The Ocular Morphology of the Southern Hemisphere Lamprey Mordacia mordax Richardson with Special Reference to a Single Class of Photoreceptor and a Retinal Tapetum

2000 ◽  
Vol 55 (3) ◽  
pp. 120-138 ◽  
Author(s):  
Shaun P. Collin ◽  
Ian C. Pottert
Keyword(s):  
Special Reference ◽  
Southern Hemisphere ◽  
Single Class ◽  
Retinal Tapetum

The genusMycoblastusin the cool temperate Southern Hemisphere, with special reference to Tasmania

2009 ◽  
Vol 41 (2) ◽  
pp. 151-178 ◽  
Author(s):  
Gintaras KANTVILAS
Keyword(s):  
New Zealand ◽  
Special Reference ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
South Eastern ◽  
Eastern Australia ◽  
The Family ◽  
Cool Temperate ◽  
Campbell Island ◽  
South Eastern Australia

AbstractThe genusMycoblastusin cool temperate latitudes of the Southern Hemisphere is reviewed. Eight species are treated in detail:M. bryophilusImshaug ex Kantvilas sp. nov., from Campbell Island and Tasmania;M. campbellianus(Nyl.) Zahlbr.,M. coniophorus(Elix & A.W. Archer) Kantvilas & Elix comb. nov. andM. dissimulans(Nyl.) Zahlbr., all widespread across the austral region;M. disporus(C. Knight) Kantvilas comb. nov., from New Zealand and Tasmania;M. kalioruberKantvilas sp. nov, from Tasmania;M. sanguinarioidesKantvilas sp. nov., from Tasmania and south-eastern Australia; andM. leprarioidesKantvilas & Elix sp. nov., from south-eastern Australia (Victoria). Notes are provided on many other species ofMycoblastus, including those recognised for the Northern Hemisphere, and those originally described from austral regions but now excluded from the genus. Major characters of the genus are discussed, including thallus morphology and chemistry, apothecial pigments and ascus structure. It is suggested that the genus is heterogeneous and that some of its closest affinities may lie with the familyMegalariaceaeand the genusJapewia.

scholarly journals Vision in the southern hemisphere lampreyMordacia mordax: Spatial distribution, spectral absorption characteristics, and optical sensitivity of a single class of retinal photoreceptor

2004 ◽  
Vol 21 (5) ◽  
pp. 765-773 ◽  
Author(s):  
SHAUN P. COLLIN ◽  
NATHAN S. HART ◽  
KATE M. WALLACE ◽  
JULIA SHAND ◽  
IAN C. POTTER
Keyword(s):  
Southern Hemisphere ◽  
Outer Segment ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Morphological Type ◽  
Resolving Power ◽  
Single Class ◽  
Optical Sensitivity ◽  
Retinal Photoreceptor ◽  
Large Width

The dorso-laterally located eyes of the southern hemisphere lampreyMordacia mordax(Agnatha) contain a single morphological type of retinal photoreceptor, which possesses ultrastructural characteristics of both rods and cones. This photoreceptor has a large refractile ellipsosome in the inner segment and a long cylindrical outer segment surrounded by a retinal pigment epithelium that contains two types of tapetal reflectors. The photoreceptors form a hexagonal array and attain their peak density (33,200 receptors/mm2) in the ventro-temporal retina. Using the size and spacing of the photoreceptors and direct measures of aperture size and eye dimensions, the peak spatial resolving power and optical sensitivity are estimated to be 1.7 cycles deg−1(minimum separable angle of 34′7′′) and 0.64 μm2steradian (white light) and 1.38 μm2steradian (preferred wavelength or λmax), respectively. Microspectrophotometry reveals that the visual pigment located within the outer segment is a rhodopsin with a wavelength of maximum absorbance (λmax) at 514 nm. The ellipsosome has very low absorptance (<0.05) across the measured spectrum (350–750 nm) and probably does not act as a spectral filter. In contrast to all other lampreys studied, the optimized receptor packing, the large width of the ellipsosome-bearing inner segment, together with the presence of a retinal tapetum in the photophobicMordacia, all represent adaptations for low light vision and optimizing photon capture.

Southern Hemisphere Seti Survey: Five Years of Project Meta II

1997 ◽  
Vol 161 ◽  
pp. 611-621
Author(s):  
Guillermo A. Lemarchand ◽  
Fernando R. Colomb ◽  
E. Eduardo Hurrell ◽  
Juan Carlos Olalde
Keyword(s):  
Southern Hemisphere ◽  
Scattering Theory ◽  
Galactic Plane ◽  
Narrow Band ◽  
Neutral Hydrogen ◽  
Sky Survey ◽  
Inertial Frames ◽  
Interstellar Scattering ◽  
Extraterrestrial Origin ◽  
Spectral Channels

AbstractProject META II, a full sky survey for artificial narrow-band signals, has been conducted from one of the two 30-m radiotelescopes of the Instituto Argentino de Radioastronomía (IAR). The search was performed near the 1420 Mhz line of neutral hydrogen, using a 8.4 million channels Fourier spectrometer of 0.05 Hz resolution and 400 kHz instantaneous bandwidth. The observing frequency was corrected both for motions with respect to three astronomical inertial frames, and for the effect of Earths rotation, which provides a characteristic changing signature for narrow-band signals of extraterrestrial origin. Among the 2 × 1013spectral channels analyzed, 29 extra-statistical narrow-band events were found, exceeding the average threshold of 1.7 × 10−23Wm−2. The strongest signals that survive culling for terrestrial interference lie in or near the galactic plane. A description of the project META II observing scheme and results is made as well as the possible interpretation of the results using the Cordes-Lazio-Sagan model based in interstellar scattering theory.

Alpha-Effect, Current and Kinetic Helicities for Magnetically Driven Turbulence, and Solar Dynamo

2000 ◽  
Vol 179 ◽  
pp. 387-388
Author(s):  
Gaetano Belvedere ◽  
V. V. Pipin ◽  
G. Rüdiger
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Convection Zone ◽  
Solar Surface ◽  
Momentum Transport ◽  
Angular Momentum Transport ◽  
Magnetic Buoyancy ◽  
Alpha Effect ◽  
Current Helicity

Extended AbstractRecent numerical simulations lead to the result that turbulence is much more magnetically driven than believed. In particular the role ofmagnetic buoyancyappears quite important for the generation ofα-effect and angular momentum transport (Brandenburg &amp; Schmitt 1998). We present results obtained for a turbulence field driven by a (given) Lorentz force in a non-stratified but rotating convection zone. The main result confirms the numerical findings of Brandenburg &amp; Schmitt that in the northern hemisphere theα-effect and the kinetic helicityℋkin= 〈u′ · rotu′〉 are positive (and negative in the northern hemisphere), this being just opposite to what occurs for the current helicityℋcurr= 〈j′ ·B′〉, which is negative in the northern hemisphere (and positive in the southern hemisphere). There has been an increasing number of papers presenting observations of current helicity at the solar surface, all showing that it isnegativein the northern hemisphere and positive in the southern hemisphere (see Rüdigeret al. 2000, also for a review).

The Hemispheric Sign Rule of Current Helicity during the Rising Phase of Cycle 23

2000 ◽  
Vol 179 ◽  
pp. 303-306
Author(s):  
S. D. Bao ◽  
G. X. Ai ◽  
H. Q. Zhang
Keyword(s):  
Solar Cycle ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Active Regions ◽  
Hemispheric Preference ◽  
Current Helicity

AbstractWe compute the signs of two different current helicity parameters (i.e., αbestandHc) for 87 active regions during the rise of cycle 23. The results indicate that 59% of the active regions in the northern hemisphere have negative αbestand 65% in the southern hemisphere have positive. This is consistent with that of the cycle 22. However, the helicity parameterHcshows a weaker opposite hemispheric preference in the new solar cycle. Possible reasons are discussed.

Measurements of the Cape Astrometric Survey of the Southern Hemisphere

1978 ◽  
Vol 48 ◽  
pp. 515-521
Author(s):  
W. Nicholson
Keyword(s):  
Southern Hemisphere ◽  
Automatic Measuring ◽  
Measuring Machine ◽  
Final Selection ◽  
Selection Of

SummaryA routine has been developed for the processing of the 5820 plates of the survey. The plates are measured on the automatic measuring machine, GALAXY, and the measures are subsequently processed by computer, to edit and then refer them to the SAO catalogue. A start has been made on measuring the plates, but the final selection of stars to be made is still a matter for discussion.

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