Life History of Elsinoe panici

Elsinoe panici Tiffany and Mathre is widespread on native Panicum virgatum L. in Iowa. In June Sphaceloma (imperfect stage) conidia develop from acervuli on overwintered stromata of wind-dispersed leaf litter and culms. Germ cubes penetrate between epidermal cells of young leaves, and 2 wk later tiny yellowish, subepidermal stromata are visible. Secondary conidia develop from acervuli on these stromata within 2 wk and are spread to adjacent leaves. Stromata become black, raised, shiny, ovoid-elongate patches, composed of thick-walled pseudoparenchymatous cells. Chlorosis or necrosis does not develop around the stromata. Stromata are visible on all leaves throughout the season. Acervuli, appearing as white spots in black stromata, open by irregular tears in the epidermis. Ascostromata develop on lower leaves infrequently from late July into September. They are tan-bronze, raised, ovoid-elongate, softer, and more loosely structured than stromata. Asci mature at different times. Ascospores are discharged from the bitunicate asci and germinate directly by budding or by germ tubes

Can a Lamb Reach a Haven Before Being Eaten by Diffusing Lions?

We study the survival of a single diffusing lamb on the positive half line in the presence of N diffusing lions that all start at the same position L to the right of the lamb and a haven at x=0. If the lamb reaches this haven before meeting any lion, the lamb survives. We investigate the survival probability of the lamb, S_N(x,L), as a function of N and the respective initial positions of the lamb and the lions, x and L. We determine S_N(x,L) analytically for the special cases of N=1 and N--->oo. For large but finite N, we determine the unusual asymptotic form whose leading behavior is S_N(z)\simN^{-z^2}, with z=x/L. Simulations of the capture process very slowly converge to this asymptotic prediction as N reaches 10^{500}.Comment: 13 pages, 6 figures, IOP format; v2: small changes in response to referee and editor comment

Distribution and Persistence of Phyllachora Species on Poaceae in Iowa

Phytlachora spp. on Poaceae were collected to determine species present, grass hosts and distribution in Iowa. From 1959-1996 the fungus was collected 240 times from 67 different sites in 35 counties. Seven species of Phytlachora were collected on 25 species from 13 genera of grasses. P. graminis was collected 89 times from 43 sites on four species of Agropyron, two species of Calamagrostis, three species of Elymus, Hystrix patula, Panicum virgatum, and Setaria glauca. Seventy-two specimens of P. luteo-maculata on Andropogon gerardii or Schiziichyrium scoparium were collected from 30 sites. The study included 20 collections of P. cynodontis on Bouteloua curtipendula from 12 sites. P. vulgata was represented by 43 collections from 21 sites on Muhlenbergia species, and P. paspalicola was collected on Paspalum spp. 13 times from five sites. P. punctum was collected once on Dicanthelium oligosanthes var. scribnerianum, and once on Panicum capillare. The study included only one collection of P. phalaridis on Phalaris arundinacea. P. paspalicola and P. phalaridis are new records for the state

Student Perceptions of Learner-Centered Teaching

The learner-centered paradigm departs from traditional teaching models by focusing on students more than teachers and learning more than teaching. Thus, classes are more egalitarian; they emphasize critical thinking, active learning, and real-world assignments. Graduate students in learner-centered classrooms were surveyed about perceptions of their experiences in relation to the key dimensions of the learner-centered paradigm and noted that the approach contributed to their feeling respected as learners, developed their critical thinking skills, and encouraged their self-directedness. Based on these findings, post-secondary instructors are encouraged to experiment with learning-centered approaches to further explore this promising model

Microscopic origin of the mobility enhancement at a spinel/perovskite oxide heterointerface revealed by photoemission spectroscopy

The spinel/perovskite heterointerface $\gamma$-Al$_2$O$_3$/SrTiO$_3$ hosts a two-dimensional electron system (2DES) with electron mobilities exceeding those in its all-perovskite counterpart LaAlO$_3$/SrTiO$_3$ by more than an order of magnitude despite the abundance of oxygen vacancies which act as electron donors as well as scattering sites. By means of resonant soft x-ray photoemission spectroscopy and \textit{ab initio} calculations we reveal the presence of a sharply localized type of oxygen vacancies at the very interface due to the local breaking of the perovskite symmetry. We explain the extraordinarily high mobilities by reduced scattering resulting from the preferential formation of interfacial oxygen vacancies and spatial separation of the resulting 2DES in deeper SrTiO$_3$ layers. Our findings comply with transport studies and pave the way towards defect engineering at interfaces of oxides with different crystal structures.Comment: Accepted as Rapid Communications in Physical Review

Functional and Morphological Studies of Mitochondria Exposed to Undecagold Clusters: Biologic Surfaces Labeling with Gold Clusters

This study reports morphological and functional alterations observed in respiring isolated mitochondria when they are exposed to nonpenetrating, positive electrostatically charged synthetic undecagold clusters. Modification of the undecagold clusters positive charges change or prevent the functional effects and the binding to the outside surface of the mitochondria. The mitochondrial functional alterations are dependent on the oxidative phosphorylation capacity of the isolated organelles. The results of these experiments indicate that artificial undecagold may be useful to explore the molecular mechanisms of biological energy transducers which require electric charges separation, ionic fluxes, and electric surface properties

Fungi of the Iowa Loess Hills

From 1981 through 1983 biological surveys of the Loess Hills were sponsored by the Iowa State Preserves Advisory Board. Twenty-four sites in 7 counties were visited during the first week in June during these years. Collections were made of all macrofungi producing identifiable fruiting structures or represented by recognizable weathered fruiting structures developed the previous fall. Plane parasitic fungi and corticolous lichens were also recorded. Fungi of the Loess Hills of Iowa had been previously documented primarily by Gilman\u27s and Gilman and Archer\u27s reports of plant parasitic fungi. This report includes 3 species of Oomycetes, 18 species of Myxomycetes, 67 species of Ascomycetes, 75 species of Basidiomycetes, 27 species of Fungi Imperfecti (Deuteromycetes) and 15 species of corticolous lichens

High-Resolution Ultraviolet Spectra of the Dwarf Seyfert 1 Galaxy NGC 4395: Evidence for Intrinsic Absorption

We present ultraviolet spectra of the dwarf Seyfert 1 nucleus of NGC 4395, obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Hubble Space Telescope's Space Telescope Imaging Spectrograph at velocity resolutions of 7 to 15 km/sec. We confirm our earlier claim of C IV absorption in low-resolution UV spectra and detect a number of other absorption lines with lower ionization potentials. In addition to the Galactic lines, we identify two kinematic components of absorption that are likely to be intrinsic to NGC 4395. We consider possible origins of the absorption, including the interstellar medium (ISM) of NGC 4395, the narrow-line region (NLR), outflowing UV absorbers, and X-ray ``warm absorbers.'' Component 1, at a radial velocity of -770 km/sec with respect to the nucleus, is only identified in the C IV 1548.2 line. It most likely represents an outflowing UV absorber, similar to those seen in a majority of Seyfert 1 galaxies, although additional observations are needed to confirm the reality of this feature. Component 2, at -114 km/sec, most likely arises in the ISM of NGC 4395; its ionic column densities cannot be matched by photoionization models with a power-law continuum. Our models of the highly ionized X-ray absorbers claimed for this active galactic nucleus indicate that they would have undetectable C IV absorption, but large O VI and H I columns should be present. We attribute our lack of detection of the O VI and Ly-beta absorption from the X-ray absorbers to a combination of noise and dilution of the nuclear spectrum by hot stars in the large FUSE aperture.Comment: 22 pages, 3 figures (2 in color), accepted for Ap

Laser treatment in diabetic retinopathy

Diabetic retinopathy is a leading cause of visual impairment and blindness in developed countries due to macular edema and proliferative diabetic retinopathy (PDR). For both complications laser treatment may offer proven therapy: the Diabetic Retinopathy Study demonstrated that panretinal scatter photocoagulation reduces the risk of severe visual loss by >= 50% in eyes with high-risk characteristics. Pan-retinal scatter coagulation may also be beneficial in other PDR and severe nonproliferative diabetic retinopathy (NPDR) under certain conditions. For clinically significant macular edema the Early Treatment of Diabetic Retinopathy Study could show that immediate focal laser photocoagulation reduces the risk of moderate visual loss by at least 50%. When and how to perform laser treatment is described in detail, offering a proven treatment for many problems associated with diabetic retinopathy based on a high evidence level. Copyright (c) 2007 S. Karger AG, Basel