Most antiferroelectric ceramics are modified from the prototype PbZrO 3 by adding Sn and Ti in conjunction with small amount of Nb or La to optimize their properties. These modifiers introduce unique nanoscale structural feature to the ceramics in the form of incommensurate modulations. It was shown previously that the modulation is strongly responsive to a change in chemical composition or temperature. However, its response to an electric field, the driving force in real applications, has not been explored before. In the present work the dynamic evolution of the incommensurate modulation during the electric field-induced antiferroelectric-to-ferroelectric transformation was observed with an in situ transmission electron microscopy (TEM) technique. The results indicate that the incommensurate modulation exists as a transverse Pb-cation displacement wave. The wavelength was found to be quite stable against external electrical stimuli, in sharp contrast to the dramatic change under thermal stimuli reported previously. It is suggested that the appeared incommensurate modulation is an average effect of a mixture of two commensurate modulations. The electric field-induced antiferroelectric-to-ferroelectric transformation proceeds with aligning the Pbcation displacements, which resembles the process of 90° reorientation and 180° reversal in normal ferroelectrics.Most antiferroelectric ceramics are modified from the prototype PbZrO 3 by adding Sn and Ti in conjunction with small amount of Nb or La to optimize their properties. These modifiers introduce unique nanoscale structural feature to the ceramics in the form of incommensurate modulations. It was shown previously that the modulation is strongly responsive to a change in chemical composition or temperature. However, its response to an electric field, the driving force in real applications, has not been explored before. In the present work the dynamic evolution of the incommensurate modulation during the electric field-induced antiferroelectric-toferroelectric transformation was observed with an in situ transmission electron microscopy ͑TEM͒ technique.The results indicate that the incommensurate modulation exists as a transverse Pb-cation displacement wave. The wavelength was found to be quite stable against external electrical stimuli, in sharp contrast to the dramatic change under thermal stimuli reported previously. It is suggested that the appeared incommensurate modulation is an average effect of a mixture of two commensurate modulations. The electric field-induced antiferroelectric-to-ferroelectric transformation proceeds with aligning the Pb-cation displacements, which resembles the process of 90°reorientation and 180°reversal in normal ferroelectrics.

Summary Neural plasticity requires protein synthesis, however the identity of newly synthesized proteins generated in response to plasticity-inducing stimuli remains unclear. We used in vivo bio-orthogonal non-canonical amino acid tagging (BONCAT) with the methionine analog, azidohomoalanine (AHA) combined with multidimensional protein identification technique (MudPIT) to identify proteins that are synthesized in tadpole brain over 24 h. We induced conditioning-dependent plasticity of visual avoidance behavior. Induction of behavioral plasticity required NMDA and Ca2+-permeable AMPA receptors, αCaMKII and rapid protein synthesis. Combining BONCAT with Western blots revealed that proteins including αCaMKII, MEK1, CPEB, and GAD65 are synthesized during conditioning. Acute synthesis of CPEB during conditioning is required for behavioral plasticity as well as conditioning-induced synaptic and structural plasticity in the tectal circuit. We outline a signaling pathway regulating protein synthesis-dependent behavioral plasticity in intact animals, identify newly synthesized proteins induced by visual experience and demonstrate a requirement for acute synthesis of CPEB in plasticity.

Detailed studies of the phase transitions in Pb 0.99 Nb 0.02 [(Zr 0.57 Sn 0.43 ) 1−y Ti y ] 0.98 O 3 (y = 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.10, and 0.12) ceramics as a function of composition, temperature, electric field, and time were conducted using Raman spectroscopy. At room temperature, the as-sintered ceramics with y = 0.03-0.08 show an antiferroelectric order while those with y = 0.10 and 0.12 show a ferroelectric order. For the ceramic with y = 0.08, however, a ferroelectric order can also be stabilized at room temperature when it is warmed up from lower temperatures. The electric field-induced ferroelectric phase in the ceramic with y = 0.07 is metastable at room temperature and ages back to the stable antiferroelectric phase on a timescale of hours.

The emergence of dendritic arbor structure in vivo depends on synaptic inputs. We tested whether inhibitory GABAergic synaptic transmission regulates Xenopus optic tectal cell dendritic arbor development in vivo by expressing a peptide corresponding to an intracellular loop (ICL) of the ␥2 subunit of type A GABA receptors (GABA A R), which is required to anchor GABA A receptors to the postsynaptic scaffold. Enhanced green fluorescent protein (EGFP)-tagged ICL (EGFP-ICL) was distributed in a punctate pattern at putative inhibitory synapses, identified by vesicular GABA transporter immunoreactive puncta. ICL expression completely blocked GABA A R-mediated transmission in 36% of transfected neurons and significantly reduced GABA A R-mediated synaptic currents relative to AMPA receptor-mediated synaptic currents in the remaining transfected neurons without altering release probability or neuronal excitability. Further analysis of ICL-expressing neurons with residual GABA A R-mediated inputs showed that the capacity of benzodiazepine to enhance GABAergic synaptic responses was reduced in ICL-expressing neurons, indicating that they were likely depleted of ␥2 subunit-containing GABA A R. Neurons expressing a mutant form of ICL were comparable to controls. In vivo time-lapse images showed that ICL-expressing neurons have more sparsely branched dendritic arbors, which expand over larger neuropil areas than EGFPexpressing control neurons. Analysis of branch dynamics indicated that ICL expression affected arbor growth by reducing rates of branch addition. Furthermore, we found that decreasing GABAergic synaptic transmission with ICL expression blocked visual experience dependent dendritic arbor structural plasticity. Our findings establish an essential role for inhibitory GABAergic synaptic transmission in the regulation of dendritic structural plasticity in Xenopus in vivo.

The synthetic approach to the core framework of the calyciphylline A-type Daphniphyllum alkaloids and total synthesis of himalensine A were described herein. Nitrone-induced 1,3-dipolar [3 + 2] cycloaddition was applied for the construction of A/C rings along with the all-carbon quaternary center. Pd-catalyzed enolate alkenylation and ring closing metathesis (RCM) were adopted to install the B/D rings to accomplish the [6,6,5,7] core framework. Nazarov reaction was utilized to install the F ring to complete the total synthesis of himalensine A.

Ceramics in the xPb(Zn 1/3 Nb 2/3 )O 3 −(1 − x)Pb(Zr 0.5 Ti 0.5 )O 3 [xPZN-(1 − x)PZT] solid solution system are expected to display excellent dielectric, piezoelectric, and ferroelectric properties in compositions close to the morphotropic phase boundary (MPB). The dielectric behavior of ceramics with x = 0.1−0.6 has been characterized in order to identify the MPB compositions in this system. Combined with X-ray diffraction results, ferroelectric hysteresis measurements, and Raman reflectivity analysis, it was consistently shown that an MPB exists between x = 0.2 and x = 0.3 in this binary system. When x ≤ 0.2, the tetragonal phase dominates at ambient temperatures. In the range of x ≥ 0.3, the rhombohedral phase dominates. For this rhombohedral phase, electrical measurements reveal a profound frequency dispersion in the dielectric response when x ≥ 0.6, suggesting a transition from normal ferroelectric to relaxor ferroelectric between 0.5 ≤ x ≤ 0.6. Excellent piezoelectric properties were found in 0.3PZN-0.7PZT, the composition closest to the MPB with a rhombohedral structure. The results are summarized in a PZN-PZT binary phase diagram. N. Vittayakorn ( )

High electric fields were delivered to specimens during imaging in the transmission electron microscopy (TEM) chamber to reveal details of electric field-induced phenomena in ferroelectric oxides. These include the polarization switching in nanometer-sized ferroelectric domains and the grain boundary cavitation in a commercial lead zirconate titanate (PZT) polycrystalline ceramic, the domain wall fracture in a Pb(Mg 1/ 3 Nb 2/3 )O 3 -PbTiO 3 single crystal, and the transformation of incommensurate modulations in Pb 0.99 Nb 0.02 [(Zr 1−x Sn x ) 1−y Ti y ] 0.98 O 3 (PZST100x/100y/2) polycrystalline ceramics. In the PZT ceramic, a cavitation process was uncovered for the electric field-induced intergranular fracture. In the ferroelectric single crystal, a preexisting crack was observed to deflect and to follow a 90° domain wall, indicating the presence of severe incompatible piezoelectric strains at thedomain wall. In the antiferroelectric PZST ceramics, the electric field-induced antiferroelectric-to-ferroelectric phase transformation was accompanied with the disappearance of incommensurate modulations. High electric fields were delivered to specimens during imaging in the transmission electron microscopy (TEM) chamber to reveal details of electric field-induced phenomena in ferroelectric oxides. These include the polarization switching in nanometer-sized ferroelectric domains and the grain boundary cavitation in a commercial lead zirconate titanate (PZT) polycrystalline ceramic, the domain wall fracture in a /2) polycrystalline ceramics. In the PZT ceramic, a cavitation process was uncovered for the electric field-induced intergranular fracture. In the ferroelectric single crystal, a preexisting crack was observed to deflect and to follow a 90°domain wall, indicating the presence of severe incompatible piezoelectric strains at the domain wall. In the antiferroelectric PZST ceramics, the electric field-induced antiferroelectric-to-ferroelectric phase transformation was accompanied with the disappearance of incommensurate modulations.

Inhibitory neurons are heterogeneous in the mature brain. It is unclear when and how inhibitory neurons express distinct structural and functional profiles. Using in vivo time-lapse imaging of tectal neuron structure and visually-evoked Ca++ responses in tadpoles we found that inhibitory neurons cluster into two groups with opposite valence of plasticity after 4h of dark and visual stimulation. Half decreased dendritic arbor size and Ca++ responses after dark and increased them after visual stimulation, matching plasticity in excitatory neurons. Half increased dendrite arbor size and Ca++ responses following dark and decreased them after stimulation. At the circuit level, visually-evoked excitatory and inhibitory synaptic inputs were potentiated by visual experience and E/I remained constant. Our results indicate that developing inhibitory neurons fall into distinct functional groups with opposite experience-dependent plasticity and as such, are well positioned to foster experience-dependent synaptic plasticity and maintain circuit stability during labile periods of circuit development.