351 research outputs found
Discovery of SiCSi in IRC+10216: A missing link between gas and dust carriers of SiC bonds
We report the discovery in space of a disilicon species, SiCSi, from
observations between 80 and 350 GHz with the IRAM 30m radio telescope. Owing to
the close coordination between laboratory experiments and astrophysics, 112
lines have now been detected in the carbon-rich star CWLeo. The derived
frequencies yield improved rotational and centrifugal distortion constants up
to sixth order. From the line profiles and interferometric maps with the
Submillimeter Array, the bulk of the SiCSi emis- sion arises from a region of 6
arcseconds in radius. The derived abundance is comparable to that of SiC2. As
expected from chemical equilibrium calculations, SiCSi and SiC2 are the most
abundant species harboring a SiC bond in the dust formation zone and certainly
both play a key role in the formation of SiC dust grains.Comment: To be published in the Astrophysical Journal Letters; Accepted May 6
201
Anisotropic Instabilities in Trapped Spinor Bose-Einstein Condensates
We theoretically investigate the effect of an anisotropic trap on the
instability of the polar phase of a spin-1 Bose-Einstein condensate.
By considering rigorously the spatial quantization, we show that the growth of
the nascent ferromagnetic phase at short times becomes anisotropic with
stronger oscillations in the magnetization correlation function along the
unconfined direction.Comment: 8 pages, 6 figure
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Selective role of the translin/trax RNase complex in hippocampal synaptic plasticity
Activity-dependent local protein synthesis is critical for synapse-specific, persistent plasticity. Abnormalities in local protein synthesis have been implicated in psychiatric disorders. We have recently identified the translin/trax microRNA-degrading enzyme as a novel mediator of protein synthesis at activated synapses. Additionally, translin knockout (KO) mice, which lack translin/trax, exhibit some of the behavioral abnormalities found in a mouse model of fragile X syndrome (fragile X mental retardation protein-FMRP-KO mice). Therefore, identifying signaling pathways interacting with translin/trax to support persistent synaptic plasticity is a translationally relevant goal. Here, as a first step to achieve this goal, we have assessed the requirement of translin/trax for multiple hippocampal synaptic plasticity paradigms that rely on distinct molecular mechanisms. We found that mice lacking translin/trax exhibited selective impairment in a form of persistent hippocampal plasticity, which requires postsynaptic protein kinase A (PKA) activity. In contrast, enduring forms of plasticity that are dependent on presynaptic PKA were unaffected. Furthermore, these mice did not display exaggerated metabotropic glutamate receptor-mediated long-term synaptic depression (mGluR-LTD), a hallmark of the FMRP KO mice. On the contrary, translin KO mice exhibited deficits in N-methyl-d-aspartate receptor (NMDAR) dependent LTD, a phenotype not observed in the FMRP knockouts. Taken together, these findings demonstrate that translin/trax mediates long-term synaptic plasticity that is dependent on postsynaptic PKA signaling and suggest that translin/trax and FMRP play distinct roles in hippocampal synaptic plasticity
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Correction to: Selective role of the translin/trax RNase complex in hippocampal synaptic plasticity
An amendment to this paper has been published and can be accessed via the original article
Neural-specific expression, genomic structure, and chromosomal localization of the gene encoding the zinc-finger transcription factor NGFI-C.
Saddle point localization of molecular wavefunctions
The quantum mechanical description of isomerization is based on bound eigenstates of the molecular potential energy surface. For the near-minimum regions there is a textbook-based relationship between the potential and eigenenergies. Here we show how the saddle point region that connects the two minima is encoded in the eigenstates of the model quartic potential and in the energy levels of the [H, C, N] potential energy surface. We model the spacing of the eigenenergies with the energy dependent classical oscillation frequency decreasing to zero at the saddle point. The eigenstates with the smallest spacing are localized at the saddle point. The analysis of the HCN???HNC isomerization states shows that the eigenstates with small energy spacing relative to the effective (v1, v3, l) bending potentials are highly localized in the bending coordinate at the transition state. These spectroscopically detectable states represent a chemical marker of the transition state in the eigenenergy spectrum. The method developed here provides a basis for modeling characteristic patterns in the eigenenergy spectrum of bound states
Thiol agents and Bcl-2 identify an alphavirus-induced apoptotic pathway that requires activation of the transcription factor NF-kappa B.
4-Aminopyridine-induced epileptogenesis depends on activation of mitogen-activated protein kinase ERK
Extracellular signal-regulated kinases such as ERK1 [p44
mitogen-activated protein kinase (MAPK)] and ERK2 (p42
MAPK) are activated in the CNS under physiological and
pathological conditions such as ischemia and epilepsy. Here,
we studied the activation state of ERK1/2 in rat hippocampal
slices during application of the K+ channel blocker 4-aminopyridine
(4AP, 50 lM), a procedure that enhances synaptic
transmission and leads to the appearance of epileptiform
activity. Hippocampal slices superfused with 4AP-containing
medium exhibited a marked activation of ERK1/2 phosphorylation
that peaked within about 20 min. These effects
were not accompanied by changes in the activation state of
c-Jun N-terminal kinase (JNK), another member of the MAP
kinase superfamily. 4AP-induced ERK1/2 activation
was inhibited by the voltage-gated Na+ channel blocker
tetrodotoxin (1 lM). We also found that application of the ERK
pathway inhibitors U0126 (50 lM) or PD98059 (100 lM)
markedly reduced 4AP-induced epileptiform synchronization,
thus abolishing ictal discharges in the CA3 area. The effects
induced by U0126 or PD98059 were not associated with
changes in the amplitude and latency of the field potentials
recorded in the CA3 area following electrical stimuli delivered
in the dentate hylus. These data demonstrate that activation of
ERK1/2 accompanies the appearance of epileptiform activity
induced by 4AP and suggest a cause-effect relationship
between the ERK pathway and epileptiform synchronization
Discovery of SiCSi in IRC+10216: A missing link between gas and dust carriers of Si-C bonds
We report the discovery in space of a disilicon species, SiCSi, from observations between 80 and 350 GHz with the IRAM 30 m radio telescope. Owing to the close coordination between laboratory experiments and astrophysics, 112 lines have now been detected in the carbon-rich star CW Leo. The derived frequencies yield improved rotational and centrifugal distortion constants up to sixth order. From the line profiles and interferometric maps with the Submillimeter Array, the bulk of the SiCSi emission arises from a region of 6'' in radius. The derived abundance is comparable to that of SiC2. As expected from chemical equilibrium calculations, SiCSi and SiC2 are the most abundant species harboring a Si−C bond in the dust formation zone and certainly both play a key role in the formation of SiC dust grains.We thank spanish MINECO for funding under grants AYA2009-07304, AYA2012-32032, CSD2009-00038, and ERC under ERC-2013-SyG, G. A. 610256 NANOCOSMOS. The new laboratory measurements in Cambridge were supported by NASA grant NNX13AE59G
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