New Phase Induced by Pressure in the Iron-Arsenide Superconductor K-Ba122

The electrical resistivity rho of the iron-arsenide superconductor Ba1-xKxFe2As2 was measured in applied pressures up to 2.6 GPa for four underdoped samples, with x = 0.16, 0.18, 0.19 and 0.21. The antiferromagnetic ordering temperature T_N, detected as a sharp anomaly in rho(T), decreases linearly with pressure. At pressures above around 1.0 GPa, a second sharp anomaly is detected at a lower temperature T_0, which rises with pressure. We attribute this second anomaly to the onset of a phase that causes a reconstruction of the Fermi surface. This new phase expands with increasing x and it competes with superconductivity. We discuss the possibility that a second spin-density wave orders at T_0, with a Q vector distinct from that of the spin-density wave that sets in at T_N.Comment: Two higher K concentrations were added, revealing a steady expansion of the new phase in the T-P phase diagra

Universal heat conduction in the iron-arsenide superconductor KFe2As2 : Evidence of a d-wave state

The thermal conductivity of the iron-arsenide superconductor KFe2As2 was measured down to 50 mK for a heat current parallel and perpendicular to the tetragonal c-axis. A residual linear term (RLT) at T=0 is observed for both current directions, confirming the presence of nodes in the superconducting gap. Our value of the RLT in the plane is equal to that reported by Dong et al. [Phys. Rev. Lett. 104, 087005 (2010)] for a sample whose residual resistivity was ten times larger. This independence of the RLT on impurity scattering is the signature of universal heat transport, a property of superconducting states with symmetry-imposed line nodes. This argues against an s-wave state with accidental nodes. It favors instead a d-wave state, an assignment consistent with five additional properties: the magnitude of the critical scattering rate for suppressing Tc to zero; the magnitude of the RLT, and its dependence on current direction and on magnetic field; the temperature dependence of the thermal conductivity.Comment: To appear in Physical Review Letter

Doping evolution of the superconducting gap structure in the underdoped iron arsenide Ba1-xKxFe2As2 revealed by thermal conductivity

The thermal conductivity kappa of the iron-arsenide superconductor Ba1-xKxFe2As2 was measured for heat currents parallel and perpendicular to the tetragonal c axis at temperatures down to 50 mK and in magnetic fields up to 15 T. Measurements were performed on samples with compositions ranging from optimal doping (x = 0.34; Tc = 39 K) down to dopings deep into the region where antiferromagnetic order coexists with superconductivity (x = 0.16; Tc = 7 K). In zero field, there is no residual linear term in kappa(T) as T goes to 0 at any doping, whether for in-plane or inter-plane transport. This shows that there are no nodes in the superconducting gap. However, as x decreases into the range of coexistence with antiferromagnetism, the residual linear term grows more and more rapidly with applied magnetic field. This shows that the superconducting energy gap develops minima at certain locations on the Fermi surface and these minima deepen with decreasing x. We propose that the minima in the gap structure arise when the Fermi surface of Ba1-xKxFe2As2 is reconstructed by the antiferromagnetic order

From d-wave to s-wave pairing in the iron-pnictide superconductor (Ba,K)Fe2As2

The nature of the pairing state in iron-based superconductors is the subject of much debate. Here we argue that in one material, the stoichiometric iron pnictide KFe2As2, there is overwhelming evidence for a d-wave pairing state, characterized by symmetry-imposed vertical line nodes in the superconducting gap. This evidence is reviewed, with a focus on thermal conductivity and the strong impact of impurity scattering on the critical temperature Tc. We then compare KFe2As2 to Ba0.6K0.4Fe2As2, obtained by Ba substitution, where the pairing symmetry is s-wave and the Tc is ten times higher. The transition from d-wave to s-wave within the same crystal structure provides a rare opportunity to investigate the connection between band structure and pairing mechanism. We also compare KFe2As2 to the nodal iron-based superconductor LaFePO, for which the pairing symmetry is probably not d-wave, but more likely s-wave with accidental line nodes

Spatial constancy of attention across eye movements is mediated by the presence of visual objects

Recent studies have shown that attentional facilitation lingers at the retinotopic coordinates of a previously attended position after an eye movement. These results are intriguing, because the retinotopic location becomes behaviorally irrelevant once the eyes have moved. Critically, in these studies participants were asked to maintain attention on a blank location of the screen. In the present study, we examined whether the continuing presence of a visual object at the cued location could affect the allocation of attention across eye movements. We used a trans-saccadic cueing paradigm in which the relevant positions could be defined or not by visual objects (simple square outlines). We find an attentional benefit at the spatiotopic location of the cue only when the object (the placeholder) has been continuously present at that location. We conclude that the presence of an object at the attended location is a critical factor for the maintenance of spatial constancy of attention across eye movements, a finding that helps to reconcile previous conflicting results

Vocal quality description of senile characters from Hollywood movies

PURPOSE: to describe the vocal quality of Hollywood movies characters playing elderly people roles. METHODS: a total of 50 aged character voice samples were used, 11 female and 39 male, from 38 Hollywood movies from the period between 1993 and 2001. Twenty speech therapists performed a perceptual auditory analysis. The listener's task required classifying each character either as elderly or as adult by their speech features, and also assessing their voices following the parameters that are most frequently addressed in the literature as being disordered at an old age. The parameters were hoarseness, vocal fry, breathiness, strain, roughness, vocal weakness, nasal resonance, tremor, vocal modulation, pitch and fundamental frequency stability. RESULTS: after the perceptual auditory analysis we noted that a great number of actors (82%) used senile voices indicating old age, even though not all of them were elderly. The most salient voice set altered was vocal quality (92%), demonstrated by vocal fry (80%), breathiness (54%), strain (38%), hoarseness (30%), and weak voice (28%). The second vocal set most used by the actors for their roles was extensive vocal modulation (44%). It was also observed that vocal instability (64%) was used by the actors. CONCLUSION: it can be concluded from the results that Hollywood movies characterize the elderly characters through evident deviations in vocal quality and modulation, using disordered types of voices and vocal unstable and extensive modulation.OBJETIVO: descrever a qualidade vocal de personagens idosos dos filmes de Hollywood. MÉTODOS: foram colhidas 50 amostras de fala de personagens idosos, 11 do sexo feminino e 39 do masculino, de 38 filmes hollywoodianos dos anos de 1993 a 2001. Através da análise perceptivo-auditiva das amostras de fala, 20 fonoaudiólogos treinados classificaram cada personagem em idoso e não idoso, além de avaliarem as vozes quanto aos seguintes parâmetros citados pela literatura como mais alterados: rouquidão, crepitação, soprosidade, tensão, aspereza, astenia, nasalidade, tremor, modulação, pitch e estabilidade da frequência fundamental. RESULTADOS: após a análise perceptivo-auditiva, foi observado que a grande maioria dos atores (82%) utilizou voz de idoso para representar seus papéis. O marcador mais evidente nas vozes foi alteração na qualidade vocal (92%), demonstrada por crepitação (80%), soprosidade (54%), tensão (38%), rouquidão (30%) e astenia (28%). O segundo marcador mais utilizado pelos atores nas suas representações foi a modulação vocal ampla e variada (44%). Também foram observadas alterações no controle da voz (36%) e instabilidade da frequência fundamental (38%). CONCLUSÃO: a partir dos resultados obtidos pode-se concluir que os filmes de Hollywood caracterizam o idoso através de desvios evidentes na qualidade e modulação da voz, utilizando tipos de vozes alteradas e modulação vocal ampla e instável.Universidade Federal de São Paulo (UNIFESP) Centro de Estudos da VozUNIFESP, Centro de Estudos da VozSciEL