Magnetic anomalies in the spin chain system, Sr3_3Cu1−x_{1-x}Znx_xIrO6_6

We report the results of ac and dc magnetization (M) and heat-capacity (C) measurements on the solid solution, Sr$_3$Cu$_{1-x}$Zn$_x$IrO$_6$. While the Zn end member is known to form in a rhombohedral pseudo one-dimensional K$_4$CdCl$_6$ structure with an antiferromagnetic ordering temperature of (T$_N$ =) 19 K, the Cu end member has been reported to form in a monoclinically distorted form with a Curie temperature of (T$_C$ =) 19 K. The magnetism of the Zn compound is found to be robust to synthetic conditions and is broadly consistent with the behavior known in the literature. However, we find a lower magnetic ordering temperature (T$_o$) for our Cu compound (~ 13 K), thereby suggesting that T$_o$ is sensitive to synthetic conditions. The Cu sample appears to be in a spin-glass-like state at low temperatures, judged by a frequency dependence of ac magnetic susceptibility and a broadening of the C anomaly at the onset of magnetic ordering, in sharp contrast to earlier proposals. Small applications of magnetic field, however, drive this system to ferromagnetism as inferred from the M data. Small substitutions for Cu/Zn (x = 0.75 or 0.25) significantly depress magnetic ordering; in other words, T$_o$ varies non-monotonically with x (T$_o$ ~ 6, 3 and 4 K for x = 0.25, 0.5, and 0.67 respectively). The plot of inverse susceptibility versus temperature is non-linear in the paramagnetic state as if correlations within (or among) the magnetic chains continuously vary with temperature. The results establishComment: 7 pages, 7 figures, Revte

Tuning the spin Hamiltonian of NENP by external pressure: a neutron scattering study

We report an inelastic neutron scattering study of antiferromagnetic spin dynamics in the Haldane chain compound Ni(C2H8N2)2NO2ClO4 (NENP) under external hydrostatic pressure P = 2.5 GPa. At ambient pressure, the magnetic excitations in NENP are dominated by a long-lived triplet mode with a gap which is split by orthorhombic crystalline anisotropy into a lower doublet centered at $\Delta_\perp\approx$ 1.2meV and a singlet at $\Delta_\parallel\approx$ 2.5meV. With pressure we observe appreciable shifts in these levels, which move to $\Delta_\perp{(2.5GPa)}\approx$ 1.45 meV and $\Delta_\parallel(2.5GPa)\approx$ 2.2meV. The dispersion of these modes in the crystalline c-direction perpendicular to the chain was measured here for the first time, and can be accounted for by an interchain exchange J'_c approximately 3e-4*J which changes only slightly with pressure. Since the average gap value $\Delta_H\approx$ 1.64 meV remains almost unchanged with P, we conclude that in NENP the application of external pressure does not affect the intrachain coupling J appreciably, but does produce a significant decrease of the single-ion anisotropy constant from D/J = 0.16(2) at ambient pressure to D/J = 0.09(7) at P = 2.5 GPa.Comment: LaTeX file nenp_p.tex, 10 pages, 1 table, 5 figures. Submitted to Phys. Rev.

Spin-Vacancy-Induced Long-Range Order in a New Haldane-Gap Antiferromagnet

Magnetic susceptibility, high-field magnetization and inelastic neutron scattering experiments are used to study the magnetic properties of a new S=1 quasi-1-dimensional antiferromagnet PbNi2V2O8. Inter-chain interactions are shown to be almost, but not quite, strong enough to destroy the nonmagnetic singlet ground state and the energy gap in the magnetic excitation spectrum. Substituting nonmagnetic Mg$^{2+}$ (S=0) ions for Ni$^{2+}$ (S=1) induces a magnetically ordered state at low temperatures. To our knowledge this is the first observation of doping-induced long-range order in a Haldane-gap system.Comment: 5 pages including 4 figure

Anxiety and threat perception abnormalities in normal children

Examined the relationship between childhood anxiety and threat perception abnormalities. 105 children (aged 8-13 yrs) were exposed to stories reflecting 3 types of anxiety: social anxiety, separation anxiety, and generalized anxiety. From children's reactions to the stories, a number of threat perception indices were derived. Children's level of anxiety was assessed by means of questionnaires and a structured diagnostic interview. Results indicate that high levels of anxiety, as measured by questionnaires and interview, were accompanied by a high frequency of threat perception, high ratings of threat, a high frequency of threatening interpretations, high levels of negative feelings and cognitions, and an early detection of threat. Furthermore, results seemed to suggest that threat perception abnormalities were mediated by children's general level of anxiety rather than by levels of specific anxiety symptoms. Examples of stories that were used in this study are appended

Zazie@60: some linguistic considerations

This article considers the colloquial language used in Zazie dans le métro from a sociolinguistic viewpoint. To the extent that a fictional work can be said to provide evidence of linguistic variation, Zazie offers glimpses into the pronunciation, grammar and vocabulary of French at the time it was written, as well as confirmation of other sources regarding social variation, notably working-class speech and the style dimension, partly in relation to regional variation, or rather its absence. For this reason, the novel remains a valuable point of reference for contemporary linguists. The novel, in conjunction with other works by Queneau, prompts further questions to do with the level of cognition at work when linguistic variation takes place

Associations of symptoms of anxiety disorders and self-reported behavior problems in normal children

61 children, aged between 14 and 18 years, completed the Screen for Child Anxiety Related Emotional Disorders, a scale of anxiety disorders symptoms, and the Youth Self-report, a measure of internalizing, i.e., emotional, and externalizing, i.e., behavioral, problems. Analysis showed that, with the exception of the Social Phobia and the Specific Phobia subscales, Screen total and subscale scores were significantly related to Internalizing problems (rs between .40 and .77). Thus, the more frequently children reported Anxiety Disorder symptoms, the more often they reported emotional problems. Furthermore, in particular, anxious-depressed problems as measured by the Youth Self-report were significantly associated with scores on Screen scales. These results further support the concurrent validity of the Screen

Correlations Between Two Multidimensional Anxiety Scales for Children

The correlation between scores on two new anxiety questionnaires for children ( ns = 54 boys, 54 girls), the Screen for Child Anxiety Related Emotional Disorders and the Multidimensional Anxiety Scale for Children was .72, with values for subtests ranging between .35 and .63. </jats:p