33 research outputs found
Chemistry of layered d-metal pnictide oxides and their potential as candidates for new superconductors
Layered d-metal pnictide oxides are a unique class of compounds which
consists of characteristic d-metal pnictide layers and metal oxide layers. More
than 100 of these layered compounds, including the recently discovered Fe-based
superconducting pnictide oxides, can be classified into 9 structure types.
These structure types and the chemical and physical properties of the
characteristic d-metal pnictide layers and metal oxide layers of the layered
d-metal pnictide oxides are reviewed and discussed. Furthermore, possible
approaches to design new superconductors based on these layered d-metal
pnictide oxides are proposed.Comment: 29 pages including 6 tables and 2 figure
Selective Optical Control of Synaptic Transmission in the Subcortical Visual Pathway by Activation of Viral Vector-Expressed Halorhodopsin
The superficial layer of the superior colliculus (sSC) receives visual inputs via two different pathways: from the retina and the primary visual cortex. However, the functional significance of each input for the operation of the sSC circuit remains to be identified. As a first step toward understanding the functional role of each of these inputs, we developed an optogenetic method to specifically suppress the synaptic transmission in the retino-tectal pathway. We introduced enhanced halorhodopsin (eNpHR), a yellow light-sensitive, membrane-targeting chloride pump, into mouse retinal ganglion cells (RGCs) by intravitreously injecting an adeno-associated virus serotype-2 vector carrying the CMV-eNpHR-EYFP construct. Several weeks after the injection, whole-cell recordings made from sSC neurons in slice preparations revealed that yellow laser illumination of the eNpHR-expressing retino-tectal axons, putatively synapsing onto the recorded cells, effectively inhibited EPSCs evoked by electrical stimulation of the optic nerve layer. We also showed that sSC spike activities elicited by visual stimulation were significantly reduced by laser illumination of the sSC in anesthetized mice. These results indicate that photo-activation of eNpHR expressed in RGC axons enables selective blockade of retino-tectal synaptic transmission. The method established here can most likely be applied to a variety of brain regions for studying the function of individual inputs to these regions
TOPICAL REVIEW Chemistry of layered d-metal pnictide oxides and their potential as candidates for new superconductors
Layered d-metal pnictide oxides are a unique class of compounds which consist of characteristic d-metal pnictide layers and metal oxide layers. More than 100 of these layered compounds, including the recently discovered Fe-based superconducting pnictide oxides, can be classified into nine structure types. These structure types and the chemical and physical properties of the characteristic d-metal pnictide layers and metal oxide layers of the layered d-metal pnictide oxides are reviewed and discussed. Furthermore, possible approaches to design new superconductors based on these layered d-metal pnictide oxides are proposed
Exploration of Mid-Temperature Alkali-Metal-Ion Extraction Route Using PTFE (AEP): Transformation of α-NaFeO<sub>2</sub>-Type Layered Oxides into Rutile-Type Binary Oxides
Alkali-metal-ion extraction reactions using poly(tetrafluoroethylene)
(PTFE; AEP reactions) were performed on two kinds of α-NaFeO<sub>2</sub>-type layered compounds: Na<sub>0.68</sub>(Li<sub>0.68/3</sub>Ti<sub>1–0.68/3</sub>)O<sub>2</sub> and K<sub>0.70</sub>(Li<sub>0.70/3</sub>Sn<sub>1–0.70/3</sub>)O<sub>2</sub>. At 400 °C
in flowing argon, these layered compounds were reacted with PTFE.
By these reactions, alkali-metal ions in the layered compounds were
successfully extracted, and TiO<sub>2</sub> and SnO<sub>2</sub> with
rutile-type structure were formed. The structural similarity between
the alkali-metal-ion-extracted layered compounds and the binary metal
oxide products in these unique alkali-metal-ion extraction reactions
was interpreted in terms of their interatomic distance distribution
by atomic pair distribution function analysis. The results of this
study indicate that PTFE is an effective agent to extract alkali-metal
ions from layered compounds, and AEP reaction is not limited to the
previously reported γ-FeOOH-type layered titania K<sub>0.8</sub>(Li<sub>0.27</sub>Ti<sub>1.73</sub>)O<sub>4</sub>, but is also applicable
to other layered titania and other non-titanium-based layered metal
oxides. Therefore, it was clarified that AEP reactions are widely
applicable routes to prepare various compounds, including those that
are difficult to synthesize by other reactions
Soft-Chemical Exfoliation of RbSrNb<sub>2</sub>O<sub>6</sub>F into Homogeneously Unilamellar Oxyfluoride Nanosheets
Interlayer Rb<sup>+</sup> of the perovskite-type layered
oxyfluoride RbSrNb<sub>2</sub>O<sub>6</sub>F was ion-exchanged with
H<sup>+</sup>, and the protonated phase was reacted with aqueous solution
of tetrabutylammonium hydroxide to exfoliate it into nanosheets. The
resulting nanosheet suspension exhibits Tyndall scattering of a laser
beam, indicating its colloidal nature. Elemental composition of the
nanosheet was estimated as Sr<sub>0.98</sub>Nb<sub>2</sub>O<sub>6</sub>F<sub>0.97</sub><sup>δ−</sup>, which was quite close
to that of the layer unit of the precursor. The homogeneously unilamellar
nature of this nanosheet was confirmed by atomic force and transmission
electron microscopy observations and X-ray scattering results. The
optical absorption edge of the nanosheet suspension was observed around
at 293 nm, and two well-defined peaks with their maxima at 229 and
278 nm were observed. Furthermore, the aqueous suspension of the nanosheet
exhibits fluorescence emission in the UV-blue region. These properties
of the oxyfluoride nanosheets are quite different from those of its
oxide analogues without F<sup>–</sup>, such as LnNb<sub>2</sub>O<sub>7</sub><sup>–</sup> nanosheets (Ln = La<sup>3+</sup>, Eu<sup>3+</sup>, Sm<sup>3+</sup>), suggesting that anion-site replacement
of oxide nanosheets can be utilized to optimize or induce various
properties
RbBiNb<sub>2</sub>O<sub>7</sub>: A New Lead-Free High‑<i>T</i><sub>c</sub> Ferroelectric
RbBiNb<sub>2</sub>O<sub>7</sub>: A New Lead-Free High‑<i>T</i><sub>c</sub> Ferroelectri
X-Ray Photoelectron Spectroscopy Studies of Yb₁₄MnSb₁₁ and Yb₁₄ZnSb₁₁
Measurements of core and valence electronic states of single crystals of the rare earth transition metal Zintl phases Yb14MnSb11 and Yb14ZnSb11 were performed using the X-ray photoelectron spectroscopy station of Beamline 7 at the Advanced Light Source. Sample surfaces of Yb14MnSb11 and Yb14ZnSb11 were measured as received, after Ar+ ion bombardment, and after cleaving in situ. The single crystal structure of Yb14ZnSb11 is also reported. Both compounds are air-sensitive and show Yb3+ due to surface oxidation. In the case of Yb14MnSb11, there is no evidence for Yb3+ that would be intrinsic to the sample, consistent with previously reported X-ray magnetic circular dichroism studies. Detailed analyses of the Yb14ZnSb11 surfaces reveal a significant contribution of both Yb3+ and Yb2+ 4f states in the valence band region. This result is predicted for the Zn analog by Zintl counting rules and support the mixed valency of Yb for Yb14ZnSb11. Further detailed analysis of the core and valence band structure of both Yb14MnSb11 and Yb14ZnSb11 is presented