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A new ternary uranium germanide U

In high temperature superconductors, local and excessive temperature rise occurs after normal transition because normal zone propagation velocities are slow at high operation temperature and then the superconductors may be degraded or burned. Therefore, it is essential to detect the temperature rise in high temperature superconducting coils and protect them as soon as possible. The authors have presented a detection method based on time-frequency visualization of AE signals. In this paper, the authors discuss detection and frequency analysis of AE signals accompanying with epoxy cracks caused by thermal expansion in an HTS coil by using the method.

The normal zone propagation velocities in high T c superconductors are slow at high operation temperature and therefore local and excessive temperature rise generates at quench occurrence, and then the superconductors are degraded or burned. Therefore it is essential to detect the temperature rise in high T c superconducting (HTS) coils as soon as possible and protect them. The authors have presented a quench detection method for HTS coils by time–frequency visualization of AE signals and have shown its usefulness for a HTS coil with height and outer diameter of 40–50 mm. In this paper, the authors present a quench detection/protection system based on superior method in quench detection time to the previous method and show its usefulness for a larger HTS coil (height and outer diameter: 160–190 mm) than the previous coil.

We have studied photoluminescence spectra in detail to clarify the character of the isoelectronic traps in dilute GaAsN alloys. Several sharp lines have been observed at the lower energy side of the GaAs bandgap and are in good agreement with the nitrogen pair-related emission lines previously reported. In addition to the nitrogen pair-related lines, some other emission lines have been also observed. Compared with the energies of these emission lines and the nitrogen pair-related emission lines, it was found that the energy differences agree with the longitudinal optical phonon energy at the Γ point of GaAs, showing that the character of isoelectronic traps due to nitrogen pairs in dilute GaAsN alloys is significantly contributed from the conduction band state at the Γ point. The temperature dependence of the peak energy of luminescence due to nitrogen pairs also indicates that the character of isoelectronic traps in dilute GaAsN alloys is due to the conduction band edge state at the Γ point of GaAs. For a dilute GaAsN alloy with lower nitrogen concentration, we have observed that the intensity of an emission line increased superlinearly with excitation power . (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Our measurements of the ^{59}Co NMR spin-spin relaxation in URh_{0.9}Co_{0.1}Ge reveal a divergence of electronic spin fluctuations in the vicinity of the field-induced quantum critical point at H_{R}≈13 T, around which reentrant superconductivity (RSC) occurs in the ferromagnetic heavy fermion compound URhGe. We map out the strength of spin fluctuations in the (H_{b},H_{c}) plane of magnetic field components and show that critical fluctuations develop in the same limited region near the field H_{R} as that where RSC is observed. This strongly suggests these quantum fluctuations as the pairing glue responsible for the RSC. The fluctuations observed are characteristic of a tricritical point, followed by a phase bifurcation toward quantum critical end points.

We have investigated the excitation power density and nitrogen concentration dependence of the changes in the radiative efficiency of GaAsN alloys to examine the mechanism of the photo-induced improvement of radiative efficiency. With increasing excitation power density, the radiative efficiency increased more rapidly. The measure of the improvement Iafter/Ibefore superlinearly increased with increasing nitrogen concentration x up to ∼1%. This suggests that the nonradiative recombination centers eliminated by photoexcitation are not defects formed by a single nitrogen atom but complexes formed by gathering of several nitrogen atoms. Micro Raman study revealed that the GaAs-like LO mode phonon peak intensity increased with photoexcitation time in a similar way to the increase in the radiative efficiency. Considering that this phenomenon is in a time scale of several seconds, the photo-induced structural changes correspond not to long range inter-diffusion but to local changes in atomic configuration which lead to the decrease in the density of nonradiative recombination centers. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We perform polarized electronic Raman scattering on URu2Si2 single crystals at low temperature down to 8 K in the hidden-order state and under a magnetic field up to 10 T. The hidden-order state is characterized by a sharp excitation at 1.7 meV and a gap in the electronic continuum below 6.8 meV. Both Raman signatures are of pure A2g symmetry. By comparing the behavior of the Raman sharp excitation and the neutron resonance at Q0=(0,0,1), we provide new evidence, constrained by selection rules of the two probes, that the hidden-order state breaks the translational symmetry along the c axis such that Γ and Z points fold on top of each other. The observation of these distinct Raman features with a peculiar A2g symmetry as a signature of the hidden-order phase places strong constraints on current theories of the hidden-order in URu2Si2.

We have studied the temperature dependence of photoluminescence (PL) spectra of GaAsN alloys. The PL peak energy shift due to the temperature change decreases with increasing N concentration of GaAsN alloys. The localized state emission partly contributes to the decrease in the PL peak energy shift. In addition, the small PL peak energy shift at high temperatures is due to the reduction in the temperature dependence of the band gap energy. From the analysis using the Bose-Einstein statistical expression, the average phonon energy is much larger than that expected from the linear interpolation between GaAs and GaN, indicating that the interaction between electrons and phonons localized at N atoms plays an important role in the reduction of the temperature dependence of the band gap energy of GaAsN alloys.

Spectroscopic ellipsometry has been used to investigate the electronic structure near the fundamental absorption edge of GaAsN alloys grown by metalorganic vapor phase epitaxy. The fundamental absorption edge is clearly observed in the imaginary part of the dielectric function and shifts to lower energies with increasing N concentration. In addition, the absorption structure is observed near the E 0 gap energy of GaAs even in GaAsN alloys. This unequivocally shows that the fundamental absorption edge of GaAsN is not shifted from the E 0 gap of GaAs but newly formed by the N incorporation. Thus, the formation of the narrowest band gap of GaAsN alloys is found to be completely different from that of conventional compound semiconductor alloys, such as AlGaAs and GaAsP.

Crack growth of cracked aluminum panels repaired with a bonded composite patch is analyzed to evaluate the effect of repair. An efficient finite element analysis using Mindlin plate elements is developed. The technique is extended to a three-layer model, which consists of patch, adhesive and plate layers. The crack growth behavior of an aluminum panel with the composite patch is discussed on the basis of the Paris relation.

Using resistivity, heat-capacity, thermal-expansion, and susceptibility measurements we study the normal-state behavior of KFe2As2. Both the Sommerfeld coefficient (γ≈103 mJ mol(-1) K(-2)) and the Pauli susceptibility (χ≈4×10(-4)) are strongly enhanced, which confirm the existence of heavy quasiparticles inferred from previous de Haas-van Alphen and angle-resolved photoemission spectroscopy experiments. We discuss this large enhancement using a Gutzwiller slave-boson mean-field calculation, which shows the proximity of KFe2As2 to an orbital-selective Mott transition. The temperature dependence of the magnetic susceptibility and the thermal expansion provide strong experimental evidence for the existence of a coherence-incoherence crossover, similar to what is found in heavy fermion and ruthenate compounds, due to Hund's coupling between orbitals.

5575 Background: The unpredictable nature of primary epithelial ovarian cancer (EOC) response to treatment necessitates the identification of factors that predict long-term outcome. CDK activity is the core regulator of the cell-cycle checkpoint for cancer cells. We previously found that cell death induced by taxanes requires increased activity of CDK1 and CDK2- fundamental kinases in cell proliferation. Thus, we hypothesized that CDK1/2 activities can determine the prognosis of patients with primary EOC. Methods: We retrospectively analyzed frozen ovarian cancer specimens from 72 women treated with cytoreductive surgery and adjuvant chemotherapy for newly diagnosed EOC. Median patient age was 61 years (range, 38–80), 91% had FIGO stage III/IV disease, and 86% were treated with platinum- or taxane-based regimens. Median follow-up was 32 months; median time to treatment failure (TTF), defined as time from surgery to first relapse for patients who had achieved complete response or time to disease progression for those who had persistent disease, was 15 months. Enzymatic activity of CDK1/2 in the tumor tissues was determined by a modified in vitro kinase activity assay using a C2P device (Sysmex Inc.). Recursive partitioning and regression trees algorithm (RPART) was used to identify the cohorts based on CDK1/2 activities. Results: In the univariate analysis, disease stage (p=0.021), type of surgery (optimal vs. suboptimal) (p=0.004), presence of ascites (p=0.043), and CA125 after the adjuvant therapy (p=0.005) were significant predictors of TTF. The cohort with CDK2 activity = 87.3 had a significantly shorter TTF (p=0.014) and the cohort with CDK1 activity = 226.35 showed a trend toward longer TTF (p=0.094). Multivariate Cox proportional hazards regression analysis revealed CDK2 activity ( [Table: see text]