Mossy fibers apparently form electrical synapses, as well as chemical synapses, with CA3 pyramidal cells potentially permitting a fast excitation to overcome a strong, but delayed, feed-forward ...inhibition. Since MF axons of dentate granule cells may be generated post-natally, Pedroni et al. Mutations in genes associated with neuronal migration in mouse models result in lamination defects of the CA3 area, a region especially vulnerable to stress and seizure-induced damage. A simplified network model shows that self-organization can lead to the emergence of multiple loosely organized discrete point-like attractors which differ from structures associated with a single, continuous attractor. Functional properties of different hippocampal subfields can be identified with high resolution fMRI and related to behavioral, and structural alterations associated with mild cognitive impairment in early Alzheimer's disease.
High-Gain Backward Lasing in Air Dogariu, Arthur; Michael, James B.; Scully, Marlan O. ...
Science (American Association for the Advancement of Science),
01/2011, Letnik:
331, Številka:
6016
Journal Article
Recenzirano
Odprti dostop
The compelling need for standoff detection of hazardous gases and vapor indicators of explosives has motivated the development of a remotely pumped, high-gain air laser that produces lasing in the ...backward direction and can sample the air as the beam returns. We demonstrate that high gain can be achieved in the near-infrared region by pumping with a focused ultraviolet laser. The pumping mechanism is simultaneous resonant two-photon dissociation of molecular oxygen and resonant two-photon pumping of the atomic oxygen fragments. The high gain from the millimeter-length focal zone leads to equally strong lasing in the forward and backward directions. Further backward amplification is achieved with the use of earlier laser spark dissociation. Low-divergence backward air lasing provides possibilities for remote detection.
We demonstrate backwards lasing in atomic argon directly excited via a three-photon pumping in air mixtures with argon mole fractions down to 10%. We achieve well collimated, narrowband coherent ...emission at 1327nm by using both broadband femtosecond excitation and narrow linewidth picosecond excitation in the vicinity of 261nm. This approach shows promise for standoff trace detection in the atmosphere.
This work reports the measurement of two-dimensional electron properties over a nanosecond scale integration time across a femtosecond laser-induced plasma filament in atmospheric pressure argon. ...Radial electron properties across the Formula: see text Formula: see textm diameter filament are obtained at discrete axial locations at 2.5 mm steps by one-dimensional high-resolution laser Thomson scattering with a spatial resolution of 10 Formula: see textm. These measurements reveal plasma structural information in the filament. The Thomson spectral lineshapes exhibit clear spectral sidebands with an Formula: see text parameter Formula: see text, enabling the measurement of both electron temperature and density profiles. These measurements yield electron densities on the order of Formula: see text/mFormula: see text and electron temperatures of Formula: see text eV. Heating from the probe laser due to inverse bremsstrahlung is taken into account to correct the Thomson scattering electron temperature measurements. Under these conditions, electron-neutral collision induced bremsstrahlung becomes the dominant laser-induced plasma heating process associated with the probe laser. The measurements reveal structural features of the filament, including an asymmetrically skewed density structure in the axial direction and reversed radial distributions of electron density and temperature.
This volume charts the radical transformation of an inner city neighbourhood in late antique Carthage which was excavated over a five-year period by a team from the University of Cambridge. Bordering ...the main thoroughfare leading from the Brysa Hill to the ports, the neighbourhood remained primarily a residential one from the second century until 530s AD when a substantial basilica was constructed over the eastern half of the insula. Further extensive modifications were made to the basilica half-a-century later when the structures on the western half of the insula were demolished and the basilica greatly enlarged with the addition of a new east-west aisles, a large monumental baptistery and a crypt. By carefully reconstructing the complex architectural plan of this innovative building, this study shows how the re-modelled Bir Messaouda basilica was transformed into a major pilgrimage centre overturning established tradition that located such complexes outside the city walls. The Bir Messaouda basilica provides important insights into the transition between Vandal and Byzantine control of the city, the development of a new Christian inter-mural urban landscape in the sixth century AD, and the significance of the pilgrimage in reinforcing ecclesiastical authority in post-Justinianic North Africa.
DEP domain-containing 5 protein (DEPDC5) is a repressor of the recently recognized amino acid-sensing branch of the mTORC1 pathway. So far, its function in the brain remains largely unknown. Germline ...loss-of-function mutations in DEPDC5 have emerged as a major cause of familial refractory focal epilepsies, with case reports of sudden unexpected death in epilepsy (SUDEP). Remarkably, a fraction of patients also develop focal cortical dysplasia (FCD), a neurodevelopmental cortical malformation. We therefore hypothesized that a somatic second-hit mutation arising during brain development may support the focal nature of the dysplasia. Here, using postoperative human tissue, we provide the proof of concept that a biallelic 2-hit - brain somatic and germline - mutational mechanism in DEPDC5 causes focal epilepsy with FCD. We discovered a mutation gradient with a higher rate of mosaicism in the seizure-onset zone than in the surrounding epileptogenic zone. Furthermore, we demonstrate the causality of a Depdc5 brain mosaic inactivation using CRISPR-Cas9 editing and in utero electroporation in a mouse model recapitulating focal epilepsy with FCD and SUDEP-like events. We further unveil a key role of Depdc5 in shaping dendrite and spine morphology of excitatory neurons. This study reveals promising therapeutic avenues for treating drug-resistant focal epilepsies with mTORC1-targeting molecules.
For an action α of ℤd by homeomorphisms of a compact metric space, D. Lind introduced a dynamical zeta function and conjectured that this function has a natural boundary when d ≥ 2. In this note, ...under the assumption that α is a mixing action by continuous automorphisms of a compact connected abelian group of finite topological dimension, it is shown that the upper growth rate of periodic points is zero and that the unit circle is a natural boundary for the dynamical zeta function.
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