5,661 research outputs found
Odd-petal states and persistent flows in spin-orbit-coupled Bose-Einstein condensates
We study the phase diagram of a Rashba spin-orbit-coupled Bose-Einstein
condensate confined in a two-dimensional toroidal trap. In the immiscible
regime we find an azimuthally periodic density distribution, with the
periodicity highly tuneable as a function of the spin-orbit coupling strength
and which favours an odd number of petals in each component. This allows for a
wide range of states that can be created. We further show that in the miscible
regime, both components possess states with persistent flows with a unit
winding number difference between them and with the absolute values of these
winding numbers depending on the spin-orbit coupling strength. All features of
the odd-petal and the persistent flow states can be explained using a simple
but effective model.Comment: 5 pages, 2 figure
Inactivation of presenilins causes pre-synaptic impairment prior to post-synaptic dysfunction
Synaptic dysfunction is widely thought to be a pathogenic precursor to neurodegeneration in Alzheimerâs disease (AD), and the extent of synaptic loss provides the best correlate for the severity of dementia in AD patients. Presenilins 1 and 2 are the major causative genes of earlyâonset familial AD. Conditional inactivation of presenilins in the adult cerebral cortex results in synaptic dysfunction and memory impairment, followed by ageâdependent neurodegeneration. To characterize further the consequence of presenilin inactivation in the synapse, we evaluated the temporal development of preâsynaptic and postâsynaptic deficits in the Schaefferâcollateral pathway of presenilin conditional double knockout (PS cDKO) mice prior to onset of neurodegeneration. Following presenilin inactivation at 4âweeks, synaptic facilitation and probability of neurotransmitter release are impaired in PS cDKO mice at 5âweeks of age, whereas postâsynaptic NMDA receptor (NMDAR)âmediated responses are normal at 5âweeks but impaired at 6âweeks of age. Longâterm potentiation induced by theta burst stimulation is also reduced in PS cDKO mice at 6âweeks of age. These results show that loss of presenilins results in preâsynaptic deficits in shortâterm plasticity and probability of neurotransmitter release prior to postâsynaptic NMDAR dysfunction, raising the possibility that presenilins may regulate postâsynaptic NMDAR function in part via a transâsynaptic mechanism.This work was supported by the National Institute of Health NS041783 (to J.S.). We would like to thank Xiaoyan Zou and Huailong Zhao for technical assistance. (NS041783 - National Institute of Health)Published versio
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