1,966 research outputs found
Interplay between mesoscopic phase separation and bulk magnetism in the layered NaxCoO2
Specific heat of the layered NaxCoO2 (x=0.65, 0.70 and 0.75) oxides has been
measured in the temperature range of 3-360 K and magnetic field of 0 and 9 T.
The analysis of data, assuming the combined effect of inter-layer superexchange
and the phase separation into mesoscopic magnetic domains with localized spins
embedded in a matrix with itinerant electronic character, suggests that the
dominant contribution to the specific heat in the region of short-range
ordering is mediated by quasi-2D antiferromagnetic clusters, perpendicular to
the CoO2 layers
Circuit and plasticity defects in the developing somatosensory cortex of FMR1 knock-out mice
Silencing of the Fmr1 gene causes fragile X syndrome. Although defects in synaptic plasticity in the cerebral cortex have been linked to cognitive impairments in Fmr1 knock-out (ko) mice, the specific cortical circuits affected in the syndrome are unknown. Here, we investigated the development of excitatory projections in the barrel cortex of Fmr1 ko mice. In 2-week-old Fmr1 ko mice, a major ascending projection connecting layer 4 (L4) to L3 (L4-->L3), was defective in multiple and independent ways: its strength was reduced, caused by a lower connection probability; the axonal arbors of L4 cells were spatially diffuse in L2/3; the L4-->L3 projection did not show experience-dependent plasticity. By 3 weeks, the strength of the L4-->L3 projection was similar to that of wild type. Our data indicate that Fmr1 shapes sensory cortical circuits during a developmental critical period
Incorporation of Bovine Herpesvirus 1 Protein Subunits into Large Unilamellar and Multilamellar Liposomes
Simplified game of life: Algorithms and complexity
Game of Life is a simple and elegant model to study dynamical system over networks. The model consists of a graph where every vertex has one of two types, namely, dead or alive. A configuration is a mapping of the vertices to the types. An update rule describes how the type of a vertex is updated given the types of its neighbors. In every round, all vertices are updated synchronously, which leads to a configuration update. While in general, Game of Life allows a broad range of update rules, we focus on two simple families of update rules, namely, underpopulation and overpopulation, that model several interesting dynamics studied in the literature. In both settings, a dead vertex requires at least a desired number of live neighbors to become alive. For underpopulation (resp., overpopulation), a live vertex requires at least (resp. at most) a desired number of live neighbors to remain alive. We study the basic computation problems, e.g., configuration reachability, for these two families of rules. For underpopulation rules, we show that these problems can be solved in polynomial time, whereas for overpopulation rules they are PSPACE-complete
Disorder promotes ferromagnetism: Rounding of the quantum phase transition in Sr_{1-x}Ca_xRuO_3
The subtle interplay of randomness and quantum fluctuations at low
temperatures gives rise to a plethora of unconventional phenomena in systems
ranging from quantum magnets and correlated electron materials to ultracold
atomic gases. Particularly strong disorder effects have been predicted to occur
at zero-temperature quantum phase transitions. Here, we demonstrate that the
composition-driven ferromagnetic-to-paramagnetic quantum phase transition in
Sr1-xCaxRuO3 is completely destroyed by the disorder introduced via the
different ionic radii of the randomly distributed Sr and Ca ions. Using a
magneto-optical technique, we map the magnetic phase diagram in the
composition-temperature space. We find that the ferromagnetic phase is
significantly extended by the disorder and develops a pronounced tail over a
broad range of the composition x. These findings are explained by a microscopic
model of smeared quantum phase transitions in itinerant magnets. Moreover, our
theoretical study implies that correlated disorder is even more powerful in
promoting ferromagnetism than random disorder.Comment: 15 pages, 4 figures, submitted to Phys. Rev. Let
The effects of irrigation on root density profiles of potato, celery, and wheat
Irrigation rate should correspond to the effective root depth, however, crop root growth
is influenced by a number of factors, and little data is available on the impact of irrigation. This
contribution presents the results of several experiments in which the influence of sprinkler or drip
irrigations on root density distribution of shallow, medium and deep rooted crops within the soil
profile were studied. Irrigation significantly increased the root density of potato, celery, and
wheat in the topsoil zone. On the contrary, at most cases there was only a slightly reduced root
density in the subsoil layers. Total root length, to maximum root depth, only increased
significantly with drip irrigation in potato. The root depths of these crops were not significantly
modified by irrigation. The results suggest that the use of a constant value for the calculation of
maximum irrigation depth in a specific crop may not correspond to the variability of root depth
nor the distribution in different years or fields
Fluctuating-friction molecular motors
We show that the correlated stochastic fluctuation of the friction
coefficient can give rise to long-range directional motion of a particle
undergoing Brownian random walk in a constant periodic energy potential
landscape. The occurrence of this motion requires the presence of two
additional independent bodies interacting with the particle via friction and
via the energy potential, respectively, which can move relative to each other.
Such three-body system generalizes the classical Brownian ratchet mechanism,
which requires only two interacting bodies. In particular, we describe a simple
two-level model of fluctuating-friction molecular motor that can be solved
analytically. In our previous work [M.K., L.M and D.P. 2000 J. Nonlinear Opt.
Phys. Mater. vol. 9, 157] this model has been first applied to understanding
the fundamental mechanism of the photoinduced reorientation of dye-doped liquid
crystals. Applications of the same idea to other fields such as molecular
biology and nanotechnology can however be envisioned. As an example, in this
paper we work out a model of the actomyosin system based on the
fluctuating-friction mechanism.Comment: to be published in J. Physics Condensed Matter
(http://www.iop.org/Journals/JPhysCM
An assortment of woody plants produced in the manor of Nové Dvory at the turn of the 18th and 19th centuries: North American taxa
The noble family of Chotek began with the realization of extensive landscaping in their manor of Nové Dvory at the end of the 18th century. Lists of woody plants produced for these purposes and for sale were preserved from the years 1794, 1800 and 1814. 276 taxa of foreign woody plants in the current concept, permanently cultivated outdoors, have been identified in all three lists at least to the level of the species. 91 taxa come from North America, with 81 being the first documented place of their presence in the territory of the Czech Republic. All North American taxa are natural, none of them originated in culture.O
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