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Rotating Squares Look Like Pincushions.
Rotating squares appeared to be distorted into pincushions with concave sides. These illusory shape changes were caused by a perceived compression along the curved path of motion
Illusory drifting within a window that moves across a flickering background.
When a striped disk moves across a flickering background, the stripes paradoxically seem to move faster than the disk itself. We attribute this new illusion to reverse-phi motion, which slows down the disk rim but does not affect the stripes
Progenitor cells of the rod-free area centralis originate in the anterior dorsal optic vesicle
BACKGROUND Nervous system development is dependent on early regional specification to create functionally distinct tissues within an initially undifferentiated zone. Within the retina, photoreceptors are topographically organized with rod free area centrales faithfully generated at the centre of gaze. How does the developing eye regulate this placement? Conventional wisdom indicates that the distal tip of the growing optic vesicle (OV) gives rise to the area centralis/fovea. Ectopic expression and ablation studies do not fully support this view, creating a controversy as to the origin of this region. In this study, the lineage of cells in the chicken OV was traced using DiI. The location of labelled cells was mapped onto the retina in relation to the rod-free zone at embryonic (E) 7 and E17.5. The ability to regenerate a rod free area after OV ablation was determined in conjunction with lineage tracing. RESULTS Anterior OV gave rise to cells in nasal retina and posterior OV became temporal retina. The OV distal tip gave rise to cells above the optic nerve head. A dorsal and anterior region of the OV correlated with cells in the developing rod free area centralis. Only ablations including the dorsal anterior region gave rise to a retina lacking a rod free zone. DiI application after ablation indicated that cells movements were greater along the anterior/posterior axis compared with the dorsal/ventral axis. CONCLUSION Our data support the idea that the chicken rod free area centralis originates from cells located near, but not at the distal tip of the developing OV. Therefore, the hypothesis that the area centralis is derived from cells at the distal tip of the OV is not supported; rather, a region anterior and dorsal to the distal tip gives rise to the rod free region. When compared with other studies of retinal development, our results are supported on molecular, morphological and functional levels. Our data will lead to a better understanding of the mechanisms underlying the topographic organization of the retina, the origin of the rod free zone, and the general issue of compartmentalization of neural tissue before any indication of morphological differentiation.This work was supported by The University of Auckland Staff Research Fund and the Australian Research Council Centres of Excellence program, at the ARC Centre of Excellence in Vision Science, Canberra. SS was supported by a University of Auckland PhD scholarship
The Capacity of Wireless Channels: A Physical Approach
In this paper, the capacity of wireless channels is characterized based on
electromagnetic and antenna theories with only minimal assumptions. We assume
the transmitter can generate an arbitrary current distribution inside a
spherical region and the receive antennas are uniformly distributed on a bigger
sphere surrounding the transmitter. The capacity is shown to be [bits/sec] in the limit of large number of receive antennas, where
is the transmit power constraint, is the normalized density of the
receive antennas and is the noise power spectral density. Although this
result may look trivial, it is surprising in two ways. First, this result holds
regardless of the bandwidth (bandwidth can even be negligibly small). Second,
this result shows that the capacity is irrespective of the size of the region
containing the transmitter. This is against some previous results that claimed
the maximum degrees of freedom is proportional to the surface area containing
the transmitter normalized by the square of the wavelength. Our result has
important practical implications since it shows that even a compact antenna
array with negligible bandwidth and antenna spacing well below the wavelength
can provide a huge throughput as if the array was big enough so that the
antenna spacing is on the order of the wavelength.Comment: 5 pages, to appear in proceedings of 2013 IEEE ISI
Cooperative Transmission for a Vector Gaussian Parallel Relay Network
In this paper, we consider a parallel relay network where two relays
cooperatively help a source transmit to a destination. We assume the source and
the destination nodes are equipped with multiple antennas. Three basic schemes
and their achievable rates are studied: Decode-and-Forward (DF),
Amplify-and-Forward (AF), and Compress-and-Forward (CF). For the DF scheme, the
source transmits two private signals, one for each relay, where dirty paper
coding (DPC) is used between the two private streams, and a common signal for
both relays. The relays make efficient use of the common information to
introduce a proper amount of correlation in the transmission to the
destination. We show that the DF scheme achieves the capacity under certain
conditions. We also show that the CF scheme is asymptotically optimal in the
high relay power limit, regardless of channel ranks. It turns out that the AF
scheme also achieves the asymptotic optimality but only when the
relays-to-destination channel is full rank. The relative advantages of the
three schemes are discussed with numerical results.Comment: 35 pages, 10 figures, submitted to IEEE Transactions on Information
Theor
Motion-Driven Transparency and Opacity.
When two adjacent surfaces move in step, this can generate a sensation of transparency, even in the absence of intersections. Stopping the motion of one surface makes it look suddenly opaque
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