H alpha spectropolarimetry of RY Tauri and PX Vulpeculae (Research Note)

Aims. To detect line effects using spectropolarimetry in order to find evidence of rotating disks and their respective symmetry axes in T Tauri stars. Methods. We used the IAGPOL imaging polarimeter along with the Eucalyptus-IFU to obtain spectropolarimetric measurements of the T Tauri stars RY Tau (two epochs) and PX Vul (one epoch). Evidence of line effects showing a loop in the Q-U diagram favors a compact rather than an extended source for the line photons in a rotating disk. In addition, the polarization position angle (PA) obtained using the line effect can constrain the symmetry axis of the disk. Results. RY Tau shows a variable H alpha double peak in 2004-2005 data. A polarization line effect is evident in the Q-U diagram for both epochs confirming a clockwise rotating disk. A single loop is evident in 2004 changing to a linear excursion plus a loop in 2005. Interestingly, the intrinsic PA calculated using the line effect is consistent between our two epochs (similar to 167 degrees). An alternative intrinsic PA computed from the interstellar polarization-corrected continuum and averaged between 2001-2005 yielded a PA similar to 137 degrees. This last value is closer to perpendicular to the observed disk direction (similar to 25 degrees), as expected from single scattering in an optically thin disk. For PX Vul, we detected spectral variability in H alpha along with non-variable continuum polarization when compared with previous data. The Q-U diagram shows a well-defined loop in H alpha associated with a counter-clockwise rotating disk. The symmetry axis inferred from the line effect has a PA similar to 91 degrees (with an ambiguity of 90 degrees). Our results confirm previous evidence that the emission line in T Tauri stars has its origin in a compact source scattered off a rotating accretion disk.

Leptin's effect on puberty in mice is relayed by the ventral premammillary nucleus and does not require signaling in Kiss1 neurons

Studies m hum ins and rodents indicate that a minimum amount of stored energy is required for normal pubertal development The adipocyte-derived hormone leptin is a key metabolic signal to the neuroendocrine reproductive axis Humans and mice lacking leptin or the leptin receptor (LepR) (ob/ob and db/db mice, respectively) are infertile and fail to enter puberty Leptin administration to leptin-deficient subjects and ob/ob mice induces puberty and restores fertility, but the exact site or sites of leptin action are unclear Here, we found that genetic deletion of LepR selectively from hypothalamic Kiss1 neurons m mice had no effect on puberty or fertility, indicating that direct leptin signaling m Kiss1 neurons is not required for these processes However, bilateral lesions of the ventral premammillary nucleus (PMV) of ob/ob mice blunted the ability of exogenous leptin to induce sexual maturation Moreover, unilateral reexpression of endogenous LepR m PMV neurons was sufficient to induce puberty and improve fertility m female LepR-null mice This LepR reexpression also normalized the increased hypothalamic GnRH content characteristic of leptin-signaling deficiency These data suggest that the PMV is a key site for leptin's permissive action at the onset of puberty and support the hypothesis that the multiple actions of leptin to control metabolism and reproduction at e anatomically dissociated

Analytical solutions for Tokamak equilibria with reversed toroidal current

In tokamaks, an advanced plasma confinement regime has been investigated with a central hollow electric current with negative density which gives rise to non-nested magnetic surfaces. We present analytical solutions for the magnetohydrodynamic equilibria of this regime in terms of non-orthogonal toroidal polar coordinates. These solutions are obtained for large aspect ratio tokamaks and they are valid for any kind of reversed hollow current density profiles. The zero order solution of the poloidal magnetic flux function describes nested toroidal magnetic surfaces with a magnetic axis displaced due to the toroidal geometry. The first order correction introduces a poloidal field asymmetry and, consequently, magnetic islands arise around the zero order surface with null poloidal magnetic flux gradient. An analytic expression for the magnetic island width is deduced in terms of the equilibrium parameters. We give examples of the equilibrium plasma profiles and islands obtained for a class of current density profile. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3624551]

Determination of the minimum value of the safety factor from geodesic Alfven eigenmodes in Joint European Torus

An analysis of the experimental conditions under which low-frequency (70-150 kHz) Alfven eigertmodes (AE) are excited during the monster sawtooth in Joint European Torus [F Romanelli et al, Proceedings of the 22nd IAEA Fusion Energy Conference, Geneva, Switzerland, 2008] is presented for the specific case of a discharge with ion cyclotron heating (5 MW) Using a simplified AE model for modes excited at the Alfven wave continuum maximum with geodesic corrections taken into account, the temporal evolution of the value of the safety factor q(0) at the magnetic axis is determined We describe a new scheme to determine the time variation of q(0) that works under conditions in which other standard diagnostics, such as the motional Stark effect do not give reliable results such as during a monster sawtooth [doi 10 1063/1 3494212]

High-p(T) pi(0) production with respect to the reaction plane in Au plus Au collisions at s(NN)=200 GeV

Measurements of the azimuthal anisotropy of high-p(T) neutral pion (pi(0)) production in Au+Au collisions at s(NN)=200 GeV by the PHENIX experiment are presented. The data included in this article were collected during the 2004 Relativistic Heavy Ion Collider running period and represent approximately an order of magnitude increase in the number of analyzed events relative to previously published results. Azimuthal angle distributions of pi(0) mesons detected in the PHENIX electromagnetic calorimeters are measured relative to the reaction plane determined event-by-event using the forward and backward beam-beam counters. Amplitudes of the second Fourier component (v(2)) of the angular distributions are presented as a function of pi(0) transverse momentum (p(T)) for different bins in collision centrality. Measured reaction plane dependent pi(0) yields are used to determine the azimuthal dependence of the pi(0) suppression as a function of p(T), R(AA)(Delta phi,p(T)). A jet-quenching motivated geometric analysis is presented that attempts to simultaneously describe the centrality dependence and reaction plane angle dependence of the pi(0) suppression in terms of the path lengths of hypothetical parent partons in the medium. This set of results allows for a detailed examination of the influence of geometry in the collision region and of the interplay between collective flow and jet-quenching effects along the azimuthal axis.

Magnetoelectric effects in an organometallic quantum magnet

Metal-organic materials constitute a new field in which to search for ferroelectricity and coupling between electricity and magnetism. We observe a magnetic field-induced change in the electric polarization, Delta P(H), that reaches 50 mu C/m(2) in single crystals of NiCl(2)-4SC(NH(2))(2) (DTN). DTN forms a tetragonal structure that breaks inversion symmetry with the electrically polar thiourea molecules [SC(NH(2))] all tilted in the same direction along the c axis. The field H induces canted antiferromagnetism of the Ni S = 1 spins between 2 and 12 T and our measurements show that the electric polarization increases monotonically in this range, saturating above 12 T. By modeling the microscopic origin of this magnetoelectric effect, we find that the leading contribution to Delta P comes from the change in the crystal electric field, with a smaller contribution from magnetic exchange striction. The finite value of Delta P induced by magnetostriction results from the polar nature of the thiourea molecules bonded to the Ni atoms, and it is amplified by the softness of these organic molecules.

Azimuthal Charged-Particle Correlations and Possible Local Strong Parity Violation

Parity-odd domains, corresponding to nontrivial topological solutions of the QCD vacuum, might be created during relativistic heavy-ion collisions. These domains are predicted to lead to charge separation of quarks along the system's orbital momentum axis. We investigate a three-particle azimuthal correlator which is a P even observable, but directly sensitive to the charge separation effect. We report measurements of charged hadrons near center-of-mass rapidity with this observable in Au+Au and Cu+Cu collisions at s(NN)=200 GeV using the STAR detector. A signal consistent with several expectations from the theory is detected. We discuss possible contributions from other effects that are not related to parity violation.

Emergence of Turbulence in an Oscillating Bose-Einstein Condensate

We report on the experimental observation of vortex tangles in an atomic Bose-Einstein condensate (BEC) of (87)Rb atoms when an external oscillatory perturbation is introduced in the trap. The vortex tangle configuration is a signature of the presence of a turbulent regime in the cloud. We also show that this turbulent cloud suppresses the aspect ratio inversion typically observed in quantum degenerate bosonic gases during free expansion. Instead, the cloud expands keeping the ratio between their axis constant. Turbulence in atomic superfluids may constitute an alternative system to investigate decay mechanisms as well as to test fundamental theoretical aspects in this field.

Low-temperature study of a new nevirapine pseudopolymorph

The title compound (systematic name: 11-cyclopropyl-4-methyl-5,11-dihydro-6H-dipyrido[3,2-b: 2',3'-e][1,4] diazepin-6-one butanol 0.3-solvate), C15H14N4O center dot 0.3C(4)H(9)OH, was crystallized in a new triclinic pseudopolymorphic form, a butanol solvate, and the crystal structure determined at 150 K. The molecular conformation of this new form differs from that reported previously, although the main intermolecular hydrogen-bond pattern remains the same. N-H center dot center dot center dot O hydrogen bonds [N center dot center dot center dot O = 2.957 (3) angstrom] form centrosymmetric dimers and the crystal packing of this new pseudopolymorph generates infinite channels along the b axis.

Bis(tetraphenylphosphonium) tris[N-(methylsulfonyl)dithiocarbimato(2-)-kappa(2)S,S ']stannate(IV)

In the title complex, (C(24)H(20)P)(2)[Sn(C(2)H(3)NO(2)S(3))(3)], the Sn(IV) atom is coordinated by three N-(methylsulfonyl) dithiocarbimate bidentate ligands through the anionic S atoms in a slightly distorted octahedral coordination geometry. There is one half-molecule in the asymmetric unit; the complex is located on a crystallographic twofold rotation axis passing through the cation and bisecting one of the (non-symmetric) ligands, which appears thus disordered over two sites of equal occupancy. In the crystal structure, weak intermolecular C-H center dot center dot center dot O and C-H center dot center dot center dot S interactions contribute to the packing stabilization.

1-Furoyl-3-[3-(trifluoromethyl)phenyl]thiourea

The title compound, C(13)H(9)F(3)N(2)O(2)S, crystallizes with two independent molecules in the asymmetric unit. The central thiourea core is roughly coplanar with the furan and benzene rings, showing O-C-N-C(S) torsion angles of 2.3 (4) and -11.4 (2) degrees and (S) C -N-C-C torsion angles of -2.4 (4) and -28.8 (4) degrees, respectively, in the two independent molecules. The trans-cis geometry of the thiourea fragment is stabilized by an intramolecular N-H center dot center dot center dot O hydrogen bond between the H atom of the cis thioamide and the carbonyl O atom. In the crystal structure, intermolecular N-H center dot center dot center dot S hydrogen bonds form centrosymmetric dimers extending along the b axis.

Lupeol

The title compound [systematic name: 3 beta-lup-20(29)-en-3-ol], C(30)H(50)O, was isolated from the leaves of Garcinia brasiliensis (common name: bacupari; a member of the Guttiferae family) and has been shown to have many useful medicinal and biological properties. The lupeol molecule consists of four six-membered rings (adopting chair conformations) and one five-membered ring (with an envelope conformation), all fused in trans fashion. Lupeol is isomorphic with the pentacyclic triterpene 3 beta,30-dihydroxylup-20(29)-ene, which differs from lupeol due to the presence of an additional hydroxy group. The crystal packing is stabilized by van der Waals interactions and intermolecular O-H center dot center dot center dot O hydrogen bonds, giving rise to an infinite helical chain along the c axis.

Redetermination of 1-benzyl-3-furoyl-1-phenylthiourea

The title compound, C(19)H(16)N(2)O(2)S, was synthesized from furoyl isothiocyanate and N-benzylaniline in dry acetone and the structure redetermined. The structure [Otazo-Sanchez et al. (2001). J. Chem. Soc. Perkin Trans. 2, pp. 2211-2218] has been re-determined in order to establish the intramolecular and intermolecular interactions. The thiourea group is in the thioamide form. The thiourea group makes a dihedral angle of 29.2 (6)degrees with the furoyl group. In the crystal structure, molecules are linked by intermolecular C-H center dot center dot center dot O interactions, forming one-dimensional chains along the a axis. An intramolecular N-H center dot center dot center dot O hydrogen bond is also present.

N-(2-furylcarbonyl)piperidine-1-carbothioamide

The title compound, C11H14N2O2S, was synthesized from furoyl isothiocyanate and piperidine in dry acetone. The thiourea group is in the thioamide form. The thiourea group makes a dihedral angle of 53.9 (1)degrees with the furan carbonyl group. In the crystal structure, molecules are linked by intermolecular N-H center dot center dot center dot O hydrogen bonds, forming one-dimensional chains along the c axis. An intramolecular N-H center dot center dot center dot O hydrogen bond is also present.

Angular dependence of the thermal-lens effect on LiSrAlF(6) and LiSrGaF(6) single crystals

We apply thermal-lens (TL) spectrometry to measure the angular dependence of the TL effect on colquiriite single crystals. The experiments were performed with LiSrAlF(6) and LiSrGaF(6) using a two-beam mode-mismatched configuration. The results show that it is possible to minimize the TL effect by selecting the appropriate crystal orientation. Our data also show that the anisotropy of the linear thermal expansion coefficient drives the amplitude of the TL effect, including the inversion from focusing to defocusing as the crystal orientation angle tends to the c-axis direction. The results may be useful for those working to develop a high-power laser using LiSrAlF(6)(:Cr) and LiSrGaF(6)(:Cr) single crystals, allowing for optimization of the designed laser cavity. (C) 2008 Optical Society of America.