Magnetoelectric Properties of (Ca1−x_{1-x}Srx_{x})2_2CoSi2_2O7_7 Crystals

We have investigated the magnetoelectric properties of (Ca$_{1-x}$Sr$_{x}$)$_2$CoSi$_2$O$_7$ ($0\leq x\leq 1$) crystals with a quasi-two-dimensional structure. In Ca$_2$CoSi$_2$O$_7$ ($x=0$), a canted antiferromagnetic transition occurs at 5.6 K. The transition temperature $T_{\rm N}$ is increasing with increasing Sr concentration, and the rises of the magnetization and dielectric constant become larger. Since the dielectric constant shows large change at $T_{\rm N}$ and the magnetocapacitance effect is observed below $T_{\rm N}$, a coupling between the magnetism and dielectricity is strong in (Ca$_{1-x}$Sr$_{x}$)$_2$CoSi$_2$O$_7$. The positive magnetocapacitance is reduced by Sr substitution, and is not observed in $x\geq 0.5$. Namely, the compound of $x\geq 0.5$ does not show the magnetic-field-induced electric polarization. On the other hand, the negative magnetocapacitance is enhanced by Sr substitution.Comment: 4 pages, 2figures, proceeding of International Conference on Magnetism 200

SiO Emission in the Multi-Lobe Outflow associated with IRAS 16293-2422

We have mapped the thermal emission line of SiO (v = 0; J = 2-1) associated with the quadrupolar molecular outflow driven by the very cold far-infrared source IRAS 16293-2422. The SiO emission is significantly enhanced in the northeastern red lobe and at the position ~50" east of the IRAS source. Strong SiO emission observed at ~50" east of the IRAS source presents evidence for a dynamical interaction between a part of the eastern blue lobe and the dense ambient gas condensation, however, such an interaction is unlikely to be responsible for producing the quadrupolar morphology. The SiO emission in the northeastern red lobe shows the spatial and velocity structure similar to those of the CO outflow, suggesting that the SiO emission comes from the molecular outflow in the northeastern red lobe itself. The observed velocity structure is reproduced by a simple spatio-kinematic model of bow shock with a shock velocity of 19-24 km/s inclined by 30-45 deg from the plane of the sky. This implies that the northeastern red lobe is independent of the eastern blue lobe and that the quadrupolar structure is due to two separate bipolar outflows. The SiO emission observed in the western red lobe has a broad pedestal shape with low intensity. Unlike the SiO emission in the northeastern red lobe, the spatial extent of the SiO emission in the western red lobe is restricted to its central region. The spatial and velocity structures and the line profiles suggest that three different types of the SiO emission are observed in this outflow; the SiO emission arises from the interface between the outflowing gas and the dense ambient gas clump, the SiO emission coming from the outflow lobe itself, and the broad SiO emission with low intensity observed at the central region of the outflow lobe.Comment: 14 pages, 6 figures (figures 1 and 4 are color), gzipped tar file, To appear in the Ap

Photoactivatable genetically encoded calcium indicators for targeted neuronal imaging.

Circuit mapping requires knowledge of both structural and functional connectivity between cells. Although optical tools have been made to assess either the morphology and projections of neurons or their activity and functional connections, few probes integrate this information. We have generated a family of photoactivatable genetically encoded Ca(2+) indicators that combines attributes of high-contrast photolabeling with high-sensitivity Ca(2+) detection in a single-color protein sensor. We demonstrated in cultured neurons and in fruit fly and zebrafish larvae how single cells could be selected out of dense populations for visualization of morphology and high signal-to-noise measurements of activity, synaptic transmission and connectivity. Our design strategy is transferrable to other sensors based on circularly permutated GFP (cpGFP)

IRCS/Subaru Observations of Water in the Inner Coma of Comet 73P-B/Schwassmann-Wachmann 3: Spatially Resolved Rotational Temperatures and Ortho-Para Ratios

Comet 73P-B/Schwassmann-Wachmann 3 was observed with IRCS/Subaru at geocentric distance of 0.074 AU on UT 10 May 2006. Multiple H2O emission lines were detected in non-resonant fluorescence near 2.9 microns. No significant variation in total H2O production rate was found during the (3 hour) duration of our observations. H2O rotational temperatures and ortho-to-para abundance ratios were measured for several positions in the coma. The temperatures extracted from two different time intervals show very similar spatial distributions. For both, the rotational temperature decreased from ~110 K to ~90 K as the projected distance from the nucleus increased from ~5 to ~30 km. We see no evidence for OPR change in the coma. The H2O ortho-para ratio is consistent with the statistical equilibrium value (3.0) for all spatially resolved measurements. This implies a nuclear spin temperature higher than ~ 45 K.Comment: accepted for Icaru

Fluorescence Imaging and Spectroscopy of Biomaterials in Air and Liquid by Scanning Near-Field Optical/Atomic Force Microscopy

We have developed scanning near-field optical/atomic force microscopy (SNOM/AFM). The SNOM/AFM uses a bent optical fiber simultaneously as a dynamic force AFM cantilever and a SNOM probe. Resonant frequency of the optical fiber cantilever is 15-40 kHz. Optical resolution of the SNOM/AFM images shows less than 50 nm. The SNOM/ AFM system contains photon counting system and polychrometer/intensified coupled charge devise (ICCD) system to observe fluorescence image and spectrograph of micro areas, respectively. Cultured cells were stained with fluorescein isothiocyanate (FITC)-labeled anti-keratin antibody or FITC-labeled phalloidin after treatment with Triton X-100. Fluorescence and topographic images were obtained in air and water. The fluorescence images showed clear images of keratin and actin filaments. The SNOM/AFM is perfect to observe biomaterials in liquid with a liquid chamber while the topographic Images showed subcellular structures which correspond to keratin and actin filaments

Anomalous Coexistence of Ferroelectric Phases (P∥aP\parallel a and P∥cP\parallel c) in Orthorhombic Eu1−y_{1-y}Yy_yMnO3_3 (y>0.5y>0.5) Crystals

We have investigated the magnetic and dielectric properties of orthorhombic Eu$_{1-y}$Y$_y$MnO$_3$ ($0\leq y\leq 0.6$) single crystals without the presence of the 4$f$ magnetic moments of the rare-earth ions. In $y\geq 0.2$, the magnetic-structure driven ferroelectricity is observed. The ferroelectric transition temperature is steeply reducing with increasing $y$. In $y\geq 0.52$, two ferroelectric phases ($P\parallel a$ and $P\parallel c$) are coexistent at low temperatures. In these phases, ferroelectricity has different origin, which is evidenced by the distinctive poling-electric-field dependence of electric polarization. Namely, the electric polarization along the c axis ($P_c$) is easily saturated by a poling electric field, therefore $P_c$ is caused by the $bc$ spiral antiferromagnetic order. On the other hand, the electric polarization along the a axis ($P_a$) is probably attributed to the collinear $E$-type antiferromagnetic order, because $P_a$ is unsaturated even in a poling field of $10^6$ V/m.Comment: 10 pages, 4figures, to be published in Journal of the Physical Society of Japa

Persistent and Reversible Phase Control in GdMnO3_3 near the Phase Boundary

We have investigated temperature and magnetic-field dependence of dielectric properties in the orthorhombic GdMnO$_3$ single crystal which is located near the phase boundary between the ferroelectric/spiral-antiferromagnetic phase and the paraelectric/$A$-type-antiferromagnetic one. In this compound, strong phase competition between these two phases results in a unique phase diagram with large temperature and magnetic-field hystereses. Based on the phase diagram, we have successfully demonstrated the persistent and reversible phase switching between them by application of magnetic fields.Comment: 4 pages, 2 figures, proceeding of 25th International Conference on Low Temperature Physics LT2

Strange filamentary structures ("fireballs") around a merger galaxy in the Coma cluster of galaxies

We found an unusual complex of narrow blue filaments, bright blue knots, and H-alpha emitting filaments and clouds, which morphologically resembled a complex of ``fireballs,'' extending up to 80 kpc south from an E+A galaxy RB199 in the Coma cluster. The galaxy has a highly disturbed morphology indicative of a galaxy--galaxy merger remnant. The narrow blue filaments extend in straight shapes toward the south from the galaxy, and several bright blue knots are located at the southern ends of the filaments. The Rc band absolute magnitudes, half light radii and estimated masses of the bright knots are -12 - -13 mag, 200 - 300 pc and 10^6-7 Msolar, respectively. Long, narrow H-alpha emitting filaments are connected at the south edge of the knots. The average color of the fireballs is B - Rc = 0.5, which is bluer than RB199 (B - R = 0.99), suggesting that most of the stars in the fireballs were formed within several times 10^8 yr. The narrow blue filaments exhibit almost no H-alpha emission. Strong H-alpha and UV emission appear in the bright knots. These characteristics indicate that star formation recently ceased in the blue filaments and now continues in the bright knots. The gas stripped by some mechanism from the disk of RB199 may be traveling in the intergalactic space, forming stars left along its trajectory. The most plausible fireball formation mechanism is ram pressure stripping by high-speed collision between the galaxy and the hot intra-cluster medium. The fireballs may be a snapshot of diffuse intra-cluster population formation, or halo star population formation in a cluster galaxy.Comment: 13 pages, 14 figures, submitted to Ap

Perilipin regulates the thermogenic actions of norepinephrine in brown adipose tissue

In response to cold, norepinephrine (NE)-induced triacylglycerol hydrolysis (lipolysis) in adipocytes of brown adipose tissue (BAT) provides fatty acid substrates to mitochondria for heat generation (adaptive thermogenesis). NE-induced lipolysis is mediated by protein kinase A (PKA)-dependent phosphorylation of perilipin, a lipid droplet-associated protein that is the major regulator of lipolysis. We investigated the role of perilipin PKA phosphorylation in BAT NE-stimulated thermogenesis using a novel mouse model in which a mutant form of perilipin, lacking all six PKA phosphorylation sites, is expressed in adipocytes of perilipin knockout (Peri KO) mice. Here, we show that despite a normal mitochondrial respiratory capacity, NE-induced lipolysis is abrogated in the interscapular brown adipose tissue (IBAT) of these mice. This lipolytic constraint is accompanied by a dramatic blunting (∼70%) of the in vivo thermal response to NE. Thus, in the presence of perilipin, PKA-mediated perilipin phosphorylation is essential for NE-dependent lipolysis and full adaptive thermogenesis in BAT. In IBAT of Peri KO mice, increased basal lipolysis attributable to the absence of perilipin is sufficient to support a rapid NE-stimulated temperature increase (∼3.0°C) comparable to that in wild-type mice. This observation suggests that one or more NE-dependent mechanism downstream of perilipin phosphorylation is required to initiate and/or sustain the IBAT thermal response