614 research outputs found
His+ reversions Caused in Salmonella typhimurium by different types of ionizing radiation
Get PDFThe yield of his+ reversions in the Ames Salmonella tester strain TA2638 has been determined for 60Co γ rays, 140 kV X rays, 5.4 keV characteristic X rays, 2.2 MeV protons, 3.1 MeV α particles, and 18 MeV/U Fe ions. Inactivation studies were performed with the same radiations. For both mutation and inactivation, the maximum effectiveness per unit absorbed dose was obtained for the characteristic X rays, which have a dose averaged linear energy transfer (LET) of roughly 10 keV/μm. The ratio of the effectiveness of this radiation to γ rays was 2 for inactivation and about 1.4 for the his+ reversion. For both end points the effectiveness decreases substantially at high LET, i.e., for the α particles and the Fe ions. The composition of the bottom and the top agar was the one recommended by Maron and Ames [Mutat. Res. 113, 173-215 (1983)] for application in chemical mutagenicity tests. The experiments with the less penetrating radiations differed from the usual protocol by utilization of a technique of plating the bacteria on the surface of the top agar. As in an earlier study [Roos et al., Radiat. Res. 104, 102-108 (1985)] greatly enhanced yields of mutations, relative to the spontaneous reversion rate, were obtained in these experiments by performing the irradiations 6 h after plating, which differs from the conventional procedure to irradiate the bacteria shortly after plating
The Bryozoan Fistulipora Candida from the Ames Limestone (Conemaugh) of Ohio
Get PDFAuthor Institution: Department of Geology, Bowling Green State University, and Department of Geology, Ohio UniversityThe bryozoan Fistulipora Candida (Moore & Dudley, 1944) has been found at two localities in the Ames Limestone; no other occurrences of massive bryozoans have been reported from Pennsylvanian rocks in Ohio. These occurrences suggest a possible correlation of the Ames Limestone with the Coal Creek Limestone (Virgilian Series) in the Western Interior Basin
First in the Nation in Education : Final Report,1984.
No full textThis report is one step in an ongoing process of change and is a plea for commitment for high standards in education in Iowa. Contains the final reports of the six subcommittees as adopted by the Excellence in Education Task Force, and the five recommendations made by the Task Force
On How to Construct a Confucian Democracy for Modern Times (or Why Democratic Practices Must Not Lose Sight of the Ideal)
No full textA&HCIARTICLE161-816
Microstructural evolutions, phase transformations and hard magnetic properties in polycrystalline Ce–Co–Fe–Cu alloys Author links open overlay panel
No full textThis work focuses on systematic studies of Ce–Co based 1:5 permanent magnet alloys of CeCo4.4-xFexCu0.6 and CeCo3.9-xFexCu1.2 (x = 0, 0.3, 0.6, 0.9, 1.2, 1.8) by varying Co:Fe. The overarching aim of this manuscript is to elucidate the hard-magnetic properties through a better understanding of phase formation by the structural, microstructural, and magnetic properties in these materials. Improved mutual solubility of Fe in the 1:5 phase has been observed with an extended homogeneity range by Cu substitution. For both composition series, Fe contents of x ≤ 0.6 show a homogeneous microstructure with a single 1:5 phase and good magnetic properties. The composition region 0.6 < x ≤ 0.9 appears to be near the boundary of solubility and evolution of other phases. At x = 1.8, it is found that the homogeneous 1:5 phase and magnetic hardness deteriorated due to the evolution of secondary phases such as 2:17, 2:7, and Fe–Co. The addition of Fe improved both the magnetization and Curie temperature via increased effective exchange interactions, while an increase in Cu content enhanced coercivity.This is a manuscript of an article published as Gandha, Kinjal, Rakesh P. Chaudhary, Matthew J. Kramer, Ryan T. Ott, Durga Paudyal, and I. C. Nlebedim. "Microstructural evolutions, phase transformations and hard magnetic properties in polycrystalline Ce–Co–Fe–Cu alloys." Materials Chemistry and Physics 286 (2022): 126179.
DOI: 10.1016/j.matchemphys.2022.126179.
Copyright 2022 Elsevier B.V.
Posted with permission.
DOE Contract Number(s): AC02-07CH11358
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Development and validation of a combustion model for a fuel cell off-gas burner
Get PDFA low-emissions power generator comprising a solid oxide fuel cell coupled to a gas
turbine has been developed by Rolls-Royce Fuel Cell Systems. As part of the cycle, a
fraction of the unreacted fuel (the off-gas) and oxidizer streams is reacted in a burner,
which is the main source of pollutant formation. In this thesis a computational model of
the burner has been developed which captures the formation of NOx and the oxidation
of CO. This model gives accurate predictions at low computational cost, making it
suitable for use as a design tool in future burner design optimization through parametric
studies.
A key factor in increasing computational efficiency was the development of a reduced
H2/CO/N2 kinetic mechanism; from a starting mechanism of 30 species to 10 and 116
reactions to 6. The results of laminar opposed-flow diffusion flames have been used to
validate the reduced mechanism.
Several different turbulent combustion models have been evaluated by creating an
interface between the reduced kinetic mechanism and the commercial CFD solver FLUENT. Comparison of model predictions with well-characterized turbulent syngas flames,
which share a similar fuel composition to the experimental work conducted on the off-
gas burner, shows acceptable agreement. These studies have demonstrated the sensitivity of modelling constants. Improved predictions were achieved by calibrating these
constants and including radiative heat losses.
Following suitable modification to reflect the predominantly laminar flow present in
the current burner design, the relevant modelling approaches were applied to the off-
gas burner. Comparison was made to previous detailed measurements, showing that the
important trends of NOx and CO are captured in general. The model was extended to
high pressure conditions, similar to those in the actual off-gas burner, with the emissions
predictions within design limits.
The outcome of this work is a fast, accurate design tool for CFD which has capabilities to simulate beyond the laminar burner studied here. It may be applied to more
general types of off-gas/syngas burners where turbulence-chemistry interaction is expected to be more significant
Validation of the mutational spectra obtained with thelacZ Escherichia coli CLP and the Ames II Salmonella typhimurium strains
No full textThe six lacZ-- E.coli CLP strains (CL10XP; where X = 1--6) are each reverted by one of the six possible base substitutions. The relative responses of the six strains taken in parallel can be used to determine a compound's mutation spectrum. The responses of these strains to a set of mutagens of known mutational spectra and modes of action were tested.The predominant mutations caused by a set of seven diagnostic mutagens and the strains that scored these mutations were: 4-nitroquinoline 1-oxide, G → A (CL102P), G → C (CL103P) and G → T (CL104P); streptonigrin, A → C (CL101P), A → T (CL105P) and A → G (CL106P); N-methyl-N'-nitro- N-nitrosoguanidine G → T (CL102P); 5-azacytidine G C, (CL103P), N4-aminocytidine G → A, (CL102P) and A → G (CL106P) and N4-hydroxycytidine A → G (CL106P) . These responses were consistent with the results reported by Gee et al., (1994) using the Salmonella 700X (X = 1--6) bacterial test system.A further validation of the responses of the six CLP strains and the six Ames II strains was performed using six polycyclic aromatic hydrocarbon diol epoxide (PAHDE) isomers, the four stereoisomeric 1,2,3,4-tetrahydrobenzo[cjphenanthrene 3,4-diol 1,2-epoxides (BcPhDEs) and two of the stereoisomeric 7,8,9,10-tetrahydrobenzo[a]pyrene 7,8-diol 9,10-epoxides (BaPDEs) for which published mutational spectra exist.Comparisons of the bacterial mutational spectra with the published mutational spectra for the PAHDEs indicate that the E. coli strain CL103P scores G → C mutations consistently lower than published values, and the E. coli strain CL106P (A → G) may be a potential low scoring strain. In the Ames II Salmonella typhimurium TA 70OX system, a high scoring strain is TA 7004 (G → A), which often scores higher than published values. The S. typhimurium AT strains (TA 7001-- 7003) often scored a lower percentage of mutations. The low responses may be due to the excess response of some of the GC strains, particularly TA 7004.Source: Dissertation Abstracts International, Volume: 60-01, Section: B, page: 1720.Advisors: Albert Cheh.Ph.D. American University 1998.Englis
ThermoPhonon
No full textThermoPhonon is a stand-alone code, which can be integrated into other software packages. Typically, it is used together with a density functional theory (DFT) code (such as VASP, Wien2k, AbInit, SIESTA) and a phonon code (such as Phonopy or Phon). The workflow is the following. Molecular dynamics (MD) in a supercell at a given temperature T is performed using another code. After sufficient equilibration, the output in the form of atomic positions and forces for a large number of selected MD steps is recorded into a file. If needed, one can modify this file by applying additional constraints, such as enforced crystal symmetry or subtracted motion of the center of mass. ThermoPhonon reads the file with atomic positions and forces and writes a new file with the force constants. Force constants can be used by another code (such as Phonopy or Phon) to produce phonon spectrum for plotting, in the assumption of known equilibrium atomic positions provided in a separate file.
Separate utilities for file conversion are not included into the ThermoPhonon code and not covered by its license and copyright. Compiling instructions are in the source code. The attachment consists of 4 files: ThermoPhonon source code (Fortran), ThermoPhonon manual (PDF), a truncated sample input file “force.txt” (text), a sample output file “FORCE_CONSTANTS” (text). Author Affiliations: Ames Laboratory</p
Thermal stability of anisotropic bonded magnets prepared by additive manufacturing
Get PDFIn this research, anisotropic NdFeB + SmFeN hybrid and NdFeB bonded magnets are additively printed in a polyphenylene sulfide (PPS) polymer binder. Printed NdFeB + SmFeN PPS bonded magnets displayed excellent magnetic properties (Br [remanence] = 6.9 kG [0.69 T], Hcj [coercivity] = 8.3 kOe [660 kA/m], and BHmax [energy product] = 9.9 MGOe [79 kJ/m3]) with superior corrosion resistance and thermal stability. The anisotropic NdFeB bonded magnet shows a high coercivity of 14.6 kOe (1162 kA/m) with a BHmax of 8.7 MGOe (69 kJ/m3). The coercivity and remanence temperature coefficients for NdFeB + SmFeN hybrid bonded magnets are −0.10%/K and −0.46%/K, and for NdFeB bonded magnets are −0.14%/K and −0.53%/K in the range of 300–400 K, indicating that the hybrid bonded magnets are thermally stable. The average flux aging loss for hybrid magnets was also determined to be very stable over 2000 h at 448 K (175°C) in air with 2.04% compared to that of NdFeB magnets with 3.62%.This article is published as Gandha, Kinjal, Mariappan Parans Paranthaman, Haobo Wang, Xubo Liu, and Ikenna C. Nlebedim. "Thermal stability of anisotropic bonded magnets prepared by additive manufacturing." Journal of the American Ceramic Society 106, no. 1 (2023): 166-171.
DOI: 10.1111/jace.18609
Copyright 2022 The Author(s).
Attribution 4.0 International (CC BY 4.0).
Posted with permission.
DOE Contract Number(s): AC02-07CH11358; AC05-00OR22725
Stability of Asymptotic Behavior Within Polarised -Symmetric Vacuum Solutions with Cosmological Constant
Get PDFWe prove the nonlinear stability of the asymptotic behavior of perturbations
of subfamilies of Kasner solutions in the contracting time direction within the
class of polarised -symmetric solutions of the vacuum Einstein equations
with arbitrary cosmological constant . This stability result
generalizes the results proven in [3], which focus on the case, and
as in that article, the proof relies on an areal time foliation and Fuchsian
techniques. Even for , the results established here apply to a wider
class of perturbations of Kasner solutions within the family of polarised
-symmetric vacuum solutions than those considered in [3] and [26]. Our
results establish that the areal time coordinate takes all values in
for some , for certain families of polarised -symmetric solutions
with cosmological constant.Comment: 20 page
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