4,245 research outputs found
Analysis of an Experimental Cortical Network: i) Architectonics of Visual Areas 17 and 18 After Neonatal Injections of Ibotenic Acid; Similarities with Human Microgyria
Lesions of cortical areas 17 and 18 have been produced in newborn kittens by local injections of the excitotoxin ibotenic acid (ibo). Twenty-four hours after an injection on postnatal days 2 or 3, the gray matter of areas 17 and 18 near the center of the injection appears completely destroyed, with the exception of a one-to-two cell-thick layer at the bottom of layer I. Intact migrating neurons and radial glia can be found light- and electron-microscopically in the region affected. During the following weeks a several hundred micron thick cortex reforms. In the adult, this cortex consists of superficial layers I, II and III as proven by cytoarchitectonics, continuity with the corresponding layers of the normal cortex and cellular composition. We believe that the recovery is due to completion of migration by neurons spared by the ibo injection. More severe destruction of cerebral cortex, i.e. complete loss of the neuronal layers or their reduction to a few cell-thick mantles can be obtained with ibo injections at the end of the second or, respectively, first postnatal week. Severity of lesion also depends on the dose of ibo injected. There are interesting similarities between the ibo-injured cortex and two human neocortical displasias: microgyria and ulegyria
Analysis of an Experimental Cortical Network: ii) Connections of Visual Areas 17 and 18 After Neonatal Injections of Ibotenic Acid
Lesions of cortical areas 17 and 18 were produced
in newborn kittens by local injections of
the excitotoxin ibotenic acid. In the adult this
results in a microcortex which consists of superficial
layers I, II and III, in the absence of granular
and infragranular layers. Horseradish peroxidase,
alone or wheat germ agglutinin conjugated,
was injected in the microcortex or in the
contralateral, intact areas 17 and 18. The microcortex
maintains several connections characteristic
of normal areas 17 and 18 of the cat. It receives
afferents from the dLGN, and several visual
areas of the ipsilateral and contralateral
hemisphere. However, it has lost its projections
to dLGN, superior colliculus, and, at least in
part, those to contralateral visual areas. Thus some parts of the microcortex receive from, but
do not project into, the corpus callosum. In addition,
the microcortex maintains afferents from
ipsilateral and contralateral auditory areas AI
and AII which are normally eliminated in development
Raman spectroscopy study of the interface structure in (CaCuO2)n/(SrTiO3)m superlattices
Raman spectra of CaCuO2/SrTiO3 superlattices show clear spectroscopic marker
of two structures formed in CaCuO2 at the interface with SrTiO3. For
non-superconducting superlattices, grown in low oxidizing atmosphere, the 425
cm-1 frequency of oxygen vibration in CuO2 planes is the same as for CCO films
with infinite layer structure (planar Cu-O coordination). For superconducting
superlattices grown in highly oxidizing atmosphere, a 60 cm-1 frequency shift
to lower energy occurs. This is ascribed to a change from planar to pyramidal
Cu-O coordination because of oxygen incorporation at the interface. Raman
spectroscopy proves to be a powerful tool for interface structure
investigation
Efficacy of foliage fungicides against eyespot of winter wheat in Northern Italy
Summary. The efficacy of foliage fungicide applications against eyespot of soft wheat cv. Serio was evaluated
under natural Oculimacula infection in an experimental area in the Po Valley (Northern Italy). The fungicide treatments prochloraz, prochloraz + propiconazole, and trifloxystrobin + cyproconazole were applied in the years
of 2006 through to 2009. Seeds were also treated with a formulated product based on guazatine. All foliage fungicides were applied at the stem extension growth stage (Zadoks growth stage 30\u201232), and at the manufacturer recommended rates. All tested treatments reduced the disease severity compared with untreated control. Prochloraz alone and particularly in combination with propiconazole gave the greatest efficacy in reducing eyespot. All treatments increased grain yield in 2006 and 2008. The effects of treatments on some yield parameters were also examined
Anomalous Spontaneous Emission Time In A Microscopic Optical Cavity
We have realized total electromagnetic mode confinement in a microscopic optical, Casimir-type, cavity and detected the resonant change of the molecular fluorescence time under short-pulse excitation due to a spontaneous-atomic-decay enhancement-inhibition process (Purcell effect). This corresponds to the first realization in optics of the resonant coupling of atoms with a single mode of the radiation field. © 1987 The American Physical Society.59262955295
Renormalization of Coulomb interactions in s-wave superconductor NaCoO
We study the renormalized Coulomb interactions due to retardation effect in
NaCoO. Although the Morel-Anderson's pseudo potential for
orbital is relatively large because the direct Coulomb repulsion
is large, that for interband transition between and
orbitals is very small since the renormalization factor for
pair hopping is square of that for . Therefore, the s-wave
superconductivity due to valence-band Suhl-Kondo mechanism will survive against
strong Coulomb interactions. The interband hopping of Cooper pairs due to shear
phonons is essential to understand the superconductivity in NaCoO.Comment: 2pages, 2figures, Proceedings of ICM in Kyoto, 200
Vision After Early-Onset Lesions of the Occipital Cortex: I. Neuropsychological and Psychophysical Studies
We analyzed the visual functions of two
patients (MS, FJ) with bilateral lesion of the
primary visual cortex, which occurred at gestational
age 33 wk in MS and at postnatal month 7
in FJ. In both patients basic visual functions—
visual acuity, contrast sensitivity, color, form,
motion perception—are similarly preserved or
modestly impaired. Functions requiring higher
visual processing, particularly figure-ground
segregation based on textural cues, are severely
impaired. In MS, studied longitudinally, the
deficits attenuated between the ages of 4.5 and 8
y, suggesting that the developing visual system
can display a considerable degree of adaptive
plasticity several years after the occurrence of a
lesion. In FJ (age 18:9 to 20:6 y), who is more
impaired, the recovery, if any, was less
Vision After Early-Onset Lesions of the Occipital Cortex: II. Physiological Studies
In one of two patients (MS and FJ) with
bilateral, early-onset lesion of the primary
visual cortex, Kiper et al. (2002) observed
a considerable degree of functional recovery. To
clarify the physiological mechanisms involved
in the recovery, we used fMRI and quantitative
EEG to study both patients. The fMRI
investigations indicated that in both patients,
isolated islands of the primary visual cortex are
functioning, in the right hemisphere in MS and
in the left in FJ. The functional recovery
observed in MS roughly correlated with the
functional maturation of interhemispheric
connections and might reflect the role of corticocortical connectivity in visual perception. The
functionality of interhemispheric connections
was assessed by analyzing the changes in
occipital inter-hemispheric coherence of EEG
signals (ICoh) evoked by moving gratings. In
the patient MS, this ICoh response was present
at 7:11 y and was more mature at 9:2 y. In the
more visually mpaired patient, FJ, a consistent
increase in ICoh to visual stimuli could not be
obtained, possibly because of the later occurrence
of the lesion
Continental rift architecture and patterns of magma migration: a dynamic analysis based on centrifuge models.
Small-scale centrifuge models were used to investigate the role of continental rift structure in controlling patterns of magma migration and emplacement. Experiments considered the reactivation of weakness zones in the lower crust and the presence of magma at Moho depths. Results suggest that surface deformation, which reflects the weakness zone geometry, exerts a major control on patterns of magma migration. In the case of a single rift segment, the experimental lower crust and magma were both transferred in an extension-parallel direction toward the rift flanks. This lateral migration reflected the dominance of far-field stresses over extension-induced buoyancy forces. Local pressure gradients favored the raise of experimental magma in correspondence of marginal grabens. The lateral migration gave rise to major accumulations below the footwall of major boundary faults, providing the magma source able to feed off-axis volcanoes in nature, as inferred for the Main Ethiopian Rift. In the case of two offset rift segments, a major transfer zone developed. This transfer zone was characterized by prominent experimental lower crust doming and strong magma accumulation. Dynamic analysis showed that the transfer zone development caused a strong pressure difference in a rift-parallel direction, which dominated over the farfield thinning. Owing to this pressure gradient, almost all the underplated experimental magma collected below the lower crust dome, suggesting a rift-parallel (extension-orthogonal) migration. This process has a direct relevance for the localization of magmatic activity at transfer zones in natural continental rifts, such as in the Western Branch of the East African Rift System. Copyright 2004 by the American Geophysical Union
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