Marine Fungi of Iceland: A Preliminary Account of Ascomycetes

This paper reports, for the first time, 25 species of marine pyrenomycetes from Icelandic waters. Taxonomic notes are included for certain species. Surtsey, a submarine volcanic upthrust off the south coast of Iceland (Thorarinsson, 1967), is a current center for cooperative geophysical, geochemical, and biological investigations on an international scale. The mycological portion of the total biological research effort of the Surtsey project has emphasized a survey of the marine and freshwater mycoflora on the mainland of Iceland itself as a necessary prerequisite to ecological studies on Surtsey. With the exception of two reports on aquatic phycomycetes (Larsen, 1931, and Johnson, 1966), the aquatic mycoflora of Iceland is unknown. Thus Iceland, rather than Surtsey, has become the immediate focal point for mycological investigations

Two New Species of Leafblight Fungi on Kalmia Latifolia

The evergreen shrub, Kalmia latifolia L., commonly known as mountain laurel, calico bush, or sheep-kill, grows widely on rocky, acid soils in the eastern United States. Whether growing in its natural habit or in cultivation, mountain laurel appears to be equally subject to attack by fungi. The following account characterizes and discusses two of these fungi. One of them has not been described previously and additional observations have been made regarding the developmental morphology of the other one. Both pathogens are Pyrenomycetes, one a Physalospora and the other a Diaporthe. Each produces a leafblight disease. Tiny brown discolorations on young leaves characterize the early stages of attack by both organisms. These small lesions gradually enlarge and become irregular brown spots that may encompass the major portion of the leaf surface. The invaded tissues are darkest near the margins of the lesions, but a reddish zone lies between the darker border and the surrounding green tissues. Severely attacked leaves are deformed and shed prematurely. The reproductive structures of the Physalospora occur on the lower surface and begin to develop before the leaves are shed. The pycnidial stromata of the Diaporthe elevate the epidermis and caticle, and consequently produce grayish spots on the leaf surface. Both fungi continue to develop after the leaves have fallen, and since the mycelia extend beyond the margins of the lesions, perithecia ultimately may occupy most of the leaf surface. [excerpt

A New Marine Ascomycete from Australia

Most marine pyrenomycetes are lignicolous, but some are epiphytic on marine phanerogims and algae. Meyers (1957) listed 30 species of algae known to be attacked by these fungi. A number of reports dealing with marine ascomycetes on algal hosts appeared before 1900, the most noteworthy being those of Winter (1887), and Jones (1898). Cotton (1908) described a pyrenomycete on Ascophyllum nodosum (L.) Le Jol. and summarized previous reports of ascomycetes found on algae. Reed (1902) collected two species, and Sutherland, in a series of papers (1914-1916), reported several alga-infesting pyrenomycetes. More recently, a number of ascomycetes occurring on algae have been noted (Feldmann, 1957, 1958; Cribb & Herbert, 1954; Cribb & Cribb, 1955, 1960a, b; Wilson & Knoyle, 1961; Kohlmeyer, 1963). This report describes a heretofore unreported pyrenomycete collected from the marine alga, Ballia callitricha Ag. The material was obtained from Warrnambool, Victoria, in waters off southern Australia

XMM-Newton Observations of Evolution of Cluster X-Ray Scaling Relations at z=0.4-0.7

We present a spatially-resolved analysis of the temperature and gas density profiles of galaxy clusters at z=0.4-0.7 observed with XMM-Newton. These data are used to derive the total cluster mass within the radius r_500 without assuming isothermality, and also to measure the average temperature and total X-ray luminosity excluding the cooling cores. We derive the high-redshift M-T and L-T relations and compare them with the local measurements. The high-redshift L-T relation has low scatter and evolves as L ~ (1+z)^{1.8\pm0.3} for a fixed T, in good agreement with several previous Chandra and XMM-Newton studies (Vikhlinin et al., Lumb et al., Maughan et al.). The observed evolution of the M-T relation follows M_500 = A T^{3/2} E(z)^{-alpha}, where we measure alpha=0.88\pm0.23. This is in good agreement with predictions of the self-similar theory, alpha=1.Comment: ApJ in press, updated to match the accepted versio

Shot noise in charge and magnetization currents of a quantum ring

The shot noise in a quantum ring, connected to leads, is studied in the presence of electron interactions in the sequential tunneling regime. Two qualitatively different noise correlations with distinctly different behaviors are identified and studied in a large range of parameters. Noise in the total current is due to the discreteness of the electron charge and can become super-Poissonian as result of electron interaction. The noise in the magnetization current is comparatively insensitive to the interaction but can be greatly enhanced if population inversion of the angular states is assumed. The characteristic time scales are studied by a Monte-Carlo simulation.Comment: 5 pages, 5 color figure

KCNQ channels regulate age-related memory impairment:KCNQ regulates age-related memory

In humans KCNQ2/3 heteromeric channels form an M-current that acts as a brake on neuronal excitability, with mutations causing a form of epilepsy. The M-current has been shown to be a key regulator of neuronal plasticity underlying associative memory and ethanol response in mammals. Previous work has shown that many of the molecules and plasticity mechanisms underlying changes in alcohol behaviour and addiction are shared with those of memory. We show that the single KCNQ channel in Drosophila (dKCNQ) when mutated show decrements in associative short- and long-term memory, with KCNQ function in the mushroom body α/βneurons being required for short-term memory. Ethanol disrupts memory in wildtype flies, but not in a KCNQ null mutant background suggesting KCNQ maybe a direct target of ethanol, the blockade of which interferes with the plasticity machinery required for memory formation. We show that as in humans, Drosophila display age-related memory impairment with the KCNQ mutant memory defect mimicking the effect of age on memory. Expression of KCNQ normally decreases in aging brains and KCNQ overexpression in the mushroom body neurons of KCNQ mutants restores age-related memory impairment. Therefore KCNQ is a central plasticity molecule that regulates age dependent memory impairment

Seed Mass and Morphology in Outcrossing and Selfing Species of Clarkia (Onagraceae): An SEM Study

Seeds from three pairs of outcrossing-selfing sister taxa from the genus Clarkia (farewell-to-spring, Onagraceae)—Clarkia unguiculata, Clarkia exilis, Clarkia xantiana ssp. xantiana and ssp. parviflora, and Clarkia concinna ssp. concinna and ssp. automixa—were studied to assess the effects of contrasting mating systems on seed mass and seed morphology. For each outcrossing-selfing comparison, the seed mass of the selfing taxon was less than that of the outcrossing taxon. Seed mass typically differed significantly among populations within a taxon. Scanning electron microscopy showed that the seeds from all these taxa share several characteristics: a bullet to shield shape, a reticulate exotesta pattern, presence of crystals in the seed coat, and a seed coat that varies in thickness over the length of the seed. No morphological feature reliably distinguished seeds of outcrossing taxa from those of selfing taxa. The lack of morphological differences in conjunction with the consistent differences in seed mass between selfing and outcrossing seeds in these taxa supports the hypothesis that evolutionary forces have acted only on seed mass and not on seed morphology

Galaxy Cluster Shapes and Systematic Errors in H0 Measured by the Sunyaev-Zel'dovich Effect

Imaging of the Sunyaev-Zel'dovich (SZ) effect in galaxy clusters combined with cluster plasma x-ray diagnostics can measure the cosmic distance scale to high redshift. Projecting the inverse-Compton scattering and x-ray emission along the cluster line-of-sight introduces systematic errors in the Hubble constant, H0, because the true shape of the cluster is not known. I present a study of the systematic errors in the value of H0, as determined by the x-ray and SZ properties of theoretical samples of triaxial isothermal ``beta'' model clusters, caused by projection effects and observer orientation. I calculate estimates for H0 for each cluster based on their large and small apparent angular core radii and their arithmetic mean. I demonstrate that the estimates for H0 for a sample of 25 clusters have 99.7% confidence intervals for the mean estimated H0 analyzing the clusters using either their large or mean angular core radius are within 14% of the ``true'' (assumed) value of H0 (and enclose it), for a triaxial beta model cluster sample possessing a distribution of apparent x-ray cluster ellipticities consistent with that of observed x-ray clusters. This limit on the systematic error in H0 caused by cluster shape assumes that each sample beta model cluster has fixed shape; deviations from constant shape within the clusters may introduce additional uncertainty or bias into this result.Comment: Accepted for publication in the Astrophysical Journal, 24 March 1998; 4 pages, 2 figure

Aquatic Ascomycetes from Lake Itasca, Minnesota

A preliminary report of the aquatic Ascomycetes of Lake Isasca, Minnesota. Included is an introduction, methods of harvesting and studying, a key, description, and illustrations of 19 common ascomycetous fungi inhabiting the study area

X-raying the Star Formation History of the Universe

The current models of early star and galaxy formation are based upon the hierarchical growth of dark matter halos, within which the baryons condense into stars after cooling down from a hot diffuse phase. The latter is replenished by infall of outer gas into the halo potential wells; this includes a fraction previously expelled and preheated, due to momentum and energy fed back by the SNe which follow the star formation. We identify such an implied hot phase with the medium known to radiate powerful X-rays in clusters and in groups of galaxies. We show that the amount of the hot component required by the current star formation models is enough to be observable out to redshifts $z \approx 1.5$ in forthcoming deep surveys from {\it Chandra} and {\it XMM}, especially in case the star formation rate is high at such and earlier $z$. These X-ray emissions constitute a necessary counterpart, and will provide a much wanted probe of the SF process itself (in particular, of the SN feedback), to parallel and complement the currently debated data from optical and IR observations of the young stars.Comment: 13 pages, 2 figures, accepted for publicatin in ApJ