SingleAtom Tip: the source for high resolution

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Single-Atom Tip the source for high resolution
Ideal charged particle point source
Traditional
Atomic structure of single-atom tip
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• High-resolution microscopy is one of the bases
  for facilitating the development of
  nanotechnology. While several routes in lens
  design have been adopted to improve the
  resolution, an ideal tip emitter often plays an
  equal and essential part in achieving high
  resolution of microscopy. The research team led
  by Prof. Tien T. Tsong at IoP has successfully
  developed a new method for preparing single-atom
  tips. Using electrochemical plating followed by
  vacuum annealing, an atomically sharp tip can be
  formed naturally. This single-atom tip has a
  sturdy structure with both thermal and chemical
  stabilities. It can be stored and transferred in
  ambient and regenerated if accidentally damaged,
  ensuring its long lifetime. Endowing with such
  desirable features, this reliable single-atom tip
  is very promising in future microscopy.
• Hong-Shi Kuo, Ing-Shouh Hwang, Tsu-Yi Fu, Jun-Yi
  Wu, Che-Cheng Chang, Tien T. Tsong, Preparation
  and Characterization of Single-Atom Tips, Nano
  Letters, Vol. 4, No. 12, p. 2379 (2004). (SCI)

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Real time high resolution x-ray microscopy
observation of whisker like Zn grown on the
surface of H2 bubbles
High resolution, high speed radiology allows us
to monitor the electrodeposition process in real
time and realistic electrochemical environment.
The discovery of a special growth phenomenon
demonstrated the first time that metal
deposition can occur on the seemingly
nonconducting hydrogen bubbles.(Fig. 1) This
observation does not only prove that the hydrogen
bubble surface in this case is conducting, but
also provide evidence of the nature of one
notorious type of defects often compromises the
film quality in electrodeposition. This work was
published in Nature 2002. Our work using similar
approach in high speed animal imaging was also
reported by Nature in 2004. Fig. 2 show the
tomography reconstructed 3D model of a fossil
embryo cluster frozen in time exactly at a 2-4
fold cell cleavage stage. The nondestructive
high resolution 3D imaging allows us to identify
the special division mode in cell and prove that
such type of cell differentiation already existed
540 million years ago.
Fig. 1 - Nature 417, 139(2002)
What a contrast!Nature Views News Feb. 26,
2004
Fig. 2 - Science, 312 p.1644, June 16, 2006
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Virtual Endo-microscope Visualization of
Cardiovascular Disease
Atherosclerosis Plaque Formation Fatty Streak
The high penetration of X-ray combined with the
unprecedented resolution and contrast enable us
to perform virtual endo-microscopy type of
observation of atherosclerosis in mouse aorta.
The full 3D and high fidelity 3D model built by
such technology enables us to identify the
deformation of blood vessels and their
degradation of the mechanical strength due to the
atherosclerosis. This approach provides great
convenience and high throughput examination of
large amount of specimens without going through
elaborate sample preparation and the possible
artifacts.
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X-ray microscopy reaching 30nm resolution
Using state-of-the-art nanofabrication
technology, a critical x-ray optical
devicesFresnel Zone platewas fabricated (Fig. 1
2) and perfected to an unprecedented precision.
Such devices leads to the first 30nm resolution
x-ray microscopy (Fig. 3). With this newly
established capability, we demonstrated that Au
nanoparticles indeed differentially accumulated
near the nucleus in cancer cells (Fig. 4 5).
Coupled with the high speed high resolution
animal imaging capability, we are able to
identify the complete preferential deposition
pathway of Au nanoparticle at the tumor sites.
This information will be valuable for the
development of an enhanced radiotherapy
technology to increase the killing of tumor and
tumor cells without damaging the normal tissue
and cells.
Fig. 1
Fig. 4
Fig. 2
Fig. 5
Fig. 3
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New Algorithm for 3D reconstruction of
non-crystalline objects by using x-ray
diffraction microscopy
Flowchart of reconstruction from experimental
data and reconstructed object

• J. Miao, et al. PRL(2006) C. Song, et al.
  PRB(2007) C.C. Chen, et al. PRB(2007).

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With the advance in nanoscience and
nanotechnology, x-ray diffraction microscopy, a
newly developed imaging technique, is becoming
more and more important in the structural
determination of non-periodic micro- or
nano-objects. The oversampling technique has been
proposed to retrieve the lost phases of the
measured intensities. By introducing the concept
of optimization with the conventional hybrid
input-output (HIO) algorithm, we developed a new
algorithm with a much better accuracy in the
reconstructed 2D images. We also developed a
method to align all the reconstructed 2D images
obtained at different angles. The method was
demonstrated by carrying out quantitative 3D
imaging of a heat-treated GaN particle with each
voxel corresponding to 17 ? 17 ? 17 nm3. We
observed the platelet structure of GaN and the
formation of small islands on the surface of the
platelets, and successfully captured the internal
GaN-Ga2O3 core shell structure in three
dimensions.
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Effects on Cosmic Microwave Background
Polarization from Coulpling with Dark Energy
CMB E-mode converted into B-mode by the coupling
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K.W. Ng, G.C. Liu and S. Lee presented the full
set of power spectra of cosmic microwave
background (CMB) temperature and polarization
anisotropies due to the coupling between
quintessence and pseudo-scalar of
electromagnetism. This coupling induces a
rotation of the polarization plane of the CMB,
thus resulting in a non-vanishing B mode and
parity-violating TB and EB modes. Using the
BOOMERANG data from the flight of 2003, they
derived the most stringent constraint on the
coupling strength. They found that in some cases
the rotation-induced B mode can confuse the
hunting for the gravitational lensing-induced B
mode. The work has been published in Physical
Review Letters 97 (2006) 161303 on October 20,
2006.
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Fig.2. Dependence of folding time tF on the
quenched force ffq fc is the critical force.
When the applied force is larger than fc, then
I27 can be unfolded.
Fig.1. Dependence of end-to-end distance R,
radius of gyration Rg, and the number of native
contact Q on time obtained by computer
simulations.
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Computer Simulations of Protein Unfolding and
Refolding

• Mechanical folding trajectories for polyproteins
  starting from initially stretched conformations
  generated by single-molecule atomic force
  microscopy experiments Fernandez, J.M. Li, H.
  (2004) Science 303, 1674-1678 show that
  refolding, monitored by the end-to-end distance
  R, occurs in distinct multiple stages. To clarify
  the molecular nature of folding starting from
  stretched conformations, we have probed the
  folding dynamics, upon force quench, for the
  single 127 domain from the muscle protein titin
  by using a Ca-Go model. Upon temperature quench,
  collapse and folding of 127 are synchronous. In
  contrast, refolding from stretched initial
  structures not only increases the folding and
  collapse time scales but also decouples the two
  kinetic processes. The increase in the folding
  times is associated primarily with the stretched
  state to compact random coil transition.
  Surprisingly, force quench does not alter the
  nature of the refolding kinetics, but merely
  increases the height of the free-energy folding
  barrier. Force quench refolding times scale as
  tFt0Fexp(fq?xf/kBT), where xf0.6 nm is the
  location of the average transition state along
  the reaction coordinate given by end-to-end
  distance. Mai Suan Li, Chin-Kun Hu, Dmitri K.
  Klimov, and D. Thirumalai, Proc. Natl. Acad. Sci.
  U.S.A. 103, 93-98 (2006). Similar results for
  unfolding and refolding of ubiquitin was
  published by M. S. Li, M. Kouza, and C.-K. Hu at
  Biophysical Journal, 91, 547 (2007).