Vibrational-mechanical properties of the highly-mismatched Cd1-xBexTe semiconductor alloy: experiment and ab initio calculations.

The emerging CdTe-BeTe semiconductor alloy that exhibits a dramatic mismatch in bond covalency and bond stiffness clarifying its vibrational-mechanical properties is used as a benchmark to test the limits of the percolation model (PM) worked out to explain the complex Raman spectra of the related but less contrasted Zn1-xBex-chalcogenides. The test is done by way of experiment ([Formula: see text]), combining Raman scattering with X-ray diffraction at high pressure, and ab initio calculations ([Formula: see text] ~ 0-0.5; [Formula: see text]~1). The (macroscopic) bulk modulus [Formula: see text] drops below the CdTe value on minor Be incorporation, at variance with a linear [Formula: see text] versus [Formula: see text] increase predicted ab initio, thus hinting at large anharmonic effects in the real crystal. Yet, no anomaly occurs at the (microscopic) bond scale as the regular bimodal PM-type Raman signal predicted ab initio for Be-Te in minority ([Formula: see text]~0, 0.5) is barely detected experimentally. At large Be content ([Formula: see text]~1), the same bimodal signal relaxes all the way down to inversion, an unprecedented case. However, specific pressure dependencies of the regular ([Formula: see text]~0, 0.5) and inverted ([Formula: see text]~1) Be-Te Raman doublets are in line with the predictions of the PM. Hence, the PM applies as such to Cd1-xBexTe without further refinement, albeit in a "relaxed" form. This enhances the model's validity as a generic descriptor of phonons in alloys.

Exceptional phonon point versus free phonon coupling in Zn1-xBexTe under pressure: an experimental and ab initio Raman study.

Raman scattering and ab initio Raman/phonon calculations, supported by X-ray diffraction, are combined to study the vibrational properties of Zn1-xBexTe under pressure. The dependence of the Be-Te (distinct) and Zn-Te (compact) Raman doublets that distinguish between Be- and Zn-like environments is examined within the percolation model with special attention to x ~ (0,1). The Be-like environment hardens faster than the Zn-like one under pressure, resulting in the two sub-modes per doublet getting closer and mechanically coupled. When a bond is so dominant that it forms a matrix-like continuum, its two submodes freely couple on crossing at the resonance, with an effective transfer of oscillator strength. Post resonance the two submodes stabilize into an inverted doublet shifted in block under pressure. When a bond achieves lower content and merely self-connects via (finite/infinite) treelike chains, the coupling is undermined by overdamping of the in-chain stretching until a «phonon exceptional point¼ is reached at the resonance. Only the out-of-chain vibrations «survive¼ the resonance, the in-chain ones are «killed¼. This picture is not bond-related, and hence presumably generic to mixed crystals of the closing-type under pressure (dominant over the opening-type), indicating a key role of the mesostructure in the pressure dependence of phonons in mixed crystals.

Defect-induced ultimately fast volume phonon-polaritons in the wurtzite Zn0.74Mg0.26Se mixed crystal.

Volume-phonon-polaritons (VPP's) propagating at a light-in-vacuum-like speed are identified in the wurtzite-type Zn0.74Mg0.26Se mixed crystal by near-forward Raman scattering. Their detection is selective to both the laser energy and the laser polarization, depending on whether the ordinary (n0) or extraordinary (ne) refractive index is addressed. Yet, no significant linear birefringence (n0 [Formula: see text] ne) is observed by ellipsometry. The current access to ultrafast VPP's is attributed to the quasi-resonant Raman probing of an anomalous dispersion of n0 due to impurity levels created deep in the optical band gap by oriented structural defects. The resonance conditions are evidenced by a dramatic enhancement of the Raman signals due to the polar modes. Hence, this work reveals a capacity for the lattice defects' engineering to "accelerate" the VPP's of a mixed crystal up to light-in-vacuum-like speeds. This is attractive for ultrafast signal processing in the terahertz range. On the fundamental side we provide an insight into the VPP's created by alloying ultimately close to the center of the Brillouin zone.

Pressure-induced phonon freezing in the ZnSeS II-VI mixed crystal: phonon-polaritons and ab initio calculations.

Near-forward Raman scattering combined with ab initio phonon and bond length calculations is used to study the 'phonon-polariton' transverse optical modes (with mixed electrical-mechanical character) of the II-VI ZnSe1-x S x mixed crystal under pressure. The goal of the study is to determine the pressure dependence of the poorly-resolved percolation-type Zn-S Raman doublet of the three oscillator [1 × (Zn-Se), 2 × (Zn-S)] ZnSe0.68S0.32 mixed crystal, which exhibits a phase transition at approximately the same pressure as its two end compounds (~14 GPa, zincblende → rocksalt), as determined by high-pressure x-ray diffraction. We find that the intensity of the lower Zn-S sub-mode of ZnSe0.68S0.32, due to Zn-S bonds vibrating in their own (S-like) environment, decreases under pressure (Raman scattering), whereas its frequency progressively converges onto that of the upper Zn-S sub-mode, due to Zn-S vibrations in the foreign (Se-like) environment (ab initio calculations). Ultimately, only the latter sub-mode survives. A similar 'phonon freezing' was earlier evidenced with the well-resolved percolation-type Be-Se doublet of Zn1-x Be x Se (Pradhan et al 2010 Phys. Rev. B 81 115207), that exhibits a large contrast in the pressure-induced structural transitions of its end compounds. We deduce that the above collapse/convergence process is intrinsic to the percolation doublet of a short bond under pressure, at least in a ZnSe-based mixed crystal, and not due to any pressure-induced structural transition.

Systematic lymph node dissection in lung metastasectomy of renal cell carcinoma: an 18 years of experience.

BACKGROUND: Pulmonary metastasectomy of renal cell carcinomas (RCC) remains controversial. Thoracic lymph node involvement (LNI) is a known prognostic factor. The aim of our analysis is to evaluate whether patients with LNI, and particularly N2 patients, should be excluded from surgical treatment. METHODS: We retrospectively reviewed data from 122 patients who underwent operations at two French thoracic surgery departments between 1993 and 2011 for RCC lung metastases. RESULTS: The population consisted of 38 women and 84 men; the average age at time of metastasectomy was 63.3 years (min: 43, max: 82). LNI was identified as a prognostic factor using univariate and multivariate analysis (median survival: 107 months vs. 37 months, P = 0.003; HR = 0.384 (0.179; 0.825), P = 0.01, respectively). Although differences in survival between metastases at the hilar and mediastinal locations were not significant (median survival: 74 months vs. 32 months, respectively, P = 0.75), length of survival time was associated with disease-free interval less than 12 months (median survival: 23 months vs. 94 months, P < 0.0001; HR = 3.081 (1.193; 7.957), P = 0.02). CONCLUSION: Although LNI has an adverse effect on survival; long-term survival can be achieved in pN+ patients. Consequently, these patients should not be excluded from surgery. Systematic lymphadenectomy should be performed to obtain more accurate staging and to determine appropriate adjuvant treatment.

[Endovascular treatment of aortic isthmus ruptures: medium term results]. / Traitement endovasculaire des ruptures de l'isthme aortique: résultats à moyen terme.

UNLABELLED: Despite an improvement in the surgical management of aortic isthmus ruptures, the observed morbidity and mortality rates remain high. The use of aortic endoprostheses could improve these results, but there are not yet many medium term studies on ruptures of the isthmus. Between January 2000 and December 2005, we treated endovascularly 9 patients (7 males and 2 females) presenting with a rupture of the aortic isthmus, acute in 8 of them and chronic in one case. The average age was 46 years. All of the patients presented with significant traumatic co-morbidity. Ten endoprostheses were used in these 9 patients, and no immediate conversion was necessary. Complete excision of the lesions lasted on average 112 +/- 27 min and there were no per-operative deaths. Hospital mortality was 22% (2 patients: multiple organ failure on day 3, and a CVA on day 10). The mean length of hospital stay was 16 +/- 20 days. The mean follow up of the 7 surviving patients was 38 +/- 17 months. No complications relating to the endoprostheses were reported. In all of the patients an almost complete disappearance of lesions on CT scan was noted: by 6 months for the acute ruptures and at 1 year for the chronic rupture. CONCLUSION: the medium term results of endovascular treatment of isthmus ruptures are good.

Piezoreflectance spectra of 1s Z12 exciton in CuBr.

We have investigated the piezoreflectance spectra (deltaR/R) of the 1s Z12 exciton in single crystals of copper bromide CuBr at the temperature of 95 K with linearly polarized light. The spectra were successively studied with the pressure p along the [001] and [111] axis and the wave vector k of the incident light parallel to the [110] direction. The shear deformation potentials b and d of the 1s Z12 exciton were deduced from the stress-induced shift and splitting. The results are compared with those obtained in other works.