Horizontal Orientation (horizontal + orientation)

Distribution by Scientific Domains


Selected Abstracts


A novel, multi-layered methanotrophic microbial mat system growing on the sediment of the Black Sea

ENVIRONMENTAL MICROBIOLOGY, Issue 8 2008
Martin Krüger
Summary A novel microbially diverse type of 1- to 5-cm-thick mat performing anaerobic oxidation of methane (AOM) and covering several square metres of the seafloor was discovered in the Black Sea at 180 m water depth. Contrary to other AOM-mat systems of the Black Sea these floating mats are not associated to free gas and are not stabilized by authigenic carbonates. However, supply of methane is ensured by the horizontal orientation of the mats acting as a cover of methane enriched fluids ascending from the underlying sediments. Thorough investigation of their community composition by molecular microbiology and lipid biomarkers, metabolic activities and elemental composition showed that the mats provide a clearly structured system with extracellular polymeric substances (EPS) building the framework of the mats. The top black zone, showing high rates of AOM (15 ,mol gdw,1 day,1), was dominated by ANME-2, while the following equally active pink layer was dominated by ANME-1 Archaea. The lowest AOM activity (2 ,mol gdw,1 day,1) and cell numbers were found in the greyish middle part delimited towards the sediment by a second pink, ANME-1-dominated and sometimes a black outer layer (ANME-2). Our work clearly shows that the different microbial populations are established along defined chemical gradients such as methane, sulfate or sulfide. [source]


Canopy structure in savannas along a moisture gradient on Kalahari sands

GLOBAL CHANGE BIOLOGY, Issue 3 2004
Robert J. Scholes
Abstract Measurements of tree canopy architecture were made at six savanna sites on deep, sandy soils, along a gradient of increasing aridity. There was substantial variation in the leaf area estimated within each site, using the same sample frame, but different measurement techniques. The trends in canopy properties in relation to the aridity gradient were consistent, regardless of the technique used for estimating the properties. The effective plant area index for the tree canopy (the sum of the stem area index and the leaf area index (LAI)) declined from around 2 to around 0.8 m2 m,2 over a gradient of mean annual rainfall from 1000 to 350 mm. Stems contributed 2,5% of the tree canopy plant area index. Since the tree canopy cover decreased from 50% to 20% over this aridity range, the leaf area index within the area covered by tree canopies remained fairly constant at 3,4 m2 m,2. Tree leaves tended from a horizontal orientation to a more random orientation as the aridity increased. On the same gradient, the leaf minor axis dimension decreased from around 30 mm to around 3 mm, and the mean specific leaf area decreased from 14 to 5 m2 kgha,1. There was good agreement between LAI observed in the field using a line ceptometer and the LAI inferred by the MODIS sensor on the Terra satellite platform, 2 months later in the same season. [source]


Planarized Star-Shaped Oligothiophenes as a New Class of Organic Semiconductors for Heterojunction Solar Cells,

ADVANCED MATERIALS, Issue 22 2003
R. de Bettignies
Although compounds 1 and 2 (see Figure) have comparable conjugation lengths, the characterization of vacuum evaporated thin solid films shows that the star-shaped geometry of compound 1 favors a preferential horizontal orientation of the molecules onto the surface of the substrate, which results in a increase of the efficiency of the corresponding heterojunction solar cells under white-light illumination by a factor of 20. [source]


Discriminate characteristics of photopsia in posterior vitreous detachment, retinal tears and retinal detachment

OPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 1 2010
Jonathan F. B. Goodfellow
Abstract Aims:, To characterize photopsia in posterior vitreous detachment (PVD), retinal tears (RT) and rhegmatogenous retinal detachment (RRD). Methods: Seventy seven patients presenting to an eye emergency department and vitreoretinal clinic with photopsia had documentation of their symptoms. Results:, A total of 27 patients had PVD alone, 7 had RTs and 25 RRD. In patients with isolated PVD, photopsia were temporal (94%), lasting seconds (81%) and vertically orientated (59%) flashes. Patients with photopsia located in quadrants other than temporal were more likely to have RRD (p = 0.0003). Patients with an oblique or horizontal orientation of their photopsia were likely to have RRD or RT (p = 0.001, specificity 96%, sensitivity 40%). Conclusions:, Most patients with PVD have a typical presentation of photopsia, with temporal, vertically orientated, momentary flashes. Patients with RTs or RRD may describe subtle differences in their photopsia which may raise the index of suspicion for the presence of a complication from PVD. [source]