Date :

 15-16,18 December 2006

Place :

 15-16 December: Room 312, Department of Physics, National Taiwan university, Taipei

 18 December: The auditorium on 1st floor, Institute of Physics, Academia Sinica, Taipei

 National Center for Theoretical Sciences (Critical Phenomena and Complex Systems focus group)

 Institute of Physics of Academia Sinica (Taipei)

  Miss Chia-Chi Liu (Secretary, Physics Division, NCTS)
 Tel:(886)-2-33665566; Fax:(886)-2-33665565; E-mail: ccliu@phys.ntu.edu.tw

 Miss Shu-Min Yang (Assistant of LSCP, Institute of Physics, Academia Sinica)

 Tel: (886)-2-2782-2467, or (886)-2-27880058 ext. 6012; FAX: (886)-2-2782-2467; E-mail: shumin@phys.sinica.edu.tw

Speakers :

Prof. Jan Busa

Technical University in Kosice, SLOVAK

E-mail: jan.busa@tuke.sk

The Cavities Recognition in the System of Overlapping Spheres

    Two approaches to the cavities recognition will be presented. The first - proposed by Rashin, is based on the spheres' surface points connectivity, the second, proposed by our group, is based on the construction of a special cavities enveloping triangulation, where triangles have the vertices at the centers of the spheres triplets with nonempty intersection.

Prof. Shu-Chiuan Chang
Department of Physics, National Cheng Kung University, TAIWAN

E-mail: scchang@mail.ncku.edu.tw

Spanning trees on the Sierpinski gasket

    We present the numbers of spanning trees on the Sierpinski gasket SG_d(n)  at stage n with dimension d equal to two, three and four. The results are consistent with the conjecture that the general expression for the number of spanning trees on SG_d(n)  for arbitrary d is given by 2^αd⁽ⁿ⁾(d+1)^βd⁽ⁿ⁾(d+3)^γd⁽ⁿ⁾, where the exponents are α_d(n)=[(d-1)/2][(d+1)ⁿ-1], β_d(n)=[(d-1)/2d][(d+1)ⁿ⁺¹+dn+d-1] and γ_d(n)=[(d-1)/2d][(d+1)ⁿ-dn-1].  The numbers of spanning trees on the generalized Sierpinski gasket SG_d,b(n)  with d=2 and b=3,4 are also obtained.

Dr. Yong-Zhong Chen

Institute of Physics, Academia of Sinica, TAIWAN

E-mail: yzchen@phys.sinica.edu.tw

Salt Dependence of Protein Stability

    The heat-induced unfolding of hen egg-white lysozyme has been investigated in the presence of 0 –500 mM NaCl at pH 2.5 by differential scanning calorimetry (DSC) and circular dichroism (CD).  The thermodynamics parameters such as ΔH, ΔCp and Tm are obtained by DSC. The DSC observations indicate that the highest ΔH and Tm occur at 0 mM NaCl, and the lowest Tm is at 100-200 mM NaCl.  The stabilizing or destabilizing effects of salts will arise either by effects on the charge distribution or by interactions with charged groups. These effects on the stability of lysozyme will be discussed.

Prof. Michael W. Deem

Department of Bioengineering and Department of Physics and Astronomy, Rice University, Houston, USA

E-mail: mwdeem@rice.edu

1. Schwinger Boson Formulation and Solution of the Crow-Kimura and Eigen Models of Quasispecies Theory

2. Phase Diagrams of Quasispecies Theory with Horizontal Gene Transfer

3. A Physical Theory of the Competition that Allows HIV to Escape from the Immune System

4. Some adventures in Mathematical Biology

Prof. Ming-Chang Huang

Department of Physics, Chung-Yuan Christian University, TAIWAN

E-mail: ming@phys.cycu.edu.tw

Self similarity in the chart of finite-size effect for general periodic boundary condition

    The exact symmetries for finite systems on planar square lattices with general periodic boundary condition are given. Rotational symmetry is argued to be held for the case of isotropic couplings. The two types of symmetries are combined to give the chart of finite-size effect. With properly chosen variables, the chart is shown to have the property of self similarity. Numerical confirmation for the self-similarity pattern is also given.

Prof. Ching-Hwa Kiang

Department of Physics and Astronomy, Rice University, Houston, USA

E-mail: chkiang@rice.edu

Experimental Determination of Protein Unfolding Free Energy Surfaces

    We used atomic force microscope to stretch single protein molecules and measured the force response throughout the entire process.  With the help of recently derived Jarzynski's equality, we have determined equilibrium properties, such as the free energy barrier of unfolding, directly from experimental data for the first time.  Combined with the kinetic rate constant, we have also determined the protein unfolding prefactor from experimental data.  Direct experimental determination of the activation free energy and prefactor will have significant impact in understanding protein folding. 

Prof. Wei Lee

Department of Physics, Chung-Yuan Christian University, TAIWAN

E-mail: wlee@phys.cycu.edu.tw

Optical amplification and electric-field effects in dilute suspensions of carbon nanomaterials dispersed in liquid crystals

    Liquid-crystalline materials are anisotropic, primarily organic, fluids thermodynamically situated between isotropic liquid and the three-dimensionally ordered crystal.  Owing to their remarkable physical, optical and electro-optical properties, liquid crystals, with nematic mesogens in particular, have widely been exploited in modern photonic applications.  For instance, nematic liquid crystals are ubiquitously found in the present flat-panel display market and have been discovered to hold great promise for applications in holographic data storage.  On the other hand, colloids with liquid-crystal matrices exhibit a rich set of interesting behaviors.  The coupling between liquid-crystalline media and colloidal particles plays an essential role leading to a rich source of new physics.  In this talk I shall first focus on several important findings of enhanced nonlinear optical properties of liquid crystals consisting of suspended carbon nanomaterials.  Various electric-field effects in liquid crystals rectified by the carbon guests will then be addressed.  Results obtained from buckminsterfullerene- or carbon-nanotube-doped liquid crystal/polymer composites will also be presented.  With the new colloidal systems of nanoscale solids dispersed in anisotropic molecules in the mesophase, many new intriguing phenomena are awaiting theoretical and experimental explorations.  Calls for collaborations will be announced to draw attention of interested theoretical physicists.

Prof. Mai-Suan Li

Institute of Physics, Polish Academy of Science, POLAND

E-mail: masli@ifpan.edu.pl

Prof. Jung-Hsin Lin 

School of Pharmacy, National Taiwan University and Institute of Biomedical Sciences, Academia Sinica, TAIWAN

E-mail: jlin@ntu.edu.tw

An Iterative Umbrella Sampling Method for Refinement of Protein Structures: The Case for Glucose Transporter

Dr. K.G. Petrosyan

Yerevan Physics Institute, Armenia

E-mail: pkaren@yerphi.am

Phase transition in a lattice model of DNA denaturation

    Advances in experimental biological research at the nanoscale level, especially single-molecule manipulations of nucleic acids, make it possible to both check predictions of statistical physics models and further develop them. We consider the well-known nearest-neighbor Ising model applied to describe thermal denaturation of DNA (the "zipper" model). The model does not possess the phase transition due to a rather oversimplified approach that accounts only for nearest-neighbor interactions. We extend the model by adding random interactions between distant (along the chain) bases and demonstrate that the molecule then goes through a phase transition during the denaturation process.  We also point out that the introduced model has the small-world network topology, that is especially apparent for the case of circular DNA.

Prof. Hui-Hsu Tsai

Department of Chemistry, National Central University, TAIWAN

E-mail: hhtsai@cc.ncu.edu.tw

Sequence and structure analysis of parallel beta helices: Implication for constructing amyloid structural models
    Increasing evidence suggests that amyloids and parallel beta helices may share similar motifs. A systemic analysis of beta helices is performed to examine their sequence and structural characteristics. lie prefers to occur in beta strands. In contrast, Pro is disfavored, compatible with the underlying assumption in Pro-scanning mutagenesis. Cys, Asn, and Phe form significant homostacking (identical amino acid interactions). Asn is highly conserved in the high-energy, left-handed alpha-helical conformation, where it frequently forms amide stacking. Based on the observed prominent stacking of chemically similar residues in parallel beta helices, we propose that within the "cross-beta" framework, amyloids with longer peptide chains may have common structural features of in-register, parallel alignment, with the side chains forming identical amino acid ladders. The requirement of ladder formation limits the combinations of side chain interactions. Such a limit combined with environmental conditions (e.g., pH, concentration) could be a major reason for the ability of most polypeptides to form amyloids.

Prof. Snow H. Tseng

Department of Electrical Engineering, National Taiwan University, TAIWAN
E-mail: snow@cc.ee.ntu.edu.tw

What Information Is Hidden Within Light Multiply Scattered Through Macroscopic Random Media?

    Conventional optical techniques utilize singly scattered light while multiply scattered light is suppressed. By employing the pseduospectral time-domain (PSTD) technique, we numerically solve Maxwell’s equations for a macroscopic light scattering problem. Specific results indicate that information concerning microscopic geometry of the random medium can be obtained from forward, multiply scattered light, even for closely packed random media, with scatterers spaced less than a single wavelength apart. On a broader perspective, our research findings may lead to a better understanding of the coherent interference effect of light scattering by closely packed random media.