thick scintillator has the highest light output, and it is 52%more » higher compared with a grooved scintillator of same thickness. The lower light output of the grooved scintillator as compared to the flat scintillator is consistent with the greater scintillator-WLSF separation and the much larger average emission angle of the grooved scintillator. We also find that the average light cone width, or photon travel-length as measured using time-of-flight powder diffraction of diamond and vanadium, decreases with increasing L in the range of L=0.6-0.8 mm. This result contrasts with the traditional Swank diffusion model for micro-composite scintillators, and could be explained by a decrease in photon diffusion-coefficient or an increase in micro-particle content in the flat scintillator matrix for the thicker scintillators.« less

Electron-impact-ionization dynamics of S F6

NASA Astrophysics Data System (ADS)

Bull, James N.; Lee, Jason W. L.; Vallance, Claire

2017-10-01

A detailed understanding of the dissociative electron ionization dynamics of S F6 is important in the modeling and tuning of dry-etching plasmas used in the semiconductor manufacture industry. This paper reports a crossed-beam electron ionization velocity-map imaging study on the dissociative ionization of cold S F6 molecules, providing complete, unbiased kinetic energy distributions for all significant product ions. Analysis of these distributions suggests that fragmentation following single ionization proceeds via formation of S F5 + or S F3 + ions that then dissociate in a statistical manner through loss of F atoms or F2, until most internal energy has been liberated. Similarly, formation of stable dications is consistent with initial formation of S F4 2 + ions, which then dissociate on a longer time scale. These data allow a comparison between electron ionization and photoionization dynamics, revealing similar dynamical behavior. In parallel with the ion kinetic energy distributions, the velocity-map imaging approach provides a set of partial ionization cross sections for all detected ionic fragments over an electron energy range of 50-100 eV, providing partial cross sections for S2 +, and enables the cross sections for S F4 2 + from S F+ to be resolved.

Long-term tropospheric trend of octafluorocyclobutane (c-C4F8 or PFC-318)

NASA Astrophysics Data System (ADS)

Oram, D. E.; Mani, F. S.; Laube, J. C.; Newland, M. J.; Reeves, C. E.; Sturges, W. T.; Penkett, S. A.; Brenninkmeijer, C. A. M.; Röckmann, T.; Fraser, P. J.

2011-07-01

Air samples collected at Cape Grim, Tasmania between 1978 and 2008 and during a series of more recent aircraft sampling programmes have been analysed to determine the atmospheric abundance and trend of octafluorocyclobutane (-C4F8 or PFC-318). c-C4F8 has an atmospheric lifetime in excess of 3000 yr and a global warming potential (GWP) of 10 300 (100 yr time horizon), making it one of the most potent greenhouse gases detected in the atmosphere to date. The abundance of c-C4F8 in the Southern Hemisphere has risen from 0.35 ppt in 1978 to 1.2 ppt in 2010, and is currently increasing at a rate of around 0.03 ppt yr-1. It is the third most abundant perfluorocarbon (PFC) in the present day atmosphere, behind CF4 (~75 ppt) and C2F6 (~4 ppt). The origin of c-C4F8 is unclear. Using a 2-D global model to derive top-down global emissions based on the Cape Grim measurements yields a recent (2007) emission rate of around 1.1 Gg yr-1 and a cumulative emission up to and including 2007 of 38.1 Gg. Emissions reported on the EDGAR emissions database for the period 1986-2005 represent less than 1 % of the top-down emissions for the same period, which suggests there is a large unaccounted for source of this compound. It is also apparent that the magnitude of this source has varied considerably over the past 30 yr, declining sharply in the late 1980s before increasing again in the mid-1990s.

Carcinogenicity of bromodichloromethane administered in drinking water to Male F344/N Rats and B6C3F1 mice.

PubMed

George, Michael H; Olson, Greg R; Doerfler, Donald; Moore, Tanya; Kilburn, Steve; DeAngelo, Anthony B

2002-01-01

A life-time exposure study was conducted to assess the carcinogenicity of bromodichloromethane (BDCM) administered in the drinking water to male F344/N rats and B6C3F(1) mice. In mouse, the calculated mean daily BDCM concentrations (measured concentrations corrected for on-cage loss of chemical) were 0.06, 0.28 and 0.49 g/l. Time-weighted water consumption of 135, 97, and 89 ml/kg/day resulted in mean daily doses of 8.1, 27.2, and 43.4 mg BDCM/kg/day. No changes in feed consumption, final body weight, or survival were observed. Kidney weights were significantly depressed at 27.2 and 43.4 mg BDCM/kg/day. There was no increase in neoplasia in the liver, kidney, spleen, testis, bladder, sections along the alimentary tract, excised lesions, or at any other organ site. In rat, the corrected mean daily BDCM concentrations were 0.06, 0.33, and 0.62 g/l. Time-weighted water consumption of 65, 63, and 59 ml/kg/day yielded 3.9, 20.6 and 36.3 mg BDCM/kg/day. No alterations in feed consumption, body weight gain, and survival were seen. Kidney weight was significantly depressed in the 36.3-mg/kg/day treatment group. There was a significantly enhanced prevalence and multiplicity of hepatocellular adenomas at 3.9 mg BDCM/kg/day (15.5% and 0.16/animal vs. 2.2% and 0.02/animal for the control). Hepatocellular carcinomas increased from 2.2% and 0.02/animal for the control and 3.9 mg BDCM/kg/day to 8.3% and 0.10/animal at 20.6 mg BDCM/kg/day. The combined neoplasms were enhanced at 3.9 and 20.6 mg BDCM/kg/day. Liver neoplasia was depressed to the control value at 36.3 mg BDCM/kg. The prevalence of basophilic and clear cell, but not eosinophilic cells, altered foci of cells declined with increasing dose. BDCM did not increase cancer in the large bowel, renal tubules, or in any of the other tissues examined. Renal tubular hyperplasia was observed at 36.3 mg BDCM/kg (15.8% vs. 8.7% for the control group). Under the conditions of the study, BDCM in the drinking water was not carcinogenic

Radiation Shielding of Lunar Regolith/Polyethylene Composites and Lunar Regolith/Water Mixtures

NASA Technical Reports Server (NTRS)

Johnson, Quincy F.; Gersey, Brad; Wilkins, Richard; Zhou, Jianren

2011-01-01

Space radiation is a complex mixed field of ionizing radiation that can pose hazardous risks to sophisticated electronics and humans. Mission planning for lunar exploration and long duration habitat construction will face tremendous challenges of shielding against various types of space radiation in an attempt to minimize the detrimental effects it may have on materials, electronics, and humans. In late 2009, the Lunar Crater Observation and Sensing Satellite (LCROSS) discovered that water content in lunar regolith found in certain areas on the moon can be up to 5.6 +/-2.8 weight percent (wt%) [A. Colaprete, et. al., Science, Vol. 330, 463 (2010). ]. In this work, shielding studies were performed utilizing ultra high molecular weight polyethylene (UHMWPE) and aluminum, both being standard space shielding materials, simulated lunar regolith/ polyethylene composites, and simulated lunar regolith mixed with UHMWPE particles and water. Based on the LCROSS findings, radiation shielding experiments were conducted to test for shielding efficiency of regolith/UHMWPE/water mixtures with various percentages of water to compare relative shielding characteristics of these materials. One set of radiation studies were performed using the proton synchrotron at the Loma Linda Medical University where high energy protons similar to those found on the surface of the moon can be generated. A similar experimental protocol was also used at a high energy spalation neutron source at Los Alamos Neutron Science Center (LANSCE). These experiments studied the shielding efficiency against secondary neutrons, another major component of space radiation field. In both the proton and neutron studies, shielding efficiency was determined by utilizing a tissue equivalent proportional counter (TEPC) behind various thicknesses of shielding composite panels or mixture materials. Preliminary results from these studies indicated that adding 2 wt% water to regolith particles could increase shielding of

Phase Transitions in MIITiF6 · 6H2O (M = Cd, Zn, Co): An EPR Study

NASA Astrophysics Data System (ADS)

Jayaram, Geetha

1994-05-01

Paramagnetic Mn2+ ions have been incorporated into CdTiF6 · 6H2O, ZnTiF6 · 6H2O and CoTiF6 · 6H2O single crystals, and EPR spectra have been utilized to investigate the structural phase transitions in these crystals. They are first order in nature with a marked hysteresis in the case of CoTiF6 · 6H2O and are attributed to hindering of rotation of the [M(H2O)6] as well as (TiF6) groups.

Jahn-Teller effect on the [TiF 4F 4F int] 6-(C 4v) and [NiF 4F 4F int] 7-(C 4v) clusters embedded into SrF 2 crystals

NASA Astrophysics Data System (ADS)

Ulanov, V. A.; Zhiteitcev, E. R.; Varlamov, A. G.

2007-07-01

By means of EPR method the associative [TiF 4F 4F int] 6-(C 4v) and [NiF 4F 4F int] 7-(C 4v) centers were revealed in the fluorite type SrF 2:Ti and SrF 2:Ni crystals grown by Bridgman method in helium atmosphere containing some amount of a fluorine gas. It was found that at low temperatures the local structures of these associative centers were exposed to a static rhombic distortion. The reasons of such distortions were accounted for by the assumption that the E ⊗ ( b1 + b2) vibronic interaction became effective due to that the ground orbital states of the [TiF 4F 4F int] 6-(C 4v) and [NiF 4F 4F int] 7-(C 4v) centers occurred to be doubly degenerated.

Bulk plasma fragmentation in a C4F8 inductively coupled plasma: A hybrid modeling study

NASA Astrophysics Data System (ADS)

Zhao, Shu-Xia; Zhang, Yu-Ru; Gao, Fei; Wang, You-Nian; Bogaerts, Annemie

2015-06-01

A hybrid model is used to investigate the fragmentation of C4F8 inductive discharges. Indeed, the resulting reactive species are crucial for the optimization of the Si-based etching process, since they determine the mechanisms of fluorination, polymerization, and sputtering. In this paper, we present the dissociation degree, the density ratio of F vs. CxFy (i.e., fluorocarbon (fc) neutrals), the neutral vs. positive ion density ratio, details on the neutral and ion components, and fractions of various fc neutrals (or ions) in the total fc neutral (or ion) density in a C4F8 inductively coupled plasma source, as well as the effect of pressure and power on these results. To analyze the fragmentation behavior, the electron density and temperature and electron energy probability function (EEPF) are investigated. Moreover, the main electron-impact generation sources for all considered neutrals and ions are determined from the complicated C4F8 reaction set used in the model. The C4F8 plasma fragmentation is explained, taking into account many factors, such as the EEPF characteristics, the dominance of primary and secondary processes, and the thresholds of dissociation and ionization. The simulation results are compared with experiments from literature, and reasonable agreement is obtained. Some discrepancies are observed, which can probably be attributed to the simplified polymer surface kinetics assumed in the model.

Crumpled Heat Shield

NASA Technical Reports Server (NTRS)

2008-01-01

The Phoenix Mars Lander's Surface Stereo Imager took this image of the spacecraft's crumpled heat shield on Sept. 16, 2008, the 111th Martian day of the mission.

The 2-1/2 meter (about 8-1/2 feet) heat shield landed southeast of Phoenix, about halfway between the spacecraft and its backshell/parachute. The backshell/parachute touched ground 300 meters (1,000 ft) to the south of the lander.

The dark area to the right of the heat shield is the 'bounce mark' it made on impact with the Red Planet. This image is the highest-resolution image that will likely be taken by the lander, and is part of the 1,500-image 'Happily Ever After' panorama.

The Phoenix mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is led by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

We are Family: the Conformations of 1-FLUOROALKANES, C_nH2n+1F (n = 2,3,4,5,6,7,8)

NASA Astrophysics Data System (ADS)

Obenchain, Daniel A.; Orellana, W.; Cooke, S. A.

2016-06-01

he pure rotational spectra of the n = 5, 6, 7, and 8 members of the 1-fluoroalkane family have been recorded between 7 GHz and 14 GHz using chirped pulse Fourier transform microwave spectroscopy. The spectra have been analyzed and results will be presented and compared with previous work on the n= 2, 3, and 4 members. The lowest energy conformer for all family members has the common feature that the fluorine is in a gauche position relative to the alkyl tail for which all other heavy atom dihedral angles, where appropriate, are 180 degrees. For the n = 3 and higher family members the second lowest energy conformer has all heavy atom dihedral angles equal to 180 degrees. For each family member transitions carried by both low energy conformers were observed in the collected rotational spectra. Quantum chemical calculations were performed and trends in the energy separations between these two common conformers will be presented as a function of chain length. Furthermore, longer chain lengths have been examined using only quantum chemical calculations and results will be presented. M. Hayashi, M. Fujitake, T. Inagusa, S. Miyazaki, J.Mol.Struct., 216, 9-26, 1990 W. Caminati, A. C. Fantoni, F. Manescalchi, F. Scappini, Mol.Phys., 64, 1089 ,1988 L. B. Favero, A. Maris, A. Degli Esposti, P. G. Favero, W. Caminati, G. Pawelke, Chem.Eur.J., 6(16), 3018-3025, 2000

Study of fluorescence quenching due to 2, 3, 5, 6-tetrafluoro-7, 7', 8, 8'-tetracyano quinodimethane and its solid state diffusion analysis using photoluminescence spectroscopy.

PubMed

Tyagi, Priyanka; Tuli, Suneet; Srivastava, Ritu

2015-02-07

In this work, we have studied the fluorescence quenching and solid state diffusion of 2, 3, 5, 6-tetrafluoro-7,  7',  8,  8'-tetracyano quinodimethane (F4-TCNQ) using photoluminescence (PL) spectroscopy. Quenching studies were performed with tris (8-hydroxyquinolinato) aluminum (Alq3) in solid state samples. Thickness of F4-TCNQ was varied in order to realize different concentrations and study the effect of concentration. PL intensity has reduced with the increase in F4-TCNQ thicknesses. Stern-Volmer and bimolecular quenching constants were evaluated to be 13.8 M(-1) and 8.7 × 10(8) M(-1) s(-1), respectively. The quenching mechanism was found to be of static type, which was inferred by the independent nature of excited state life time from the F4-TCNQ thickness. Further, solid state diffusion of F4-TCNQ was studied by placing a spacing layer of α-NPD between F4-TCNQ and Alq3, and its thickness was varied to probe the diffusion length. PL intensity was found to increase with the increase in this thickness. Quenching efficiency was evaluated as a function of distance between F4-TCNQ and Alq3. These studies were performed for the samples having 1, 2.5, and 5.5 nm thicknesses of F4-TCNQ to study the thickness dependence of diffusion length. Diffusion lengths were evaluated to be 12.5, 15, and 20 nm for 1, 2.5, and 5.5 nm thicknesses of F4-TCNQ. These diffusion lengths were found to be very close to that of determined by secondary ion mass spectroscopy technique.

Rangitoto Volcano Drilling Project: Life of a Small 'Monogenetic' Basaltic Shield in the Auckland Volcanic Field

NASA Astrophysics Data System (ADS)

Shane, P. A. R.; Linnell, T.; Lindsay, J. M.; Smith, I. E.; Augustinus, P. M.; Cronin, S. J.

2014-12-01

Rangitoto is a small basaltic shield volcano representing the most recent and most voluminous episode of volcanism in the Auckland Volcanic Field, New Zealand. Auckland City is built on the field, and hence, Rangitoto's importance in hazard-risk modelling. The symmetrical edifice, ~6 km wide and 260 m high, has volume of 1.78 km3. It comprises summit scoria cones and a lava field. However, the lack of deep erosion dissection has prevented the development of an eruptive stratigraphy. Previous studies suggested construction in a relatively short interval at 550-500 yrs BP. However, microscopic tephra have been interpreted as evidence of intermittent activity from 1498 +/- 140 to 504 +/- 6 yrs BP, a longevity of 1000 years. A 150-m-deep hole was drilled through the edifice in February 2014 to obtain a continuous core record. The result is an unparalleled stratigraphy of the evolution of a small shield volcano. The upper 128 m of core comprises at least 27 lava flows with thicknesses in the range 0.3-15 m, representing the main shield-building phase. Underlying marine sediments are interbedded with 8 m of pyroclastic lapilli, and a thin lava flow, representing the explosive phreatomagmatic birth of the volcano. Preliminary geochemical analyses reveal suite of relatively uniform transitional basalts (MgO = 8.1 to 9.7 wt %). However, 4 compositional groups are distinguished that were erupted in sequential order. High-MgO magmas were erupted first, followed by a two more heterogeneous groups displaying differentiation trends with time. Finally, distinct low-MgO basalts were erupted. Each magma type appears to represent a new magma batch. The core places the magma types in a time series, which can be correlated to the surface lava field. Hence, allowing a geometrical reconstruction of the shield growth. Additional petrologic investigations are providing insight to magmatic ascent processes, while radiocarbon and paleomagnetic secular variation studies will reveal the

Electron impact ionization cross section studies of C2Fx (x = 1 - 6) and C3Fx (x = 1 - 8) fluorocarbon species

NASA Astrophysics Data System (ADS)

Gupta, Dhanoj; Choi, Heechol; Song, Mi-Young; Karwasz, Grzegorz P.; Yoon, Jung-Sik

2017-05-01

The total ionization cross section for C2Fx (x = 1 - 6) and C3Fx (x = 1 - 8) fluorocarbon species are studied with the Binary-Encounter Bethe (BEB) model using various orbital parameters calculated from restricted/unrestricted Hartree-Fock (RHF/UHF) and Density Functional Theory (DFT). All the targets were optimized for their minimal structures and energies with several ab-initio methods with the aug-cc-pVTZ basis set. Among them, the present results with RHF/UHF orbital energies showed good agreement with the experimental results for stable targets C2F6, C2F4, C3F6 and C3F8. The results with the DFT (ωB97X/ωB97X-D) showed a reasonable agreement with the recent calculation of Bull et al. [J.N. Bull, M. Bart, C. Vallance, P.W. Harland, Phys. Rev. A 88, 062710 (2013)] for C2F6, C3F6 and C3F8 targets. The ionization cross section for C2F, C2F2, C2F3, C3F, C3F2, C3F3, C3F4, C3F5 and C3F7 were computed for the first time in the present study. We have also computed the vertical ionization potentials and polarizability for all the targets and compared them with other experimental and theoretical values. A good agreement is found between the present and the previous results. The calculated polarizability in turn is used to study the correlation with maximum ionization cross section and in general a good correlation is found among them, confirming the consistency and reliability of the present data. The cross section data reported in this article are very important for plasma modeling especially related to fluorocarbon plasmas. Contribution to the Topical Issue "Atomic and Molecular Data and their Applications", edited by Gordon W.F. Drake, Jung-Sik Yoon, Daiji Kato, Grzegorz Karwasz.

Comparative antioxidant and anti-inflammatory effects of [6]-gingerol, [8]-gingerol, [10]-gingerol and [6]-shogaol.

PubMed

Dugasani, Swarnalatha; Pichika, Mallikarjuna Rao; Nadarajah, Vishna Devi; Balijepalli, Madhu Katyayani; Tandra, Satyanarayana; Korlakunta, Jayaveera Narsimha

2010-02-03

Zingiber officinale Rosc. (Zingiberaceae) has been traditionally used in Ayurvedic, Chinese and Tibb-Unani herbal medicines for the treatment of various illnesses that involve inflammation and which are caused by oxidative stress. Although gingerols and shogaols are the major bioactive compounds present in Zingiber officinale, their molecular mechanisms of actions and the relationship between their structural features and the activity have not been well studied. The aim of the present study was to examine and compare the antioxidant and anti-inflammatory activities of gingerols and their natural analogues to determine their structure-activity relationship and molecular mechanisms. The in vitro activities of the compounds [6]-gingerol, [8]-gingerol, [10]-gingerol and [6]-shogaol were evaluated for scavenging of 1,1-diphenyl-2-picyrlhydrazyl (DPPH), superoxide and hydroxyl radicals, inhibition of N-formyl-methionyl-leucyl-phenylalanine (f-MLP) induced reactive oxygen species (ROS) production in human polymorphonuclear neutrophils (PMN), inhibition of lipopolysaccharide induced nitrite and prostaglandin E(2) production in RAW 264.7 cells. In the antioxidant activity assay, [6]-gingerol, [8]-gingerol, [10]-gingerol and [6]-shogaol exhibited substantial scavenging activities with IC(50) values of 26.3, 19.47, 10.47 and 8.05 microM against DPPH radical, IC(50) values of 4.05, 2.5, 1.68 and 0.85 microM against superoxide radical and IC(50) values of 4.62, 1.97, 1.35 and 0.72 microM against hydroxyl radical, respectively. The free radical scavenging activity of these compounds also enhanced with increasing concentration (P<0.05). On the other hand, all the compounds at a concentration of 6 microM have significantly inhibited (P<0.05) f-MLP-stimulated oxidative burst in PMN. In addition, production of inflammatory mediators (NO and PGE(2)) has been inhibited significantly (P<0.05) and dose-dependently. 6-Shogaol has exhibited the most potent antioxidant and anti

Long-term tropospheric trend of octafluorocyclobutane (c-C4F8 or PFC-318)

NASA Astrophysics Data System (ADS)

Oram, D. E.; Mani, F. S.; Laube, J. C.; Newland, M. J.; Reeves, C. E.; Sturges, W. T.; Penkett, S. A.; Brenninkmeijer, C. A. M.; Röckmann, T.; Fraser, P. J.

2012-01-01

Air samples collected at Cape Grim, Tasmania between 1978 and 2008 and during a series of more recent aircraft sampling programmes have been analysed to determine the atmospheric abundance and trend of octafluorocyclobutane (c-C4F8 or PFC-318). c-C4F8 has an atmospheric lifetime in excess of 3000 yr and a global warming potential (GWP) of 10 300 (100 yr time horizon), making it one of the most potent greenhouse gases detected in the atmosphere to date. The abundance of c-C4F8 in the Southern Hemisphere has risen from 0.35 ppt in 1978 to 1.2 ppt in 2010, and is currently increasing at a rate of around 0.03 ppt yr-1. It is the third most abundant perfluorocarbon (PFC) in the present day atmosphere, behind CF4 (~75 ppt) and C2F6 (~4 ppt). Although a number of potential sources of c-C4F8 have been reported, including the electronics and semi-conductor industries, there remains a large discrepancy in the atmospheric budget. Using a 2-D global model to derive top-down global emissions based on the Cape Grim measurements yields a recent (2007) emission rate of around 1.1 Gg yr-1 and a cumulative emission up to and including 2007 of 38.1 Gg. Emissions reported on the EDGAR emissions database for the period 1986-2005 represent less than 1% of the top-down emissions for the same period, which suggests there is a large unaccounted for source of this compound. It is also apparent that the magnitude of this source has varied considerably over the past 30 yr, declining sharply in the late 1980s before increasing again in the mid-1990s.

Medium-power diode-pumped Nd:BaY2F8 laser

NASA Astrophysics Data System (ADS)

Agnesi, Antonio; Guandalini, Annalisa; Lucca, Andrea; Sani, Elisa; Toncelli, Alessandra; Tonelli, Mauro; dell'Acqua, Stefano

2003-05-01

We report what is to our knowledge the first Nd:BaY2F8 (Nd:BaYF) laser pumped with a multiwatt fiber-coupled diode array tuned at approximately 804 nm. As much as 2.4 W were obtained with 6.2 W of absorbed pump power, showing efficient operation (51% slope efficiency), excellent beam quality (M2=1.1), and weak thermal lensing. Small intracavity losses (<1%) were measured, indicating both reduced thermally induced aberrations and good optical quality of the laser crystal.

Effectiveness of metal matrix and ceramic matrix composites as orbital debris shield materials

NASA Technical Reports Server (NTRS)

Mcgill, Preston B.; Mount, Angela R.

1992-01-01

The effectiveness of two metal matrix composites and one ceramic matrix material in defeating hypervelocity impacts at about 3.8 km/s are evaluated to determine the potential of these composites as spacecraft shield materials. The metal matrix composites investigated consist of SiC particles (70 percent by volume) in an aluminum matrix and Al2O3 particles (50 percent by volume) in an Al matrix. The ceramic composite consists of ZrB2 platelets in a ZrC matrix. Both the metal matrix and ceramic matrix composites are found to perform as well or better than 6061-T6 aluminum, which is presently used in the Whipple type bumper shield of Space Station Freedom. Test results indicate that the composites tested may have applications as micrometeoroid/orbital debris shield materials.

Manganese Vanadate Chemistry in Hydrothermal BaF 2 Brines: Ba 3 Mn 2 (V 2 O 7 ) 2 F 2 and Ba 7 Mn 8 O 2 (VO 4 ) 2 F 23

DOE PAGES

Sanjeewa, Liurukara D.; McMillen, Colin D.; McGuire, Michael A.; ...

2016-12-05

We synthesized manganese vanadate fluorides using high-temperature hydrothermal techniques with BaF 2 as a mineralizer. Ba 3Mn 2(V 2O 7) 2F 2 crystallizes in space group C2/c and consists of dimers built from edge-sharing MnO 4F 2 trigonal prisms with linking V 2O 7 groups. Ba 7Mn 8O 2(VO 4) 2F 23 crystallizes in space group Cmmm, with a manganese oxyfluoride network built from edge- and corner-sharing Mn 2+/3+(O,F) 6 octahedra. The resulting octahedra form alternating Mn 2+ and Mn 2+/3+ layers separated by VO 4 tetrahedra. This latter compound exhibits a canted antiferromagnetic order below TN = 25 K.

NEUTRON REACTOR HAVING A Xe$sup 135$ SHIELD

DOEpatents

Stanton, H.E.

1957-10-29

Shielding for reactors of the type in which the fuel is a chain reacting liquid composition comprised essentially of a slurry of fissionable and fertile material suspended in a liquid moderator is discussed. The neutron reflector comprises a tank containing heavy water surrounding the reactor, a shield tank surrounding the reflector, a gamma ray shield surrounding said shield tank, and a means for conveying gaseous fission products, particularly Xe/sup 135/, from the reactor chamber to the shield tank, thereby serving as a neutron shield by capturing the thermalized neutrons that leak outwardly from the shield tank.

Novel shielding materials for space and air travel.

PubMed

Vana, N; Hajek, M; Berger, T; Fugger, M; Hofmann, P

2006-01-01

The reduction of dose onboard spacecraft and aircraft by appropriate shielding measures plays an essential role in the future development of space exploration and air travel. The design of novel shielding strategies and materials may involve hydrogenous composites, as it is well known that liquid hydrogen is most effective in attenuating charged particle radiation. As precursor for a later flight experiment, the shielding properties of newly developed hydrogen-rich polymers and rare earth-doped high-density rubber were tested in various ground-based neutron and heavy ion fields and compared with aluminium and polyethylene as reference materials. Absorbed dose, average linear energy transfer and gamma-equivalent neutron absorbed dose were determined by means of LiF:Mg,Ti thermoluminescence dosemeters and CR-39 plastic nuclear track detectors. First results for samples of equal aerial density indicate that selected hydrogen-rich plastics and rare-earth-doped rubber may be more effective in attenuating cosmic rays by up to 10% compared with conventional aluminium shielding. The appropriate adaptation of shielding thicknesses may thus allow reducing the biologically relevant dose. Owing to the lower density of the plastic composites, mass savings shall result in a significant reduction of launch costs. The experiment was flown as part of the European Space Agency's Biopan-5 mission in May 2005.

Wing shielding of high velocity jet and shock-associated noise with cold and hot flow jets

NASA Technical Reports Server (NTRS)

Vonglahn, U.; Groesbeck, D.; Wagner, J.

1976-01-01

Jet exhaust noise shielding data are presented for cold and hot flows (ambient to 1,100 K) and pressure ratios from 1.7 to 2.75. A nominal 9.5-cm diameter conical nozzle was used with simple shielding surfaces that were varied in length from 28.8 to 114.3 cm. The nozzle was located 8.8 cm above the surfaces. The acoustic data with the various sheilding lengths are compared to each other and to that for the nozzle alone. In general, short shielding surfaces that provided shielding for subsonic jets did not provide as much shielding for jets with shock noise, however, long shielding surfaces did shield shock noise effectively.

INHIBITION OF ERN1 SIGNALING ENZYME AFFECTS HYPOXIC REGULATION OF THE EXPRESSION OF E2F8, EPAS1, HOXC6, ATF3, TBX3 AND FOXF1 GENES IN U87 GLIOMA CELLS.

PubMed

Minchenko, O H; Tsymbal, D O; Minchenko, D O; Kovalevska, O V; Karbovskyi, L L; Bikfalvi, A

2015-01-01

Hypoxia as well as the endoplasmic reticulum stress are important factors of malignant tumor growth and control of the expression of genes, which regulate numerous metabolic processes and cell proliferation. Furthermore, blockade of ERN1 (endoplasmic reticulum to nucleus 1) suppresses cell proliferation and tumor growth. We studied the effect of hypoxia on the expression of genes encoding the transcription factors such as E2F8 (E2F transcription factor 8), EPAS1 (endothelial PAS domain protein 1), TBX3 (T-box 3), ATF3 (activating transcription factor 3), FOXF1 (forkhead box F), and HOXC6 (homeobox C6) in U87 glioma cells with and without ERN1 signaling enzyme function. We have established that hypoxia enhances the expression of HOXC6, E2F8, ATF3, and EPAS1 genes but does not change TBX3 and FOXF1 gene expression in glioma cells with ERNI function. At the same time, the expression level of all studied genes is strongly decreased, except for TBX3 gene, in glioma cells without ERN1 function. Moreover, the inhibition of ERN1 signaling enzyme function significantly modifies the effect of hypoxia on the expression of these transcription factor genes. removes or introduces this regulation as well as changes a direction or magnitude of hypoxic regulation. Present study demonstrates that fine-tuning of the expression of proliferation related genes depends upon hypoxia and ERN1-mediated endoplasmic reticulum stress signaling and correlates with slower proliferation rate of glioma cells without ERN1 function.

Open Rotor Noise Shielding by Blended-Wing-Body Aircraft

NASA Technical Reports Server (NTRS)

Guo, Yueping; Czech, Michael J.; Thomas, Russell H.

2015-01-01

This paper presents an analysis of open rotor noise shielding by Blended Wing Body (BWB) aircraft by using model scale test data acquired in the Boeing Low Speed Aeroacoustic Facility (LSAF) with a legacy F7/A7 rotor model and a simplified BWB platform. The objective of the analysis is the understanding of the shielding features of the BWB and the method of application of the shielding data for noise studies of BWB aircraft with open rotor propulsion. By studying the directivity patterns of individual tones, it is shown that though the tonal energy distribution and the spectral content of the wind tunnel test model, and thus its total noise, may differ from those of more advanced rotor designs, the individual tones follow directivity patterns that characterize far field radiations of modern open rotors, ensuring the validity of the use of this shielding data. Thus, open rotor tonal noise shielding should be categorized into front rotor tones, aft rotor tones and interaction tones, not only because of the different directivities of the three groups of tones, but also due to the differences in their source locations and coherence features, which make the respective shielding characteristics of the three groups of tones distinctly different from each other. To reveal the parametric trends of the BWB shielding effects, results are presented with variations in frequency, far field emission angle, rotor operational condition, engine installation geometry, and local airframe features. These results prepare the way for the development of parametric models for the shielding effects in prediction tools.

Paddle-based rotating-shield brachytherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yunlong; Xu, Weiyu; Flynn, Ryan T.

Purpose: The authors present a novel paddle-based rotating-shield brachytherapy (P-RSBT) method, whose radiation-attenuating shields are formed with a multileaf collimator (MLC), consisting of retractable paddles, to achieve intensity modulation in high-dose-rate brachytherapy. Methods: Five cervical cancer patients using an intrauterine tandem applicator were considered to assess the potential benefit of the P-RSBT method. The P-RSBT source used was a 50 kV electronic brachytherapy source (Xoft Axxent™). The paddles can be retracted independently to form multiple emission windows around the source for radiation delivery. The MLC was assumed to be rotatable. P-RSBT treatment plans were generated using the asymmetric dose–volume optimizationmore » with smoothness control method [Liu et al., Med. Phys. 41(11), 111709 (11pp.) (2014)] with a delivery time constraint, different paddle sizes, and different rotation strides. The number of treatment fractions (fx) was assumed to be five. As brachytherapy is delivered as a boost for cervical cancer, the dose distribution for each case includes the dose from external beam radiotherapy as well, which is 45 Gy in 25 fx. The high-risk clinical target volume (HR-CTV) doses were escalated until the minimum dose to the hottest 2 cm{sup 3} (D{sub 2cm{sup 3}}) of either the rectum, sigmoid colon, or bladder reached their tolerance doses of 75, 75, and 90 Gy{sub 3}, respectively, expressed as equivalent doses in 2 Gy fractions (EQD2 with α/β = 3 Gy). Results: P-RSBT outperformed the two other RSBT delivery techniques, single-shield RSBT (S-RSBT) and dynamic-shield RSBT (D-RSBT), with a properly selected paddle size. If the paddle size was angled at 60°, the average D{sub 90} increases for the delivery plans by P-RSBT on the five cases, compared to S-RSBT, were 2.2, 8.3, 12.6, 11.9, and 9.1 Gy{sub 10}, respectively, with delivery times of 10, 15, 20, 25, and 30 min/fx. The increases in HR-CTV D{sub 90}, compared to D

Hypervelocity impact testing of L-band truss cable meteoroid shielding on Skylab

NASA Technical Reports Server (NTRS)

Jex, D. W.

1973-01-01

A series of tests was performed to determine the protection provided by the L-band truss cable meteoroid shielding installed on Skylab space station at space environment temperatures of minus 180 F. The damage sustained when three test specimens were impacted by spherical projectiles at hypersonic speed was investigated. It is concluded that the L-band truss cable meteoroid shielding provides adequate protection at the indicated temperature.

Therapeutic effects of visual standard channel combined with F4.8 visual puncture super-mini percutaneous nephrolithotomy on multiple renal calculi.

PubMed

Cui, Zhenyu; Gao, Yanjun; Yang, Wenzeng; Zhao, Chunli; Ma, Tao; Shi, Xiaoqiang

2018-01-01

To evaluate the therapeutic effects of visual standard channel combined with F4.8 visual puncture super-mini percutaneous nephrolithotomy (SMP) on multiple renal calculi. The clinical data of 46 patients with multiple renal calculi treated in Affiliated Hospital of Hebei University from October 2015 to September 2016 were retrospectively analyzed. There were 28 males and 18 females aged from 25 to 65 years old, with an average of 42.6. The stone diameters were 3.0-5.2 cm, (4.3 ± 0.8) cm on average. F4.8 visual puncture-assisted balloon expansion was used to establish a standard channel. After visible stones were removed through nephroscopy combined with ultrasound lithotripsy, the stones of other parts were treated through F4.8 visual puncture SMP with holmium laser. Indices such as the total time of channel establishment, surgical time, decreased value of hemoglobin, phase-I stone clearance rate and surgical complications were summarized. Single standard channel was successfully established in all cases with the assistance of F4.8 visual puncture, of whom 24 were combined with a single microchannel, 16 were combined with double microchannels, and six were combined with three microchannels. All patients were placed with nephrostomy tube which was not placed in the microchannels. Both F5 double J tubes were placed after surgery. The time for establishing a standard channel through F4.8 visual puncture was (6.8 ± 1.8) min, and that for establishing a single F4.8 visual puncture microchannel was (4.5 ± 0.9) min. The surgical time was (92 ± 15) min. The phase-I stone clearance rate was 91.3% (42/46), and the decreased value of hemoglobin was (12.21 ± 2.5) g/L. There were 8 cases of postoperative fever which was relieved after anti-inflammatory treatment. Four cases had 0.5-0.8 cm of stone residue in the lower calyx, and all stones were discharged one month after surgery by in vitro shock wave lithotripsy combined with position nephrolithotomy, without stone

Angular dependence of etch rates in the etching of poly-Si and fluorocarbon polymer using SF6, C4F8, and O2 plasmas

NASA Astrophysics Data System (ADS)

Min, Jae-Ho; Lee, Gyeo-Re; Lee, Jin-Kwan; Moon, Sang Heup; Kim, Chang-Koo

2004-05-01

The dependences of etch rates on the angle of ions incident on the substrate surface in four plasma/substrate systems that constitute the advanced Bosch process were investigated using a Faraday cage designed for the accurate control of the ion-incident angle. The four systems, established by combining discharge gases and substrates, were a SF6/poly-Si, a SF6/fluorocarbon polymer, an O2/fluorocarbon polymer, and a C4F8/Si. In the case of SF6/poly-Si, the normalized etch rates (NERs), defined as the etch rates normalized by the rate on the horizontal surface, were higher at all angles than values predicted from the cosine of the ion-incident angle. This characteristic curve shape was independent of changes in process variables including the source power and bias voltage. Contrary to the earlier case, the NERs for the O2/polymer decreased and eventually reached much lower values than the cosine values at angles between 30° and 70° when the source power was increased and the bias voltage was decreased. On the other hand, the NERs for the SF6/polymer showed a weak dependence on the process variables. In the case of C4F8/Si, which is used in the Bosch process for depositing a fluorocarbon layer on the substrate surface, the deposition rate varied with the ion incident angle, showing an S-shaped curve. These characteristic deposition rate curves, which were highly dependent on the process conditions, could be divided into four distinct regions: a Si sputtering region, an ion-suppressed polymer deposition region, an ion-enhanced polymer deposition region, and an ion-free polymer deposition region. Based on the earlier characteristic angular dependences of the etch (or deposition) rates in the individual systems, ideal process conditions for obtaining an anisotropic etch profile in the advanced Bosch process are proposed. .

48 CFR 6.204 - Section 8(a) competition.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Section 8(a) competition. 6.204 Section 6.204 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION ACQUISITION PLANNING COMPETITION REQUIREMENTS Full and Open Competition After Exclusion of Sources 6.204...

Performance of solar shields. [Skylab 1 micrometeoroid shield difficulties

NASA Technical Reports Server (NTRS)

Schwinghamer, R. J.

1974-01-01

The loss of the micrometeoroid shield from the Orbital Workshop section of Skylab 1 about 63 seconds after lift-off, was the catalyst for a prodigious effort to develop a substitute for the passive portion of the thermal control system. An intensive effort is described in which numerous potential thermal shield materials were assessed, and during which period ten specific shield designs were developed and carried through various stages of development and test. Thermal shield materials data are discussed, including optical, strength, fatigue, outgassing, tackiness, ultraviolet radiation, and material memory properties. Specifically addressed are thermal shield materials selection criteria and the design, development, and test requirements associated with the successful development of Skylab thermal shields, and specifically the two thermal shields subsequently deployed over the exposed gold foil skin of the Orbital Workshop. Also considered are the general performance and thermal improvements provided by both the parasol design deployed by the Skylab 1 crew, and the sail design deployed by the Skylab 2 crew.

Plasma 8-iso-Prostaglandin F2α, a possible prognostic marker in aneurysmal subarachnoid hemorrhage.

PubMed

Pan, De-Sheng; Yan, Min; Hassan, Muhammad; Fang, Ze-Bin; Chen, Man-Tao

2017-06-01

8-iso-Prostaglandin F2α (8-iso-PGF2α) is a potential biomarker of oxidative stress. This study clarified whether plasma 8-iso-PGF2α concentrations were affected and its underlying relevance to prognosis in aneurysmal subarachnoid hemorrhage (aSAH). In this prospective, observational study, a total of 170 controls and 170 aSAH patients were enrolled. Plasma 8-iso-PGF2α concentrations were detected using an ELISA. Severity was assessed by World Federation of Neurological Surgeons (WFNS) scale and modified Fisher grading scale. Clinical outcomes included 6-month mortality and poor outcome referred to as Glasgow outcome scale score of 1-3. As compared to controls, admission plasma 8-iso-PGF2α concentrations were significantly enhanced. Increased concentrations of plasma 8-iso-PGF2α correlated with WFNS scores and modified Fisher scores. 8-iso-PGF2α in plasma was an independent predictor for clinical outcomes. Under ROC curve, the predictive values of 8-iso-PGF2α concentrations resembled those of WFNS scores and modified Fisher scores for clinical outcomes. An elevation in plasma 8-iso-PGF2α concentrations is associated with the severity and poor outcome after aSAH, substantializing 8-iso-PGF2α as a potential prognostic biomarker of aSAH. Copyright © 2017. Published by Elsevier B.V.

Methyl fluoride-13C in nematic liquid crystals: Anisotropy of the indirect 13C-19F spin-spin coupling and of the 1H, 13C, and 19F chemical shieldings

NASA Astrophysics Data System (ADS)

Jokisaari, J.; Hiltunen, Y.; Lounila, J.

1986-09-01

The anisotropy of the indirect 13C-19F spin-spin coupling tensor of methyl fluoride-13C in the liquid crystals ZLI 1167, EBBA, their mixtures, phase IV, and phase 1221 was studied by applying 1H and 19F NMR spectroscopy. The relative anisotropy ΔJCF/JCF gets values between -4.3 (in ZLI 1167) and +30.7 (in EBBA) when determined in the conventional way from the experimental dipolar coupling constants taking into account only harmonic vibrational corrections. The inclusion of the deformational corrections in both the direct and indirect C-F coupling tensors leads to a constant, solvent independent relative anisotropy of -2.5±0.2. This result is also obtained when a mixture of the liquid crystals ZLI 1167 and EBBA is used which mixture gives an undistorted geometry for methyl fluoride. The chemical shielding anisotropies ΔσH, ΔσC, and ΔσF for methyl fluoride were determined by applying the method of mixing two thermotropic nematogens (ZLI 1167 and EBBA) with opposite anisotropies of diamagnetic susceptibility. The results ΔσH =+5.2±0.2 ppm, ΔσC =+87±4 ppm, and ΔσF =-90±4 ppm are in fair agreement with theoretical calculations.

Fetal shielding combined with state of the art CT dose reduction strategies during maternal chest CT.

PubMed

Chatterson, Leslie C; Leswick, David A; Fladeland, Derek A; Hunt, Megan M; Webster, Stephen; Lim, Hyun

2014-07-01

Custom bismuth-antimony shields were previously shown to reduce fetal dose by 53% on an 8DR (detector row) CT scanner without dynamic adaptive section collimation (DASC), automatic tube current modulation (ATCM) or adaptive statistical iterative reconstruction (ASiR). The purpose of this study is to compare the effective maternal and average fetal organ dose reduction both with and without bismuth-antimony shields on a 64DR CT scanner using DASC, ATCM and ASiR during maternal CTPA. A phantom with gravid prosthesis and a bismuth-antimony shield were used. Thermoluminescent dosimeters (TLDs) measured fetal radiation dose. The average fetal organ dose and effective maternal dose were determined using 100 kVp, scanning from the lung apices to the diaphragm utilizing DASC, ATCM and ASiR on a 64DR CT scanner with and without shielding in the first and third trimester. Isolated assessment of DASC was done via comparing a new 8DR scan without DASC to a similar scan on the 64DR with DASC. Average third trimester unshielded fetal dose was reduced from 0.22 mGy ± 0.02 on the 8DR to 0.13 mGy ± 0.03 with the conservative 64DR protocol that included 30% ASiR, DASC and ATCM (42% reduction, P<0.01). Use of a shield further reduced average third trimester fetal dose to 0.04 mGy ± 0.01 (69% reduction, P<0.01). The average fetal organ dose reduction attributable to DASC alone was modest (6% reduction from 0.17 mGy ± 0.02 to 0.16 mGy ± 0.02, P=0.014). First trimester fetal organ dose on the 8DR protocol was 0.07 mGy ± 0.03. This was reduced to 0.05 mGy ± 0.03 on the 64DR protocol without shielding (30% reduction, P=0.009). Shields further reduced this dose to below accurately detectable levels. Effective maternal dose was reduced from 4.0 mSv on the 8DR to 2.5 mSv on the 64DR scanner using the conservative protocol (38% dose reduction). ASiR, ATCM and DASC combined significantly reduce effective maternal and fetal organ dose during CTPA. Shields continue to be an effective

Evaluation of coated columbium alloy heat shields for space shuttle thermal protection system application. Final report. [For us to 2400F

DOE Office of Scientific and Technical Information (OSTI.GOV)

Black, W.E.

1977-04-01

A three-phase program to develop and demonstrate the feasibility of a metallic heat shield suitable for use on Space Shuttle Orbiter class vehicles at operating surface temperatures of up to 1590 K (2400 F) is summarized. An orderly progression of configuration studies, material screening tests, and subscale structural tests was performed. Scale-up feasibility was demonstrated in the final phase when a sizable nine-panel array was fabricated and successfully tested. The full-scale tests included cyclic testing at reduced air pressure to 1590 K (2400 F) and up to 158 dB overall sound pressure level. The selected structural configuration and design techniquesmore » succesfully eliminated thermal induced failures. The thermal/structural performance of the system was repeatedly demonstrated. Practical and effective field repair methods for coated columbium alloys were demonstrated. Major uncertainties of accessibility, refurbishability, and durability were eliminated.« less

Shielded Heavy-Ion Environment Linear Detector (SHIELD): an experiment for the Radiation and Technology Demonstration (RTD) Mission.

PubMed

Shavers, M R; Cucinotta, F A; Miller, J; Zeitlin, C; Heilbronn, L; Wilson, J W; Singleterry, R C

2001-01-01

Radiological assessment of the many cosmic ion species of widely distributed energies requires the use of theoretical transport models to accurately describe diverse physical processes related to nuclear reactions in spacecraft structures, planetary atmospheres and surfaces, and tissues. Heavy-ion transport models that were designed to characterize shielded radiation fields have been validated through comparison with data from thick-target irradiation experiments at particle accelerators. With the RTD Mission comes a unique opportunity to validate existing radiation transport models and guide the development of tools for shield design. For the first time, transport properties will be measured in free-space to characterize the shielding effectiveness of materials that are likely to be aboard interplanetary space missions. Target materials composed of aluminum, advanced composite spacecraft structure and other shielding materials, helium (a propellant) and tissue equivalent matrices will be evaluated. Large solid state detectors will provide kinetic energy and charge identification for incident heavy-ions and for secondary ions created in the target material. Transport calculations using the HZETRN model suggest that 8 g cm -2 thick targets would be adequate to evaluate the shielding effectiveness during solar minimum activity conditions for a period of 30 days or more.

Evaluation of clinically applied treatment beams with respect to bunker shielding parameters for a Cyberknife M6.

PubMed

Henzen, Dominik; Schmidhalter, Daniel; Zanella, Claudia Christina; Volken, Werner; Mackeprang, Paul-Henry; Malthaner, Marco; Fix, Michael Karl; Manser, Peter

2018-01-01

Compared to a conventional linear accelerator, the Cyberknife (CK) is a unique system with respect to radiation protection shielding and the variety and number of non-coplanar beams are two key components regarding this aspect. In this work, a framework to assess the direction distribution and modulation factor (MF) of clinically applied treatment beams of a CyberKnife M6 is developed. Database filtering options allow studying the influence of different parameters such as collimator types, treatment sites or different bunker sizes. A distribution of monitor units (MU) is generated by projecting treatment beams onto the walls, floor and ceiling of the CyberKnife bunker. This distribution is found to be highly heterogeneous and depending, among other parameters, on the bunker size. For our bunker design, 10%-13% of the MUs are delivered to the right and left wall, each. The floor receives more than 64% of the applied MUs, while the wall behind the patient's head is not hit by primary treatment beams. Between 0% and 5% of the total MUs are delivered to the wall at the patient's feet. This number highly depends on the treatment site, e.g., for extracranial patients no beams hit that wall. Collimator choice was found to have minor influence on the distribution of MUs. On the other hand, the MF depends on the collimator type as well as on the treatment site. The MFs (delivered MU/prescribed dose) for all treatments, all MLC treatments, cranial and extracranial treatments are 8.3, 6.4, 7.7, and 9.9 MU/cGy, respectively. The developed framework allows assessing and monitoring important parameters regarding radiation protection of a CK-M6 using the actually applied treatment beams. Furthermore, it enables evaluating different clinical and constructional situations using the filtering options. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Carcinogenicity of acrylamide in B6C3F(1) mice and F344/N rats from a 2-year drinking water exposure.

PubMed

Beland, Frederick A; Mellick, Paul W; Olson, Greg R; Mendoza, Maria C B; Marques, M Matilde; Doerge, Daniel R

2013-01-01

Acrylamide is a component of roasted coffee and certain baked and fried carbohydrate-rich foods prepared at high temperatures. We have assessed the carcinogenicity of acrylamide in male and female B6C3F(1) mice and F344/N rats administered 0, 0.0875, 0.175, 0.35, or 0.70mM acrylamide in the drinking water ad libitum for 2 years. Acrylamide caused significant dose-related decreasing trends in the body weights of F344/N rats. Acrylamide administration resulted in significant dose-related decreasing trends in survival in both sexes of B6C3F(1) mice and in female F344/N rats. Histopathological analyses indicated significant dose-related increases in Harderian gland and lung tumors in male and female B6C3F(1) mice. Male B6C3F(1) mice also had a significantly increased incidence of forestomach tumors, while female B6C3F(1) mice had significant dose-related increases in mammary gland, ovary, and skin tumors. In male and female F344/N rats, there were significant increases in thyroid tumors. Male F344/N rats also had significant dose-related increases in testes, heart, and pancreas tumors, while female F344 rats demonstrated significant increases in clitoral gland, mammary gland, oral cavity, and skin tumors. These results, combined with previous mechanistic studies, provide strong support for the concept that acrylamide is activated to a carcinogen through metabolism to glycidamide. Published by Elsevier Ltd.

Multi-Shock Shield Performance at 15 MJ for Catalogued Debris

NASA Technical Reports Server (NTRS)

Miller, J. E.; Davis, B. A.; Christiansen, E. L.; Lear, D. M.

2015-01-01

While orbital debris of ten centimeters or more are tracked and catalogued, the difficulty of finding and accurately accounting for forces acting on the objects near the ten centimeter threshold results in both uncertainty of their presence and location. These challenges result in difficult decisions for operators balancing potential costly operational approaches with system loss risk. In this paper, the assessment of the feasibility of protecting a spacecraft from this catalogued debris is described using numerical simulations and a test of a multi-shock shield system against a cylindrical projectile impacting normal to the surface with approximately 15 MJ of kinetic energy. The hypervelocity impact test has been conducted at the Arnold Engineering Development Complex (AEDC) with a 598 g projectile at 6.905 km/s on a NASA supplied multi-shock shield. The projectile used is a hollow aluminum and nylon cylinder with an outside diameter of 8.6 cm and length of 10.3 cm. Figure 1 illustrates the multi-shock shield test article, which consisted of five separate bumpers, four of which are fiberglass fabric and one of steel mesh, and two rear walls, each consisting of Kevlar fabric. The overall length of the test article was 2.65 m. The test article was a 5X scaled-up version of a smaller multi-shock shield previously tested using a 1.4 cm diameter aluminum projectile for an inflatable module project. The distances represented by S1 and S1/2 in the figure are 61 cm and 30.5 cm, respectively. Prior to the impact test, hydrodynamic simulations indicated that some enhancement to the standard multi-shock system is needed to address the effects of the cylindrical shape of the projectile. Based on the simulations, a steel mesh bumper has been added to the shield configuration to enhance the fragmentation of the projectile. The AEDC test occurred as planned, and the modified NASA multi-shock shield successfully stopped 598 g projectile using 85.6 kg/m(exp 2). The fifth bumper

Evaluation Of Shielding Efficacy Of A Ferrite Containing Ceramic Material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verst, C.

2015-10-12

The shielding evaluation of the ferrite based Mitsuishi ceramic material has produced for several radiation sources and possible shielding sizes comparative dose attenuation measurements and simulated projections. High resolution gamma spectroscopy provided uncollided and scattered photon spectra at three energies, confirming theoretical estimates of the ceramic’s mass attenuation coefficient, μ/ρ. High level irradiation experiments were performed using Co-60, Cs-137, and Cf-252 sources to measure penetrating dose rates through steel, lead, concrete, and the provided ceramic slabs. The results were used to validate the radiation transport code MCNP6 which was then used to generate dose rate attenuation curves as a functionmore » of shielding material, thickness, and mass for photons and neutrons ranging in energy from 200 keV to 2 MeV.« less

On the morphometry of terrestrial shield volcanoes

NASA Astrophysics Data System (ADS)

Grosse, Pablo; Kervyn, Matthieu

2016-04-01

Shield volcanoes are described as low angle edifices that have convex up topographic profiles and are built primarily by the accumulation of lava flows. This generic view of shields' morphology is based on a limited number of monogenetic shields from Iceland and Mexico, and a small set of large oceanic islands (Hawaii, Galapagos). Here, the morphometry of over 150 monogenetic and polygenetic shield volcanoes, identified inthe Global Volcanism Network database, are analysed quantitatively from 90-meter resolution DEMs using the MORVOLC algorithm. An additional set of 20 volcanoes identified as stratovolcanoes but having low slopes and being dominantly built up by accumulation of lava flows are documented for comparison. Results show that there is a large variation in shield size (volumes range from 0.1 to >1000 km3), profile shape (height/basal width ratios range from 0.01 to 0.1), flank slope gradients, elongation and summit truncation. Correlation and principal component analysis of the obtained quantitative database enables to identify 4 key morphometric descriptors: size, steepness, plan shape and truncation. Using these descriptors through clustering analysis, a new classification scheme is proposed. It highlights the control of the magma feeding system - either central, along a linear structure, or spatially diffuse - on the resulting shield volcano morphology. Genetic relationships and evolutionary trends between contrasted morphological end-members can be highlighted within this new scheme. Additional findings are that the Galapagos-type morphology with a central deep caldera and steep upper flanks are characteristic of other shields. A series of large oceanic shields have slopes systematically much steeper than the low gradients (<4-8°) generally attributed to large Hawaiian-type shields. Finally, the continuum of morphologies from flat shields to steeper complex volcanic constructs considered as stratovolcanoes calls for a revision of this oversimplified

Geraniol suppresses prostate cancer growth through down-regulation of E2F8.

PubMed

Lee, Sanghoon; Park, Yu Rang; Kim, Su-Hwa; Park, Eun-Jung; Kang, Min Ji; So, Insuk; Chun, Jung Nyeo; Jeon, Ju-Hong

2016-10-01

Geraniol, an acyclic dietary monoterpene, has been found to suppress cancer survival and growth. However, the molecular mechanism underlying the antitumor action of geraniol has not been investigated at the genome-wide level. In this study, we analyzed the microarray data obtained from geraniol-treated prostate cancer cells. Geraniol potently altered a gene expression profile and primarily down-regulated cell cycle-related gene signatures, compared to linalool, another structurally similar monoterpene that induces no apparent phenotypic changes. Master regulator analysis using the prostate cancer-specific regulatory interactome identified that the transcription factor E2F8 as a specific target molecule regulates geraniol-specific cell cycle signatures. Subsequent experiments confirmed that geraniol down-regulated E2F8 expression and the knockdown of E2F8 was sufficient to suppress cell growth by inducing G 2 /M arrest. Epidemiological analysis showed that E2F8 is up-regulated in metastatic prostate cancer and associated with poor prognosis. These results indicate that E2F8 is a crucial transcription regulator controlling cell cycle and survival in prostate cancer cells. Therefore, our study provides insight into the role of E2F8 in prostate cancer biology and therapeutics. © 2016 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.

Aligning flaky FeSiAl particles with a two-dimensional rotating magnetic field to improve microwave-absorbing and shielding properties of composites

NASA Astrophysics Data System (ADS)

Liu, Chang; Cai, Jun; Duan, Yubing; Li, Xinghao; Zhang, Deyuan

2018-07-01

In order to enhance the microwave-absorbing and shielding properties of the composites, the flaky FeSiAl particles embedded in an epoxy polymer were aligned with a two-dimensional rotating magnetic field. The morphologies, electromagnetic (EM) characteristics, and microwave-absorbing and shielding properties of the unaligned and aligned FeSiAl/epoxy composites were investigated. The results showed that after alignment treatment, the flaky FeSiAl particles tend to orient uniformly in the rotating magnetic field, and the permittivity and permeability of the aligned composites were increased in the frequency range of 1-18 GHz compared with that of randomly distributed composites. The calculated microwave-absorbing properties indicated that the peak value of the return loss (RL) of the aligned composites can reach 8.8 dB, compared with 5.8 dB of the unaligned composites of 2.5 mm in thickness (60 wt%); and the bandwidth with RL value more than 6 dB is in a wider frequency range from 1 to 2.8 GHz. And the calculated shielding effectiveness (SE) of the aligned composites is 1.1-3 times higher than that of unaligned one in every thickness, and the maximum SE of the aligned one is 31.8 dB at 18 GHz with a thickness of 2.5 mm.

Synthesis of Defect Perovskites (He 2–x⟂ x)(CaZr)F 6 by Inserting Helium into the Negative Thermal Expansion Material CaZrF 6

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hester, Brett R.; dos Santos, António M.; Molaison, Jamie J.

Defect perovskites (He 2–x⟂ x)(CaZr)F 6 can be prepared by inserting helium into CaZrF 6 at high pressure. They can be recovered to ambient pressure at low temperature. There are no prior examples of perovskites with noble gases on the A-sites. The insertion of helium gas into CaZrF 6 both elastically stiffens the material and reduces the magnitude of its negative thermal expansion. It also suppresses the onset of structural disorder, which is seen on compression in other media. Measurements of the gas released on warming to room temperature and Rietveld analyses of neutron diffraction data at low temperature indicatemore » that exposure to helium gas at 500 MPa leads to a stoichiometry close to (He 1⟂ 1)(CaZr)F 6. Helium has a much higher solubility in CaZrF 6 than silica glass or crystobalite. An analogue with composition (H 2) 2(CaZr)F 6 would have a volumetric hydrogen storage capacity greater than current US DOE targets. We anticipate that other hybrid perovskites with small neutral molecules on the A-site can also be prepared and that they will display a rich structural chemistry.« less

Jet Noise Shielding Provided by a Hybrid Wing Body Aircraft

NASA Technical Reports Server (NTRS)

Doty, Michael J.; Brooks, Thomas F.; Burley, Casey L.; Bahr, Christopher J.; Pope, Dennis S.

2014-01-01

One approach toward achieving NASA's aggressive N+2 noise goal of 42 EPNdB cumulative margin below Stage 4 is through the use of novel vehicle configurations like the Hybrid Wing Body (HWB). Jet noise measurements from an HWB acoustic test in NASA Langley's 14- by 22-Foot Subsonic Tunnel are described. Two dual-stream, heated Compact Jet Engine Simulator (CJES) units are mounted underneath the inverted HWB model on a traversable support to permit measurement of varying levels of shielding provided by the fuselage. Both an axisymmetric and low noise chevron nozzle set are investigated in the context of shielding. The unshielded chevron nozzle set shows 1 to 2 dB of source noise reduction (relative to the unshielded axisymmetric nozzle set) with some penalties at higher frequencies. Shielding of the axisymmetric nozzles shows up to 6.5 dB of reduction at high frequency. The combination of shielding and low noise chevrons shows benefits beyond the expected additive benefits of the two, up to 10 dB, due to the effective migration of the jet source peak noise location upstream for increased shielding effectiveness. Jet noise source maps from phased array results processed with the Deconvolution Approach for the Mapping of Acoustic Sources (DAMAS) algorithm reinforce these observations.

Low-Temperature Sintering Li3Mg1.8Ca0.2NbO6 Microwave Dielectric Ceramics with LMZBS Glass

NASA Astrophysics Data System (ADS)

Wang, Gang; Zhang, Huaiwu; Liu, Cheng; Su, Hua; Jia, Lijun; Li, Jie; Huang, Xin; Gan, Gongwen

2018-05-01

Li3Mg1.8Ca0.2NbO6 ceramics doped with Li2O-MgO-ZnO-B2O3-SiO2 glass (LMZBS) were prepared via a solid-state route. The LMZBS glass effectively reduced the sintering temperature of Li3Mg1.8Ca0.2NbO6 ceramics to 950°C. The effects of the LMZBS glass on the sintering behavior, microstructures and microwave dielectric properties of Li3Mg1.8Ca0.2NbO6 ceramics are discussed in detail. Among all the LMZBS doped Li3Mg1.8Ca0.2NbO6 ceramics, the sample with 1 wt.% of LMZBS glass sintered at 950°C for 4 h exhibited good dielectric properties: ɛ r = 16.7, Q × f = 31,000 GHz (9.92 GHz), τ f = - 1.3 ppm/°C. The Li3Mg1.8Ca0.2NbO6 ceramics possessed excellent chemical compatibility with Ag electrodes, and could be applied in low temperature co-fired ceramics (LTCC) applications.

16Oxygen irradiation enhances cued fear memory in B6D2F1 mice

NASA Astrophysics Data System (ADS)

Raber, Jacob; Marzulla, Tessa; Kronenberg, Amy; Turker, Mitchell S.

2015-11-01

The space radiation environment includes energetic charged particles that may impact cognitive performance. We assessed the effects of 16O ion irradiation on cognitive performance of C57BL/6J × DBA/2J F1 (B6D2F1) mice at OHSU (Portland, OR) one month following irradiation at Brookhaven National Laboratory (BNL, Upton, NY). Hippocampus-dependent contextual fear memory and hippocampus-independent cued fear memory of B6D2F1 mice were tested. 16O ion exposure enhanced cued fear memory. This effect showed a bell-shaped dose response curve. Cued fear memory was significantly stronger in mice irradiated with 16O ions at a dose of 0.4 or 0.8 Gy than in sham-irradiated mice or following irradiation at 1.6 Gy. In contrast to cued fear memory, contextual fear memory was not affected following 16O ion irradiation at the doses used in this study. These data indicate that the amygdala might be particularly susceptible to effects of 16O ion exposure.

Optical spectroscopy of low-phonon Ho3+ doped BaY2F8 single crystal

NASA Astrophysics Data System (ADS)

Li, Chun; Zeng, Fanming; Lin, Hai; Zheng, Dongyang; Yang, Xiaodong; Liu, Wang; Liu, Jinghe

2014-12-01

The Ho:BaY2F8 crystal was grown by Czochralski method. The crystal phase structure and absorption spectra were tested, the absorption peak exists near 899 nm, the absorption cross section was 1.27 × 10-21 cm2. The emission spectra of crystals in the vicinity of 2 and 3.9 μm were measured, the 2 μm near infrared light induced by 5I7 → 5I8 transition of Ho3+ ions was observed, as well as the fluorescence output at 3.9 μm (5I5 → 5I6), emission cross section at 3.9 μm was calculated to be 0.86 × 10-21 cm2. We suppose that the Ho:BaY2F8 crystal has a large application prospect for the 2-4 μm wavelength near infrared laser.

Combined measurement system for double shield tunnel boring machine guidance based on optical and visual methods.

PubMed

Lin, Jiarui; Gao, Kai; Gao, Yang; Wang, Zheng

2017-10-01

In order to detect the position of the cutting shield at the head of a double shield tunnel boring machine (TBM) during the excavation, this paper develops a combined measurement system which is mainly composed of several optical feature points, a monocular vision sensor, a laser target sensor, and a total station. The different elements of the combined system are mounted on the TBM in suitable sequence, and the position of the cutting shield in the reference total station frame is determined by coordinate transformations. Subsequently, the structure of the feature points and matching technique for them are expounded, the position measurement method based on monocular vision is presented, and the calibration methods for the unknown relationships among different parts of the system are proposed. Finally, a set of experimental platforms to simulate the double shield TBM is established, and accuracy verification experiments are conducted. Experimental results show that the mean deviation of the system is 6.8 mm, which satisfies the requirements of double shield TBM guidance.

Kasatkinite, Ba2Ca8B5Si8O32(OH)3 · 6H2O6, a new mineral from the Bazhenovskoe deposit, the Central Urals, Russia

NASA Astrophysics Data System (ADS)

Pekov, I. V.; Chukanov, N. V.; Filinchuk, Ya. E.; Zadov, A. E.; Kononkova, N. N.; Epanchintsev, S. G.; Kaden, P.; Kutzer, A.; Göttlicher, J.

2013-12-01

A new mineral, kasatkinite, Ba2Ca8B5Si8O32(OH)3 · 6H2O, has been found at the Bazhenovskoe chrysotile asbestos deposit, the Central Urals, Russia in the cavities in rhodingite as a member of two assemblages: (l) on prehnite, with pectolite, calcite, and clinochlore; and (2) on grossular, with diopside and pectolite. Kasatkinite occurs as spherulites or bunches up to 3 mm in size, occasionally combined into crusts. Its individuals are acicular to hair-like, typically split, with a polygonal cross section, up to 0.5 mm (rarely, to 6 mm) in length and to 20 μm in thickness. They consist of numerous misoriented needle-shaped subindividuals up to several dozen μm long and no more than 1 μm thick. Kasatkinite individuals are transparent and colorless; its aggregates are snow white. The luster is vitreous or silky. No cleavage was observed; the fracture is uneven or splintery for aggregates. Individuals are flexible and elastic. The Mohs' hardness is 4-4.5. D meas = 2.95(5), D calc = 2.89 g/cm3. Kasatkinite is optically biaxial (+), α = 1.600(5), β = 1.603(2), γ = 1.626(2), 2 V meas = 30(20)°, 2 V calc = 40°. The IR spectrum is given. The 11B MAS NMR spectrum shows the presence of BO4 in the absence of BO3 groups. The chemical composition of kasatkinite (wt %; electron microprobe, H2O by gas chromatography) is as follows: 0.23 Na2O, 0.57 K2O, 28.94 CaO, 16.79 BaO, 11.57 B2O3, 0.28 Al2O3, 31.63 SiO2, 0.05 F, 9.05 H2O, -0.02 -O=F2; the total is 99.09. The empirical formula (calculated on the basis of O + F = 41 apfu, taking into account the TGA data) is: Na0.11K0.18Ba1.66Ca7.84B5.05Al0.08Si8.00O31.80(OH)3.06F0.04 · 6.10H2O. Kasatkinite is monoclinic, space group P21/ c, P2/ c, or Pc; the unit-cell dimensions are a = 5.745(3), b = 7.238(2), c = 20.79 (1) Å, β = 90.82(5)°, V = 864(1) Å3, Z = 1. The strongest reflections ( d Å- I[ hkl]) in the X-ray powder diffractions pattern are: 5.89-24[012], 3.48-2.1[006], 3.36-24[114]; 3.009-100[, 121, ], 2

Neutron Shielding Effectiveness of Multifunctional Composite Materials

DTIC Science & Technology

2013-03-01

greater degree of flexibility in design and engineering of specialized space vehicle shielding applications compared to aluminum. A new design for...photon/electron transport. Specific areas of application include, but are not limited to, radiation protection and dosimetry, radiation shielding...of 37.8%. The reaction of interest is 64Zn(n,p)64Cu, where 64Cu has a half-life of 12.7 hours [5]. When this reaction occurs a positron

Single-tube tetradecaplex panel of highly polymorphic microsatellite markers < 1 Mb from F8 for simplified preimplantation genetic diagnosis of hemophilia A.

PubMed

Zhao, M; Chen, M; Tan, A S C; Cheah, F S H; Mathew, J; Wong, P C; Chong, S S

2017-07-01

Essentials Preimplantation genetic diagnosis (PGD) of severe hemophilia A relies on linkage analysis. Simultaneous multi-marker screening can simplify selection of informative markers in a couple. We developed a single-tube tetradecaplex panel of polymorphic markers for hemophilia A PGD use. Informative markers can be used for linkage analysis alone or combined with mutation detection. Background It is currently not possible to perform single-cell preimplantation genetic diagnosis (PGD) to directly detect the common inversion mutations of the factor VIII (F8) gene responsible for severe hemophilia A (HEMA). As such, PGD for such inversion carriers relies on indirect analysis of linked polymorphic markers. Objectives To simplify linkage-based PGD of HEMA, we aimed to develop a panel of highly polymorphic microsatellite markers located near the F8 gene that could be simultaneously genotyped in a multiplex-PCR reaction. Methods We assessed the polymorphism of various microsatellite markers located ≤ 1 Mb from F8 in 177 female subjects. Highly polymorphic markers were selected for co-amplification with the AMELX/Y indel dimorphism in a single-tube reaction. Results Thirteen microsatellite markers located within 0.6 Mb of F8 were successfully co-amplified with AMELX/Y in a single-tube reaction. Observed heterozygosities of component markers ranged from 0.43 to 0.84, and ∼70-80% of individuals were heterozygous for ≥ 5 markers. The tetradecaplex panel successfully identified fully informative markers in a couple interested in PGD for HEMA because of an intragenic F8 point mutation, with haplotype phasing established through a carrier daughter. In-vitro fertilization (IVF)-PGD involved single-tube co-amplification of fully informative markers with AMELX/Y and the mutation-containing F8 amplicon, followed by microsatellite analysis and amplicon mutation-site minisequencing analysis. Conclusions The single-tube multiplex-PCR format of this highly polymorphic

Isolation and structures of sulfonium salts derived from thioethers: [{o-C(6)H(4)(CH(2)SMe)(2)}H][NbF(6)] and [{[9]aneS(3)}H][NbF(6)].

PubMed

Jura, Marek; Levason, William; Reid, Gillian; Webster, Michael

2009-10-07

Two very unusual sulfonium salts, [{o-C(6)H(4)(CH(2)SMe)(2)}H][NbF(6)] and [{[9]aneS(3)}H][NbF(6)], obtained from reaction of the thioethers with NbF(5) in CH(2)Cl(2) solution, are reported and their structures described; the eight-coordinate tetrafluoro Nb(v) cation of the dithioether is obtained from the same reaction.

TaHsfA6f is a transcriptional activator that regulates a suite of heat stress protection genes in wheat (Triticum aestivum L.) including previously unknown Hsf targets

PubMed Central

Xue, Gang-Ping; Drenth, Janneke; McIntyre, C. Lynne

2015-01-01

Heat stress is a significant environmental factor adversely affecting crop yield. Crop adaptation to high-temperature environments requires transcriptional reprogramming of a suite of genes involved in heat stress protection. This study investigated the role of TaHsfA6f, a member of the A6 subclass of heat shock transcription factors, in the regulation of heat stress protection genes in Triticum aestivum (bread wheat), a poorly understood phenomenon in this crop species. Expression analysis showed that TaHsfA6f was expressed constitutively in green organs but was markedly up-regulated during heat stress. Overexpression of TaHsfA6f in transgenic wheat using a drought-inducible promoter resulted in up-regulation of heat shock proteins (HSPs) and a number of other heat stress protection genes that included some previously unknown Hsf target genes such as Golgi anti-apoptotic protein (GAAP) and the large isoform of Rubisco activase. Transgenic wheat plants overexpressing TaHsfA6f showed improved thermotolerance. Transactivation assays showed that TaHsfA6f activated the expression of reporter genes driven by the promoters of several HSP genes (TaHSP16.8, TaHSP17, TaHSP17.3, and TaHSP90.1-A1) as well as TaGAAP and TaRof1 (a co-chaperone) under non-stress conditions. DNA binding analysis revealed the presence of high-affinity TaHsfA6f-binding heat shock element-like motifs in the promoters of these six genes. Promoter truncation and mutagenesis analyses identified TaHsfA6f-binding elements that were responsible for transactivation of TaHSP90.1-A1 and TaGAAP by TaHsfA6f. These data suggest that TaHsfA6f is a transcriptional activator that directly regulates TaHSP, TaGAAP, and TaRof1 genes in wheat and its gene regulatory network has a positive impact on thermotolerance. PMID:25428996

TaHsfA6f is a transcriptional activator that regulates a suite of heat stress protection genes in wheat (Triticum aestivum L.) including previously unknown Hsf targets.

PubMed

Xue, Gang-Ping; Drenth, Janneke; McIntyre, C Lynne

2015-02-01

Heat stress is a significant environmental factor adversely affecting crop yield. Crop adaptation to high-temperature environments requires transcriptional reprogramming of a suite of genes involved in heat stress protection. This study investigated the role of TaHsfA6f, a member of the A6 subclass of heat shock transcription factors, in the regulation of heat stress protection genes in Triticum aestivum (bread wheat), a poorly understood phenomenon in this crop species. Expression analysis showed that TaHsfA6f was expressed constitutively in green organs but was markedly up-regulated during heat stress. Overexpression of TaHsfA6f in transgenic wheat using a drought-inducible promoter resulted in up-regulation of heat shock proteins (HSPs) and a number of other heat stress protection genes that included some previously unknown Hsf target genes such as Golgi anti-apoptotic protein (GAAP) and the large isoform of Rubisco activase. Transgenic wheat plants overexpressing TaHsfA6f showed improved thermotolerance. Transactivation assays showed that TaHsfA6f activated the expression of reporter genes driven by the promoters of several HSP genes (TaHSP16.8, TaHSP17, TaHSP17.3, and TaHSP90.1-A1) as well as TaGAAP and TaRof1 (a co-chaperone) under non-stress conditions. DNA binding analysis revealed the presence of high-affinity TaHsfA6f-binding heat shock element-like motifs in the promoters of these six genes. Promoter truncation and mutagenesis analyses identified TaHsfA6f-binding elements that were responsible for transactivation of TaHSP90.1-A1 and TaGAAP by TaHsfA6f. These data suggest that TaHsfA6f is a transcriptional activator that directly regulates TaHSP, TaGAAP, and TaRof1 genes in wheat and its gene regulatory network has a positive impact on thermotolerance. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology.

A learning flight control system for the F8-DFBW aircraft. [Digital Fly-By-Wire

NASA Technical Reports Server (NTRS)

Montgomery, R. C.; Mekel, R.; Nachmias, S.

1978-01-01

This report contains a complete description of a learning control system designed for the F8-DFBW aircraft. The system is parameter-adaptive with the additional feature that it 'learns' the variation of the control system gains needed over the flight envelope. It, thus, generates and modifies its gain schedule when suitable data are available. The report emphasizes the novel learning features of the system: the forms of representation of the flight envelope and the process by which identified parameters are used to modify the gain schedule. It contains data taken during piloted real-time 6 degree-of-freedom simulations that were used to develop and evaluate the system.

Advanced Multifunctional MMOD Shield: Radiation Shielding Assessment

NASA Technical Reports Server (NTRS)

Rojdev, Kristina; Christiansen, Eric

2013-01-01

Deep space missions must contend with a harsh radiation environment Impacts to crew and electronics. Need to invest in multifunctionality for spacecraft optimization. MMOD shield. Goals: Increase radiation mitigation potential. Retain overall MMOD shielding performance.

Hypervelocity impact testing above 10 km/s of advanced orbital debris shields

NASA Astrophysics Data System (ADS)

Christiansen, Eric L.; Crews, Jeanne Lee; Kerr, Justin H.; Chhabildas, Lalit C.

1996-05-01

NASA has developed enhanced performance shields to improve the protection of spacecraft from orbital debris and meteoroid impacts. One of these enhanced shields includes a blanket of Nextel™ ceramic fabric and Kevlar™ high strength fabric that is positioned midway between an aluminum bumper and the spacecraft pressure wall. As part of the evaluation of this new shielding technology, impact data above 10 km/sec has been obtained by NASA Johnson Space Center (JSC) from the Sandia National Laboratories HVL ("hypervelocity launcher") and the Southwest Research Institute inhibited shaped charge launcher (ISCL). The HVL launches flyer-plates in the velocity range of 10 to 15 km/s while the ISCL launches hollow cylinders at ˜11.5 km/s. The >10 km/s experiments are complemented by hydrocode analysis and light-gas gun testing at the JSC Hypervelocity Impact Test Facility (HIT-F) to assess the effects of projectile shape on shield performance. Results from the testing and analysis indicate that the Nextel™/Kevlar™ shield provides superior protection performance compared to an all-aluminum shield alternative.

F-8C adaptive flight control laws

NASA Technical Reports Server (NTRS)

Hartmann, G. L.; Harvey, C. A.; Stein, G.; Carlson, D. N.; Hendrick, R. C.

1977-01-01

Three candidate digital adaptive control laws were designed for NASA's F-8C digital flyby wire aircraft. Each design used the same control laws but adjusted the gains with a different adaptative algorithm. The three adaptive concepts were: high-gain limit cycle, Liapunov-stable model tracking, and maximum likelihood estimation. Sensors were restricted to conventional inertial instruments (rate gyros and accelerometers) without use of air-data measurements. Performance, growth potential, and computer requirements were used as criteria for selecting the most promising of these candidates for further refinement. The maximum likelihood concept was selected primarily because it offers the greatest potential for identifying several aircraft parameters and hence for improved control performance in future aircraft application. In terms of identification and gain adjustment accuracy, the MLE design is slightly superior to the other two, but this has no significant effects on the control performance achievable with the F-8C aircraft. The maximum likelihood design is recommended for flight test, and several refinements to that design are proposed.

8-Substituted 1,3-dimethyltetrahydropyrazino[2,1-f]purinediones: Water-soluble adenosine receptor antagonists and monoamine oxidase B inhibitors.

PubMed

Brunschweiger, Andreas; Koch, Pierre; Schlenk, Miriam; Rafehi, Muhammad; Radjainia, Hamid; Küppers, Petra; Hinz, Sonja; Pineda, Felipe; Wiese, Michael; Hockemeyer, Jörg; Heer, Jag; Denonne, Frédéric; Müller, Christa E

2016-11-01

Multitarget approaches, i.e., addressing two or more targets simultaneously with a therapeutic agent, are hypothesized to offer additive therapeutic benefit for the treatment of neurodegenerative diseases. Validated targets for the treatment of Parkinson's disease are, among others, the A 2A adenosine receptor (AR) and the enzyme monoamine oxidase B (MAO-B). Additional blockade of brain A 1 ARs may also be beneficial. We recently described 8-benzyl-substituted tetrahydropyrazino[2,1-f]purinediones as a new lead structure for the development of such multi-target drugs. We have now designed a new series of tetrahydropyrazino[2,1-f]purinediones to extensively explore their structure-activity-relationships. Several compounds blocked human and rat A 1 and A 2A ARs at similar concentrations representing dual A 1 /A 2A antagonists with high selectivity versus the other AR subtypes. Among the best dual A 1 /A 2A AR antagonists were 8-(3-(4-chlorophenyl)propyl)-1,3-dimethyl-6,7,8,9-tetrahydropyrazino[2,1-f]purine-2,4(1H,3H)-dione (41, K i human A 1 : 65.5nM, A 2A : 230nM; K i rat A 1 : 352nM, A 2A : 316nM) and 1,3-dimethyl-8-((2-(thiophen-2-yl)thiazol-4-yl)methyl)-6,7,8,9-tetrahydropyrazino[2,1-f]purine-2,4(1H,3H)-dione (57, K i human A 1 : 642nM, A 2A : 203nM; K i rat A 1 : 166nM, A 2A : 121nM). Compound 57 was found to be well water-soluble (0.7mg/mL) at a physiological pH value of 7.4. One of the new compounds showed triple-target inhibition: (R)-1,3-dimethyl-8-(2,1,3,4-tetrahydronaphthalen-1-yl)-6,7,8,9-tetrahydropyrazino[2,1-f]purine-2,4(1H,3H)-dione (49) was about equipotent at A 1 and A 2A ARs and at MAO-B (K i human A 1 : 393nM, human A 2A : 595nM, IC 50 human MAO-B: 210nM) thus allowing future in vivo explorations of the intended multi-target approach. Copyright © 2016 Elsevier Ltd. All rights reserved.

F-8 SCW on ramp with test pilot Tom McMurtry

NASA Image and Video Library

1972-12-20

A Vought F-8A Crusader was selected by NASA as the testbed aircraft (designated TF-8A) to install an experimental Supercritical Wing (SCW) in place of the conventional wing. The unique design of the Supercritical Wing reduces the effect of shock waves on the upper surface near Mach 1, which in turn reduces drag. In this photograph the TF-8A Crusader with Supercritical Wing is shown on the ramp with project pilot Tom McMurtry standing beside it. McMurtry received NASA's Exceptional Service Medal for his work on the F-8 SCW aircraft. He also flew the AD-1, F-15 Digital Electronic Engine Control, the KC-130 winglets, the F-8 Digital Fly-By-Wire and other flight research aircraft including the remotely piloted 720 Controlled Impact Demonstration and sub-scale F-15 research projects. In addition, McMurtry was the 747 co-pilot for the Shuttle Approach and Landing Tests and made the last glide flight in the X-24B. McMurtry was Dryden’s Director for Flight Operations from 1986 to 1998, when he became Associate Director for Operations at NASA Dryden. In 1982, McMurtry received the Iven C. Kincheloe Award from the Society of Experimental Test Pilots for his contributions as project pilot on the AD-1 Oblique Wing program. In 1998 he was named as one of the honorees at the Lancaster, Calif., ninth Aerospace Walk of Honor ceremonies. In 1999 he was awarded the NASA Distinguished Service Medal. He retired in 1999 after a distinguished career as pilot and manager at Dryden that began in 1967.

Minot AFB, North Dakota. Revised Uniform Summary of Surface Weather Observations (RUSSWO). Parts A-F.

DTIC Science & Technology

1983-04-01

DEC I I. T! 8.61 57.9 6 1.5 21.1 1.3 19.8 37.9 71 TO~S8.3 2c.7t 2.1 26.8 .~5G* 18.A 1.? 8.% . 25. 8 43 USAFETAC 0 10 SIOL Al, P,.f usl 0-O .S n...N ih T m.p w.ato r. R[ .I. T0 F 32 F 6 F 73 IF 8 R P *93 F 1 ,To - Dry Bulb 4 W., SoIl 51 . -- - - -- - -- - - - - - ~ --- ----D..- - -~ GLOBAL

Theoretical prediction of nuclear magnetic shieldings and indirect spin-spin coupling constants in 1,1-, cis-, and trans-1,2-difluoroethylenes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nozirov, Farhod, E-mail: teobaldk@gmail.com, E-mail: farhod.nozirov@gmail.com; Stachów, Michał, E-mail: michal.stachow@gmail.com; Kupka, Teobald, E-mail: teobaldk@gmail.com, E-mail: farhod.nozirov@gmail.com

2014-04-14

A theoretical prediction of nuclear magnetic shieldings and indirect spin-spin coupling constants in 1,1-, cis- and trans-1,2-difluoroethylenes is reported. The results obtained using density functional theory (DFT) combined with large basis sets and gauge-independent atomic orbital calculations were critically compared with experiment and conventional, higher level correlated electronic structure methods. Accurate structural, vibrational, and NMR parameters of difluoroethylenes were obtained using several density functionals combined with dedicated basis sets. B3LYP/6-311++G(3df,2pd) optimized structures of difluoroethylenes closely reproduced experimental geometries and earlier reported benchmark coupled cluster results, while BLYP/6-311++G(3df,2pd) produced accurate harmonic vibrational frequencies. The most accurate vibrations were obtained using B3LYP/6-311++G(3df,2pd)more » with correction for anharmonicity. Becke half and half (BHandH) density functional predicted more accurate {sup 19}F isotropic shieldings and van Voorhis and Scuseria's τ-dependent gradient-corrected correlation functional yielded better carbon shieldings than B3LYP. A surprisingly good performance of Hartree-Fock (HF) method in predicting nuclear shieldings in these molecules was observed. Inclusion of zero-point vibrational correction markedly improved agreement with experiment for nuclear shieldings calculated by HF, MP2, CCSD, and CCSD(T) methods but worsened the DFT results. The threefold improvement in accuracy when predicting {sup 2}J(FF) in 1,1-difluoroethylene for BHandH density functional compared to B3LYP was observed (the deviations from experiment were −46 vs. −115 Hz)« less

48 CFR 47.303-6 - F.o.b. destination.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false F.o.b. destination. 47.303... MANAGEMENT TRANSPORTATION Transportation in Supply Contracts 47.303-6 F.o.b. destination. (a) Explanation of delivery term. F.o.b. destination means— (1) Free of expense to the Government delivered, on board the...

Qualitative analysis of ionospheric disorders in Solok earthquake (March 6, 2007) viewed from anomalous critical frequency of layer F (f0F2) and genesis spread F

NASA Astrophysics Data System (ADS)

Pujiastuti, D.; Daniati, S.; Taufiqurrahman, E.; Mustafa, B.; Ednofri

2018-03-01

A qualitative analysis has been conducted by comparing the critical frequency anomalies of layer F (f0F2) and Spread F events to see the correlation with seismic activity before the Solok earthquake (March 6, 2007) in West Sumatra. The ionospherics data used was taken using the FMCW ionosonde at LAPAN SPD Kototabang, Palupuah, West Sumatra. The process of ionogramme scaling is done first to get the daily value of f0F2. The value of f0F2 is then compared with its monthly median to see the daily variations that appear. Anomalies of f0F2 and Spread F events were observed from February 20, 2007 to March 6, 2007. The presence of f0F2 anomalies was the negative deviation and the presence of Spread F before earthquake events were recommended as Solok earthquake precursors as they occurred when geomagneticsics and solar activities were normal.

NbF5 and TaF5: Assignment of 19F NMR resonances and chemical bond analysis from GIPAW calculations

NASA Astrophysics Data System (ADS)

Biswal, Mamata; Body, Monique; Legein, Christophe; Sadoc, Aymeric; Boucher, Florent

2013-11-01

The 19F isotropic chemical shifts (δiso) of two isomorphic compounds, NbF5 and TaF5, which involve six nonequivalent fluorine sites, have been experimentally determined from the reconstruction of 1D 19F MAS NMR spectra. In parallel, the corresponding 19F chemical shielding tensors have been calculated using the GIPAW method for both experimental and DFT-optimized structures. Furthermore, the [M4F20] units of NbF5 and TaF5 being held together by van der Waals interactions, the relevance of Grimme corrections to the DFT optimization processes has been evaluated. However, the semi-empirical dispersion correction term introduced by such a method does not show any significant improvement. Nonetheless, a complete and convincing assignment of the 19F NMR lines of NbF5 and TaF5 is obtained, ensured by the linearity between experimental 19F δiso values and calculated 19F isotropic chemical shielding σiso values. The effects of the geometry optimizations have been carefully analyzed, confirming among other matters, the inaccuracy of the experimental structure of NbF5. The relationships between the fluorine chemical shifts, the nature of the fluorine atoms (bridging or terminal), the position of the terminal ones (opposite or perpendicular to the bridging ones), the fluorine charges, the ionicity and the length of the M-F bonds have been established. Additionally, for three of the 19F NMR lines of NbF5, distorted multiplets, arising from 1J-coupling and residual dipolar coupling between the 19F and 93Nb nuclei, were simulated yielding to values of 93Nb-19F 1J-coupling for the corresponding fluorine sites.

Omni-directional selective shielding material based on amorphous glass coated microwires.

PubMed

Ababei, G; Chiriac, H; David, V; Dafinescu, V; Nica, I

2012-01-01

The shielding effectiveness of the omni-directional selective shielding material based on CoFe-glass coated amorphous wires in 0.8 GHz-3 GHz microwave frequency range is investigated. The measurements were done in a controlled medium using a TEM cell and in the free space using horn antennas, respectively. Experimental results indicate that the composite shielding material can be developed with desired shielding effectiveness and selective absorption of the microwave frequency range by controlling the number of the layers and the length of microwires.

Effects of methyl gallate and gallic acid on the production of inflammatory mediators interleukin-6 and interleukin-8 by oral epithelial cells stimulated with Fusobacterium nucleatum.

PubMed

Kang, Mi-Sun; Jang, Hee-Sook; Oh, Jong-Suk; Yang, Kyu-Ho; Choi, Nam-Ki; Lim, Hoi-Soon; Kim, Seon-Mi

2009-12-01

Interactions between periodontal bacteria and human oral epithelial cells can lead to the activation and expression of a variety of inflammatory mediators in epithelial cells. Fusobacterium nucleatum is a filamentous human pathogen that is strongly associated with periodontal diseases. This study examined the effects of methyl gallate (MG) and gallic acid (GA) on the production of inflammatory mediators, interleukin (IL)-6 and IL-8, by oral epithelial cells stimulated by F. nucleatum. In a real-time reverse transcription-polymerase chain reaction and an enzyme-linked immunosorbent assay, live F. nucleatum induced high levels of gene expression and protein release of IL-6 and IL-8. The effects of MG and GA were examined by treating KB oral epithelial cells with MG and GA and stimulating them with F. nucleatum. MG and GA inhibited significantly the increases in the IL-6 and IL-8 gene and protein levels in a dose-dependent manner. These Compounds also inhibited the growth of F. nucleatum. No visible effects of MG and GA on the adhesion and invasion of KB cells by F. nucleatum were observed. In conclusion, both MG and GA inhibit IL-6 and IL-8 production from F. nucleatum-activated KB cells.

A direct method for fabricating tongue-shielding stent.

PubMed

Wang, R R; Olmsted, L W

1995-08-01

During oral cancer radiotherapy, a tongue-shielding radiation stent guides the patient's upper and lower jaws to a repeatable position, attenuates radiation doses, and protects the tongue and structures adjacent to the irradiated field. Conventionally, a tongue-shielding radiation stent is made of heat-cured polymethyl methacrylate resin in which a low-melting Pb-Bi-Sn alloy is embedded as a shielding layer. Its use involves multiple and lengthy clinical and laboratory procedures. An improved polyvinyl siloxane-metal composite shielding system for radioprotection has recently been developed. This two-component, base and catalyst, putty material offers a shielding effect similar to that of the conventional shielding alloys. Its major advantages are that it is simple to use, requires only one clinical appointment, and affords efficient collaboration between dental and medical teams during cancer treatment. This article describes a simplified direct method of fabricating a tongue-shielding stent with the use of a new polyvinylsiloxane-metal composite in conjunction with impression putty material.

Structural Shielding Design of a 6 MV Flattening Filter Free Linear Accelerator: Indian Scenario.

PubMed

Mishra, Bibekananda; Selvam, T Palani; Sharma, P K Dash

2017-01-01

Detailed structural shielding of primary and secondary barriers for a 6 MV medical linear accelerator (LINAC) operated with flattening filter (FF) and flattening filter free (FFF) modes are calculated. The calculations have been carried out by two methods, one using the approach given in National Council on Radiation Protection (NCRP) Report No. 151 and the other based on the monitor units (MUs) delivered in clinical practice. Radiation survey of the installations was also carried out. NCRP approach suggests that the primary and secondary barrier thicknesses are higher by 24% and 26%. respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes with an assumption that only 20% of the workload is shared in FFF mode. Primary and secondary barrier thicknesses calculated from MUs delivered on clinical practice method also show the same trend and are higher by 20% and 19%, respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes. Overall, the barrier thickness for a LINAC operated in FF mode is higher about 20% to that of a LINAC operated in both FF and FFF modes.

Structural Shielding Design of a 6 MV Flattening Filter Free Linear Accelerator: Indian Scenario

PubMed Central

Mishra, Bibekananda; Selvam, T. Palani; Sharma, P. K. Dash

2017-01-01

Detailed structural shielding of primary and secondary barriers for a 6 MV medical linear accelerator (LINAC) operated with flattening filter (FF) and flattening filter free (FFF) modes are calculated. The calculations have been carried out by two methods, one using the approach given in National Council on Radiation Protection (NCRP) Report No. 151 and the other based on the monitor units (MUs) delivered in clinical practice. Radiation survey of the installations was also carried out. NCRP approach suggests that the primary and secondary barrier thicknesses are higher by 24% and 26%. respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes with an assumption that only 20% of the workload is shared in FFF mode. Primary and secondary barrier thicknesses calculated from MUs delivered on clinical practice method also show the same trend and are higher by 20% and 19%, respectively, for a LINAC operated in FF mode to that of a LINAC operated in both FF and FFF modes. Overall, the barrier thickness for a LINAC operated in FF mode is higher about 20% to that of a LINAC operated in both FF and FFF modes. PMID:28405104

CTC Sentinel. Volume 1, Issue 6, May 2008. Abu Yahya al-Libi’s Human Shields in Modern Jihad

DTIC Science & Technology

2008-05-01

own include The Healing of the Believers’ Chests and The Exoneration. 7 Although the essay is dated January 6, 2006, it was not published and widely...Yahya’s small essay on al-Tatarrus is nothing short of a religious revolution. Early Islamic thinkers typically used three general forms of shielding...traditional Islamic discussions in that it simplifies mat- ters considerably. MAY 2008 . VoL 1 . IssUE 6 “Abu Yahya’s small essay on al-Tatarrus is nothing

26 CFR 1.280F-6 - Special rules and definitions.

Code of Federal Regulations, 2014 CFR

2014-04-01

... purpose, e.g., commuting to work, is reported by X as income to the employee and is withheld upon by X... service before July 7, 2003, see § 1.280F-6T as in effect prior to July 7, 2003 (§ 1.280F-6T as contained... automobile under § 1.280F-6T as in effect prior to July 7, 2003 (pre-effective date vehicle): (i) Except as...

26 CFR 1.280F-6 - Special rules and definitions.

Code of Federal Regulations, 2013 CFR

2013-04-01

... purpose, e.g., commuting to work, is reported by X as income to the employee and is withheld upon by X... service before July 7, 2003, see § 1.280F-6T as in effect prior to July 7, 2003 (§ 1.280F-6T as contained... automobile under § 1.280F-6T as in effect prior to July 7, 2003 (pre-effective date vehicle): (i) Except as...

26 CFR 1.280F-6 - Special rules and definitions.

Code of Federal Regulations, 2011 CFR

2011-04-01

... purpose, e.g., commuting to work, is reported by X as income to the employee and is withheld upon by X... service before July 7, 2003, see § 1.280F-6T as in effect prior to July 7, 2003 (§ 1.280F-6T as contained... automobile under § 1.280F-6T as in effect prior to July 7, 2003 (pre-effective date vehicle): (i) Except as...

26 CFR 1.280F-6 - Special rules and definitions.

Code of Federal Regulations, 2012 CFR

2012-04-01

... purpose, e.g., commuting to work, is reported by X as income to the employee and is withheld upon by X... service before July 7, 2003, see § 1.280F-6T as in effect prior to July 7, 2003 (§ 1.280F-6T as contained... automobile under § 1.280F-6T as in effect prior to July 7, 2003 (pre-effective date vehicle): (i) Except as...

Shielding of substations against direct lightning strokes by shield wires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chowdhuri, P.

1994-01-01

A new analysis for shielding outdoor substations against direct lightning strokes by shield wires is proposed. The basic assumption of this proposed method is that any lightning stroke which penetrates the shields will cause damage. The second assumption is that a certain level of risk of failure must be accepted, such as one or two failures per 100 years. The proposed method, using electrogeometric model, was applied to design shield wires for two outdoor substations: (1) 161-kV/69-kV station, and (2) 500-kV/161-kV station. The results of the proposed method were also compared with the shielding data of two other substations.

Evaluation of anti-melanoma activities of (1S,2E,4R,6E,8R,11S,12R)-8,12-epoxy-2,6-cembradiene-4,11-diol, (1S,2E,4R,6E,8S,11R,12S)-8,11-epoxy-4,12-epoxy-2,6-cembradiene and (1S,4R,13S)-cembra-2E,7E,11E-trien-4,13-diol from the Red Sea soft coral Sarcophyton glaucum.

PubMed

Szymanski, Pawel T; Ahmed, Safwat A; Radwan, Mohamed M; Khalifa, Sherief I; Fahmy, Hesham

2014-08-01

Three natural cembranoids from the Red Sea soft coral Sarcophyton glaucum namely (1S,2E,4R,6E,8R,11S,12R)-8,12-epoxy-2,6-cembradiene-4,11-diol, (1S,2E,4R,6E,8S,11R,12S)-8,11-epoxy-4,12-epoxy-2,6-cembradiene and (1S,4R,13S)-cembra-2E,7E,11E-trien-4,13-diol were evaluated for their inhibitory effects on mouse melanoma B16F10 cell growth. Results show that all the cembranoids strongly inhibit viability of melanoma cells particularly during 48 -72 hrs treatment and also inhibit de novo DNA synthesis and PARP activity and stimulate fragmentation of DNA. (1S,2E,4R,6E,8R,11S,12R)-8,12-epoxy-2,6-cembradiene-4,11-diol was not cytotoxic to monkey kidney CV-1 cells at the concentration that produces the anti-melanoma effects which indicates that this compound may be a good candidate for further development. (1S,2E,4R,6E,8S,11R,12S)-8,11-epoxy-4,12-epoxy-2,6-cembradiene and (1S,4R,13S)-cembra-2E,7E,11E-trien-4,13-diol were found to be cytotoxic to healthy cells.

Luminosity and Stellar Mass Functions from the 6dF Galaxy Survey

NASA Astrophysics Data System (ADS)

Colless, M.; Jones, D. H.; Peterson, B. A.; Campbell, L.; Saunders, W.; Lah, P.

2007-12-01

The completed 6dF Galaxy Survey includes redshifts for over 124,000 galaxies. We present luminosity functions in optical and near-infrared passbands that span a range of 10^4 in luminosity. These luminosity functions show systematic deviations from the Schechter form. The corresponding luminosity densities in the optical and near-infrared are consistent with an old stellar population and a moderately declining star formation rate. Stellar mass functions, derived from the K band luminosities and simple stellar population models selected by b_J-r_F colour, lead to an estimate of the present-day stellar mass density of ρ_* = (5.00 ± 0.11) × 10^8 h M_⊙ Mpc^{-3}, corresponding to Ω_* h = (1.80 ± 0.04) × 10^{-3}.

Inorganic nanotubes reinforced polyvinylidene fluoride composites as low-cost electromagnetic interference shielding materials

PubMed Central

2011-01-01

Novel polymer nanocomposites comprising of MnO2 nanotubes (MNTs), functionalized multiwalled carbon nanotubes (f-MWCNTs), and polyvinylidene fluoride (PVDF) were synthesized. Homogeneous distribution of f-MWCNTs and MNTs in PVDF matrix were confirmed by field emission scanning electron microscopy. Electrical conductivity measurements were performed on these polymer composites using four probe technique. The addition of 2 wt.% of MNTs (2 wt.%, f-MWCNTs) to PVDF matrix results in an increase in the electrical conductivity from 10-16S/m to 4.5 × 10-5S/m (3.2 × 10-1S/m). Electromagnetic interference shielding effectiveness (EMI SE) was measured with vector network analyzer using waveguide sample holder in X-band frequency range. EMI SE of approximately 20 dB has been obtained with the addition of 5 wt.% MNTs-1 wt.% f-MWCNTs to PVDF in comparison with EMI SE of approximately 18 dB for 7 wt.% of f-MWCNTs indicating the potential use of the present MNT/f-MWCNT/PVDF composite as low-cost EMI shielding materials in X-band region. PMID:21711633

Noise shielding by a hot subsonic jet

NASA Technical Reports Server (NTRS)

Vijayaraghavan, A.; Parthasarathy, S. P.

1981-01-01

An analysis is conducted of the shielding of the noise emitted by a high speed round jet by a hot, subsonic, semicircular jet. A plane wave front in the primary jet is resolved into elementary plane waves which undergo multiple reflections at the jet boundaries of the primary and the shielding jets. The jet boundaries are idealized to be vortex sheets. The far field sound is evaluated asymptotically by a superposition of the waves that penetrate the shielding jet. The angular directivities are plotted for several values of jet temperature and velocity to examine the effectiveness of shielding by the semicircular jet layer.

The crystal structure of synthetic simmonsite, Na 2LiAlF 6

NASA Astrophysics Data System (ADS)

Ross, Kirk C.; Mitchell, Roger H.; Chakhmouradian, Anton R.

2003-04-01

The structure of the synthetic fluoroperovskite, Na 2LiAlF 6 (simmonsite), has been determined by powder X-ray diffraction using the Rietveld method of structure refinement. The compound adopts space group P2 1/ n [#14; a=5.2842(1); b=5.3698(1); c=7.5063(2) Å; β=89.98(1)°; Z=4), and is a member of the cryolite (Na 2NaAlF 6) structural group characterized by ordering of the B-site cations (Li, Al) and tilting of the BF 6 octahedra according to the tilt scheme a-b-c+. Rotations of the B-site polyhedra are less ( ΦLi=14.9°; ΦAl=17.0°) than those found in cryolite ( ΦNa=18.6; ΦAl=23.5°) because of the larger difference in the ionic radii of the B-site cations in cryolite as compared to those in simmonsite. Na at the A-site is displaced from the special position resulting in 10- and 8-fold coordination in simmonsite and cryolite, respectively. By analogy with the synthetic compound, naturally occurring simmonsite is considered to adopt space group P2 1/ n (#14) and not the P2 1(#4) or P2 1/ m(#11) space groups.

Picosecond Nd:BaY2F8 laser discretely tunable around 1 μm

NASA Astrophysics Data System (ADS)

Agnesi, A.; Pirzio, F.; Reali, G.; Toncelli, A.; Tonelli, M.

2010-09-01

Passive mode-locking of a diode-pumped Nd:BaY2F8 (Nd:BaYF) was achieved on four lines in the range 1040-1074 nm, employing a semiconductor saturable absorber mirror (SAM). Nearly Fourier-limited pulses with durations of 2.6 to 7.2 ps and output power ≈50 mW were generated in a dispersion-controlled resonator using a single prism for wavelength selection, tuning and dispersion management.

A Review of Radiolysis Concerns for Water Shielding in Fission Surface Power Applications

NASA Technical Reports Server (NTRS)

Schoenfeld, Michael P.

2008-01-01

This paper presents an overview of radiolysis concerns with regard to water shields for fission surface power. A review of the radiolysis process is presented and key parameters and trends are identified. From this understanding of the radiolytic decomposition of water, shield pressurization and corrosion are identified as the primary concerns. Existing experimental and modeling data addressing concerns are summarized. It was found that radiolysis of pure water in a closed volume results in minimal, if any net decomposition, and therefore reduces the potential for shield pressurization and corrosion. With the space program focus m emphasize more on permanent return to the Moon and eventually manned exploration of Mars, there has been a renewed look at fission power to meet the difficult technical & design challenges associated with this effort. This is due to the ability of fission power to provide a power rich environment that is insensitive to solar intensity and related aspects such as duration of night, dusty environments, and distance from the sun, etc. One critical aspect in the utilization of fission power for these applications of manned exploration is shielding. Although not typically considered for space applications, water shields have been identified as one potential option due to benefits in mass savings and reduced development cost and technical risk (Poston, 2006). However, the water shield option requires demonstration of its ability to meet key technical challenges including such things as adequate natural circulation for thermal management and capability for operational periods up to 8 years. Thermal management concerns have begun to be addressed and are not expected to be a problem (Pearson, 2007). One significant concern remaining is the ability to maintain the shield integrity through its operational lifetime. Shield integrity could be compromised through shield pressurization and corrosion resulting from the radiolytic decomposition of water.

Hypervelocity impact testing of advanced materials and structures for micrometeoroid and orbital debris shielding

NASA Astrophysics Data System (ADS)

Ryan, Shannon; Christiansen, Eric L.

2013-02-01

A series of 66 hypervelocity impact experiments have been performed to assess the potential of various materials (aluminium, titanium, copper, stainless steel, nickel, nickel/chromium, reticulated vitreous carbon, silver, ceramic, aramid, ceramic glass, and carbon fibre) and structures (monolithic plates, open-cell foam, flexible fabrics, rigid meshes) for micrometeoroid and orbital debris (MMOD) shielding. Arranged in various single-, double-, and triple-bumper configurations, screening tests were performed with 0.3175 cm diameter Al2017-T4 spherical projectiles at nominally 6.8 km/s and normal incidence. The top performing shields were identified through target damage assessments and their respective weight. The top performing candidate shield at the screening test condition was found to be a double-bumper configuration with a 0.25 mm thick Al3003 outer bumper, 6.35 mm thick 40 PPI aluminium foam inner bumper, and 1.016 mm thick Al2024-T3 rear wall (equal spacing between bumpers and rear wall). In general, double-bumper candidates with aluminium plate outer bumpers and foam inner bumpers were consistently found to be amongst the top performers. For this impact condition, potential weight savings of at least 47% over conventional all-aluminium Whipple shields are possible by utilizing the investigated materials and structures. The results of this study identify materials and structures of interest for further, more in-depth, impact investigations.

Internal motion and its pressure dependence in FeSiF6+6/H2O/.

NASA Technical Reports Server (NTRS)

Vaughan, R. W.; Nicolaides, G. L.; Elleman, D. D.

1972-01-01

Both wideline and pulsed NMR techniques were used to examine the internal motion in FeSiF6+6(H2O). Corrections of second moments for bulk paramagnetic effects were essential. At room temperature and pressure, the fluorine-fluorine contribution to the 19F second moment is 0.38 (plus or minus 0.06) G2, and indicates rapid orientation of the SiF6(--) group. Analysis of the second moment within the transition region allows calculation of an activation volume which is 2.4 (plus or minus 0.4) % of the molar volume. The application of pressure slows the internal motion such that the rigid lattice values of the 19F second moment are obtained above 50 kbar.

Pseudopotential SCF-MO studies of hypervalent compounds. II. XeF+5 and XeF6

NASA Astrophysics Data System (ADS)

Rothman, Michael J.; Bartell, Lawrence S.; Ewig, Carl S.; Van Wazer, John R.

1980-07-01

New evidence bearing upon the anomalous properties of xenon hexafluoride has been obtained via the ab initio molecular orbital approach applied successfully to the di- and tetrafluorides in paper I. Structures of both XeF+5 and XeF6 are governed by a stereochemically active lone pair. In the case of the square-pyramidal cation the Fax-Xe-Feq angle calculated for the bare ion is within 2° of the value observed in the crystalline complex. For the hexafluoride, however, the calculated deformation from Oh symmetry is appreciably greater than that deduced from electron diffraction intensities. Nevertheless, the results of calculations are in sufficient conformity with the Bartell-Gavin, Pitzer-Bernstein interpretation and at variance with the ''electronic-isomers'' interpretation to leave little doubt about the answer. With increasing fluorination in the XeFn series the HOMO-LUMO energy difference decreases and the second-order Jahn-Teller effect is enhanced. Increasing fluorination (and increased positive charge on Xe) also shortens bond lengths; calculated shortenings parallel observed shortenings. The deformation of XeF6 from Oh is along t1u bend and stretch coordinates to a C3v structure with long bonds adjacent to the lone pair, as expected according to the valence-shell-electron-pair-repulsion model. Pure t2g deformations are destabilizing but anharmonic t1u-t2g coupling significantly stabilizes the deformation. Steric aspects of the structure and force field are diagnosed and found to be minor. Values for the force constants f44, f55, f¯4444, f¯444'4', and f¯445 are derived and found to be of the magnitude forecast in the Bartell-Gavin and Pitzer-Bernstein treatments except that the calculations do not reproduce the delicate balances believed to lead to almost free pseudorotation in XeF6.

Absolute Position Sensing Based on a Robust Differential Capacitive Sensor with a Grounded Shield Window

PubMed Central

Bai, Yang; Lu, Yunfeng; Hu, Pengcheng; Wang, Gang; Xu, Jinxin; Zeng, Tao; Li, Zhengkun; Zhang, Zhonghua; Tan, Jiubin

2016-01-01

A simple differential capacitive sensor is provided in this paper to measure the absolute positions of length measuring systems. By utilizing a shield window inside the differential capacitor, the measurement range and linearity range of the sensor can reach several millimeters. What is more interesting is that this differential capacitive sensor is only sensitive to one translational degree of freedom (DOF) movement, and immune to the vibration along the other two translational DOFs. In the experiment, we used a novel circuit based on an AC capacitance bridge to directly measure the differential capacitance value. The experimental result shows that this differential capacitive sensor has a sensitivity of 2 × 10−4 pF/μm with 0.08 μm resolution. The measurement range of this differential capacitive sensor is 6 mm, and the linearity error are less than 0.01% over the whole absolute position measurement range. PMID:27187393

Ab initio calculation of Ti NMR shieldings for titanium oxides and halides

NASA Astrophysics Data System (ADS)

Tossell, J. A.

Titanium NMR shielding constants have been calculated using ab initio coupled Hartree-Fock perturbation theory and polarized double-zeta basis sets for TiF 4, TiF 62-, TiCI 4, Ti(OH) 4, Ti(OH 2) 64+, Ti(OH) 4O, and Ti(OH) 3O -. In all cases the calculations were performed at Hartree-Fuck energy-optimized geometries. For Ti(OH) 4 a S4-symmetry geometry with nonlinear ∠ TiOH was employed. Relative shieldings are in reasonable agreement with experiment for TiF 62-, TiCI 4, and Ti(OR) 4, where R = H or alkyl. Ti(OH 2) 64+ is predicted to be more highly shielded than Ti(OH) 4 by about 340 ppm. The five-coordinate complex Ti(OH) 4O, whose calculated structure matches well that measured by extended X-ray absorption fine structure in K 2O · TiO 2 · SiO 2 glass, is actually deshielded compared to Ti(OH) 4 by about 40 ppm. X-ray absorption-near-edge spectral energies have also been calculated for TiF 4, TiCI 4, Ti(OH) 4, and Ti(OH) 4O using an equivalent ionic core virtual-orbital method and the observed reduction in term energy for the five-coordinate species compared to Ti(OH) 4 has been reproduced. Replacement of the H atoms in Ti(OH) 4 by point charges has only a slight effect upon σTi, suggesting a possible means of incorporating second-neighbor effects in NMR calculations for condensed phases.

The Poplar GT8E and GT8F Glycosyltransferases are Functional Orthologs of Arabidopsis PARVUS Involved in Gulcuronoxylan Biosynthesis

EPA Science Inventory

The poplar GT8E and GT8F glycosyltransferases have previously been shown to be associated with wood formation, but their roles in the biosynthesis of wood components are not known. Here, we show that PoGT8E and PoGT8F are expressed in vessels and fibers during wood formation and ...

Shielding of Turbomachinery Broadband Noise from a Hybrid Wing Body Aircraft Configuration

NASA Technical Reports Server (NTRS)

Hutcheson, Florence V.; Brooks, Thomas F.; Burley, Casey L.; Bahr, Christopher J.; Stead, Daniel J.; Pope, D. Stuart

2014-01-01

The results of an experimental study on the effects of engine placement and vertical tail configuration on shielding of exhaust broadband noise radiation are presented. This study is part of the high fidelity aeroacoustic test of a 5.8% scale Hybrid Wing Body (HWB) aircraft configuration performed in the 14- by 22-Foot Subsonic Tunnel at NASA Langley Research Center. Broadband Engine Noise Simulators (BENS) were used to determine insertion loss due to shielding by the HWB airframe of the broadband component of turbomachinery noise for different airframe configurations and flight conditions. Acoustics data were obtained from flyover and sideline microphones traversed to predefined streamwise stations. Noise measurements performed for different engine locations clearly show the noise benefit associated with positioning the engine nacelles further upstream on the HWB centerbody. Positioning the engine exhaust 2.5 nozzle diameters upstream (compared to 0.5 nozzle diameters downstream) of the HWB trailing edge was found of particular benefit in this study. Analysis of the shielding performance obtained with and without tunnel flow show that the effectiveness of the fuselage shielding of the exhaust noise, although still significant, is greatly reduced by the presence of the free stream flow compared to static conditions. This loss of shielding is due to the turbulence in the model near-wake/boundary layer flow. A comparison of shielding obtained with alternate vertical tail configurations shows limited differences in level; nevertheless, overall trends regarding the effect of cant angle and vertical location are revealed. Finally, it is shown that the vertical tails provide a clear shielding benefit towards the sideline while causing a slight increase in noise below the aircraft.

Mild hydrothermal crystal growth of new uranium(IV) fluorides, Na3.13Mg1.43U6F30 and Na2.50Mn1.75U6F30: Structures, optical and magnetic properties

NASA Astrophysics Data System (ADS)

Yeon, Jeongho; Smith, Mark D.; Tapp, Joshua; Möller, Angela; zur Loye, Hans-Conrad

2016-04-01

Two new uranium(IV) fluorides, Na3.13Mg1.43U6F30 (1) and Na2.50Mn1.75U6F30 (2), were synthesized through an in situ mild hydrothermal route, and were structurally characterized by single crystal X-ray diffraction. The compounds exhibit complex crystal structures composed of corner- or edge-shared UF9 and MF6 (M=Mg, Mn) polyhedra, forming hexagonal channels in the three-dimensional framework, in which ordered or disordered divalent metal and sodium atoms reside. The large hexagonal voids contain the nearly regular M(II)F6 octahedra and sodium ions, whereas the small hexagonal cavities include M(II) and sodium ions on a mixed-occupied site. Magnetic susceptibility measurements yielded effective magnetic moments of 8.36 and 11.6 μB for 1 and 2, respectively, confirming the presence and oxidation states of U(IV) and Mn(II). The large negative Weiss constants indicate the spin gap between a triplet and a singlet state in the U(IV). Magnetization data as a function of applied fields revealed that 2 exhibits paramagnetic behavior due to the nonmagnetic singlet ground state of U(IV) at low temperature. UV-vis diffuse reflectance and X-ray photoelectron spectroscopy data were also analyzed.

Light flavor-singlet scalars and walking signals in N f = 8 QCD on the lattice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aoki, Yasumichi; Aoyama, Tatsumi; Bennett, Ed

Based on the highly improved staggered quark action, we perform in this paper lattice simulations of N f = 8 QCD and confirm our previous observations, both of a flavor-singlet scalar meson (denoted as σ) as light as the pion and of various “walking signals” through the low-lying spectra, with higher statistics, smaller fermion masses m f, and larger volumes. We measure M π, F π, M ρ, M a0, M a1, M b1, M N, M σ, F σ, (φφ) (both directly and through the Gell-Mann-Oakes-Renner relation), and the string tension. The data are consistent with the spontaneously brokenmore » phase of the chiral symmetry, in agreement with the previous results: Ratios of the quantities to M π monotonically increase in the smaller m f region towards the chiral limit similarly to N f = 4 QCD, in sharp contrast to N f = 12 QCD where the ratios become flattened. We perform fits to chiral perturbation theory, with the value of F π found in the chiral limit extrapolation reduced dramatically to roughly 2/3 of the previous result, suggesting the theory is much closer to the conformal window. In fact, each quantity obeys the respective hyperscaling relation throughout a more extensive m f region compared with earlier works. The hyperscaling relation holds with roughly a universal value of the anomalous dimension, γ m ≃ 1, with the notable exception of M π with γ m ≃ 0.6 as in the previous results, which reflects the above growing up of the ratios towards the chiral limit. This is a salient feature (walking signal) of N f = 8, unlike either N f = 4, which has no hyperscaling relation at all, or N f = 12 QCD, which exhibits universal hyperscaling. The effective γ m Ξ γ m(m f) of M π defined for each m f region has a tendency to grow towards unity near the chiral limit, in conformity with the Nambu-Goldstone boson nature, as opposed to the case of N f = 12 QCD where it is almost constant. We further confirm the previous observation of the light σ with mass comparable to

Light flavor-singlet scalars and walking signals in N f = 8 QCD on the lattice

DOE PAGES

Aoki, Yasumichi; Aoyama, Tatsumi; Bennett, Ed; ...

2017-07-18

Based on the highly improved staggered quark action, we perform in this paper lattice simulations of N f = 8 QCD and confirm our previous observations, both of a flavor-singlet scalar meson (denoted as σ) as light as the pion and of various “walking signals” through the low-lying spectra, with higher statistics, smaller fermion masses m f, and larger volumes. We measure M π, F π, M ρ, M a0, M a1, M b1, M N, M σ, F σ, (φφ) (both directly and through the Gell-Mann-Oakes-Renner relation), and the string tension. The data are consistent with the spontaneously brokenmore » phase of the chiral symmetry, in agreement with the previous results: Ratios of the quantities to M π monotonically increase in the smaller m f region towards the chiral limit similarly to N f = 4 QCD, in sharp contrast to N f = 12 QCD where the ratios become flattened. We perform fits to chiral perturbation theory, with the value of F π found in the chiral limit extrapolation reduced dramatically to roughly 2/3 of the previous result, suggesting the theory is much closer to the conformal window. In fact, each quantity obeys the respective hyperscaling relation throughout a more extensive m f region compared with earlier works. The hyperscaling relation holds with roughly a universal value of the anomalous dimension, γ m ≃ 1, with the notable exception of M π with γ m ≃ 0.6 as in the previous results, which reflects the above growing up of the ratios towards the chiral limit. This is a salient feature (walking signal) of N f = 8, unlike either N f = 4, which has no hyperscaling relation at all, or N f = 12 QCD, which exhibits universal hyperscaling. The effective γ m Ξ γ m(m f) of M π defined for each m f region has a tendency to grow towards unity near the chiral limit, in conformity with the Nambu-Goldstone boson nature, as opposed to the case of N f = 12 QCD where it is almost constant. We further confirm the previous observation of the light σ with mass comparable to

Magnetic properties of the Tb4 + ion in Li2TbF6

NASA Astrophysics Data System (ADS)

Guillot, M.; El-Ghozzi, M.; Avignant, D.; Ferey, G.

1993-05-01

Both oxygen and fluorine have a partiality towards the stabilization of high oxidation states of rare earths such as Ce, Pr, and Tb. During the study of the MF-M'F4 (M=alkaline metal; M' rare ion) the compound Li2TbF6 was found to constitute the only representative obtained under ambient pressure of a structural type, namely α-Li2ZrF6, known until now only through the high pressure form. Magnetic measurements were carried out over the 1.4-300 K temperature range in continuous magnetic fields up to 20 T produced by a Bitter magnet. At low temperature and in H higher than 15 T, the magnetization M was observed to be field independent and very close to the calculated Tb4+ free ion value, i.e., 7μB; on the other hand, the data do not present any departure from the Brillouin function of the pure 8S7/2 state. The reciprocal magnetic susceptibility obeys a Curie-Weiss law leading to an effective moment of 7.86μB. A very unusual behavior of the terbium ion which presents a 4+ oxidation state is concluded: to the best of our knowledge, it is the first observation of this form. The so-found spherical 4f7 electronic configuration is the most compatible with the high coordination number of eight. Finally, the discussion within the series Li2MIVF6 compounds to understand the influence of both electronic configuration and size effects is presented.

Gravity Scaling of a Power Reactor Water Shield

NASA Technical Reports Server (NTRS)

Reid, Robert S.; Pearson, J. Boise

2008-01-01

Water based reactor shielding is being considered as an affordable option for use on initial lunar surface power systems. Heat dissipation in the shield from nuclear sources must be rejected by an auxiliary thermal hydraulic cooling system. The mechanism for transferring heat through the shield is natural convection between the core surface and an array of thermosyphon radiator elements. Natural convection in a 100 kWt lunar surface reactor shield design has been previously evaluated at lower power levels (Pearson, 2007). The current baseline assumes that 5.5 kW are dissipated in the water shield, the preponderance on the core surface, but with some volumetric heating in the naturally circulating water as well. This power is rejected by a radiator located above the shield with a surface temperature of 370 K. A similarity analysis on a water-based reactor shield is presented examining the effect of gravity on free convection between a radiation shield inner vessel and a radiation shield outer vessel boundaries. Two approaches established similarity: 1) direct scaling of Rayleigh number equates gravity-surface heat flux products, 2) temperature difference between the wall and thermal boundary layer held constant on Earth and the Moon. Nussult number for natural convection (laminar and turbulent) is assumed of form Nu = CRa(sup n). These combined results estimate similarity conditions under Earth and Lunar gravities. The influence of reduced gravity on the performance of thermosyphon heat pipes is also examined.

Shielding effectiveness of multiple-shield cables with arbitrary terminations via transmission line analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campione, Salvatore; Basilio, Lorena I.; Warne, Larry Kevin

Our paper reports on a transmission-line model for calculating the shielding effectiveness of multiple-shield cables with arbitrary terminations. Since the shields are not perfect conductors and apertures in the shields permit external magnetic and electric fields to penetrate into the interior regions of the cable, we use this model to estimate the effects of the outer shield current and voltage (associated with the external excitation and boundary conditions associated with the external conductor) on the inner conductor current and voltage. It is commonly believed that increasing the number of shields of a cable will improve the shielding performance. But thismore » is not always the case, and a cable with multiple shields may perform similar to or worse than a cable with a single shield. Furthermore, we want to shed more light on these situations, which represent the main focus of this paper.« less