Quasiparticles of string solutions in the spin-1/2 antiferromagnetic Heisenberg chain in a magnetic field

Spectral properties of the spin-1/2 antiferromagnetic Heisenberg chain in a magnetic field are investigated by using exact Bethe-ansatz solutions. We argue that not only quasiparticles called psinon and antipsinon but also a quasiparticle representing a 2-string in the Bethe ansatz plays an important role for dynamical properties in a magnetic field. Combined with psinon and antipsinon, the quasiparticle for a 2-string forms a continuum in the high-energy regime for transverse dynamical structure factor $S^{+-}(k,\omega)$. In the zero-field limit, the continuum is located on the mode of the lowest excited states in zero field called the des Cloizeaux-Pearson mode. In a magnetic field, the continuum separates from other low-energy continua, and reduces to the mode of bound states of overturned spins from the fully polarized state near the saturation field. We confirm the relevance through comparisons with available experimental results on the quasi-one-dimensional antiferromagnet CuCl$_2\cdot$2N(C$_5$D$_5$).Comment: 4 pages, 1 figure, 1 tabl

Tracing star formation in galaxies with molecular line and continuum observations

We report our recent progress on extragalactic spectroscopic and continuum observations, including HCN(J=1-0), HCO$^+$(J=1-0), and CN(N=1-0) imaging surveys of local Seyfert and starburst galaxies using the Nobeyama Millimeter Array, high-J CO observations (J=3-2 observations using the Atacama Submillimeter Telescope Experiment (ASTE) and J=2-1 observations with the Submillimeter Array) of galaxies, and $\lambda$ 1.1 mm continuum observations of high-z violent starburst galaxies using the bolometer camera AzTEC mounted on ASTE.Comment: 6 pages, 5 figures, To appear in proceedings of "Far-Infrared and Submillimeter Emission of the Interstellar Medium", EAS Publication Series, Bad Honnef, November 2007, Eds. C. Kramer, S. Aalto, R. Simon. See http://www.nro.nao.ac.jp/~f0212kk/FIR07/kk-ver20.pdf for a version with high resolution figure

Childhood maltreatment and amygdala connectivity in methamphetamine dependence: a pilot study.

IntroductionChildhood maltreatment, a well-known risk factor for the development of substance abuse disorders, is associated with functional and structural abnormalities in the adult brain, particularly in the limbic system. However, almost no research has examined the relationship between childhood maltreatment and brain function in individuals with drug abuse disorders.MethodsWe conducted a pilot study of the relationship between childhood maltreatment (evaluated with the Childhood Trauma Questionnaire; Bernstein and Fink 1998) and resting-state functional connectivity of the amygdala (bilateral region of interest) with functional magnetic resonance imaging in 15 abstinent, methamphetamine-dependent research participants. Within regions that showed connectivity with the amygdala as a function of maltreatment, we also evaluated whether amygdala connectivity was associated positively with negative affect and negatively with healthy emotional processing.ResultsThe results indicated that childhood maltreatment was positively associated with resting-state connectivity between the amygdala and right hippocampus, right parahippocampal gyrus, right inferior temporal gyrus, right orbitofrontal cortex, cerebellum, and brainstem. Furthermore, connectivity between the amygdala and hippocampus was positively related to measures of depression, trait anxiety, and emotion dysregulation, and negatively related to self-compassion and dispositional mindfulness.ConclusionsThese findings suggest that childhood maltreatment may contribute to increased limbic connectivity and maladaptive emotional processing in methamphetamine-dependent adults, and that healthy emotion regulation strategies may serve as a therapeutic target to ameliorate the associated behavioral phenotype. Childhood maltreatment warrants further investigation as a potentially important etiological factor in the neurobiology and treatment of substance use disorders

Dense Molecular Gas and the Role of Star Formation in the Host Galaxies of Quasi-Stellar Objects

New millimeter-wave CO and HCN observations of the host galaxies of infrared-excess Palomar Green quasi-stellar objects (PG QSOs) previously detected in CO are presented. These observations are designed to assess the validity of using the infrared luminosity to estimate star formation rates of luminous AGN by determining the relative significance of dust-heating by young, massive stars and active galactic nuclei (AGN) in QSO hosts and IRAS galaxies with warm, AGN-like infrared colors. The HCN data show the PG QSO host IZw1 and most of the warm IRAS galaxies to have high L_IR / L'_HCN (>1600) relative to the cool IRAS galaxy population for which the median L_IR / L'_HCN ~ 890(+440,-470). If the assumption is made that the infrared emission from cool IRAS galaxies is reprocessed light from embedded star-forming regions, then high values of L_IR / L'_HCN are likely the result of dust heating by the AGN. Further, if the median ratio of L'_HCN / L'_CO ~ 0.06 observed for Seyfert galaxies and IZw1 is applied to the PG QSOs not detected in HCN, then the derived L_IR / L'_HCN correspond to a stellar contribution to the production of L_IR of ~ 7-39%, and star formation rates ~ 2-37 M_sun/yr are derived for the QSO hosts. Alternatively, if the far-infrared is adopted as the star formation component of the total infrared in cool galaxies, the stellar contributions in QSO hosts to their L_FIR are up to 35% higher than the percentages derived for L_IR. This raises the possibility that the L_FIR in several of the PG QSO hosts, including IZw1, could be due entirely to dust heated by young, massive stars. Finally, there is no evidence that the global HCN emission is enhanced relative to CO in galaxies hosting luminous AGN.Comment: LaTex, 31 pages, including 9 postscript figures, AJ, in press (December 2006