Ultrastructural observations on a marine lignicolous ascomycete: Bovicornua intricata gen. et sp.nov.

1993 ◽  
Vol 71 (2) ◽  
pp. 346-352 ◽  
Author(s):  
M. Yusoff ◽  
J. Koch ◽  
E. B. Gareth Jones ◽  
S. T. Moss
Keyword(s):  
Key Words ◽  
Outer Region ◽  
Spore Wall ◽  
Wall Layer ◽  
Fibrillar Material ◽  
South Wales ◽  
Inner Region

Bovicornua intricata sp.nov. is described from driftwood found at Marloes, South Wales, U.K. and Stenbjerg, Jutland, Denmark and compared with species of Ceriosporopsis Linder. Bovicornua intricata is separated from Ceriosporopsis species by the greater complexity of the structure of the appendaged ascospores. In ascospores of B. intricata, the exosporic wall layer enrobes both the spore wall and the polar appendages which arise as outgrowths of the spore. The exosporium is bipartite, the inner region has regular, parallel electron-dense lamellations that radiate from the episporium. The outer region of the exosporium consists of electron-dense fibrillar material at which the lamellae terminate. Key words: ascospore, marine ascomycete, spore appendage, taxonomy, ultrastructure.

Mycoparasitism of teliospores of Ustilago bullata by an oomycete

1990 ◽  
Vol 68 (11) ◽  
pp. 2415-2421 ◽  
Author(s):  
Robert W. Roberson ◽  
E. S. Luttrell ◽  
Melvin S. Fuller
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Key Words ◽  
Enzymatic Degradation ◽  
Spore Wall ◽  
Wall Layer ◽  
Smut Fungus ◽  
Pythium Vexans ◽  
Transmission Electron ◽  
Host Parasite

The mycoparasitism of teliospores of the smut fungus Ustilago bullata was discovered by transmission electron microscopy (TEM). Large, multinucleate chlamydospores germinated, producing hyphae that directly penetrated the walls of mature teliospores after forming an appressorium-like structure. Invagination of the exosporium at the point of penetration suggested mechanical penetration of this outer spore wall layer. The inner endosporium layer was fibrillar in appearance, with irregular electron-transparent regions suggesting enzymatic degradation. The cytoplasm and endosporium of parasitized teliospores were completely disintegrated, leaving only the spiny exosporium layer distributed throughout the sorus. Hyphae of the mycoparasite emerged from the teliospore shell, and their tips penetrated surrounding teliospores. TEM characteristics of the parasite confirmed oomycetous affinities. Pythium vexans was isolated from smutted tissue collected at the same time as tissue used for TEM observations. Pythium vexans was able to parasitize U. bullata teliospores in culture. Key words: hyperparasitism, ultrastructure, smut, Pythium, host–parasite relationships, infection.

Spore wall ontogeny in Pseudoplectania nigrella and Plectania nannfeldtii (Ascomycotina, Pezizales)

1995 ◽  
Vol 73 (11) ◽  
pp. 1761-1767 ◽  
Author(s):  
Li-Tzu Li ◽  
James W. Kimbrough
Keyword(s):  
Key Words ◽  
Light Microscope ◽  
Secondary Wall ◽  
Spore Wall ◽  
Wall Layer ◽  
Ultrastructural Studies ◽  
Blue Stain ◽  
Spore Wall Ornamentation

Pseudoplectania and Plectania currently belong to the Sarcosomataceae, tribe Sarcosomateae, a group with members lacking cyanophilic spore markings (absorbing a blue stain). The two genera are morphologically similar in having blackish discoid-shaped apothecia but differ in having globose and ellipsoid spores, respectively. Ultrastructural studies show that ascospores of Pseudoplectania nigrella (Pers. ex Fr.) Fuckel lack a secondary wall layer. On the contrary, Plectania nannfeldtii Korf has secondary spore wall ornamentation that is cyanophilic under a light microscope. The data suggest retention of Pseudoplectania nigrella in the Sarcosomateae; however, the position of certain species of Plectania needs to be reevaluated. Key words: Pezizales, Plectania, Pseudoplectania, Sarcosomataceae, spore ontogeny, ultrastructure.

Measurement and Analysis of Buoyancy-Induced Heat Transfer in Aero-Engine Compressor Rotors

2020 ◽  
Author(s):  
Richard W. Jackson ◽  
Dario Luberti ◽  
Hui Tang ◽  
Oliver J. Pountney ◽  
James A. Scobie ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Outer Region ◽  
Conjugate Problem ◽  
Radial Temperature ◽  
Nusselt Numbers ◽  
Induced Flow ◽  
Aero Engines ◽  
Inner Region ◽  
Buoyancy Induced Flow

Abstract The flow inside cavities between co-rotating compressor discs of aero-engines is driven by buoyancy, with Grashof numbers exceeding 1013. This phenomenon creates a conjugate problem: the Nusselt numbers depend on the radial temperature distribution of the discs, and the disc temperatures depend on the Nusselt numbers. Furthermore, Coriolis forces in the rotating fluid generate cyclonic and anti-cyclonic circulations inside the cavity. Such flows are three-dimensional, unsteady and unstable, and it is a challenge to compute and measure the heat transfer from the discs to the axial throughflow in the compressor. In this paper, Nusselt numbers are experimentally determined from measurements of steady-state temperatures on the surfaces of both discs in a rotating cavity of the Bath Compressor-Cavity Rig. The data are collected over a range of engine-representative parameters and are the first results from a new experimental facility specifically designed to investigate buoyancy-induced flow. The radial distributions of disc temperature were collected under carefully-controlled thermal boundary conditions appropriate for analysis using a Bayesian model combined with the equations for a circular fin. The Owen-Tang buoyancy model has been used to compare predicted radial distributions of disc temperatures and Nusselt numbers with some of the experimentally determined values, taking account of radiation between the interior surfaces of the cavity. The experiments show that the average Nusselt numbers on the disc increase as the buoyancy forces increase. At high rotational speeds the temperature rise in the core, created by compressibility effects in the air, attenuates the heat transfer and there is a critical rotational Reynolds number for which the Nusselt number is a maximum. In the cavity, there is an inner region dominated by forced convection and an outer region dominated by buoyancy-induced flow. The inner region is a mixing region, in which entrained cold throughflow encounters hot flow from the Ekman layers on the discs. Consequently, the Nusselt numbers on the downstream disc in the inner region tend to be higher than those on the upstream disc.

Small Péclet-number mass transport to a finite strip: An advection–diffusion–reaction model of surface-based biosensors

2019 ◽  
Vol 31 (5) ◽  
pp. 763-781
Author(s):  
EHUD YARIV
Keyword(s):  
Shear Flow ◽  
Mass Transport ◽  
Sherwood Number ◽  
Peclet Number ◽  
Outer Region ◽  
Diffusion Reaction ◽  
Background Concentration ◽  
Leading Order ◽  
Péclet Number ◽  
Inner Region

AbstractWe consider two-dimensional mass transport to a finite absorbing strip in a uniform shear flow as a model of surface-based biosensors. The quantity of interest is the Sherwood number Sh, namely the dimensionless net flux onto the strip. Considering early-time absorption, it is a function of the Péclet number Pe and the Damköhler number Da, which, respectively, represent the characteristic magnitude of advection and reaction relative to diffusion. With a view towards modelling nanoscale biosensors, we consider the limit Pe«1. This singular limit is handled using matched asymptotic expansions, with an inner region on the scale of the strip, where mass transport is diffusively dominated, and an outer region at distances that scale as Pe-1/2, where advection enters the dominant balance. At the inner region, the mass concentration possesses a point-sink behaviour at large distances, proportional to Sh. A rescaled concentration, normalised using that number, thus possesses a universal logarithmic divergence; its leading-order correction represents a uniform background concentration. At the outer region, where advection by the shear flow enters the leading-order balance, the strip appears as a point singularity. Asymptotic matching with the concentration field in that region provides the Sherwood number as $${\rm{Sh}} = {\pi \over {\ln (2/{\rm{P}}{{\rm{e}}^{1/2}}) + 1.0559 + \beta }},$$ wherein β is the background concentration. The latter is determined by the solution of the canonical problem governing the rescaled inner concentration, and is accordingly a function of Da alone. Using elliptic-cylinder coordinates, we have obtained an exact solution of the canonical problem, valid for arbitrary values of Da. It is supplemented by approximate solutions for both small and large Da values, representing the respective limits of reaction- and transport-limited conditions.

scholarly journals Photophoresis in the circumjovian disk and its impact on the orbital configuration of the Galilean satellites

2019 ◽  
Vol 629 ◽  
pp. A106 ◽  
Author(s):  
Sota Arakawa ◽  
Yuhito Shibaike
Keyword(s):  
Density Distribution ◽  
Accretion Disks ◽  
Surface Density ◽  
Outer Region ◽  
Dust Particles ◽  
Magnetorotational Instability ◽  
Galilean Satellites ◽  
Ionization Fraction ◽  
Orbital Configuration ◽  
Inner Region

Jupiter has four large regular satellites called the Galilean satellites: Io, Europa, Ganymede, and Callisto. The inner three of the Galilean satellites orbit in a 4:2:1 mean motion resonance; therefore their orbital configuration may originate from the stopping of the migration of Io near the bump in the surface density distribution and following resonant trapping of Europa and Ganymede. The formation mechanism of the bump near the orbit of the innermost satellite, Io, is not yet understood, however. Here, we show that photophoresis in the circumjovian disk could be the cause of the bump using analytic calculations of steady-state accretion disks. We propose that photophoresis in the circumjovian disk could stop the inward migration of dust particles near the orbit of Io. The resulting dust-depleted inner region would have a higher ionization fraction, and thus admit increased magnetorotational-instability-driven accretion stress in comparison to the outer region. The increase of the accretion stress at the photophoretic dust barrier would form a bump in the surface density distribution, halting the migration of Io.

scholarly journals Bacteria Associated with Spores of the Arbuscular Mycorrhizal Fungi Glomus geosporum and Glomus constrictum

2005 ◽  
Vol 71 (11) ◽  
pp. 6673-6679 ◽  
Author(s):  
David Roesti ◽  
Kurt Ineichen ◽  
Olivier Braissant ◽  
Dirk Redecker ◽  
Andres Wiemken ◽  
...  
Keyword(s):  
Arbuscular Mycorrhizal Fungi ◽  
Mycorrhizal Fungi ◽  
Denaturing Gradient Gel Electrophoresis ◽  
Plantago Lanceolata ◽  
Arbuscular Mycorrhizal ◽  
Spore Wall ◽  
Wall Layer ◽  
Single Spore ◽  
Bacterial Populations ◽  
Glomus Geosporum

ABSTRACT Spores of the arbuscular mycorrhizal fungi (AMF) Glomus geosporum and Glomus constrictum were harvested from single-spore-derived pot cultures with either Plantago lanceolata or Hieracium pilosella as host plants. PCR-denaturing gradient gel electrophoresis analysis revealed that the bacterial communities associated with the spores depended more on AMF than host plant identity. The composition of the bacterial populations linked to the spores could be predominantly influenced by a specific spore wall composition or AMF exudate rather than by specific root exudates. The majority of the bacterial sequences that were common to both G. geosporum and G. constrictum spores were affiliated with taxonomic groups known to degrade biopolymers (Cellvibrio, Chondromyces, Flexibacter, Lysobacter, and Pseudomonas). Scanning electron microscopy of G. geosporum spores revealed that these bacteria are possibly feeding on the outer hyaline spore layer. The process of maturation and eventual germination of AMF spores might then benefit from the activity of the surface microorganisms degrading the outer hyaline wall layer.

Investigation on the Radial Heat-Transfer of Pumping Secondary Flow in Semiclosed Rotating Disk Cavity

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Guohu Luo ◽  
Zhenqiang Yao
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Outer Region ◽  
Rotating Disk ◽  
Mean Flow ◽  
Coolant Pump ◽  
Radial Temperature ◽  
Type Flow ◽  
Radial Heat ◽  
Inner Region

Abstract This study investigates the mean flow and radial heat-transfer behaviors in semiclosed rotating disk cavity within the canned reactor coolant pump. The flow in the semiclosed cavity contains the Stewartson type flow at inner region and the Batchelor type flow at outer region. The heat is radially transported from the outer rim of the semiclosed disk cavity to discharge-hole through the nondirect discharge (ND) portion of the superimposed flow from inlet. The effects of rotating Reynolds numbers, cavity aspect ratio and radial location of discharge-hole on the discharge ratio, pumping mass flow rate, local wall shear stress and radial heat-transfer coefficient are examined in the semiclosed rotating cavity flow, respectively. Based on the radial heat transfer behaviors of pumping secondary flow, an equivalent thermal network is proposed and validated by experiments, which can effectively predict the radial temperature distribution from the discharge hole to periphery with the viscous-heating and nonisothermal effects.

scholarly journals 11.16. On the origin of density cusp in galactic nuclei by central black hole

1998 ◽  
Vol 184 ◽  
pp. 487-488
Author(s):  
T. Nakano ◽  
T. Fukushige ◽  
J. Makino
Keyword(s):  
Black Hole ◽  
Hubble Space Telescope ◽  
Outer Region ◽  
Elliptical Galaxies ◽  
Heating Process ◽  
Massive Black Hole ◽  
Weak Density ◽  
The Galaxy ◽  
Galaxy Model ◽  
Inner Region

We investigated the dynamical reaction of the central region of galaxies to a falling massive black hole by N-body simulations. As the initial galaxy model, we used an isothermal King model and placed a massive black hole at around the half-mass radius of the galaxy. We found that the central core of the galaxy is destroyed by the heating due to the black hole and a very weak density cusp (ρ ∝ r−α, with α ∼ 0.5) is formed around the center. This result is consistent with recent observations of large elliptical galaxies by Hubble Space Telescope (Lauer et al. 1995; Byun et al. 1996; Gebhardt et al. 1996; Faber et al. 1996; Kormendy et al. 1996). The radius of the weak cusp region is large for large black hole mass. The velocity of the stars become tangentially anisotropic in the inner region, while in the outer region the stars have radially anisotropic velocity dispersion. Our result naturally explains the mechanism of the formation of the weak cusp found in the previous simulations of galaxy merging, and implies that the weak cusp observed in large elliptical galaxies may be formed by the heating process by sinking black holes during merging events.

scholarly journals Changes in Morphological and Physicochemical Properties of Waxy and Non-waxy Proso Millets during Cooking Process

Foods ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 583 ◽  
Author(s):  
Qinghua Yang ◽  
Long Liu ◽  
Weili Zhang ◽  
Jing Li ◽  
Xiaoli Gao ◽  
...  
Keyword(s):  
Physicochemical Properties ◽  
Cross Sections ◽  
Nutritional Value ◽  
Outer Region ◽  
Pasting Properties ◽  
Cooking Time ◽  
Ordered Structures ◽  
Proso Millet ◽  
Cooking Process ◽  
Inner Region

Proso millet, a grain which is principally consumed in cooked form, is favored by consumers because of its rich nutritional value. However, the changes in morphological and physicochemical properties of proso millet grains occurring during the cooking process have rarely been reported. In this study, we investigated the changes in morphological and physicochemical properties of cooked waxy and non-waxy proso millets. During the cooking process, starch granules in the grains were gradually gelatinized starting from the outer region to the inner region and were gelatinized earlier in waxy proso millet than in non-waxy proso millet. Many filamentous network structures were observed in the cross sections of cooked waxy proso millet. As the cooking time increased, the long- and short-range, ordered structures of proso millets were gradually disrupted, and the ordered structures were fully disrupted by 20 min of cooking. In both waxy and non-waxy proso millets, thermal and pasting properties significantly changed with an increase in the cooking time. This study provides useful information for the processing of proso millet in the food industry.

scholarly journals A new model for dark matter fluid sphere

2020 ◽  
Vol 35 (34) ◽  
pp. 2050280
Author(s):  
Shyam Das ◽  
Nayan Sarkar ◽  
Monimala Mondal ◽  
Farook Rahaman
Keyword(s):  
Dark Matter ◽  
Compact Star ◽  
Outer Region ◽  
Fluid Sphere ◽  
Constant Density ◽  
Spherically Symmetric ◽  
Causality Condition ◽  
New Model ◽  
Inner Region ◽  
Tov Equation

We develop a new model for a spherically symmetric dark matter fluid sphere containing two regions: (i) Isotropic inner region with constant density and (ii) Anisotropic outer region. We solve the system of field equation by assuming a particular density profile along with a linear equation of state. The obtained solutions are well-behaved and physically acceptable which represent equilibrium and stable matter configuration by satisfying the Tolman–Oppenheimer–Volkoff (TOV) equation and causality condition, condition on adiabatic index, Harrison–Zeldovich–Novikov criterion, respectively. We consider the compact star EXO 1785-248 (Mass [Formula: see text] and radius R[Formula: see text]8.8 km) to analyze our solutions by graphical demonstrations.

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