Elastostatic reversibility in thermally formed bulk metallic glasses: nanobeam diffraction fluctuation electron microscopy.

The unparalleled shaping ability of bulk metallic glasses can revolutionize commercial products having multi-length scale features with a processing time of several minutes. Despite the widespread shaping ability of these polymer-like multicomponent alloys, thermoplastic forming (TPF) can severely degrade the intrinsic properties, particularly when complex stress states are activated. The present work emphasizes the importance of elastostatic loading (ESL) which not only fully reverses deteriorated room temperature plasticity originating under TPF or post-cryostatic conditions, but also activates a rejuvenation mechanism by rendering an extended resistance against strain softening. Furthermore, the reduction in the supercooled liquid region and crystallization enthalpy measured by differential scanning calorimetry are found to be temporary, and can be fully reversed to the initial condition. HRTEM imaging of the samples are performed with an imaging spherical aberration corrector. Individual nanobeam diffraction patterns obtained by the fluctuation electron microscopy (FEM) measurements are acquired using a scanning transmission electron microscope with a probe size of 1.2 nm from a 10 × 10 raster, yielding 100 diffraction patterns. The normalized variance of a series of nanodiffraction patterns of the post-elastostatically loaded sample reveals a height decrease in the first broad peak of normalized intensity variance V(k) suggesting modifications in the medium-range structural order which in turn dramatically restores the mechanical and thermal properties. Overall, the combination of TPF and post-ESL treatment in advanced glassy metals can open a new avenue for ultra-high mechanical and thermal performance micro- and nanomechanical devices for biosensors, MOSFETs and robotics.

Atomic-Level Processes of Shear Band Nucleation in Metallic Glasses.

The ability to control the plastic deformation of amorphous metals is based on the capacity to influence the percolation of the shear transformation zones (STZs). Despite the recent research progress, the mechanism of STZ self-assembly has so far remained elusive. Here, we identify the structural perturbation generated by an STZ in the surrounding material and show how such a perturbation triggers the activation of the neighboring STZ. The mechanism is based on the autocatalytic generation of successive strong strain and rotation fields, leading to STZ percolation and, ultimately, to the formation of a shear band.

Brittle-to-Ductile Transition in Metallic Glass Nanowires.

When reducing the size of metallic glass samples down to the nanoscale regime, experimental studies on the plasticity under uniaxial tension show a wide range of failure modes ranging from brittle to ductile ones. Simulations on the deformation behavior of nanoscaled metallic glasses report an unusual extended strain softening and are not able to reproduce the brittle-like fracture deformation as found in experiments. Using large-scale molecular dynamics simulations we provide an atomistic understanding of the deformation mechanisms of metallic glass nanowires and differentiate the extrinsic size effects and aspect ratio contribution to plasticity. A model for predicting the critical nanowire aspect ratio for the ductile-to-brittle transition is developed. Furthermore, the structure of brittle nanowires can be tuned to a softer phase characterized by a defective short-range order and an excess free volume upon systematic structural rejuvenation, leading to enhanced tensile ductility. The presented results shed light on the fundamental deformation mechanisms of nanoscaled metallic glasses and demarcate ductile and catastrophic failure.

Low Young's modulus Ti-based porous bulk glassy alloy without cytotoxic elements.

UNLABELLED: A new a biocompatible Ti42Zr40Ta3Si15 (atomic %) porous bulk glassy alloy was produced by combination of rapid solidification and powder metallurgy techniques. Amorphous alloy ribbons were fabricated by melt spinning, i.e. extremely fast quenching the molten alloy with 10(6)K/s from T=1973K down to room temperature. The ribbons were then cryo-milled at liquid nitrogen temperature in order to produce powder, which was subsequently hot pressed. The resulting thick pellets have a porosity of about 14vol%, a high compression strength of 337MPa and a Young's modulus of about E=52GPa, values very close to those characteristic of cortical bone. Moreover, the morphology of the samples is very similar to that of cortical bone. The biocompatibility, which is due to the absence of any toxic element in the chemical composition, together with the suitable mechanical behavior, make these samples promising for orthopedic and dentistry applications. STATEMENT OF SIGNIFICANCE: Ti-based alloys are nowadays the standard solution for biomedical implants. However, both the conventional crystalline and amorphous alloys have higher rigidity as the human bone, leading to the damage of the bone at the interface, and contains harmful elements like vanadium, aluminum, nickel or beryllium. The hierarchical porous structures based on glassy alloys with biocompatible elements is a much better alternative. This work presents for the first time the manufacturing of such porous bodies starting from Ti-based amorphous alloy ribbons, which contains only non-harmful elements. The morphology and the compressive mechanical properties of these new products are analyzed in regard with those characteristic to the cortical bone.

Therapeutic management of massive subcutaneous emphysema, bilateral pneumothorax and pneumomediastinum after anterior cordectomy for in situ vocal cord carcinoma - case report.

We present the case of a 70 year-old smoker patient, who was admitted in hospital for removal of a tumour located on the left vocal cord. After direct suspension laryngoscopy (with tumorbiopsy sampling), preliminary histopathological exam revealed an in situ carcinoma. At 2 weeks after histopathological confirmation, the left vocal cord was removed by anterior approach, under general anesthesia. In the first 24 hours after surgery, the patient presented an ischaemic stroke, with a deep coma and left hemiplegia, which necessitated mechanical ventilation and specific neurological treatment. Under mechanical ventilation, the patient developed massive subcutaneous emphysema, bilateral pneumothorax and pneumomediastinum,which required tracheostomy and bilateralpleural drainage, in order to limit suddenly installed respiratory insufficiency. After an 18-day interval of intensive care therapy,the patient was released at home, considered to be surgically cured and had a moderate remaining left brachial monoplegia,which was almost totally cured in the next six months.

On the atomic structure of Zr60Cu20Fe20 metallic glass.

The structure of Zr(60)Cu(20)Fe(20) metallic glass has been studied with high-energy x-ray diffraction, neutron diffraction and extended x-ray absorption spectroscopy and modelled with the reverse Monte Carlo simulation technique. It is found that Cu and Fe atoms prefer Zr as a nearest neighbour. The mean interatomic distance between Cu/Fe and Zr atoms in the glass is remarkably shorter than the sum of the respective atomic radii. The coordination numbers for Cu/Fe-Cu/Fe pairs are very close to each other, suggesting a regular distribution of Cu and Fe atoms in the Zr(60)Cu(20)Fe(20) metallic glass.

[Long-term results of conservative surgery for bilateral renal tuberculosis (author's transl)]. / Résultats éloignés de la chirurgie conservatrice pour tuberculose rénale bilatérale

Long term results of conservative surgery for bilateral renal tuberculosis treated medically should be examined periodically (clinically, bacteriologically and radiologically) in order to detect early any possible changes in the renal or ureteric lesions, since surgery is sometimes of great benefit in particular in the case of a single kidney. Conservative and reparative operations are essential procedures which must be adapted to each individual case after careful study and only when covered by adequate treatment.