446 research outputs found
Determination of [S,S′]-Ethylenediaminedisuccinic Acid by High-Performance Liquid Chromatography
A new high-performance liquid chromatography (HPLC) method for the determination of ethylenediaminedisuccinic acid (EDDS) is presented. Free EDDS4- and EDDS complexes with divalent metals undergo conversion to the Fe(III) complex in the presence of Fe(III)Cl3. Fe(III)EDDS is separated by HPLC on an ion exchange column using (NH4)2SO4 eluent with detection at 258 nm. The detection limit is 0.01µM. The method is applied to natural waters and soil solution samples. A background of natural water results in a reduction in EDDS peak area. The method is suited for EDDS analysis in samples with well-defined, simple matrices such as those used in laboratory experiments or biodegradation studie
An empirical analysis of the petroleum refining industry's participation in the FASB's standard-setting process: Working paper series--99-04
Despite the recognized importance of constituent input in the Financial Accounting Standards Board's (FASB's) standard-setting process, corporate participation has been limited. Results from prior research indicate that differences exist between the petroleum industry and other industries for lobbying behavior, accounting choices, and tax rates. This study explores further the participation of Fortune 500 petroleum refining corporations in the FASB's standard-setting process from 1973-1997. Results in this study indicate that while petroleum companies comprise only 6.6 percent of Fortune 500 companies, they submitted approximately 18 percent of all Fortune 500 comment letters on the 173 documents preceding FAS Nos. 1-133, with an average of 18.4 percent of petroleum companies participating per document. The level of petroleum industry participation is affected by the scope of the standard under consideration and the time period the document was issued. Substantive standards generate significantly more letters from petroleum companies than amendments or industry standards. However, industry standards in the period 1973-1977 attracted the highest level of petroleum refining industry participation driven by the oil and gas industry documents issued in that period. All of the individual petroleum refining companies that are listed on the Fortune 500 throughout the 25-year period submitted comment letters, ranging from nine to 94 letters. Compared to individual companies in other industries, petroleum companies participate much more frequently. This provides some evidence of greater benefits of participation by the petroleum refining industry which may be the result of greater government regulation than for other industrie
Dyson-Schwinger Equation Approach to the QCD Deconfinement Transition and J/Psi Dissociation
We consider an extension of the finite-temperature Dyson-Schwinger equation
(DSE) approach to heavy mesons and quarkonia and apply it to calculate the
cross section for the J/Psi breakup reaction J/Psi + pi --> D + D. We study the
effects of chiral symmetry restoration in the light quark sector on this
process and obtain a critical enhancement of the reaction rate at the chiral/
deconfinement transition. Implications for the kinetics of charmonium
production in ultrarelativistic heavy-ion collisions are discussed with
particular emphasis on the recently observed anomalous J/Psi suppression as a
possible signal for quark matter formation.Comment: 10 pages, 6 figures, sprocl.sty, to appear in: "Progress in
Nonequilibrium Green's functions", M. Bonitz (Ed.), World Scientific,
Singapore, 200
The Quark-Photon Vertex and the Pion Charge Radius
The rainbow truncation of the quark Dyson-Schwinger equation is combined with
the ladder Bethe-Salpeter equation for the dressed quark-photon vertex to study
the low-momentum behavior of the pion electromagnetic form factor. With model
gluon parameters previously fixed by the pion mass and decay constant, the pion
charge radius is found to be in excellent agreement with the data. When
the often-used Ball-Chiu Ansatz is used to construct the quark-photon vertex
directly from the quark propagator, less than half of is generated.
The remainder of is seen to be attributable to the presence of the
-pole in the solution of the ladder Bethe-Salpeter equation.Comment: 21 pages, 9 figure
Soliton with a Pion Field in the Global Color Symmetry Model
We calculate the property of the global color symmetry model soliton with the
pion field being included explicitly. The calculated results indicate that the
pion field provides a strong attraction so that the eigen-energy of a quark and
the mass of a soliton reduce drastically, in contrast to those with only the
sigma field.Comment: 15 pages, 2 figure
Selected nucleon form factors and a composite scalar diquark
A covariant, composite scalar diquark, Fadde'ev amplitude model for the
nucleon is used to calculate pseudoscalar, isoscalar- and isovector-vector,
axial-vector and scalar nucleon form factors. The last yields the nucleon
sigma-term and on-shell sigma-nucleon coupling. The calculated form factors are
soft, and the couplings are generally in good agreement with experiment and
other determinations. Elements in the dressed-quark-axial-vector vertex that
are not constrained by the Ward-Takahashi identity contribute ~20% to the
magnitude of g_A. The calculation of the nucleon sigma-term elucidates the only
unambiguous means of extrapolating meson-nucleon couplings off the meson
mass-shell.Comment: 12 pages, REVTEX, 5 figures, epsfi
Consequences Of Fully Dressing Quark-Gluon Vertex Function With Two-Point Gluon Lines
We extend recent studies of the effects of quark-gluon vertex dressing upon
the solutions of the Dyson-Schwinger equation for the quark propagator. A
momentum delta function is used to represent the dominant infrared strength of
the effective gluon propagator so that the resulting integral equations become
algebraic. The quark-gluon vertex is constructed from the complete set of
diagrams involving only 2-point gluon lines. The additional diagrams, including
those with crossed gluon lines, are shown to make an important contribution to
the DSE solutions for the quark propagator, because of their large color
factors and the rapid growth in their number
Incidental finding of a microsporidian parasite from an AIDS patient
Light microscopic examination of feces from a human immunodeficiency virus-positive patient with chronic diarrhea, anorexia, and lethargy revealed the presence of numerous refractile bodies resembling microsporidian spores. They were subsequently identified as belonging to the genus Nosema on the basis of their ultrastructural characteristics. However, the microsporidia were enclosed within striated muscle cells, suggesting that they were probably ingested in food; thus, this represented an incidental finding rather than a true infection
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