THE INCOMPLETENESS OF KRUSKAL–SZEKERES SPACETIME

1999 ◽  
Vol 14 (16) ◽  
pp. 2593-2606 ◽  
Author(s):  
RONALD GAUTREAU
Keyword(s):  
Reference System ◽  
Left Hand ◽  
Spatial Coordinate ◽  
Black And White ◽  
Physical Spacetime

Novikov has developed a reference system built around times measured by radially moving geodesic clocks that is equivalent to Kruskal–Szekeres coordinates. From analysis of the construction of Novikov's reference system, I give arguments showing that the reference system is not maximally extended, as is commonly reported in the literature. On both Novikov and Kruskal–Szekeres spacetime diagrams, the left-hand side, corresponding to negative values of the spatial coordinate, should not be included when describing a physical spacetime. In turn, this means we have to rethink widely-accepted concepts such as black and white holes that arise from the usual picture of a maximally-extended Kruskal–Szekeres spacetime.

scholarly journals Crenicichla hu, a new species of cichlid fish (Teleostei: Cichlidae) from the Paraná basin in Misiones, Argentina

Zootaxa ◽  
2010 ◽  
Vol 2537 (1) ◽  
pp. 33 ◽  
Author(s):  
LUBOMÍR PIÁLEK ◽  
OLDŘICH ŘÍČAN ◽  
JORGE CASCIOTTA ◽  
ADRIANA ALMIRÓN
Keyword(s):  
New Species ◽  
Cichlid Fish ◽  
Color Pattern ◽  
Left Hand ◽  
Black And White ◽  
Dorsal Fin ◽  
La Plata Basin ◽  
Molecular Phylogenetic ◽  
Misiones Province ◽  
A New Species

A new species of Crenicichla Heckel, C. hu, is described from the arroyo Piray–Miní, a left-hand tributary of the río Paraná, Misiones province, Argentina. This new species is easily distinguished from its congeners in the La Plata basin and adjacent coastal rivers by the dark coloration (dark grey or dark brown to black), a color pattern consisting of 7 to 9 black irregular blotches on the flank, and 47–54 scales in the E1 row. Adult females have dorsal fin with an irregular color pattern formed by wide black and white longitudinal stripes and blotches. In addition to standard morphological comparisons, a brief molecular phylogenetic analysis of Crenicichla species from the province of Misiones is also introduced.

scholarly journals Let's Find Momo by A. Knapp

2018 ◽  
Vol 7 (3) ◽  
Author(s):  
Janice Kung
Keyword(s):  
Picture Book ◽  
Health Sciences ◽  
University Of Alberta ◽  
Left Hand ◽  
New Words ◽  
Black And White ◽  
Young Readers ◽  
Good Book ◽  
Wide Range ◽  
The University

Knapp, Andrew. Let’s Find Momo. Quirk Books, 2017.This hide-and-seek board book is the latest from photographer, Andrew Knapp and his extremely photogenic border collie named Momo. The black and white border collie loves hiding and invites young readers to find itself and other objects. Left-hand pages list three different objects and Momo who are hidden in the corresponding right pages. Each page explores different environments along with objects that are typically found therein, but not always. For instance, in the library, readers are tasked to find a lollipop, a banana, a balloon, and Momo.Similar to Where’s Waldo, this picture book allows readers to find objects and the cute little dog that does his very best at staying hidden. The border collie takes readers on many adventures such as to a merry-go-round, gymnasium, garden, bedroom, and even a farm. With themes carefully selected, they provide a wide range of new words for young readers to learn. Each location is beautifully photographed with vibrant colours and unique angles while, at the same time, teaches new vocabulary to young children, aged 2-4.  Highly Recommended: 4 out of 4 starsReviewer: Janice KungJanice Kung is a Public Services Librarian at the University of Alberta, John W. Scott Health Sciences Library. She obtained her undergraduate degree in commerce and completed her MLIS degree in 2013. She believes that the best thing to beat the winter blues is to cuddle up on a couch and lose oneself in a good book.

scholarly journals The visual centring response in desert ants,Cataglyphis fortis

2002 ◽  
Vol 205 (5) ◽  
pp. 585-590 ◽  
Author(s):  
Daniel Heusser ◽  
Rüdiger Wehner
Keyword(s):  
Visual Fields ◽  
The Self ◽  
Spatial Period ◽  
Vertical Angle ◽  
Cluttered Environments ◽  
Left Hand ◽  
Black And White ◽  
Desert Ants ◽  
Left And Right ◽  
Cataglyphis Fortis

SUMMARYWhen negotiating their way through cluttered environments, desert ants, Cataglyphis fortis, tend to run along the midlines of the alleys formed by adjacent low shrubs. This ‘centring response’ was investigated by inducing foraging ants to walk through artificial channels. The sidewalls of the channel were either homogeneously black or provided with stationary or moving black-and-white gratings. The speed of motion and the spatial period of the gratings and the height of the walls could be varied independently on the left-hand and right-hand sides of the channel. The results clearly show that the ants, while exhibiting their centring responses, try to balance neither the self-induced image speeds nor the contrast frequencies seen in their left and right visual fields, but the vertical angle subtended by the landmarks on either side. When manoeuvring through the channel, the ants always adjust the lateral positions of their walking trajectories in such a way that the vertical angles subtended by the walls are identical for both eyes.

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