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

The FERRUM project: Transition probabilities for forbidden lines in [FeII] and experimental metastable lifetimes

Accurate transition probabilities for forbidden lines are important diagnostic parameters for low-density astrophysical plasmas. In this paper we present experimental atomic data for forbidden [FeII] transitions that are observed as strong features in astrophysical spectra. Aims: To measure lifetimes for the 3d^6(^3G)4s a ^4G_{11/2} and 3d^6(^3D)4s b ^4D_{1/2} metastable levels in FeII and experimental transition probabilities for the forbidden transitions 3d^7 a ^4F_{7/2,9/2}- 3d^6(^3G)4s a ^4G_{11/2}. Methods: The lifetimes were measured at the ion storage ring facility CRYRING using a laser probing technique. Astrophysical branching fractions were obtained from spectra of Eta Carinae, obtained with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope. The lifetimes and branching fractions were combined to yield absolute transition probabilities. Results: The lifetimes of the a ^4G_{11/2} and the b ^4D_{1/2} levels have been measured and have the following values, 0.75(10) s and 0.54(3) s respectively. Furthermore, we have determined the transition probabilities for two forbidden transitions of a ^4F_{7/2,9/2}- a ^4G_{11/2} at 4243.97 and 4346.85 A. Both the lifetimes and the transition probabilities are compared to calculated values in the literature.Comment: 5 pages, accepted for publication in A&

Anti-pancreatic cancer potential of secalonic acid derivatives from endophytic fungi isolated from Ocimum basilicum.

The word endophyte means "in the plant" and refers to all microorganisms that live in the intercellular spaces of stems, petioles, roots and leaves of plants causing no apparent symptoms of disease. Seven endophytic fungi were isolated from the medicinal plant of Ocimum basilicum L. The fungal strain, labeled as 2L, was cultivated at large scale on the potato dextrose agar semi solid medium and was extracted with ethyl acetate. Normal phase silica gel column chromatography of the ethyl acetate extract afforded ergosterol (1), secalonic acid A (2) and secalonic acid D (3). The structures of these compounds (1-3) were elucidated unequivocally by UV, IR, MS, a series of 1D & 2D NMR analyses. The cytotoxicity of these compounds was evaluated by the MTT assay against human pancreatic cancer cell line. Secalonic acid A (2) and secalonic acid D (3) exhibited significant anti-pancreatic cancer activity with IC 50 values of 7.3 and 1.6 µM, respectively

Actividad antibacteriana y antioxidante de los extractos de Piper cubeba (Piperaceae)

Piper cubeba L. (Piperaceae), commonly known as ‘cubeb’, is native to Indonesia, and also found in many other countriesof the South-East Asia, and in some African countries. This plant has been used as a popular food additive, andin folklore medicine to treat various ailments, particularly bacterial infections. The n-hexane, dichloromethane (DCM)and methanol (MeOH) extracts of the dried berries (fruit) of this plant were assessed for their antioxidant (free radicalscavenging) and antibacterial activities using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and the micro titre basedantimicrobial assay incorporating resazurin as an indicator of cell growth, respectively. While all extracts showed antioxidantactivity in the qualitative assay, the most prominent antioxidant activity was observed with the MeOH extract inthe quantitative assay with a RC50 value of 2.71 x 10-1 mg/mL. The antioxidant potency of the DCM extract was about3 fold less (RC50 = 6.50 x 10-1 mg/mL) than that of the MeOH extract. None of the extracts showed any antibacterialproperty against Bacillus subtilis, Escherichia coli, and ampicillin resistant Escherichia coli. While both the n-hexaneand the DCM extracts inhibited the growth of Bacillus cereus, Pseudomonas aeruginosa and Staphylococcus aureus, theMeOH extract was active only against B. cereus and P. aeruginosa. The most potent antibacterial activity was displayedby the n-hexane extract against B. cereus with an MIC value of 1.56 mg/mL. All antibacterial activities of the extractswere found to be bacteriostatic rather than bactericidal.Piper cubeba L. (Piperaceae), conocida comúnmente como ‘cubeb’, es autóctona de Indonesia y también se encuentraen muchos otros países del sureste de Asia, así como en algunos países africanos.Esta planta se ha utilizado como un popular aditivo alimentario y, en la medicina tradicional, para tratar diversasdolencias, especialmente infecciones bacterianas. Para evaluar la actividad antioxidante (barrido de radicales libres)y la actividad antibacteriana de los extractos de n-hexano, diclorometano (DCM) y metanol (MeOH) de las bayassecas (fruto) de esta planta, se llevó a cabo un ensayo 2,2-difenil-1-picrilhidracil (DPPH) y un ensayo antimicrobianobasado en microtitulación que incorporaba resazurina como indicador del crecimiento celular, respectivamente. Aunquetodos los extractos mostraron actividad antioxidante en el ensayo cualitativo, la actividad antioxidante más destacadase observó con el extracto de MeOH en el ensayo cuantitativo con un valor de RC50 de 2,71 x 10-1 mg/mL.La potencia antioxidante del extracto de DCM fue aproximadamente 3 veces menor (RC50 = 6,50 x 10-1 mg/mL)que la del extracto de MeOH.Ninguno de los extractos mostró propiedades antibacterianas frente a Bacillus subtilis, Escherichia coli y Escherichiacoli resistente a la ampicilina. Aunque ambos extractos, el n-hexano y el DCM, inhibieron el crecimiento de Bacilluscereus, Pseudomonas aeruginosa y Staphylococcus aureus, el extracto de MeOH sólo mostró actividad frente a B.cereus y P. aeruginosa. El extracto de n-hexano fue el que mostró mayor potencia antibacteriana frente a B. cereus,con un valor de concentración inhibitoria mínima (CIM) de 1,56 mg/mL. Se observó que todas las actividades antibacterianasde los extractos resultaron más bacteriostáticas que bactericidas

Unsupervised Learning in Detection of Gene Transfer

The tree representation as a model for organismal evolution has been in use since before Darwin. However, with the recent unprecedented access to biomolecular data, it has been discovered that, especially in the microbial world, individual genes making up the genome of an organism give rise to different and sometimes conflicting evolutionary tree topologies. This discovery calls into question the notion of a single evolutionary tree for an organism and gives rise to the notion of an evolutionary consensus tree based on the evolutionary patterns of the majority of genes in a genome embedded in a network of gene histories. Here, we discuss an approach to the analysis of genomic data of multiple genomes using bipartition spectral analysis and unsupervised learning. An interesting observation is that genes within genomes that have evolutionary tree topologies, which are in substantial conflict with the evolutionary consensus tree of an organism, point to possible horizontal gene transfer events which often delineate significant evolutionary events

Highly Excited Core Resonances in Photoionization of Fe XVII : Implications for Plasma Opacities

A comprehensive study of high-accuracy photoionization cross sections is carried out using the relativistic Breit-Pauli R-matrix (BPRM) method for (hnu + Fe XVII --> Fe XVIII + e). Owing to its importance in high-temperature plasmas the calculations cover a large energy range, particularly the myriad photoexciation-of-core (PEC) resonances including the n = 3 levels not heretofore considered. The calculations employ a close coupling wave function expansion of 60 levels of the core ion Fe XVIII ranging over a wide energy range of nearly 900 eV between the n = 2 and n = 3 levels. Strong coupling effects due to dipole transition arrays 2p^5 --> 2p^4 (3s,3d) manifest themselves as large PEC resonances throughout this range, and enhance the effective photoionization cross sections orders of magnitude above the background. Comparisons with the erstwhile Opacity Project (OP) and other previous calculations shows that the currently available cross sections considerably underestimate the bound-free cross sections. A level-identification scheme is used for spectroscopic designation of the 454 bound fine structure levels of Fe XVII. Level-specific photoionization cross sections are computed for all levels. In addition, partial cross sections for leaving the core ion Fe XVII in the ground state are also obtained. These results should be relevant to modeling of astrophysical and laboratory plasma sources requiring (i) photoionization rates, (ii) extensive non-local-thermodynamic-equilibrium models, (iii) total unified electron-ion recombination rates including radiative and dielectronic recombination, and (iv) plasma opacities. We particularly examine PEC and non-PEC resonance strengths and emphasize their expanded role to incorporate inner-shell excitations for improved opacities, as shown by the computed monochromatic opacity of Fe XVII.Comment: 12 pages, 5 figures, Physical Review A (in press

An Empirical Ultraviolet Template for Iron Emission in Quasars as Derived from I Zw 1

We present an empirical template spectrum suitable for fitting/subtracting and studying the FeII and FeIII line emission in the restframe UV spectra of active galatic nuclei (AGNs), the first empirical UV iron template to cover the full 1250 - 3090 A range. Iron emission is often a severe contaminant in optical--UV spectra of AGNs. Its presence complicates and limits the accuracy of measurements of both strong and weak emission lines and the continuum emission, affecting studies of line and continuum interrelations, the ionization structure, and elemental abundances in AGNs. Despite the wealth of work on modeling the AGN FeII emission and the need to account for it in observed AGN spectra, there is no UV template electronically available to aid this process. The iron template we present is based on HST spectra of the Narrow Line Seyfert 1, IZw1. Its intrinsic narrow lines (~900 km/s) and rich iron spectrum make the template particularly suitable for use with most AGN spectra. The iron emission spectrum and the line identifications and measurements are presented and compared with the work of Laor et al. We illustrate the application of the derived FeII and FeIII templates by fitting and subtracting the iron emission from UV spectra of four high-z quasars and of the nearby quasar, 3C273. We briefly discuss the small discrepancies between this observed iron emission and the UV template, and compare the template with previously published ones. We discuss the advantages and limitations of the templates and of the template fitting method. We conclude that the templates work sufficiently well to be a valuable and important tool for eliminating and studying the iron emission in AGNs, at least until accurate theoretical iron emission models are developed. (Abridged)Comment: 73 pages including 7 figures, 6 tables. To appear in ApJS. Preprint is also available at http://www.astronomy.ohio-state.edu/~vester/IronEmission

Nonlinear Models of Convergence

A sufficient issue in studies of economic development is whether economies (countries, regions of a country, etc.) converge to one another in terms of per capita income. In this paper, nonlinear asymptotically subsiding trends of income gap in a pair of economies model the convergence process. A few specific forms of such trends are proposed: log-exponential trend, exponential trend, and fractional trend. A pair of economies is deemed converging if time series of their income gap is stationary about any of these trends. To test for stationarity, standard unit root tests are applied with non-standard test statistics that are estimated for each kind of the trends

Antioxidant property, traditional uses and chemical composition of seed oil plants of North-east India: A mini- review

Apart from being used as food, seed oils have also been used traditionally as medicinal products by several communities. However, the full medicinal potential of many seed oil plants is yet to be properly reviewed, particularly for their antimicrobial and antioxidant properties. North-East India has rich resources of seed oil plants. The availability of detailed information on these plants is quite limited. This review aims to explore and evaluate these seed oil plants of the North-East India with particular emphasis on their antimicrobial and antioxidant activities as well as chemical compositions. A comprehensive literature search on seed oil plants of this region has been performed. Seed oil yielding plants of this region can be categorized into two categories: plants that are used traditionally as sources of edible or medicinal oils and plants that are used for purposes other than as sources of oils. Many seed oil plants of this region have been reported to possess antimicrobial and antioxidant properties, and to produce various types of compounds. This review also highlights the importance of these plants in contributing to the local as well as the national economy of India