Simulation of cellular irradiation with the CENBG microbeam line using GEANT4

Light-ion microbeams provide a unique opportunity to irradiate biological samples at the cellular level and to investigate radiobiological effects at low doses of high LET ionising radiation. Since 1998 a single-ion irradiation facility has been developed on the focused horizontal microbeam line of the CENBG 3.5 MV Van de Graaff accelerator. This setup delivers in air single protons and alpha particles of a few MeV onto cultured cells, with a spatial resolution of a few microns, allowing subcellular targeting. In this paper, we present results from the use of the GEANT4 toolkit to simulate cellular irradiation with the CENBG microbeam line, from the entrance to the microprobe up to the cellular medium.Comment: 6 pages, 8 figures, presented at the 2003 IEEE-NSS conference, Portland, OR, USA, October 20-24, 200

Target annihilation by diffusing particles in inhomogeneous geometries

The survival probability of immobile targets, annihilated by a population of random walkers on inhomogeneous discrete structures, such as disordered solids, glasses, fractals, polymer networks and gels, is analytically investigated. It is shown that, while it cannot in general be related to the number of distinct visited points, as in the case of homogeneous lattices, in the case of bounded coordination numbers its asymptotic behaviour at large times can still be expressed in terms of the spectral dimension $\widetilde {d}$, and its exact analytical expression is given. The results show that the asymptotic survival probability is site independent on recurrent structures ($\widetilde{d}\leq2$), while on transient structures ($\widetilde{d}>2$) it can strongly depend on the target position, and such a dependence is explicitly calculated.Comment: To appear in Physical Review E - Rapid Communication

The Possible Effects of Deleterious Rhizobacterial Combinations on the Growth of the Weed Velvetleaf

The use of biological agents in the control of the invasive weed velvetleaf Abutilon theophrasti is attractive due to this weeds development of herbicide resistance. One option is the utilization of deleterious rhizobacteria with amendments to optimize their effectiveness. Indole acetic acid (IAA)- producing Rhizobium rubi (AT3-4RS/6 (RS) and cyanogenic Pseudomonas putida ATH2-1RI/9 (RI) were used to inoculate soil with and without amino acid amendments. RS & tryptophan (a precursor of IAA synthesis) caused the least velvetleaf shoot growth. All roots were colonized by rhizobacteria, on average, 1.40E+10 CFU/ gram of dry root

Effect of the Negative Ion Band on Athletic Performance

Negative Ion bands have been suggested to increase various areas of athletic performance. At this time, the authors are not aware of any studies on these bands. Purpose: To determine if a True Power Energy Band (True Power LLC, Melrose, MA) had an effect on various measures of performance. Methods: Forty-one subjects (age = 29.3±7.1 yrs, ht = 171.5±9.7 cm, wt = 85.4±23.2 kg) had their height and weight measured and were then randomized to wear the True Power band (TB) or a silver bracelet placebo band (PB) (Hobby Lobby). After 5 days, subjects were assessed on reaction time using a color response test and a response test in which the subject clicked a highlighted dot as it appeared in a 5x5 table (www.intelligencetest.com/reflex/index). The subjects then performed a standard balance test (stork test) without shoes, two flexibility tests (V-sit-and-reach & trunk rotation), and two strength tests (hand grip using a dynamometer & push-ups to exhaustion). The tests were conducted in this order with as much rest between trials as needed. One week later, this same procedure was followed but with the opposing band. Repeated measures ANOVA was used to determine if differences exist between the bands, with Alpha set at .05. Results: There were no significant differences in the tests of color (TB = 0.43±0.14, PB = 0.41±0.11 sec), dots (TB = 16.9±3.0, PB = 17.0±2.6 score), stork (TB = 4.4±3.4, PB = 4.7±4.1 sec), V-sit-and-reach (TB = 15.2±16.8, PB = 15.5±17.3 cm), trunk rotation (TB = 35.8±15.0, PB = 37.3±14.0 cm), hand grip (TB = 42.4±12.1, PB = 42.8±11.0 kg), and push-ups (TB = 23.4±10.5, PB = 25.8±11.7 total), p \u3e .05 for all tests. Conclusion: There seems to be no effect of Negative Ion bands on tests of reaction time, balance, flexibility, or muscular strength. The claims of performance in these types of bands have yet to be validated

Simultaneous Observations of GRS 1758-258 in 1997 by VLA, IRAM, SEST, RXTE and OSSE: Spectroscopy and Timing

We report the results of our multi-wavelength observations of GRS 1758-258 made in August 1997. The energy bands include radio, millimeter, X-ray, and gamma-ray. The observations enable us to obtain a complete spectrum of the source over an energy range of 2 - 500 keV. The spectrum shows that GRS 1758-258 was in its hard state. It is well fitted by the Sunyaev-Titarchuk (ST) Compton scattering model. The spectrum is also fit by a power law with an exponential cutoff (PLE) plus a soft black-body component. The temperature of the soft component is about 1.2 keV, and the energy flux is less than 1.5% of the total X- and gamma-ray flux. The deduced hydrogen column density is in the range of (0.93 - 2.0) 10^{22} cm^{-2}. No significant iron lines are detected. The radio emission has a flat energy spectrum. The daily radio, X-ray and gamma-ray light curves show that GRS 1758-258 was stable during the observation period, but was highly variable on smaller time scales in X- and gamma-rays. The power density spectra are typical for the low-state, but we find the photon flux for the 5 to 10 keV band to be more variable than that in the other two energy bands (2 - 5 keV and 10 - 40 keV). Harmonically spaced quasi-periodic oscillations (QPOs) are observed in the power spectra. The phase lags between the hard photons and the soft photons have a flat distribution over a wide range of frequencies. A high coherence of about 1.0 (0.01 - 1 Hz) between the hard photons and the soft photons is also obtained in our observations. We compare these results with two variation models. Our millimeter observations did not reveal any conclusive signatures of an interaction between the jet from GRS 1758-258 and the molecular cloud that lies in the direction of GRS 1758-258.Comment: 32 pages, 13 figures, to appear in ApJ, 2000, V.533, no. 1, Apr. 10. For better figure resolution, please directly download the paper from http://spacsun.rice.edu/~lin/publication.htm

Compositional Inversion Symmetry Breaking in Ferroelectric Perovskites

Ternary cubic perovskite compounds of the form A_(1/3)A'_(1/3)A''_(1/3)BO_3 and AB_(1/3)B'_(1/3)B''_(1/3)O_3, in which the differentiated cations form an alternating series of monolayers, are studied using first-principles methods. Such compounds are representative of a possible new class of materials in which ferroelectricity is perturbed by compositional breaking of inversion symmetry. For isovalent substitution on either sublattice, the ferroelectric double-well potential is found to persist, but becomes sufficiently asymmetric that minority domains may no longer survive. The strength of the symmetry breaking is enormously stronger for heterovalent substitution, so that the double-well behavior is completely destroyed. Possible means of tuning between these behaviors may allow for the optimization of resulting materials properties.Comment: 4 pages, two-column style with 3 postscript figures embedded. Uses REVTEX and epsf macros. Also available at http://www.physics.rutgers.edu/~dhv/preprints/index.html#sai_is

Evidence of an asymmetrical Keplerian disk in the Br{\gamma} and He I emission lines around the Be star HD 110432

Context. HD 110432 was classified as a "\gamma Cas X-ray analog" since it has similar peculiar X-ray and optical characteristics, i.e. a hard-thermal X-ray variable emission and an optical spectrum affected by an extensive disk. Lopes de Oliveira et al. (2007) suggest that it might be a Be star harboring an accreting white dwarf or that the X-rays may come from an interaction between the surface of the star and its disk. Aims. To investigate the disk around this Be star we used the VLTI/AMBER instrument, which combines high spectral (R=12000) and high spatial (\theta min =4 mas) resolutions. Methods. We constrain the geometry and kinematics of its circumstellar disk from the highest spatial resolution ever achieved on this star. Results. We obtain a disk extension in the Br{\gamma} line of 10.2 D\ast and 7.8 D\ast in the He I line at 2.05 \mu m assuming a Gaussian disk model. The disk is clearly following a Keplerian rotation. We obtained an inclination angle of 55\degree, and the star is a nearly critical rotator with Vrot /Vc =1.00$\pm$0.2. This inclination is greater than the value found for \gamma Cas (about 42\degree, Stee et al. 2012), and is consistent with the inference from optical Fe II emission profiles by Smith & Balona (2006) that the inclination should be more than the \gamma Cas value. In the near-IR continuum, the disk of HD 110432 is 3 times larger than \gamma Cas's disk. We have no direct evidence of a companion around HD 110432, but it seems that we have a clear signature for disk inhomogeneities as detected for {\zeta} Tau. This asymmetrical disk detection may be interpreted within the one-armed oscillation viscous disk framework. Another finding is that the disk size in the near-IR is similar to other Be stars with different spectral types and thus may be independent of the stellar parameters, as found for classical Be stars.Comment: 9 page

Electron localization : band-by-band decomposition, and application to oxides

Using a plane wave pseudopotential approach to density functional theory we investigate the electron localization length in various oxides. For this purpose, we first set up a theory of the band-by-band decomposition of this quantity, more complex than the decomposition of the spontaneous polarization (a related concept), because of the interband coupling. We show its interpretation in terms of Wannier functions and clarify the effect of the pseudopotential approximation. We treat the case of different oxides: BaO, $\alpha$-PbO, BaTiO$_3$ and PbTiO$_3$. We also investigate the variation of the localization tensor during the ferroelectric phase transitions of BaTiO$_3$ as well as its relationship with the Born effective charges

Respondents' ratings of expressions from response scales: a two-country, two-language investigation on equivalence and translation

"The paper presents German-American research on expressions from response scales used in cross-national and cross-lingual survey research. Respondents in the United States and Germany were asked to rate expression for the degrees of intensity they were held to express. The scales used were scales of agreement, importance and for/against. The findings of the study raise as many questions as they answer. Translation-based pairings of expressions across English and German work well but not perfectly. Symmetrical response scales often lead to artificial-sounding 'scalespeak' constructions: their effect on scale responses is unknown. Well-matched translation pairings were sometimes differently scored across the populations. Germans and Americans differed in the range of scale points they employed and in the range of vocabulary used to 'explain' expressions. The study is seen as a first step towards understanding cross-national response scale issues." (author's abstract

Anisotropic mass ejection in binary mergers

We investigate the mass loss from a rotationally distorted envelope following the early, rapid in-spiral of a companion star inside a common envelope. For initially wide, massive binaries (M_1+M_2=20M_{\odot}, P\sim 10 yr), the primary has a convective envelope at the onset of mass transfer and is able to store much of the available orbital angular momentum in its expanded envelope. Three-dimensional smoothed particle hydrodynamics calculations show that mass loss is enhanced at mid-latitudes due to shock reflection from a torus-shaped outer envelope. Mass ejection in the equatorial plane is completely suppressed if the shock wave is too weak to penetrate the outer envelope in the equatorial direction (typically when the energy deposited in the star is less than about one-third of the binding energy of the envelope). We present a parameter study to show how the geometry of the ejecta depends on the angular momentum and the energy deposited in the envelope during a merging event. Applications to the nearly axisymmetric, but very non-spherical nebulae around SN1987A and Sheridan 25 are discussed, as well as possible links to RY Scuti and the Small Magellanic Cloud object R4.Comment: 10 pages, 11 figures, accepted for publication in MNRAS. Figs 1, 2 and 10 reduced in siz