The key physical parameters governing frictional dissipation in a precipitating atmosphere

Precipitation generates small-scale turbulent air flows the energy of which ultimately dissipates to heat. The power of this process has previously been estimated to be around 2-4 W m-2 in the tropics: a value comparable in magnitude to the dynamic power of the global circulation. Here we suggest that this previous power estimate is approximately double the true figure. Our result reflects a revised evaluation of the mean precipitation path length Hp. We investigate the dependence of Hp on surface temperature,relative humidity,temperature lapse rate and degree of condensation in the ascending air. We find that the degree of condensation,defined as the relative change of the saturated water vapor mixing ratio in the region of condensation, is a major factor determining Hp. We estimate from theory that the mean large-scale rate of frictional dissipation associated with total precipitation in the tropics lies between 1 and 2 W m-2 and show that our estimate is supported by empirical evidence. We show that under terrestrial conditions frictional dissipation constitutes a minor fraction of the dynamic power of condensation-induced atmospheric circulation,which is estimated to be at least 2.5 times larger. However,because Hp increases with surface temperature Ts, the rate of frictional dissipation would exceed that of condensation-induced dynamics, and thus block major circulation, at Ts >~320 K in a moist adiabatic atmosphere.Comment: 12 pp, 2 figure

Genetic analysis of a major international collection of cultivated apple varieties reveals previously unknown historic heteroploid and inbred relationships

Domesticated apple (Malus x domestica Borkh.) is a major global crop and the genetic diversity held within the pool of cultivated varieties is important for the development of future cultivars. The aim of this study was to investigate the diversity held within the domesticated form, through the analysis of a major international germplasm collection of cultivated varieties, the UK National Fruit Collection, consisting of over 2,000 selections of named cultivars and seedling varieties. We utilised Diversity Array Technology (DArT) markers to assess the genetic diversity within the collection. Clustering attempts, using the software STRUCTURE revealed that the accessions formed a complex and historically admixed group for which clear clustering was challenging. Comparison of accessions using the Jaccard similarity coefficient allowed us to identify clonal and duplicate material as well as revealing pairs and groups that appeared more closely related than a standard parent-offspring or full-sibling relations. From further investigation, we were able to propose a number of new pedigrees, which revealed that some historically important cultivars were more closely related than previously documented and that some of them were partially inbred. We were also able to elucidate a number of parent-offspring relationships that had resulted in a number of important polyploid cultivars. This included reuniting polyploid cultivars that in some cases dated as far back as the 18th century, with diploid parents that potentially date back as far as the 13th century

Molecular systematics of the marine Dothideomycetes

Phylogenetic analyses of four nuclear genes, namely the large and small subunits of the nuclear ribosomal RNA, transcription elongation factor 1-alpha and the second largest RNA polymerase II subunit, established that the ecological group of marine bitunicate ascomycetes has representatives in the orders Capnodiales, Hysteriales, Jahnulales, Mytilinidiales, Patellariales and Pleosporales. Most of the fungi sequenced were intertidal mangrove taxa and belong to members of 12 families in the Pleosporales: Aigialaceae, Didymellaceae, Leptosphaeriaceae, Lenthitheciaceae, Lophiostomataceae, Massarinaceae, Montagnulaceae, Morosphaeriaceae, Phaeosphaeriaceae, Pleosporaceae, Testudinaceae and Trematosphaeriaceae. Two new families are described: Aigialaceae and Morosphaeriaceae, and three new genera proposed: Halomassarina, Morosphaeria and Rimora. Few marine species are reported from the Dothideomycetidae (e.g. Mycosphaerellaceae, Capnodiales), a group poorly studied at the molecular level. New marine lineages include the Testudinaceae and Manglicola guatemalensis in the Jahnulales. Significantly, most marine Dothideomycetes are intertidal tropical species with only a few from temperate regions on salt marsh plants (Spartina species and Juncus roemerianus), and rarely totally submerged (e.g. Halotthia posidoniae and Pontoporeia biturbinata on the seagrasses Posidonia oceanica and Cymodocea nodosum). Specific attention is given to the adaptation of the Dothideomycetes to the marine milieu, new lineages of marine fungi and their host specificity

Biological Notes On Drosophila Guttifera (Diptera, Drosophilidae), A Consumer Of Mushrooms

Volume: 101Start Page: 161End Page: 16

Acalyptrate Diptera Reared From Higher Fungi In Northeastern Ohio

Volume: 101Start Page: 117End Page: 12

Microstructure development and properties of novel Ba-doped phase Sialon ceramics

Herein, we report the microstructure and properties of the newly developed near monophasic S-Sialon ceramic, based on the composition of Ba2Si12-xAlxO2+xN16-x (x=20.2). Appropriate amount of the precursor powders (BaCO3, alpha-Si3N4, AlN, Al2O3) with a targeted composition of BaAlSi5O2N7 was ball milled and hot pressed to full density in the temperature range of 1600-1750 degrees C for 2 In in nitrogen atmosphere. Extensive transmission electron microscopy (TEM) study has been conducted to understand the microstructure development and characterise the various morphological features in hot pressed S-Sialon. The sintering mechanism is based on the liquid phase sintering route, which involves the formation of a Ba-Al silicate liquid (< 5%) with dissolved nitrogen at intergranular pockets. The experimental observation suggests that the S-phase crystallises in elongated platelet morphology with preferred growth parallel to the orthorhombic V axis and primary facet planes parallel to (100) and (010). The Ba-S-phase ceramic has an acoustically measured Young modulus of 210-230 GPa, a hardness of 13 GPa and a fracture toughness of 4 MPa m(1/2), little lower than typical of a ceramic with morphologically anisotropic grains contributing to bridging and pullout mechanisms. (c) 2006 Elsevier Ltd. All rights reserved