Iwasawa N=8 Attractors

Starting from the symplectic construction of the Lie algebra e_7(7) due to Adams, we consider an Iwasawa parametrization of the coset E_7(7)/SU(8), which is the scalar manifold of N=8, d=4 supergravity. Our approach, and the manifest off-shell symmetry of the resulting symplectic frame, is determined by a non-compact Cartan subalgebra of the maximal subgroup SL(8,R) of E_7(7). In absence of gauging, we utilize the explicit expression of the Lie algebra to study the origin of E_7(7)/SU(8) as scalar configuration of a 1/8-BPS extremal black hole attractor. In such a framework, we highlight the action of a U(1) symmetry spanning the dyonic 1/8-BPS attractors. Within a suitable supersymmetry truncation allowing for the embedding of the Reissner-Nordstrom black hole, this U(1) is interpreted as nothing but the global R-symmetry of pure N=2 supergravity. Moreover, we find that the above mentioned U(1) symmetry is broken down to a discrete subgroup Z_4, implying that all 1/8-BPS Iwasawa attractors are non-dyonic near the origin of the scalar manifold. We can trace this phenomenon back to the fact that the Cartan subalgebra of SL(8,R) used in our construction endows the symplectic frame with a manifest off-shell covariance which is smaller than SL(8,R) itself. Thus, the consistence of the Adams-Iwasawa symplectic basis with the action of the U(1) symmetry gives rise to the observed Z_4 residual non-dyonic symmetry.Comment: 1+26 page

SHG microscopic observations of polar state in Li-doped KTaO3 under electric field

Incipient ferroelectric KTaO3 with off-center Li impurity of the critical concentration of 2.8 mol% was investigated in order to clarify the dipole glass state under electric field. Using optical second-harmonic generation (SHG) microscope, we observed a marked history dependence of SHG intensity through zero-field cooling (ZFC), zero-field heating (ZFH), field heating after ZFC (FH/ZFC) and FH after field cooling (FH/FC). These show different paths with respect to temperature: In the ZFC/ZFH process, weak SHG was observed at low temperature, while in the FH/ZFC process, relatively high SHG appears in a limited temperature range below TF depending on the field strength, and in the FC and FH/FC processes, the SHG exhibits ferroelectric-like temperature dependence: it appears at the freezing temperature of 50K, increases with decreasing temperature and has a tendency of saturation. These experimental results strongly suggest that dipole glass state or polar nano-clusters which gradually freezes with decreasing temperature is transformed into semi-macroscopic polar state under the electric field. However at sufficiently low temperature, the freezing is so strong that the electric field cannot enlarge the polar clusters. These experimental results show that the polar nano-cluster model similar to relaxors would be more relevant in KTaO3 doped with the critical concentration of Li. Further experiments on the anisotropy of SHG determine that the average symmetry of the field-induced polar phase is tetragonal 4mm or 4, which is also confirmed by the X-ray diffraction measurement.Comment: 26 pages, 8 figures, 1 tabl

EVALUATION OF XYLEM MATURTATION PROCESS AND EFFECTS OF RADIAL GROWTH RATE ON CELL MORPHOLOGIES IN WOOD OF BALSA (OCHROMA PRYAMIDALE) TREES

The radial variations of cell morphologies (cell lengths, vessel diameter, vessel frequency and cell wall thickness of wood fibers) were investigated for 7-year-old Ochroma pyramidale trees planted in East Java, Indonesia by developing the linear or nonlinear mixed-effects models. In addition, xylem maturation process based on the cell morphologies and effects of radial growth rate on cell morphologies were discussed. The mean values of cell morphology were as follow: vessel element length 0.59 mm, fiber length 2.16 mm, vessel diameter 221 µm, and fiber wall thickness 1.03 µm. Radial variations of cell length and vessel diameter were well explained by Michaelis-Menten equation: values increased from pith to certain position and then it became almost stable. Vessel frequency, wood fiber diameter, and wood fiber wall thickness was expressed by the formula of logarithmic formula, quadratic formula, and linear formula, respectively. Variance component ration of category was 66.8%, 46.1%, 31.4%, 1.5%, and 33.7% for vessel element length, wood fiber length, vessel diameter, vessel frequency, and wood fiber wall thickness, respectively, suggesting that many cell morphologies influenced by the radial growth rate. Smaller values of mean absolute error obtained in the models in relation to distance from pith were found in all cell morphologies, except for vessel frequency and wood fiber diameter. Thus, xylem maturation of this species depended on diameter growth rather than cambial age. Boundary of core wood and outer wood was 5 to 10 cm from pith in which increasing ratio of cell length reached less than 0.3%. Core wood was characterized as lower wood density and mechanical properties with shorter cell lengths and thinner wood fiber walls, whereas outer wood was characterized as higher wood density and mechanical properties with longer cell length and thicker wood fiber walls

Infrared absorption and Raman scattering on coupled plasmon--phonon modes in superlattices

We consider theoretically a superlattice formed by thin conducting layers separated spatially between insulating layers. The dispersion of two coupled phonon-plasmon modes of the system is analyzed by using Maxwell's equations, with the influence of retardation included. Both transmission for the finite plate as well as absorption for the semi-infinite superlattice in the infrared are calculated. Reflectance minima are determined by the longitudinal and transverse phonon frequencies in the insulating layers and by the density-state singularities of the coupled modes. We evaluate also the Raman cross section from the semi-infinite superlattice.Comment: 20 pages,14 figure

Meridional Distribution of Middle-Energy Protons and Pressure-Driven Currents in the Nightside Inner Magnetosphere: Arase Observations

We examined the average meridional distribution of middle‐energy protons (10–180 keV) and pressure‐driven currents in the nightside (20–04 hr magnetic local time) ring current region during moderately disturbed times using the Arase satellite\u27s data. Because the Arase satellite has a large inclination orbit of 31°, it covers the magnetic latitude (MLAT) in the range of −40° to 40° and a radial distance of <6RE. We found that the plasma pressure decreased significantly with increasing MLAT. The plasma pressure on the same L* shell at 30° < MLAT < 40° was ∼10–60% of that at 0° < 4 MLAT < 10°, and the rate of decrease was larger on lower L* shells. The pressure anisotropy, derived as the perpendicular pressure divided by the parallel pressure minus 1, decreased with radial distance and showed a weak dependence on MLAT. The magnitude of the plasma beta at 30°<MLAT<40° was 1 or 2 orders smaller than that at 0°<MLAT<10°. The plasma pressure normalized by the value at 0°<MLAT<10° estimated from the magnetic strength and anisotropy was roughly consistent with the observed plasma pressure for L*=3.5–5.5. The azimuthal pressure‐gradient current derived from the plasma pressure was distributed over MLAT∼0–20°, while the curvature current was limited within MLAT∼0–10°. We suggest that the latitudinal dependence should be taken into account in interpretations of plasma parameters in successive orbits during magnetic storms

Magneto infra-red absorption in high electronic density GaAs quantum wells

Magneto infra-red absorption measurements have been performed in a highly doped GaAs quantum well which has been lifted off and bonded to a silicon substrate, in order to study the resonant polaron interaction. It is found that the pinning of the cyclotron energy occurs at an energy close to that of the transverse optical phonon of GaAs. This unexpected result is explained by a model taking into account the full dielectric constant of the quantum well.Comment: 4 pages, 4 figures, to be published in Phys. Rev. Let

Exact Effective Action for (1+1 Dimensional) Fermions in an Abelian Background at Finite Temperature

In an effort to further understand the structure of effective actions for fermions in an external gauge background at finite temperature, we study the example of 1+1 dimensional fermions interacting with an arbitrary Abelian gauge field. We evaluate the effective action exactly at finite temperature. This effective action is non-analytic as is expected at finite temperature. However, contrary to the structure at zero temperature and contrary to naive expectations, the effective action at finite temperature has interactions to all (even) orders (which, however, do not lead to any quantum corrections). The covariant structure thus obtained may prove useful in studying 2+1 dimensional models in arbitrary backgrounds. We also comment briefly on the solubility of various 1+1 dimensional models at finite temperature.Comment: A few clarifying remarks added;21 page

Expression of ZIC family genes in meningiomas and other brain tumors

<p>Abstract</p> <p>Background</p> <p>Zic zinc finger proteins are present in the developing rodent meninges and are required for cell proliferation and differentiation of meningeal progenitors. Although human <it>ZIC </it>genes are known to be molecular markers for medulloblastomas, their expression in meningioma has not been addressed to date.</p> <p>Methods</p> <p>We examined the mRNA and protein expression of human <it>ZIC1</it>, <it>ZIC2</it>, <it>ZIC3</it>, <it>ZIC4 </it>and <it>ZIC5 </it>genes in meningiomas in comparison to other brain tumors, using RT-PCR, analysis of published microarray data, and immunostaining.</p> <p>Results</p> <p><it>ZIC1</it>, <it>ZIC2 </it>and <it>ZIC5 </it>transcript levels in meningiomas were higher than those in whole brain or normal dura mater, whereas all five <it>ZIC </it>genes were abundantly expressed in medulloblastomas. The expression level of <it>ZIC1 </it>in public microarray data was greater in meningiomas classified as World Health Organization Grade II (atypical) than those classified as Grade I (benign). Immunoscreening using anti-ZIC antibodies revealed that 23 out of 23 meningioma cases were ZIC1/2/3/5-immunopositive. By comparison, nuclear staining by the anti-ZIC4 antibody was not observed in any meningioma case, but was strongly detected in all four medulloblastomas. ZIC-positive meningiomas included meningothelial, fibrous, transitional, and psammomatous histological subtypes. In normal meninges, ZIC-like immunoreactivities were detected in vimentin-expressing arachnoid cells both in human and mouse.</p> <p>Conclusions</p> <p>ZIC1, ZIC2, and ZIC5 are novel molecular markers for meningiomas whereas <it>ZIC4 </it>expression is highly selective for medulloblastomas. The pattern of <it>ZIC </it>expression in both of these tumor types may reflect the properties of the tissues from which the tumors are derived.</p

Cortisol-Induced Masculinization: Does Thermal Stress Affect Gonadal Fate in Pejerrey, a Teleost Fish with Temperature-Dependent Sex Determination?

BACKGROUND: Gonadal fate in many reptiles, fish, and amphibians is modulated by the temperature experienced during a critical period early in life (temperature-dependent sex determination; TSD). Several molecular processes involved in TSD have been described but how the animals "sense" environmental temperature remains unknown. We examined whether the stress-related hormone cortisol mediates between temperature and sex differentiation of pejerrey, a gonochoristic teleost fish with marked TSD, and the possibility that it involves glucocorticoid receptor- and/or steroid biosynthesis-modulation. METHODOLOGY/PRINCIPAL FINDINGS: Larvae maintained during the period of gonadal sex differentiation at a masculinizing temperature (29 degrees C; 100% males) consistently had higher cortisol, 11-ketotestoterone (11-KT), and testosterone (T) titres than those at a feminizing temperature (17 degrees C; 100% females). Cortisol-treated animals had elevated 11-KT and T, and showed a typical molecular signature of masculinization including amh upregulation, cyp19a1a downregulation, and higher incidence of gonadal apoptosis during sex differentiation. Administration of cortisol and a non-metabolizable glucocorticoid receptor (GR) agonist (Dexamethasone) to larvae at a "sexually neutral" temperature (24 degrees C) caused significant increases in the proportion of males. CONCLUSIONS/SIGNIFICANCE: Our results suggest a role of cortisol in the masculinization of pejerrey and provide a possible link between stress and testicular differentiation in this gonochoristic TSD species. Cortisol role or roles during TSD of pejerrey seem(s) to involve both androgen biosynthesis- and GR-mediated processes. These findings and recent reports of cortisol effects on sex determination of sequential hermaphroditic fishes, TSD reptiles, and birds provide support to the notion that stress responses might be involved in various forms of environmental sex determination