YSix closely related YbT2_2Zn20_{20} (T = Fe, Co, Ru, Rh, Os, Ir) heavy fermion compounds with large local moment degeneracy

Heavy fermion compounds represent one of the most strongly correlated forms of electronic matter and give rise to low temperature states that range from small moment ordering to exotic superconductivity, both of which are often in close proximity to quantum critical points. These strong electronic correlations are associated with the transfer of entropy from the local moment degrees of freedom to the conduction electrons, and, as such, are intimately related to the low temperature degeneracy of the (originally) moment bearing ion. Here we report the discovery of six closely related Yb-based heavy fermion compounds, YbT$_2$Zn$_{20}$, that are members of the larger family of dilute rare earth bearing compounds: RT$_2$Zn$_{20}$ (T = Fe, Co, Ru, Rh, Os, Ir). This discovery doubles the total number of Yb-based heavy fermion materials. Given these compounds' dilute nature, systematic changes in T only weakly perturb the Yb site and allow for insight into the effects of degeneracy on the thermodynamic and transport properties of these model correlated electron systems

Modifying the surface electronic properties of YBa2Cu3O7-delta with cryogenic scanning probe microscopy

We report the results of a cryogenic study of the modification of YBa2Cu3O7-delta surface electronic properties with the probe of a scanning tunneling microscope (STM). A negative voltage applied to the sample during STM tunneling is found to modify locally the conductance of the native degraded surface layer. When the degraded layer is removed by etching, the effect disappears. An additional surface effect is identified using Scanning Kelvin Probe Microscopy in combination with STM. We observe reversible surface charging for both etched and unetched samples, indicating the presence of a defect layer even on a surface never exposed to air.Comment: 6 pages, 4 figures. To appear in Superconductor Science and Technolog

Influence of impurity-scattering on tunneling conductance in d-wave superconductors with broken time reversal symmetry

Effects of impurity scattering on tunneling conductance in dirty normal-metal/insulator/superconductor junctions are studied based on the Kubo formula and the recursive Green function method. The zero-bias conductance peak (ZBCP) is a consequence of the unconventional pairing symmetry in superconductors. The impurity scattering in normal metals suppresses the amplitude of the ZBCP. The degree of the suppression agrees well with results of the quasiclassical Green function theory. When superconductors have $d$+is-wave pairing symmetry, the time-reversal symmetry is broken in superconductors and the ZBCP splits into two peaks. The random impurity scattering reduces the height of the two splitting peaks. The position of the splitting peaks, however, almost remains unchanged even in the presence of the strong impurity scattering. Thus the two splitting peaks never merge into a single ZBCP.Comment: 12 pages, 5 figures, using jpsj2.cls and overcite.st

Josephson effect in d-wave superconductor junctions in a lattice model

Josephson current between two d-wave superconductors is calculated by using a lattice model. Here we consider two types of junctions, $i.e.$, the parallel junction and the mirror-type junction. The maximum Josephson current $(J_{c})$ shows a wide variety of temperature ($T$) dependence depending on the misorientation angles and the types of junctions. When the misorientation angles are not zero, the Josephson current shows the low-temperature anomaly because of a zero energy state (ZES) at the interfaces. In the case of mirror-type junctions, $J_c$ has a non monotonic temperature dependence. These results are consistent with the previous results based on the quasiclassical theory. [Y. Tanaka and S. Kashiwaya: Phys. Rev. B \textbf{56} (1997) 892.] On the other hand, we find that the ZES disappears in several junctions because of the Freidel oscillations of the wave function, which is peculiar to the lattice model. In such junctions, the temperature dependence of $J_{c}$ is close to the Ambegaokar-Baratoff relation.Comment: 17 pages, 10 figures, using jpsj2.cls and oversite.st

Sport, War and Democracy in Classical Athens

This article concerns the paradox of athletics in classical Athens. Democracy may have opened up politics to every class of Athenian but it had little impact on sporting participation. The city’s athletes continued to drawn predominantly from the upper class. It comes as a surprise then that lower-class Athenians actually esteemed athletes above every other group in the public eye, honoured them very generously when they won, and directed a great deal of public and private money to sporting competitions and facilities. In addition athletics escaped the otherwise persistent criticism of upper-class activities in the popular culture of the democracy. The research of social scientists on sport and aggression suggests this paradox may have been due to the cultural overlap between athletics and war under the Athenian democracy. The article concludes that the practical and ideological democratization of war by classical Athens legitimized and supported upper-class sport

Molecular Identification of Atlantic Bluefin Tuna (Thunnus thynnus, Scombridae) Larvae and Development of a DNA Character-Based Identification Key for Mediterranean Scombrids

The Atlantic bluefin tuna, Thunnus thynnus, is a commercially important species that has been severely over-exploited in the recent past. Although the eastern Atlantic and Mediterranean stock is now showing signs of recovery, its current status remains very uncertain and as a consequence their recovery is dependent upon severe management informed by rigorous scientific research. Monitoring of early life history stages can inform decision makers about the health of the species based upon recruitment and survival rates. Misidentification of fish larvae and eggs can lead to inaccurate estimates of stock biomass and productivity which can trigger demands for increased quotas and unsound management conclusions. Herein we used a molecular approach employing mitochondrial and nuclear genes (CO1 and ITS1, respectively) to identify larvae (n = 188) collected from three spawning areas in the Mediterranean Sea by different institutions working with a regional fisheries management organization. Several techniques were used to analyze the genetic sequences (sequence alignments using search algorithms, neighbour joining trees, and a genetic character-based identification key) and an extensive comparison of the results is presented. During this process various inaccuracies in related publications and online databases were uncovered. Our results reveal important differences in the accuracy of the taxonomic identifications carried out by different ichthyoplanktologists following morphology- based methods. While less than half of larvae provided were bluefin tuna, other dominant taxa were bullet tuna (Auxis rochei), albacore (Thunnus alalunga) and little tunny (Euthynnus alletteratus). We advocate an expansion of expertise for a new generation of morphology-based taxonomists, increased dialogue between morphology-based and molecular taxonomists and increased scrutiny of public sequence databases.Versión del editor4,411