Critical behavior of ion mobilities near the superfluid transition

Measurements are reported of the mobilities of helium ions in superfluid helium very close to the λ transition. The mobilities of both positive and negative ions appear to be singular in the sense of having infinite slope at the transition. The measurements are made by a new differential technique, based on the space-charge-limited method, which makes possible a sensitivity to changes in mobility of the order of parts in 104. This allows mobility measurements into the range |ε|<10-4, where ε=(T/Tλ)-1. Most of the reported measurements are taken along isotherms which cross the λ line at elevated pressures, although a series at saturated vapor pressure is also reported. Means of transforming the data between various thermodynamic paths are discussed. Uncertainty as to which thermodynamic path should be considered fundamental together with experimental problems in the technique at this stage in its development make quantitative assessment of the singularity difficult. However, if we assume a limiting form (μ-μλ)/μλ∼(-ε)ρ′, where μ is the mobility and μλ its value at the transition, we find for the exponent ρ′=0.94±0.02

Experiments on Quantum and Thermal Desorption from ^4He Films

Desorption of He atoms from thin films may be resolved experimentally into quantum and thermal components. We show that quantum desorption becomes the dominant part of the signal in submonolayer films. We also show that, when all effects of collisions between desorbed atoms are eliminated, quantum desorption is not focused normal to the surface of optically polished sapphire crystals

Arte de “arremedar”: atos de criação entre humanos e animais no Alto Trombetas (Pará, Brasil)

Entre quilombolas do Alto rio Trombetas, Amazônia, norte do estado do Pará, o conjunto de artifícios usados nas atividades cinegéticas destinados a criar encontros com animais alvos da caça e da pesca é designado sob o termo “arremedar”. O “arremedar” ocorre tanto pela produção humana de movimentos e de sons ritmicamente e melodicamente semelhantes àqueles produzidos por animais, como também pela criação, por caçadores e pescadores, dos traços sensíveis dos habitats e das relações das espécies caçadas e pescadas com outros seres vivos. O presente artigo parte do “arremedar” para abordar como o conhecimento dos quilombolas ligado às esferas do meio ambiente, da percepção, da técnica e do comportamento dos seres vivos atua na configuração das relações entre humanos e animais que ocorrem no espectro das atividades cinegéticas. Pretende-se, por fim, abordar as formas de aprendizado do “arremedar” para elucidar as conexões do praticante com as relações que se dão entre seres vivos e ambientes nos contextos de ocorrência desta prática.Among the Quilombolas of upper Trombetas river, in northern Pará state, arremedar is a set of devices used in hunting activities in order to create encounters with animals that are being chased in land or water. Arremedar includes not only the production of sounds rhythmically and melodically similar to those produced by animals, but also the creation by hunters and fishers of physical and sensible elements that are part of the habitats where these animals live and of its relations with other beings. In this article I argue that the notion of arremedar is part of a form of knowledge that acts in the constitution of human-animal relations. Arremedar, therefore, is associated to the environment and to perceptions, techniques and behaviors of different living beings. Finally, it is intended to address ways of learning how to arremedar to further elucidate the relationship between living beings and environments in the scope of processes and contexts in which this practice is employed

Yokoyama procedure efficacy on non-highly myopic patients with acquired esotropia and hypotropia

Objective: To assess the efficacy of \u201cYokoyama Procedure,\u201d on non-highly myopic patients with acquired esotropia and hypotropia. Methods: The study involved 10 eyes of 5 patients with eso-hypotropia. Inclusion criteria were acquired esotropic-hypotropic strabismus with lateral rectus inferior displacement and superior rectus nasal displacement confirmed by magnetic resonance imaging, refractive errors between \ub16 D, and axial length &lt; 27 mm. Range of full duction movements and maximum angles of abduction-sursumduction was measured in each eye before and after surgery. All patients underwent T1- and T2-weighted magnetic resonance imaging. The surgery was aimed at creating a junction between the muscle bellies of the superior and lateral rectus muscles. This junction was made approximately 14 mm behind the insertions using a non-absorbable mersilene 5/0 suture (Yokoyama procedure). Results: Mean patient age was 64.8 \ub1 4.8 years. The mean globe axial length was 25.4 \ub1 0.76 mm and a mean corresponding spherical equivalent refraction of 123.7 \ub1 1.7 D was observed. Eight eyes on 10 had mild limitation in abduction, while the remaining 2 had no limitation. Three out of 10 eyes showed a moderate limited sursumduction, 5 eyes were categorized as mild, and the remaining 2 had no limitation. No evident post-operative limitation was present in any eye, in both abduction and sursumduction (p &lt; 0.01). Pre-operative esotropia and hypotropia were, respectively, 32 \ub1 11 prismatic diopters and 25 \ub1 5 prismatic diopters, and they were significantly reduced after surgery as 9 \ub1 1.7 prismatic diopters and 6 \ub11 prismatic diopters (p = 0.043), respectively. Conclusion: Yokoyama procedure is an effective, fast, reversible procedure to face eso-hypotropic acquired strabismus, even in patients with a clear magnetic resonance imaging displacement of superior and lateral rectus muscles, and absence of globe dislocation and of elevated myopia