Glass-Like Phonon Dynamics and Thermal Transport in a GeTe Nano-Composite at Low Temperature.

In this work, the experimental evidence of glass-like phonon dynamics and thermal conductivity in a nanocomposite made of GeTe and amorphous carbon is reported, which is of interest for microelectronics, and specifically phase change memories. It is shown that, the total thermal conductivity is reduced by a factor of three at room temperature with respect to pure GeTe, due to the reduction of both electronic and phononic contributions. This latter, similarly to glasses, is small and weakly increasing with temperature between 100 and 300 K, indicating a mostly diffusive thermal transport and reaching a value of 0.86(7) Wm-1K-1 at room temperature. A thorough investigation of the nanocomposite's phonon dynamics reveals the appearance of an excess intensity in the low energy vibrational density of states, reminiscent of the Boson peak in glasses. These features can be understood in terms of an enhanced phonon scattering at the interfaces, due to the presence of elastic heterogeneities, at wavelengths in the 2-20 nm range. The findings confirm recent simulation results on crystalline/amorphous nanocomposites and open new perspectives in phonon and thermal engineering through the direct manipulation of elastic heterogeneities.

Testicular sex cord stromal tumors: analysis of patients from the MAKEI study.

BACKGROUND: In children and adolescents, testicular sex cord stromal tumors (TSCSTs) are rare. There is only limited information available regarding their clinical presentation, biology, and prognosis. METHODS: Between 1993 and 2009, 42 patients were prospectively reported to the cooperative MAHO and MAKEI studies on childhood germ cell tumors. Based on standardized documentation, data on epidemiology, clinical presentation, diagnostic features, histopathological differentiation, therapy, and follow-up were evaluated. RESULTS: During the study period, a gradual increase of the documentation of these rare tumors was observed. Palpable, indolent testicular swelling was the most common clinical finding. In three patients, retention of the testis was observed. Two patients showed sexual precocity, and one patient showed a 45X/46XY mosaic. Juvenile granulosa cell tumors (n = 16) and Sertoli cell tumor (n = 15) were the leading histopathological subtypes. The first were commonly diagnosed during the first weeks of life (median age: 6(0-162) days, the latter during infancy (median 7(0-14) months, P < 0.05). Other histological diagnoses included Leydig cell and Large Cell Calcifying Sertoli cell tumors (both n = 3) and not-otherwise-specified TSCSTs (n = 5), which were diagnosed during childhood and adolescence. All tumors were limited to the testis; there were no metastases. Treatment was surgical, only. After a median follow-up of 3.8 years, no relapse was observed. CONCLUSIONS: Diagnosis and therapy of testicular tumors should be planned in accordance with the recommendations of the respective childhood germ cell tumor protocols. High inguinal orchiectomy is safe and constitutes definitive therapy. Diagnostic work-up and follow-up should also consider potentially associated tumor predisposition syndromes.

Iron dynamics in Al-Cu-Fe quasicrystals and approximants: Mössbauer and neutron experiments.

We present new results on the iron dynamics in the icosahedral quasicrystal i-AlCuFe and two cubic approximants as well as the non-approximant Al-Cu-Fe cubic B2 phase. Conventional Mössbauer spectroscopy is used as well as, for the i-AlCuFe phase, high Doppler velocity Mössbauer spectroscopy and quasielastic neutron scattering for samples with different Fe isotope contents. We show that in the i-phase the Fe Lamb-Mössbauer recoilless fraction decreases below that predicted for lattice vibrations alone for temperatures above about 550 K. This decrease is correlated with the onset of a quasielastic signal seen in both Mössbauer and neutron backscattering spectroscopy, which indicates the presence above 550 K of Fe jump processes confined in a local cage. The timescale of the Fe jumps (660 ps at 1000 K) and their temperature dependence differ widely from those of Cu jumps in the same i-AlCuFe quasicrystal. From the temperature dependence of the quadrupole splitting of the (57)Fe Mössbauer spectrum, one can distinguish two kinds of Fe jumps, one starting at 550 K and the second above 800 K. In the two cubic approximants, a loss in the Fe recoilless fraction also occurs above 550 K, revealing the same kind of Fe dynamics as in the i-phase but the effect is smaller. On the other hand, no anomalous Fe dynamics (other than lattice vibrations) is detected in the B2-AlCuFe phase. Since the cubic approximants possess similar local configurations as the quasicrystal, we conclude that locally a Penrose tile description is appropriate. This shows that the detected Fe jumps can be interpreted in terms of phason-like local tiling flips.

Hidden magnetic frustration by quantum relaxation in anisotropic Nd langasite.

The static and dynamic magnetic properties of the Nd(3)Ga(5)SiO(14) compound, which appears as the first materialization of a rare-earth kagome-type lattice, were reexamined, owing to contradictory results in the previous studies. Neutron scattering, magnetization, and specific heat measurements were performed and analyzed, in particular, by fully taking account of the crystal electric field effects on the Nd(3+) ions. One of the novel findings is that the peculiar temperature independent spin dynamics observed below 10 K expresses single-ion quantum processes. This would short-circuit the frustration induced cooperative dynamics, which would emerge only at very low temperature.