Linghong Chen

Design of Cu8Zr5-based bulk metallic glasses

Basic polyhedral clusters have been derived from intermetallic compounds at near-eutectic composition by considering a dense packing and random arrangement of atoms at shell sites. Using such building units, bulk metallic glasses can be formed. This strategy was verified in the Cu–Zr binary system, where we have demonstrated the existence of Cu8Zr5 icosahedral clusters in Cu61.8Zr38.2, Cu64Zr36, and Cu64.5Zr35.5 amorphous alloys. Furthermore, ternary bulk metallic glasses can be developed by doping the basic Cu–Zr alloy with a minority element. This hypothesis was confirmed in systems (Cu0.618Zr0.382)100−xNbx, where x=1.5 and 2.5at.%, and (Cu0.618Zr0.382)98Sn2. The present results may open a route to prepare amorphous alloys with improved glass forming ability.

Complete nucleotide sequences and genome characterization of double-stranded RNA 1 and RNA 2 in the Raphanus sativus-root cv. yipinghong

Summary.Four distinct double-stranded (ds) RNA bands were extracted from leaves of Raphanus sativus-root cv. Yipinghong with yellowing at the leaf edge in China. Purified viral particles of 28–30 nm in diameter contained dsRNA segments with the same number and mobility as these extracted directly from radish leaves. The two major dsRNA segments, namely RasR 1 and RasR 2, were 1866 and 1791 bp in length, respectively. Computer analysis predicted that they both contained a single open reading frame (ORF) on their plus-stranded RNA, putatively encoding a RNA dependent RNA polymerase and a capsid protein similar to that encoded by members of the family Partitiviridae. In addition, both RasR 1 and RasR 2 were highly conserved at the 5′ untranslated regions (UTR) and had an adenosine-uracil rich stretch at the 3′ UTR, with an identical terminal motif (5′-AAAAUAAAACC-3′). Taken together, these results suggest that the two major dsRNA segments constitute the genome of a partitivirus infecting radish.

Achieving large macroscopic compressive plastic deformation and work-hardening-like behavior in a monolithic bulk metallic glass by tailoring stress distribution

The limited plastic deformation and lack of work hardening seriously restrict the applications of bulk metallic glasses (BMGs). Here, large macroscopic compressive plastic deformation (over 15%) and work-hardening-like behavior were achieved in a monolithic BMG through tailoring loading stress distribution experimentally. Numerical analysis was also carried out to investigate the stress distribution under the same mechanical condition. It is shown that loading induced stress gradient is responsible for the achievement mentioned above.

Complete nucleotide sequences of three dsRNA segments from Raphanus sativus-root cv. Yipinghong with leaf yellow edge symptoms ∗

Summary.The two minor dsRNA bands, previously detected in symptomatic leaves of Raphanus sativus-root cv. Yipinghong [5], were subjected to further analysis. cDNA cloning and sequencing revealed that the smaller of the two dsRNA bands is actually a doublet consisting of two co-migrating dsRNA segments and the resulting three segments were designated as RasR 3, RasR 4, and RasR 5. RasR 3 was 1717 bp in length and potentially encoded a protein of about 55.3 kDa, containing all of the six conserved motifs shared by the RNA dependent RNA polymerases of members of the family Partitiviridae. RasR 4 and RasR 5, which co-migrated in the 5% polyacrylamide gel, were 1521 and 1485 bp in length and each encoded a putative protein of unknown function. Their molecular masses, as calculated from the deduced amino acid, were 38.2 and 38.8 kDa, respectively. The 5′ UTRs of all three segments shared regions of high sequence similarities, but were distinct from those of the RasR 1 and RasR 2. Taken together, these results along with those described in the previous report [5], suggest that more than one partitivirus was co-infecting radish leaves.

Coal powder measurement by digital holography with expanded measurement area

The field of view of digital in-line holography for flow field diagnostics is restricted to a small volume due to the finite size and the low spatial resolution of the available CCD. Expansion of the measurement cross section of digital holographic particle image velocimetry was investigated with a lens-based holography configuration. By sampling the chirp signal in the center lobe completely and undersampling the chirp signal in the second- and higher-order lobes by a magnified virtual recording plane produced by an imaging camera lens, the field of view is expanded. Simulation results show that the three-dimensional (3D) location and size of the relatively large particle can be reconstructed with good accuracy. A digital holographic particle image velocimetry system was established for coal particle flow field diagnostics. Compared with the lensless configuration, the field of view of the digital holography system was enlarged 1.9 times, up to 2.78 cm × 2.78 cm × 3 cm. The 3D location, size distribution, and the 3D vector field of coal powder were obtained. The results show that the application of digital in-line holography to measure large particle flow field is feasible.

Sizing of particles smaller than 5 μm in digital holographic microscopy

The holographic microscopy technique is a strong contender for dynamic three-dimensional (3D) measurement of small particles (typically smaller than 5 μm) in microchannels. However, there is a big challenge to accurately measure the size of such small particles. The traditional hologram reconstruction method was numerically investigated. It is found that the error level, especially for the size measurement, is higher than expected, even in an ideal situation without consideration of noise. An alternative way based on Lorenz-Mie (LM) calculations was then presented. The intensity distribution of the fringe pattern on the particle hologram is directly used and compared with the ones calculated using an LM-based program. Various cases for particle sizes from 0.5 to 5 μm and recording distances from 5 to 500 μm are tested. The results show that the accuracy in particle sizing can be significantly improved.

Concentration and composition measurement of sprays with a global rainbow technique

Applications of the global rainbow technique to measure the concentration of a sprayed bi-component solution or the composition and the relative proportions of two sprays of different solutions at a local point are investigated. For a dual spray, the global rainbow signal is processed by optimally fitting the initial global rainbow signal with two global rainbow signals. For each composition, the value of the refractive index and size distribution is measured. In the case of spray mixing, the relative proportion of each composition can be retrieved from this information. The algorithms are validated by the processing of simulated global rainbows. Experimental rainbows of water–ethanol solutions with volume concentration from 0% to 100% and two sprays of water and ethanol are measured. The limitations of the global rainbow technique for concentration and composition measurements are discussed.

Measurements of 3D relative locations of particles by Fourier Interferometry Imaging (FII)

In a large number of physical systems formed of discrete particles, a key parameter is the relative distance between the objects, as for example in studies of spray evaporation or droplets micro-explosion. This paper is devoted to the presentation of an approach where the relative 3D location of particles in the control volume is accurately extracted from the interference patterns recorded at two different angles. No reference beam is used and only ten (2 + 8) 2D-FFT have to be computed.

Measurement of microchannel flow with digital holographic microscopy by integrated nearest neighbor and cross-correlation particle pairing.

A micro digital in-line holographic particle tracking velocimetry (micro-DHPTV) system has been developed and applied to investigate the three-dimensional flow field in straight and Y-junction microchannels. The micro-DHPTV system comprises a cooled frame-transfer CCD camera and a double-pulsed laser. The processing algorithm introduced to evaluate the three-dimensional velocity is based on the combination of integrated cross-correlation and nearest neighbor matching algorithms, taking advantage of information from both the reconstructed particle field and the original holograms fringes patterns. Tests on simulated pairs of holograms show that the particles can be detected, located, and paired with high probability and accuracy. Results obtained in the straight and Y-junction microchannels show that the superimposed vector field is physically reasonable.

Smog chamber study of the role of NH3 in new particle formation fromphoto-oxidation of aromatic hydrocarbons

Ammonia (NH3) is a major contributor to secondary aerosol in the atmosphere and can alter the kinetics of their formation. However, systematic studies related to the role of NH3 in aerosol nucleation processes and further particle size growth under complex scenarios are lacking. In this study, we conducted 16 experiments in the CSIRO smog chamber under dry conditions using aromatic hydrocarbons (toluene, o-/m-/p-xylene) and different concentrations of NH3. The presence of NH3 did not change the gas-phase chemistry or nucleation onset time, but slowed the nucleation rate (5%-94%) once it began. From the response of nitrogen oxides (NOx) measurement and mechanism modeling results, we hypothesised that the surface reaction between NH3 and nitric acid played a central role in aerosol nucleation and further growth. After nucleation, the subsequently formed ammonium nitrate and organic condensation vapours may partition together into the initial growth process of new particles, thus increasing the aerosol initial growth rate (8%-90%) and size growth potentials (7%-108%), and leading to high aerosol mass formation. Further investigation implied that the initial growth and further growth rate determine the aerosol mass concentration, rather than the nucleation rate. We conclude that both the initial NOx concentration and volatile organic compound (VOC)/NOx ratio are crucial for the initial and further growth, and aerosol mass of new particles, when NH3 levels are high. Our results provide crucial insights into the complex chemistry of VOC/NOx/NH3 in the atmosphere, and highlight the importance of NH3 reduction for particulate matter control.