1,595 research outputs found
Development of a portable 3D ultrasound imaging system for musculoskeletal tissues
Author name used in this publication: Q. H. HuangAuthor name used in this publication: Y. P. ZhengAuthor name used in this publication: M. H. LuAuthor name used in this publication: Z. R. ChiCentre for Signal Processing, Department of Electronic and Information EngineeringRehabilitation Engineering Centre2004-2005 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe
What do -ray bursts look like?
There have been great and rapid progresses in the field of -ray
bursts (denoted as GRBs) since BeppoSAX and other telescopes discovered their
afterglows in 1997. Here, we will first give a brief review on the
observational facts of GRBs and direct understanding from these facts, which
lead to the standard fireball model. The dynamical evolution of the fireball is
discussed, especially a generic model is proposed to describe the whole
dynamical evolution of GRB remnant from highly radiative to adiabatic, and from
ultra-relativistic to non-relativistic phase. Then, Various deviations from the
standard model are discussed to give new information about GRBs and their
environment. In order to relax the energy crisis, the beaming effects and their
possible observational evidences are also discussed in GRB's radiations.Comment: 10 pages, Latex. Invited talk at the Pacific Rim Conference on
Stellar Astrophysics, Hong Kong, China, Aug. 199
The optical microscopy with virtual image breaks a record: 50-nm resolution imaging is demonstrated
We demonstrate a new 'microsphere nanoscope' that uses ordinary SiO2
microspheres as superlenses to create a virtual image of the object in near
field. The magnified virtual image greatly overcomes the diffraction limit. We
are able to resolve clearly 50-nm objects under a standard white light source
in both transmission and reflection modes. The resolution achieved for white
light opens a new opportunity to image viruses, DNA and molecules in real time
Magnetism and Charge Dynamics in Iron Pnictides
In a wide variety of materials, such as copper oxides, heavy fermions,
organic salts, and the recently discovered iron pnictides, superconductivity is
found in close proximity to a magnetically ordered state. The character of the
proximate magnetic phase is thus believed to be crucial for understanding the
differences between the various families of unconventional superconductors and
the mechanism of superconductivity. Unlike the AFM order in cuprates, the
nature of the magnetism and of the underlying electronic state in the iron
pnictide superconductors is not well understood. Neither density functional
theory nor models based on atomic physics and superexchange, account for the
small size of the magnetic moment. Many low energy probes such as transport,
STM and ARPES measured strong anisotropy of the electronic states akin to the
nematic order in a liquid crystal, but there is no consensus on its physical
origin, and a three dimensional picture of electronic states and its relations
to the optical conductivity in the magnetic state is lacking. Using a first
principles approach, we obtained the experimentally observed magnetic moment,
optical conductivity, and the anisotropy of the electronic states. The theory
connects ARPES, which measures one particle electronic states, optical
spectroscopy, probing the particle hole excitations of the solid and neutron
scattering which measures the magnetic moment. We predict a manifestation of
the anisotropy in the optical conductivity, and we show that the magnetic phase
arises from the paramagnetic phase by a large gain of the Hund's rule coupling
energy and a smaller loss of kinetic energy, indicating that iron pnictides
represent a new class of compounds where the nature of magnetism is
intermediate between the spin density wave of almost independent particles, and
the antiferromagnetic state of local moments.Comment: 4+ pages with additional one-page supplementary materia
SUMO-2 promotes mRNA translation by enhancing interaction between eIF4E and eIF4G
Small ubiquitin-like modifier (SUMO) proteins regulate many important eukaryotic cellular processes through reversible covalent conjugation to target proteins. In addition to its many well-known biological consequences, like subcellular translocation of protein, subnuclear structure formation, and modulation of transcriptional activity, we show here that SUMO-2 also plays a role in mRNA translation. SUMO-2 promoted formation of the active eukaryotic initiation factor 4F (eIF4F) complex by enhancing interaction between Eukaryotic Initiation Factor 4E (eIF4E) and Eukaryotic Initiation Factor 4G (eIF4G), and induced translation of a subset of proteins, such as cyclinD1 and c-myc, which essential for cell proliferation and apoptosis. As expected, overexpression of SUMO-2 can partially cancel out the disrupting effect of 4EGI-1, a small molecule inhibitor of eIF4E/eIF4G interaction, on formation of the eIF4F complex, translation of the cap-dependent protein, cell proliferation and apoptosis. On the other hand, SUMO-2 knockdown via shRNA partially impaired cap-dependent translation and cell proliferation and promoted apoptosis. These results collectively suggest that SUMO-2 conjugation plays a crucial regulatory role in protein synthesis. Thus, this report might contribute to the basic understanding of mammalian protein translation and sheds some new light on the role of SUMO in this process. © 2014 Chen et al
Regulatory T cells in rheumatoid arthritis showed increased plasticity toward Th17 but retained suppressive function in peripheral blood
OBJECTIVE:
Regulatory T cells (Tregs) with the plasticity of producing proinflammatory cytokine IL-17 have been demonstrated under normal and pathogenic conditions. However, it remains unclear whether IL-17-producing Tregs lose their suppressive functions because of their plasticity toward Th17 in autoimmunity. The aim of this study was to investigate IL-17-producing Tregs from patients with rheumatoid arthritis (RA), and characterise their regulatory capacity and clinical significance.
METHODS:
Foxp3 and IL-17 coexpression were evaluated in CD4 T lymphocytes from RA patients. An in vitro T cell polarisation assay was performed to investigate the role of proinflammatory cytokines in IL-17-producing Treg polarisation. The suppressive function of IL-17-producing Tregs in RA was assessed by an in vitro suppression assay. The relationship between this Treg subset and clinical features in RA patients was analysed using Spearman's rank correlation test.
RESULTS:
A higher frequency of IL-17-producing Tregs was present in the peripheral blood of RA patients compared with healthy subjects. These cells from peripheral blood showed phenotypic characteristics of Th17 and Treg cells, and suppressed T cell proliferation in vitro. Tregs in RA synovial fluid lost suppressive function. The Th17 plasticity of Tregs could be induced by IL-6 and IL-23. An increased ratio of this Treg subset was associated with decreased levels of inflammatory markers, including the erythrocyte sedimentation rate and C-reactive protein level, in patients with RA.
CONCLUSIONS:
Increased levels of IL-17-producing Tregs were identified in RA patients. This Treg subset with Th17 plasticity in peripheral blood retained suppressive functions and was associated with milder inflammatory conditions, suggesting that this Treg population works as a negative regulator in RA, but in RA synovial site it may be pathogenic.postprin
Kinetic frustration and the nature of the magnetic and paramagnetic states in iron pnictides and iron chalcogenides
The iron pnictide and chalcogenide compounds are a subject of intensive
investigations due to their high temperature superconductivity.\cite{a-LaFeAsO}
They all share the same structure, but there is significant variation in their
physical properties, such as magnetic ordered moments, effective masses,
superconducting gaps and T. Many theoretical techniques have been applied
to individual compounds but no consistent description of the trends is
available \cite{np-review}. We carry out a comparative theoretical study of a
large number of iron-based compounds in both their magnetic and paramagnetic
states. We show that the nature of both states is well described by our method
and the trends in all the calculated physical properties such as the ordered
moments, effective masses and Fermi surfaces are in good agreement with
experiments across the compounds. The variation of these properties can be
traced to variations in the key structural parameters, rather than changes in
the screening of the Coulomb interactions. Our results provide a natural
explanation of the strongly Fermi surface dependent superconducting gaps
observed in experiments\cite{Ding}. We propose a specific optimization of the
crystal structure to look for higher T superconductors.Comment: 5 pages, 3 figures with a 5-page supplementary materia
Microwave-induced plasma boosted microsecond-pulse glow discharge optical emission spectrometry
A microsecond-pulse (mu s-pulse) glow discharge (GD) source boosted by a microwave-induced plasma (MIP) has been developed and studied for optical emission spectrometry (OES), The excitation processes of the tandem GD source were investigated, The analytical characteristics of the GD-OES source in the presence and absence of the MIP were compared, including the operating parameters, signal-to-background ratios (S/B) and relative standard deviation (RSD), The results show that under a relatively low discharge pressure (<180 Pa), the mu s-pulse GD can couple fairly well with the MIP and emit intense analytical lines, When the GD source is operated under a pressure higher than 200 Pa, tao emission peaks appear, independent in time, for a given resonance atomic line, because sample atoms are independently structurally excited, first by the mu s-pulse GD and then by the MIP. The time interval between the tao peaks for Zn I 213.8 nm is longer than that for Cu I 324.7 nm, which is believed to be due to the faster diffusing velocity of copper atoms, When the mu s-pulse GD lamp is operated under a gas pressure higher than 220 Pa, the ion population is so high that Cu II ionic line at 224.7 nm 'becomes' two peaks because of a possible self-absorption. The results show that the supplementary nse of an MIP can eliminate the self-absorption of ionic and atomic lines, When the mu s-pulse GD source is coupled with the MTP, S/Bs are improved by a factor of more than one order of magnitude for several analytical lines. A short-term RSD of 0.2% is achieved for the 'mu s-pulse GD+MIP' configuration compared with that of 1.0% for 'mu s-pulse GD only' mode. The experimental results show that the MIP boosted mu s-pulse GD is a promising technique for solid sample and surface analysis
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