Humans demonstrate behavioural advantages (biases) towards particular dimensions (colour or shape of visual objects), but such biases are significantly altered in neuropsychological disorders. Recent ...studies have shown that lesions in the prefrontal cortex do not abolish dimensional biases, and therefore suggest that such biases might not depend on top-down prefrontal-mediated attention and instead emerge as bottom-up processing advantages. We hypothesised that if dimensional biases merely emerge from an enhancement of object features, the presence of visual objects would be necessary for the manifestation of dimensional biases. In a specifically-designed working memory task, in which macaque monkeys and humans performed matching based on the object memory rather than the actual object, we found significant dimensional biases in both species, which appeared as a shorter response time and higher accuracy in the preferred dimension (colour and shape dimension in humans and monkeys, respectively). Moreover, the mnemonic demands of the task influenced the magnitude of dimensional bias. Our findings in two primate species indicate that the dichotomy of top-down and bottom-up processing does not fully explain the emergence of dimensional biases. Instead, dimensional biases may emerge when processed information regarding visual object features interact with mnemonic and executive functions to guide goal-directed behaviour.
A modified back-projection approach deduced from an exact reconstruction solution was applied to our photoacoustic tomography of the optical absorption in biological tissues. Pulses from a ...Ti:sapphire laser (4.7 ns FWHM at 789.2 nm) were employed to generate a distribution of photoacoustic sources in a sample. The sources were detected by a wide-band nonfocused ultrasonic transducer at different positions around the imaging cross section perpendicular to the axis of the laser irradiation. Reconstructed images of phantoms made from chicken breast tissue agreed well with the structures of the samples. The resolution in the imaging cross section was experimentally demonstrated to be better than 60 μm when a 10 MHz transducer (140% bandwidth at −60 dB) was employed, which was nearly diffraction limited by the detectable photoacoustic waves of the highest frequency.
We outline three new ideas in a program to obtain standard physics, including standard supersymmetry, from a Planck-scale statistical theory: (1) The initial spin 1/2 bosonic fields are transformed ...to spin 0 fields together with their auxiliary fields. (2) Time is defined by the progression of 3-geometries, just as originally proposed by DeWitt. (3) The initial (D-1)-dimensional "path integral" is converted from Euclidean to Lorentzian form by transformation of the fields in the integrand.
In Lorentz-violating supergravity, sfermions have spin 1/2 and other unusual
properties. If the dark matter consists of such particles, there is a natural
explanation for the apparent absence of ...cusps and other small scale structure:
The Lorentz-violating dark matter is cold because of the large particle mass,
but still moves at nearly the speed of light. Although the R-parity of a
sfermion, gaugino, or gravitino is +1 in the present theory, these particles
have an "S-parity'' which implies that the LSP is stable and that they are
produced in pairs. On the other hand, they can be clearly distinguished from
the superpartners of standard supersymmetry by their highly unconventional
properties.
Nuclear Physics B (Proc. Suppl.) 134, 139 (2004) Astrophysical, terrestrial, and space-based searches for Lorentz violation
are very briefly reviewed. Such searches are motivated by the fact that all
...superunified theories (and other theories that attempt to include quantum
gravity) have some potential for observable violations of Lorentz invariance.
Another motivation is the exquisite sensitivity of certain well-designed
experiments and observations to particular forms of Lorentz violation. We also
review some new predictions of a specific Lorentz-violating theory: If a
fundamental energy \bar{m} in this theory lies below the usual GZK cutoff
E_{GZK}, the cutoff is shifted to infinite energy; i.e., it no longer exists.
On the other hand, if \bar{m} lies above E_{GZK}, there is a high-energy branch
of the fermion dispersion relation which provides an alternative mechanism for
super-GZK cosmic-ray protons.
In Lorentz-violating supergravity, sfermions have spin 1/2 and other unusual properties. If the dark matter consists of such particles, there is a natural explanation for the apparent absence of ...cusps and other small scale structure: The Lorentz-violating dark matter is cold because of the large particle mass, but still moves at nearly the speed of light. Although the R-parity of a sfermion, gaugino, or gravitino is +1 in the present theory, these particles have an "S-parity'' which implies that the LSP is stable and that they are produced in pairs. On the other hand, they can be clearly distinguished from the superpartners of standard supersymmetry by their highly unconventional properties.
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