Gapped and gapless short range ordered magnetic states with (12,12,12)(\frac{1}{2},\frac{1}{2},\frac{1}{2}) wavevectors in the pyrochlore magnet Tb2+x_{2+x}Ti2−x_{2-x}O7+δ_{7+\delta}

Recent low temperature heat capacity (C$_P$) measurements on polycrystalline samples of the pyrochlore antiferromagnet Tb$_{2+x}$Ti$_{2-x}$O$_{7+\delta}$ have shown a strong sensitivity to the precise Tb concentration $x$, with a large anomaly exhibited for $x \sim 0.005$ at $T_C \sim 0.5$ K and no such anomaly and corresponding phase transition for $x \le 0$. We have grown single crystal samples of Tb$_{2+x}$Ti$_{2-x}$O$_{7+\delta}$, with approximate composition $x=-0.001, +0.0042$, and $+0.0147$, where the $x=0.0042$ single crystal exhibits a large C$_P$ anomaly at $T_C$=0.45 K, but neither the $x=-0.001$ nor the $x=+0.0147$ single crystals display any such anomaly. We present new time-of-flight neutron scattering measurements on the $x=-0.001$ and the $x=+0.0147$ samples which show strong $\left(\frac{1}{2},\frac{1}{2},\frac{1}{2}\right)$ quasi-Bragg peaks at low temperatures characteristic of short range antiferromagnetic spin ice (AFSI) order at zero magnetic field but only under field-cooled conditions, as was previously observed in our $x = 0.0042$ single crystal. These results show that the strong $\left(\frac{1}{2},\frac{1}{2},\frac{1}{2}\right)$ quasi-Bragg peaks and gapped AFSI state at low temperatures under field cooled conditions are robust features of Tb$_2$Ti$_2$O$_7$, and are not correlated with the presence or absence of the C$_P$ anomaly and phase transition at low temperatures. Further, these results show that the ordered state giving rise to the C$_P$ anomaly is confined to $0 \leq x \leq 0.01$ for Tb$_{2+x}$Ti$_{2-x}$O$_{7+\delta}$, and is not obviously connected with conventional order of magnetic dipole degrees of freedom.Comment: 7 pages, 3 figure

Are Microbubbles Necessary for the Breakdown of Liquid Water Subjected to a Submicrosecond Pulse?

Electrical breakdown in homogeneous liquid water for an ∼ 100 ns voltage pulse is analyzed. It is shown that electron-impact ionization is not likely to be important and could only be operative for low-density situations or possibly under optical excitation. Simulation results also indicate that field ionization of liquid water can lead to a liquid breakdown provided the ionization energies were very low in the order of 2.3eV. Under such conditions, an electric-field collapse at the anode and plasma propagation toward the cathode, with minimal physical charge transport, is predicted. However, the low, unphysical ionization energies necessary for matching the observed current and experimental breakdown delays of ∼ 70 ns precludes this mechanism. Also, an ionization within the liquid cannot explain the polarity dependence nor the stochastic-dendritic optical emission structures seen experimentally. It is argued here that electron-impact ionization within randomly located microbubbles is most likely to be responsible for the collective liquid breakdown behaviors

Les enjeux éthiques de l’enseignement en ergothérapie : des pistes de solutions

Cet article consiste en la 2e partie des résultats d’une étude que notre équipe a menée sur les enjeux éthiques de l’enseignement en ergothérapie et leurs pistes de solutions. Tandis que le premier article de 2020 a mis en lumière ces enjeux, le présent article porte sur les moyens de les résoudre. L’ergothérapeute qui enseigne à des étudiants en ergothérapie est tôt ou tard confronté à des enjeux éthiques. Or, ces enjeux sont peu documentés dans les écrits, de même que les pistes de solutions que les ergothérapeutes qui enseignent utilisent ou envisagent. Cette étude qualitative a permis à onze ergothérapeutes-enseignantes des quatre universités francophones du Québec qui préparent la relève ergothérapique de partager leurs bons coups. Dix unités de sens relatives à ces pistes de solutions émergent des résultats, lesquelles ont été regroupées suivant les trois domaines de l’éthique (micro, méso et macro) de Glaser. Les quatre pistes de solutions micro-environnementales sont : a) développer ses compétences éthiques; b) se soutenir entre pairs; c) développer ses compétences en lien avec sa tâche; et d) prendre soin de soi. Les quatre pistes de solutions méso-environnementales sont : a) créer des espaces de parole; b) offrir de la formation en éthique; c) faire de l’advocacy méso; et d) changer la culture académique. Les deux pistes de solutions macro-environnementales sont : a) faire de l’advocacy macro et b) travailler en partenariat avec les milieux cliniques. Bien que des pistes de solutions documentées dans les écrits n’aient pas été discutées par les participantes, celles que ces dernières discutent rejoignent les pistes de solutions abordées dans les écrits. Il ressort des résultats que l’éthique occupe une place limitée dans la préparation et la formation continue des enseignants en ergothérapie et que le contexte organisationnel, c’est-à-dire la culture du monde académique en général et de la recherche en particulier, est susceptible d’occasionner des enjeux éthiques préoccupants. This article presents the second part of the results of a study our team conducted on the ethical issues in occupational therapy education and their solutions. While the first article in 2020 highlighted these issues, this article focuses on ways to address them. The occupational therapist who teaches occupational therapy students is sooner or later confronted with ethical issues. However, these issues are not well documented in the literature, nor are the solutions used or considered by occupational therapists educators. In this qualitative study, eleven occupational therapist educators from four francophone universities in Quebec who are preparing the next generation of occupational therapists shared their success stories. Ten units of meaning related to these solutions emerge from the results, which have been grouped according to Glaser’s three domains of ethics (micro, meso and macro). The four micro-environmental solutions include: a) developing ethical skills; b) peer support; c) developing task-related skills; and d) self-care. The four meso-environmental solutions are: a) creating spaces for discussion; b) providing ethics training; c) doing meso advocacy; and d) changing the academic culture. The two macro-environmental solutions are: a) macro-level advocacy; and b) working in partnership with clinical settings. Although some of the solutions documented in the literature were not discussed by the participants, those discussed by the participants were consistent with the solutions discussed in the literature. The results indicate that ethics has a limited place in the preparation and continuing education of occupational therapy educators and that the organizational context, i.e., the culture of academia in general and research in particular, is likely to create ethical issues of concern