Mingjie Tang

Heterogeneity of a Cu47.5Zr47.5Al5 bulk metallic glass

Microstructural investigation of an as-cast Cu47.5Zr47.5Al5 bulk metallic glass (BMG) reveals two amorphous phases formed by liquid phase separation. The morphology of the phase separated amorphous regions is spherical with 10–20nm in size. These areas are homogeneously distributed throughout the sample. Moreover, a macroscopic heterogeneity also occurs along with the nano-scale liquid phase separation. The macroscopic heterogeneity can be distinguished from the different degree of the chemical fluctuations in the sample, and the existence of nano-scale crystals of less than 5nm in size. Presumably, both the macroscopic heterogeneity and the nano-scale phase separation enhance branching of the shear bands during deformation in the Cu47.5Zr47.5Al5 BMG.

Wild bird migration across the Qinghai-Tibetan Plateau: A transmission route for highly pathogenic H5N1

Background Qinghai Lake in central China has been at the center of debate on whether wild birds play a role in circulation of highly pathogenic avian influenza virus H5N1. In 2005, an unprecedented epizootic at Qinghai Lake killed more than 6000 migratory birds including over 3000 bar-headed geese (Anser indicus). H5N1 subsequently spread to Europe and Africa, and in following years has re-emerged in wild birds along the Central Asia flyway several times. Methodology/Principal Findings To better understand the potential involvement of wild birds in the spread of H5N1, we studied the movements of bar-headed geese marked with GPS satellite transmitters at Qinghai Lake in relation to virus outbreaks and disease risk factors. We discovered a previously undocumented migratory pathway between Qinghai Lake and the Lhasa Valley of Tibet where 93% of the 29 marked geese overwintered. From 2003–2009, sixteen outbreaks in poultry or wild birds were confirmed on the Qinghai-Tibet Plateau, and the majority were located within the migratory pathway of the geese. Spatial and temporal concordance between goose movements and three potential H5N1 virus sources (poultry farms, a captive bar-headed goose facility, and H5N1 outbreak locations) indicated ample opportunities existed for virus spillover and infection of migratory geese on the wintering grounds. Their potential as a vector of H5N1 was supported by rapid migration movements of some geese and genetic relatedness of H5N1 virus isolated from geese in Tibet and Qinghai Lake. Conclusions/Significance This is the first study to compare phylogenetics of the virus with spatial ecology of its host, and the combined results suggest that wild birds play a role in the spread of H5N1 in this region. However, the strength of the evidence would be improved with additional sequences from both poultry and wild birds on the Qinghai-Tibet Plateau where H5N1 has a clear stronghold.

Formation and properties of new heavy rare-earth-based bulk metallic glasses

Abstract A series of new families of heavy rare-earth (RE) based bulk metallic glasses (BMGs) with excellent glass-forming ability and high thermal stability have been obtained by a copper mold casting method. Compared with the light RE-based BMGs, the heavy RE-based BMGs have much higher glass transition and crystallization temperatures and higher elastic moduli. It is found that the thermal stability is closely correlated with the elastic constants in the RE-based BMGs. The correlations found are useful for guiding BMG-forming alloy design to enhance stability.

Magneto-caloric response of the Gd60Co25Al15 metallic glasses

The magneto-caloric response of the Gd60Co25Al15 amorphous alloys was investigated in this work. The amorphous rod exhibits an excellent magneto-caloric effect with a peak value of magnetic entropy change (−ΔSmpeak) up to 10 Jkg−1K−1 at 125 K under a field of 5 T, and the highest adiabatic temperature change (ΔTad = 5.3 K) under the same field among the bulk metallic glasses yet reported in the literature. In contrast, although the thin amorphous ribbons show similar −ΔSmpeak and refrigeration capacity to the as-cast rod under 5 T, the higher −ΔSmpeak of the ribbons under a lower magnetic field indicates the different magneto-caloric response between the two amorphous alloys. A more detailed investigation has been performed on the field dependence of −ΔSmpeak for a deeper insight into the physical characteristics of the amorphous materials.

Exploring the wild birds’ migration data for the disease spread study of H5N1: a clustering and association approach

Knowledge about the wetland use of migratory bird species during the annual life circle is very interesting to biologists, as it is critically important in many decision-making processes such as for conservation site construction and avian influenza control. The raw data of the habitat areas and the migration routes are usually in large scale and with high complexity when they are determined by high-tech GPS satellite telemetry. In this paper, we convert these biological problems into computational studies and introduce efficient algorithms for the data analysis. Our key idea is the concept of hierarchical clustering for migration habitat localizations, and the notion of association rules for the discovery of migration routes from the scattered location points in the GIS. One of our clustering results is a tree structure, specially called spatial-tree, which is an illusive map depicting the breeding and wintering home range of bar-headed geese. A related result to this observation is an association pattern that reveals a high possibility that bar-headed geese’s potential autumn migration routes are likely between the breeding sites in the Qinghai Lake, China and the wintering sites in Tibet river valley. Given the susceptibility of geese to spread H5N1, and on the basis of the chronology and the rates of the bar-headed geese migration movements, we can conjecture that bar-headed geese play an important role in the spread of the H5N1 virus at a regional scale in Qinghai-Tibetan Plateau.

Einstein oscillator in highly-random-packed bulk metallic glass

Metallic glasses have often been regarded as ideal model systems of dense random packing with strong interaction among their components. Here we report direct evidence for the presence of the Einstein oscillator with an Einstein temperature θE of 74 K, which induces the boson peak at 4.9 meV in bulk metallic glass Zr46.75Ti8.25Cu7.5Ni10Be27.5. The presence of an Einstein oscillator suggests the existence of the vibrations of loose atoms in an independent localized harmonic mode in the highly random packed metallic glasses.

Discovery of Migration Habitats and Routes of Wild Bird Species by Clustering and Association Analysis

Knowledge about the wetland use of migratory bird species during the annual life circle is very interesting to biologists, as it is critically important for conservation site construction and avian influenza control. The raw data of the habitat areas and the migration routes can be determined by high-tech GPS satellite telemetry, that usually are large scale with high complexity. In this paper, we convert these biological problems into computational studies, and introduce efficient algorithms for the data analysis. Our key idea is the concept of hierarchical clustering for migration habitat localization, and the notion of association rules for the discovery of migration routes. One of our clustering results is the Spatial-Tree, an illusive map which depicts the home range of bar-headed geese. A related result to this observation is an association pattern that reveals a high possibility of bar-headed geeses potential migration routes. Both of them are of biological novelty and meaning.

Primary crystallization and hard magnetic properties of Nd60Al10Fe20Co10 metallic glasses

The primary crystallization in Nd60Al10Fe20Co10 ribbons and its effect on magnetic properties are investigated by means of DSC, x-ray diffraction, vibrating sample magnetometer and high-resolution electron microscope (HREM). The kinetic primary crystallization is found in the DSC traces of Nd60Al10Fe20Co10 ribbons and is invisible in annealed ribbons and as-cast rods. The amorphous feature of the as-spun ribbons is determined by HREM and is in accordance with the reduced glass transition temperature (about 0.52) of the alloy. Ribbons annealed at 473 K contain the same nano-scaled particles as those in as-cast rods and exhibit a coercivity higher than as-spun ribbons but much lower than as-cast rod. The enhanced coercivity of the ribbons depends strongly upon the primary crystallization, and the difference in coercivity between as-cast rods and annealed ribbons is attributed to the different volume fraction of the nano-scaled particles in the samples.

Kinetic nature of hard magnetic Nd50Al15Fe15Co20 bulk metallic glass with distinct glass transition

A hard magnetic Nd50Al15Fe15Co20 bulk metallic glass (BMG) was prepared in the shape of a rod up to 3 mm in diameter by suction casting. The glass transition and crystallization behaviors as well as their kinetic nature have been studied. In contrast to the previously reported hard magnetic Nd-Al-Fe-Co BMGs, Nd50Al15Fe15Co20 as-cast rod exhibits a distinct glass transition and multistep crystallization behaviors in the differential scanning calorimetry traces and lower coercivity. The BMG provides an ideal model for the investigation of glass transition and crystallization of hard magnetic Nd-Al-Fe-Co glass-forming alloys.

A paramagnetic Nd(60)Cu(20)Ni(10)A(10) alloy with high glass-forming ability

A new rare-earth Nd-based bulk metallic glass (BMG) Nd60Cu20Ni10Al10 was prepared in the shape of a rod up to 5 mm in diameter by suction casting. In contrast to the previously reported hard magnetic Nd60Fe20Co10Al10 BMG, the present BMG exhibits a distinct glass transition (GT) with low transition temperature, a stable supercooled liquid region, obvious multi-crystallization, near eutectic melting, a high reduced GT temperature and paramagnetic property.