892 research outputs found
Recombination Rate Coefficients for KLL Di-electronic Satellite Lines of Fe XXV and Ni XXVII
The unified method for total electron-ion recombination is extended to study
the dielectronic satellite (DES) lines. These lines, formed from radiative
decay of autoionizing states, are highly sensitive temperature diagnostics of
astrophysical and laboratory plasma sources. The computation of the unified
recombination rates is based on the relativistic Breit-Pauli R-matrix method
and close coupling approximation. Extending the theoretical formulation
developed earlier we present recombination rate coefficients for the 22
satellite lines of KLL complexes of helium-like Fe XXV and Ni XXVII. The
isolated resonance approximation, commonly used throughout plasma modeling,
treats these resonances essentially as bound features except for dielectronic
capture into, and autoionization out of, these levels. A line profile or cross
section shape is often assumed. On the other hand, by including the coupling
between the autoionizing and continuum channels, the unified method gives the
intrinsic spectrum of DES lines which includes not only the energies and
strengths, but also the natural line or cross section shapes. A formulation is
presented to derive autoionization rates from unified resonance strengths and
enable correspondence with the isolated resonance approximation. While the
rates compare very well with existing rates for the strong lines to <20%, the
differences for weaker DES lines are larger. We also illustrate the application
of the present results to the analysis of K ALPHA complexes observed in
high-temperature X-ray emission spectra of Fe XXV and Ni XXVII. There are
considerable differences with previous results in the total KLL intensity for
Fe XXV at temperatures below the temperature of maximum abundance in coronal
equilibrium. (Abbreviated Abstract)Comment: 21 pages, 5 figures, to appear in Physica Script
Electron-Ion Recombination Rate Coefficients and Photoionization Cross Sections for Astrophysically Abundant Elements. IX. Ni XXVI and Ni XXVII for UV and X-ray modeling
The inverse processes of photoionization and electron-ion recombination of
(hnu + Ni XXVI --> Ni XXVII + e and (hnu + Ni XXVII --> Ni XXVIII + e) are
studied using the unified method for the total recombination. The method
subsumes both the radiative and di-electronic recombination processes and
enables self-consistent sets of results for photoionization and electron-ion
recombination by using the same wavefunction expansion. Photoionization cross
sections (sigma_PI), recombination cross sections (sigma_{RC}), recombination
collision strengths (Omega_{RC}), and recombination rate coefficients
(alpha_{RC}) are obtained for ionization balance and spectral analysis of UV
and X-ray lines. Level-specific photoionization cross sections and
recombination rates are presented to enable accurate computation of
recombination-cascade matrices for all fine structure levels n(SLJ) up to n <=
10: 98 bound fine structure levels of Ni XXVI with 0 <= l <= 9, 0 <= L <= 11,
1/2 <= J <= 17/2, and 198 levels of Ni XXVII with 0 <= l <= 9, 0 <= L <= 14, 0
<= J <= 10. Total alpha_{RC} for Ni XXVI and Ni XXVII are compared with the
existing values with very good agreement. Total recombination rate coefficients
for the hydrogen-like recombined ion, Ni XXVIII, are also presented. The
calculations are carried out in relativistic Breit-Pauli R-matrix (BPRM)
approximation with inclusion of radiation damping of resonances. With
consideration of all details of the processes, the results, which include the
level specific sigma_{PI} and alpha_{R} calculated for the first time, should
be the most accurate for these ions.Comment: 27 pages, 10 figures, to appear in Astrophys. J. Supplement
Photoionization cross sections of O II, O III, O IV, and O V: benchmarking R-matrix theory and experiments
For crucial tests between theory and experiment, ab initio close coupling
calculations are carried out for photoionization of O II, O III, O IV, O V. The
relativistic fine structure and resonance effects are studied using the
R-matrix and its relativistic variant the Breit Pauli R-matrix (BPRM)
approximation. Detailed comparison is made with high resolution experimental
measurements carried out in three different set-ups: Advanced Light Source at
Berkeley, and synchrotron radiation experiments at University of Aarhus and
University of Paris-Sud. The comparisons illustrate physical effects in
photoionization such as (i) fine structure, (ii) resolution, and (iii)
metastable components. Photoionization cross sections sigma{PI} of the ground
and a few low lying excited states of these ions obtained in the experimental
spectrum include combined features of these states. Theoretically calculated
resonances need to be resolved with extremely fine energy mesh for precise
comparison. In addition, prominent resonant features are observed in the
measured spectra from transitions allowed with relativistic fine structure, but
not in LS coupling. The sigma_{PI} are obtained for ground and metastable (i)
2s^22p^3(^4S^o, ^2D^o, ^2P^o) states of O II, (ii) 2s^22p^2(^3P,^1D,^1S) and
2s2p^3(^5S^o) states of O III, (iii) 2s^22p(^2P^o_J) and 2s2p^2(^4P_J) levels
of O IV, and (iv) 2s^2(^1S) and 2s2p(^3P^o,^1P^o) states of O V. It is found
that resonances in ground and metastable cross sections can be a diagnostic of
experimental beam composition, with potential ap plications to astrophysical
and laboratory plasma environments.Comment: 27 pages, 7 figs., submitted to Phys. Rev. A., text with high
resolution figures at http://www.astronomy.ohio-state.edu/~pradhan/Oions.p
Electron-Ion Recombination Rate Coefficients and Photoionization Cross Sections for Astrophysically Abundant Elements. V. Relativistic calculations for Fe XXIV and Fe XXV for X-ray modeling
Photoionization and recombination cross sections and rate coefficients are
calculated for Li-like Fe XXIV and He-like Fe XXV using the Breit-Pauli
R-matrix (BPRM) method. A complete set of total and level-specific parameters
is obtained to enable X-ray photoionization and spectral modeling. The ab
initio calculations for the unified (e + ion) recombination rate coefficients
include both the non-resonant and the resonant recombination (radiative and
di-electronic recombination, RR and DR, respectively) for (e + Fe XXV) -> Fe
XXIV and (e + Fe XXVI) -> Fe XXV. The level specific rates are computed for all
fine structure levels up to n = 10, enabling accurate computation of
recombination-cascade matrices and effective rates for the X-ray lines. The
total recombination rate coefficients for both Fe XXIV and Fe XXV differ
considerably, by several factors, from the sum of RR and DR rates currently
used to compute ionization fractions in astrophysical models. As the
photoionization/recombination calculations are carried out using an identical
eigenfunction expansion, the cross sections for both processes are
theoretically self-consistent; the overall uncertainty is estimated to be about
10-20%. All data for Fe XXIV and Fe XXV (and also for H-like Fe XXVI, included
for completeness) are available electronically.Comment: 31 pages, 10fug
GABA-B receptor function in healthy volunteers, a pharmacokinetic and pharmacodynamic study of two doses of baclofen compared to placebo
AIMS AND HYPOTHESIS To assess the subjective and objective effects of baclofen on brain function in healthy volunteers. BACKGROUND Recent evidence suggests baclofen, a Îł-aminobutyric acid type B (GABA-B) receptor agonist, reduces alcohol consumption and craving and promotes abstinence in alcoholics. However, characterisation of the GABA-B receptor system in clinical addiction is limited, and it is unclear why some patients require, or tolerate, higher doses to treat alcoholism. This study assesses the effects of baclofen on brain function in healthy volunteers to inform future studies investigating the sensitivity of GABA-B receptors in alcohol addiction. METHODS Eight healthy male volunteers completed a double blind randomised 3-way cross over study, receiving oral placebo (vitamin C 100mg), 10mg and 60mg baclofen. Subjective and objective measurements were taken at baseline (before medication) and at +30mins, 1, 2, 3, 4 and 6 hours after dosing. Objective measures included blood plasma samples, heart rate and blood pressure. Subjective measures included; the Subjective High Assessment Questionnaire (SHAS), visual analogue scales for sleepy, relaxed, tense and alert and a motor coordination task (zig-zag task). Pharmacokinetic data was obtained using liquid chromatography mass-spectrometry (LC-MS) to measure plasma baclofen concentrations. RESULTS 60mg Baclofen showed changes in subjective measures peaking at 2 hours post dosing compared with placebo, including a significant increase (p<0.05) in total SHAS scores with individual items, including feeling âdrunk or intoxicatedâ, effects of alcohol and âmuddled or confusedâ particular affected.. Systolic blood pressure was significantly increased (p<0.05) at the 2 hours post 60mg dose. For both 10mg and 60mg baclofen, peak plasma concentration was achieved 60 minutes post dose. Pharmacokinetic data will be presented. There were no significant changes in these measures between 10mg Baclofen and placebo. CONCLUSIONS The objective and subjective measures used in this study are able to differentiate between placebo and 60mg baclofen. These findings will inform further research investigating the sensitivity of GABA-B receptors in alcohol addiction
K-shell dielectronic resonances in photoabsorption: differential oscillator strengths for Li-like C IV, O VI, and Fe XXIV
Recently X-ray photoabsorption in KLL resonances of O VI was predicted
[Pradhan, Astrophys.J. Lett. 545, L165 (2000)], and detected by the Chandra
X-ray Observatory [Lee et al, Astrophys. J. {\it Lett.}, submitted].
The required resonance oscillator strengths f_r, are evaluated in terms of
the differential oscillator strength df/de that relates bound and continuum
absorption. We present the f_r values from radiatively damped and undamped
photoionization cross sections for Li-like C,O, and Fe calculated using
relativistic close coupling Breit-Pauli R-matrix method. The KLL resonances of
interest here are: 1s2p (^3P^o) 2s [^4P^o_{1/2,3/2}, ^2P^o_{1/2,3/2}] and 1s2p
(^1P^o) 2s [^2P^o_{1/2,3/2}]. The KLL photoabsorption resonances in Fe XXIV are
fully resolved up to natural autoionization profiles for the first time. It is
demonstrated that the undamped f_r independently yield the resonance radiative
decay rates, and thereby provide a precise check on the resolution of
photoionization calculations in general. The predicted photoabsorption features
should be detectable by the X-ray space observatories and enable column
densities in highly ionized astrophysical plasmas to be determined from the
calculated f_r. The dielectronic satellites may appear as redward broadening of
resonances lines in emission and absorption.Comment: 9 pages, 2 figurs, Phys. Rev. A, Rapid Communication (submitted
Electron-Ion Recombination Rate Coefficients and Photoionization Cross Sections for Astrophysically Abundant Elements VI. Ni II
We present the first detailed ab initio quantum mechanical calculations for
total and state-specific recombination rate coefficients for e + Ni III --> Ni
II. These rates are obtained using a unified treatment for total electron-ion
recombination that treats the nonresonant radiative recombination and the
resonant dielectronic recombination in a self-consistent unified manner in the
close coupling approximation. Large-scale calculations are carried out using a
49-state wavefunction expansion from core configurations 3d^8, 3d^74s, and
3d^64p that permits the inclusion of prominent dipole allowed core transitions.
These extensive calculations for the recombination rates of Ni II required
hundreds of CPU hours on the Cray T90. The total recombination rate
coefficients are provided for a wide range of temperature. The state-specific
recombination rates for 532 bound states of doublet and quartet symmetries, and
the corresponding photoionization cross sections for leaving the core in the
ground state, are presented. Present total recombination rate coefficients
differ considerably from the currently used data in astrophysical models.Comment: ApJ Suppl. (submitted), 4 figure
Sinteza i spektroskopska analiza 5beta-kolan derivata
The facile synthesis and spectroscopic data analyses of three 5beta-cholane derivatives, 3beta-tosyloxy-5beta-cholan-24-ol (3), 5beta-cholan-24-ol (4) and 5eta-cholan-24-yl tosylate (5), have been described.Opisana je jednostavna sinteza i spektroskopska analiza tri derivata 5beta-kolana, 3beta-tosiloksi-5beta-kolan-24-ol (3), 5beta-kolan-24-ol (4) i 5beta-kolan-24-il tosilat (5)
Sinteza i spektroskopska analiza 5beta-kolan derivata
The facile synthesis and spectroscopic data analyses of three 5beta-cholane derivatives, 3beta-tosyloxy-5beta-cholan-24-ol (3), 5beta-cholan-24-ol (4) and 5eta-cholan-24-yl tosylate (5), have been described.Opisana je jednostavna sinteza i spektroskopska analiza tri derivata 5beta-kolana, 3beta-tosiloksi-5beta-kolan-24-ol (3), 5beta-kolan-24-ol (4) i 5beta-kolan-24-il tosilat (5)
Therapeutic potential of Leea indica (Vitaceae)
Background
Leea indica (Burm. f.) Merr. (fam. Vitaceae), commonly known as âbandicoot berryâ, is a Thai medicinal plant, and distributed widely in the far-east and south-east Asian countries, and in some parts of northern Australia. In Thailand, this plant has traditionally been used for the treatment of diarrhoea, pain, gastric ulcer, viral infections and some forms of cancers.
Aims
To review published findings on medicinal properties of L. indica and to critically appraise its therapeutic potential.
Methods
A comprehensive literature search was performed utilizing several databases, notably, Web of Science, PubMed and Google Scholar, and other relevant published materials. The keywords used in the search, individually as well as in combinations, were Leea indica, Vitaceae and traditional medicine.
Results
In vitro assays and in vivo animal studies displayed efficacy of the extracts and fractions of L. indica as an analgesic, antidiabetic, anti-inflammatory, antimicrobial, antioxidant and antiproliferative agent and indicated their therapeutic potential. Phytochemical studies revealed the presence of alkaloids, flavonoids, polyphenolics and terpenoids as major bioactive components in L. indica.
Conclusion
Preliminary bioactivity studies on L. indica provided some scientific basis for its traditional therapeutic applications. The presence of certain bioactive compounds in this plant could further support its therapeutic potential and traditional medicinal uses
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