916 research outputs found
Cerebral differences in explicit and implicit emotional processing - An fMRI study
The processing of emotional facial expression is a major part of social communication and understanding. In addition to explicit processing, facial expressions are also processed rapidly and automatically in the absence of explicit awareness. We investigated 12 healthy subjects by presenting them with an implicit and explicit emotional paradigm. The subjects reacted significantly faster in implicit than in explicit trials but did not differ in their error ratio. For the implicit condition increased signals were observed in particular in the thalami, the hippocampi, the frontal inferior gyri and the right middle temporal region. The analysis of the explicit condition showed increased blood-oxygen-level-dependent signals especially in the caudate nucleus, the cingulum and the right prefrontal cortex. The direct comparison of these 2 different processes revealed increased activity for explicit trials in the inferior, superior and middle frontal gyri, the middle cingulum and left parietal regions. Additional signal increases were detected in occipital regions, the cerebellum, and the right angular and lingual gyrus. Our data partially confirm the hypothesis of different neural substrates for the processing of implicit and explicit emotional stimuli. Copyright (c) 2007 S. Karger AG, Basel
Models for the magnetic ac susceptibility of granular superferromagnetic CoFe/AlO
The magnetization and magnetic ac susceptibility, ,
of superferromagnetic systems are studied by numerical simulations. The
Cole-Cole plot, vs. , is used as a tool for classifying
magnetic systems by their dynamical behavior. The simulations of the
magnetization hysteresis and the ac susceptibility are performed with two
approaches for a driven domain wall in random media. The studies are motivated
by recent experimental results on the interacting nanoparticle system
CoFe/AlO showing superferromagnetic behavior. Its
Cole-Cole plot indicates domain wall motion dynamics similarly to a disordered
ferromagnet, including pinning and sliding motion. With our models we can
successfully reproduce the features found in the experimental Cole-Cole plots.Comment: 8 pages, 6 figure
Magnetic phase diagram of the diluted metamagnet Fe\u3csub\u3e0.95\u3c/sub\u3eMg\u3csub\u3e0.05\u3c/sub\u3eBr\u3csub\u3e2\u3c/sub\u3e
The axial magnetic phase diagram of the antiferromagnet Fe0.95Mg0.05Br2 is studied by specific heat, superconducting quantum interference device, and Faraday rotation techniques. The diamagnetic impurities give rise to random-field criticality along the second-order phase line Hc(T) between TN=13.1 K and a multicritical point at Tm≈5 K, and to a spin-flop line between Tm and the critical end-point temperature Te≈3.5 K. The phase line H1(T)c(T) ending at Tm is probably due to symmetric nondiagonal exchange
Interface driven magnetoelectric effects in granular CrO2
Antiferromagnetic and magnetoelectric Cr2O3-surfaces strongly affect the
electronic properties in half metallic CrO2. We show the presence of a Cr2O3
surface layer on CrO3 grains by high-resolution transmission electron
microscopy. The effect of these surface layers is demonstrated by measurements
of the temperature variation of the magnetoelectric susceptibility. A major
observation is a sign change at about 100 K followed by a monotonic rise as a
function of temperature. These electric field induced moments in CrO3 are
correlated with the magnetoelectric susceptibility of pure Cr2O3. This study
indicates that it is important to take into account the magnetoelectric
character of thin surface layers of Cr2O3 in granular CrO2 for better
understanding the transport mechanism in this system. The observation of a
finite magnetoelectric susceptibility near room temperature may find utility in
device applications.Comment: Figure 1 with strongly reduced resolutio
Coexistence of the Critical Slowing Down and Glassy Freezing in Relaxor Ferroelectrics
We have developed a dynamical model for the dielectric response in relaxor
ferroelectrics which explicitly takes into account the coexistence of the
critical slowing down and glassy freezing. The application of the model to the
experiment in PMN allowed for the reconstruction of the nonequilibrium spin
glass state order parameter and its comparison with the results of recent NMR
experiment (Blinc et al., Phys. Rev. Lett. 83, No. 2 (1999)). It is shown that
the degree of the local freezing is rather small even at temperatures where the
field-cooled permittivity exceeds the frequency dependent permittivity by an
order of magnitude. This observation indicates the significant role of the
critical slowing down (accompanying the glass freezing) in the system dynamics.
Also the theory predicts an important interrelationship between the frequency
dependent permittivity and the zero-field-cooled permittivity, which proved to
be consistent with the experiment in PMN (A. Levstik et. al., Phys. Rev. B 57,
11204 (1998))
Cytokines and atherosclerosis: a comprehensive review of studies in mice
In the past few years, inflammation has emerged as a major driving force of atherosclerotic lesion development. It is now well-established that from early lesion to vulnerable plaque formation, numerous cellular and molecular inflammatory components participate in the disease process. The most prominent cells that invade in evolving lesions are monocyte-derived macrophages and T-lymphocytes. Both cell types produce a wide array of soluble inflammatory mediators (cytokines, chemokines) which are critically important in the initiation and perpetuation of the disease. This review summarizes the currently available information from mouse studies on the contribution of a specified group of cytokines expressed in atherosclerotic lesions, viz. interleukins (IL-1, IL-2, IL-3, IL-4, IL-5, IL-6, IL-10, IL-12, IL-18, IL-20) and macrophage-associated cytokines [tumour necrosis factor-α (TNF-α); macrophage migration inhibitory factor (MIF); interferon-γ (IFN-γ); colony stimulating factors G-CSF,-M-CSF,-GM-CSF) to atherogenesis. Emphasis is put on the consistency of the effects of these cytokines, i.e. inasmuch an effect depends on the experimental approach applied (overexpression/deletion, strain, gender, dietary conditions, and disease stage). An important outcome of this survey is (i) that only for a few cytokines there is sufficient consistent data allowing classifying them as typically proatherogenic (IL-1, IL-12, IL-18, MIF, IFN-γ, TNF-α, and M-CSF) or antiatherogenic (IL-10) and (ii) that some cytokines (IL-4, IL-6 and GM-CSF) can exert pro- or anti-atherogenic effects depending on the experimental conditions. This knowledge can be used for improved early detection, prevention and treatment of atherosclerosis
Susceptibility and Percolation in 2D Random Field Ising Magnets
The ground state structure of the two-dimensional random field Ising magnet
is studied using exact numerical calculations. First we show that the
ferromagnetism, which exists for small system sizes, vanishes with a large
excitation at a random field strength dependent length scale. This {\it
break-up length scale} scales exponentially with the squared random
field, . By adding an external field we then study the
susceptibility in the ground state. If , domains melt continuously and
the magnetization has a smooth behavior, independent of system size, and the
susceptibility decays as . We define a random field strength dependent
critical external field value , for the up and down spins to
form a percolation type of spanning cluster. The percolation transition is in
the standard short-range correlated percolation universality class. The mass of
the spanning cluster increases with decreasing and the critical
external field approaches zero for vanishing random field strength, implying
the critical field scaling (for Gaussian disorder) , where and .
Below the systems should percolate even when H=0. This implies that
even for H=0 above the domains can be fractal at low random fields, such
that the largest domain spans the system at low random field strength values
and its mass has the fractal dimension of standard percolation .
The structure of the spanning clusters is studied by defining {\it red
clusters}, in analogy to the ``red sites'' of ordinary site-percolation. The
size of red clusters defines an extra length scale, independent of .Comment: 17 pages, 28 figures, accepted for publication in Phys. Rev.
Neutron scattering study of transverse magnetism
In order to clarify the nature of the additional phase transition at H1 (T) \u3c Hc (T) of the layered antiferromagnetic (AF) insulator FeBr2 as found by Aruga Katori et al. (1996) we measured the intensity of different Bragg-peaks in different scattering geometries. Transverse AF ordering is observed in both AF phases, AFI and AFII. Its order parameter exhibits a peak at T1 = T (H1) in temperature scans and does not vanish in zero field. Possible origins of the step-like increase of the transverse ferromagnetic ordering induced by a weak in-plane field component when entering AFI below T1 are discussed
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