8 research outputs found
Dynamic transitions and hysteresis
When an interacting many-body system, such as a magnet, is driven in time by
an external perturbation, such as a magnetic field,the system cannot respond
instantaneously due to relaxational delay. The response of such a system under
a time-dependent field leads to many novel physical phenomena with intriguing
physics and important technological applications. For oscillating fields, one
obtains hysteresis that would not occur under quasistatic conditions in the
presence of thermal fluctuations. Under some extreme conditions of the driving
field, one can also obtain a non-zero average value of the variable undergoing
such dynamic hysteresis. This non-zero value indicates a breaking of symmetry
of the hysteresis loop, around the origin. Such a transition to the
spontaneously broken symmetric phase occurs dynamically when the driving
frequency of the field increases beyond its threshold value which depends on
the field amplitude and the temperature. Similar dynamic transitions also occur
for pulsed and stochastically varying fields. We present an overview of the
ongoing researches in this not-so-old field of dynamic hysteresis and
transitions.Comment: 30 Pages Revtex, 10 Postscript figures. To appear in Reviews of
Modern Physics, April, 199
Neural correlates of enhanced visual short-term memory for angry faces: An fMRI study
Copyright: © 2008 Jackson et al.Background: Fluid and effective social communication requires that both face identity and emotional expression information are encoded and maintained in visual short-term memory (VSTM) to enable a coherent, ongoing picture of the world and its players. This appears to be of particular evolutionary importance when confronted with potentially threatening displays of emotion - previous research has shown better VSTM for angry versus happy or neutral face identities.Methodology/Principal Findings: Using functional magnetic resonance imaging, here we investigated the neural correlates of this angry face benefit in VSTM. Participants were shown between one and four to-be-remembered angry, happy, or neutral faces, and after a short retention delay they stated whether a single probe face had been present or not in the previous display. All faces in any one display expressed the same emotion, and the task required memory for face identity. We find enhanced VSTM for angry face identities and describe the right hemisphere brain network underpinning this effect, which involves the globus pallidus, superior temporal sulcus, and frontal lobe. Increased activity in the globus pallidus was significantly correlated with the angry benefit in VSTM. Areas modulated by emotion were distinct from those modulated by memory load.Conclusions/Significance: Our results provide evidence for a key role of the basal ganglia as an interface between emotion and cognition, supported by a frontal, temporal, and occipital network.The authors were supported by a Wellcome Trust grant (grant number 077185/Z/05/Z) and by BBSRC (UK) grant BBS/B/16178
A p130<sup><it>Cas</it></sup> tyrosine phosphorylated substrate domain decoy disrupts v-Crk signaling
Abstract Background The adaptor protein p130Cas (Cas) has been shown to be involved in different cellular processes including cell adhesion, migration and transformation. This protein has a substrate domain with up to 15 tyrosines that are potential kinase substrates, able to serve as docking sites for proteins with SH2 or PTB domains. Cas interacts with focal adhesion plaques and is phosphorylated by the tyrosine kinases FAK and Src. A number of effector molecules have been shown to interact with Cas and play a role in its function, including c-crk and v-crk, two adaptor proteins involved in intracellular signaling. Cas function is dependent on tyrosine phosphorylation of its substrate domain, suggesting that tyrosine phosphorylation of Cas in part regulates its control of adhesion and migration. To determine whether the substrate domain alone when tyrosine phosphorylated could signal, we have constructed a chimeric Cas molecule that is phosphorylated independently of upstream signals. Results We found that a tyrosine phosphorylated Cas substrate domain acts as a dominant negative mutant by blocking Cas-mediated signaling events, including JNK activation by the oncogene v-crk in transient and stable lines and v-crk transformation. This block was the result of competition for binding partners as the chimera competed for binding to endogenous c-crk and exogenously expressed v-crk. Conclusion Our approach suggests a novel method to study adaptor proteins that require phosphorylation, and indicates that mere tyrosine phosphorylation of the substrate domain of Cas is not sufficient for its function.</p