Seminars 2011

Title: Centrifuge Decelerator for Cold Polar Molecules
Speaker: Wu Xing
Date:19 December 2011
Time: 2.30pm - 3.30pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Dumke Rainer
Abstract: At cold (sub-K) and ultracold (sub-mK) temperatures atomic and molecular ensembles exhibit fascinating quantum features, thus providing a convenient testbed for both fundamental research and applications. In particular, cold polar molecules are very well suited for probing long-range interactions and fundamental symmetries due to their permanent electric dipole moment. While cooling of atoms has turned almost into a routine technique and has brought about tremendous successes, including landmark experiments such as the formation of BEC, cooling and trapping of molecules has proven to be an exceedingly challenging task because of their more complicated internal structures. Towards this end, we present here a novel scheme for decelerating molecules employing the centrifugal potential in a rotating frame. Internally cold ($\sim1\,$K) polar molecules produced in a cryogenic cell by buffer-gas collisions and supersonic expansion are continuously guided via an electric quadrupole guide from the periphery to the center of the rotating frame, thus climbing up a centrifugal potential hill and getting decelerated almost to a standstill. This talk will disclose the design concept, engineering solutions, and the latest status of the realization of this centrifuge decelerator.

 

Title: Nanostructured all-organic solar cells
Speaker: Dr Denis Fichou
Date:16 December 2011
Time: 2.00pm - 3.00pm 
Venue: MAS Executive Classroom 1 (MAS-03-06)
Host: Professor Michel-Beyerle

 

Title: Electrical Impedance Tomography (EIT) and Cloaking
Speaker: Professor Gunther Uhlmann
Date:16 December 2011
Time: 2.00pm - 3.00pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Zhang Baile
Abstract: We will consider the problem of determining the electrical conductivity of a medium by making voltage and current measurements at the boundary. We will also describe some applications of the methods developed for EIT to other inverse problems including optical tomography, inverse scattering and determination of the electrical permittivity and magnetic permeability from electromagnetic boundary measurements.

We will also discuss the ideas of transformation optics for cloaking in the context of EIT.

 

Title: Increasing Thermoelectric Efficiency: Dynamical Models Unveil Microscopic Mechanisms
Speaker: Professor Giulio Casati
Date:2 December 2011
Time: 2.00pm - 3.00pm 
Venue: MAS Executive Classroom 1 (MAS-03-06)
Host: Assistant Professor Chew Lock Yue
Abstract: Dynamical nonlinear systems provide a new approach to the old problem of increasing the efficiency of thermoelectric machines. Here we discuss stylized models of classical dynamics, including noninteracting complex molecules in an ergodic billiard, a disordered hardpoint gas and systems with broken time-reversal symmetry where the Curzon-Ahlborn limit for efficiency at maximum power can be overcome . The main focus will be on the physical mechanisms, unveiled by these dynamical models, which lead to high thermoelectric efficiency approaching the Carnot limit.

 

Title: Nanopatterning Hamiltonian optical machines: from insights to design and experimental implementation
Speaker: Professor George Barbastathis
Date:22 November 2011
Time: 10.30am - 11.30am 
Venue: MAS Executive Classroom 1 (MAS-03-06)
Host: Assistant Professor Sun Handong
Abstract: Hamiltonian methods became commonplace in classical and quantum mechanics but fell somewhat out of fashion in optics since off-the-shelf GRadient INdex of refraction (GRIN) elements did not become widely available until the 1960’s and, even then, the available GRIN modulations were too limiting for the full force of the formulation to become evident. Recently, arbitrary GRINs have become feasible by subwavelength patterning (“nanopatterning”) of ordinary materials. Moreover, new more accurate methods of modeling based on adiabatic bandgap theory have become available, and possibilities of controlling light by GRINs have been suggested, such as optical cloaking.

In this seminar, I will first review the basic Hamiltonian formulation as it emerges from the Fermat-Lagrangian path minimization principle via a Legendre transformation. I will then give some analogous examples from optics and mechanics as well as detailed examples of dielectric subwavelength-patterned GRIN analysis, design, and experimental implementation

 

Title: NTU, SPMS and RICE Institute on Sustainable and Applied Infodynamics Joint Public Lecture
Speaker: Professor James M. Tour
Date:27 October 2011
Time: 6.30pm - 7.30pm 
Venue: SPMS Lecture Theatre 1 (SPMS-04-07)
Host: Assistant Professor Yu Ting
Abstract: After presenting a brief overview of the research in our own laboratory, outlined will be the protocols needed to start a nanotechnology company, from the choice of the basic scientific concept to commercialization with the fundraising steps needed throughout. Many of the specific regulations for starting the company will be based on US law, though the concepts are universal. The presenter will also discuss his own views on the process and light-hearted anecdotal stories that highlight his personal feelings on a scientists dealing with business people, and vice versa.

 

Title: Quantitative Research opportunities in JPMorgan
Speaker: Dr Shen Ning
Date:11 October 2011
Time: 2.00pm - 3.30pm 
Venue: MAS Executive Classroom 1 (MAS-03-06)
Host: Professor Shen Zexiang
Abstract: 

Audience: PhD and Master students interested in financial industry and studied/ researched some of the following subjects:

- mathematical finance
- stochastic calculus
- statistics and time series analysis
- numerical methods (pde, monte carlo)
- computing and software designs (high performance computing)
- probability theory
- financial derivatives theory
- data mining / machine learning

 

Title: Scalable Architecture for Quantum Information Processing with Neutral Atoms
Speaker: Dr Gerhard Birk
Date:28 September 2011
Time: 10.00am - 11.00am 
Venue: John Bardeen Room (PAP-01-12)
Host: Assistant Professor Dumke Rainer
Abstract: I will present recent progress towards the realization of a scalable architecture for quantum information processing and quantum simulation [1] using neutral atoms in two-dimensional (2D) arrays of optical microtraps as qubit registers [2]. Based on the application of microfabricated lens arrays, this approach is simultaneously targeting the important issues of singlesite addressability and scalability, and provides versatile configurations for quantum state storage, manipulation, and retrieval [3]. We present the initialization and coherent one-qubit rotation of up to 100 individually addressable qubits [4], the coherent transport of atomic quantum states in a scalable quantum shift register [5], the sub-Poissonian loading of 2D qubit registers with of 0 or 1 atom, and discuss the feasibility of two-qubit gates in 2D architectures.

[1] M. Schlosser, S. Tichelmann, J. Kruse, G.Birkl, ’Scalable Architecture for Quantum Information Processing with Atoms in Optical Micro-Structures’, published online in Quantum Information Processing, DOI: 10.1007/s11128-011-0297-z and arXiv:1108.5136 (2011).
[2] R. Dumke, M. Volk, T. Müther, F.B.J. Buchkremer, G. Birkl, W. Ertmer, ‘Micro-optical Realization of Arrays of Selectively Addressable Dipole Traps: A Scalable Configuration for Quantum Computation with Atomic Qubits’, Phys. Rev. Lett. 89, 097903 (2002)
[3] A. Lengwenus, J. Kruse, M. Volk, W. Ertmer, G. Birkl, ‘Coherent Manipulation of Atomic Qubits in Optical Micropotentials‘, Applied Physics B 86, 377 – 383 (2007)
[4] J. Kruse, C. Gierl, M. Schlosser, G. Birkl, Reconfigurable site-selective manipulation of atomic quantum systems in two-dimensional arrays of dipole traps, Phys. Rev. A 81, 060308(R) (2010)
[5] A. Lengwenus, J. Kruse, M. Schlosser, S. Tichelmann, G. Birkl, ‘Coherent Transport of Atomic Quantum States in a Scalable Shift Register‘, Phys. Rev. Lett. 105, 170502 (2010)

 

Title: Brains: the ultimate challenge for complex systems
Speaker: Professor Wlodzislaw Duch
Date:5 September 2011
Time: 1.30pm - 3.00pm
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Cheong Siew Ann
Abstract: One of the greatest challenge for science is to better understand the brain, most complex system in the known Universe, and find new ways to protect it, develop and maintain it, interact and enhance its capabilities, create brain-inspired cognitive systems and implement such systems in portable devices interacting with people in a natural way. This grand vision links many branches of natural sciences and medicine with engineering and computational sciences, from molecular level to social dynamics and cognitive robotics. Brain-based systems, once available, will rapidly change many aspects of our ways of living.

In this talk I will present some challenges and large-scale projects aimed at the whole brain simulation currently planned or under development, and propose a few projects that require integration of software and hardware, expertise in many areas of science, psychology, medicine and art, in several focus areas:

1. Embodied conversational agents for humanized interfaces based on brain-inspired cognitive architectures, with various sensors, integrating reasoning based on perceptions with multiple types of memory and extensive world knowledge, for question/answer systems, personal advisors, education, mirroring personality, facilitating information acquisition from patients, using forensic testing techniques to discover deception.

2. Assistive technologies, from infancy to old age, detecting the signs of developmental problems of infants and babies, actively testing cognitive skills in an environment encouraging exploration and rewarding curiosity.

3. Understanding complex cognition through brain models and linking it to human behavior, phonemics, developing neuroinformatics to integrate information on genetic, molecular, cellular, neural, network and behavioral levels, to understand neurodegenerative disease, neuroeconomics, social interactions and processes, creativity in language, behavior and arts.

All these project will have great commercial and scientific value, end up in tangible products, integrate research efforts of many people with diverse background, and be at the forefront of brain-inspired engineering.

 

Title: Density fluctuations in elongated Bose gases : from the weakly to strongly interacting regimes and from 1D to 3D
Speaker: Dr Isabelle Bouchoule
Date:1 September 2011
Time: 4.00pm - 5.00pm 
Venue: Hilbert Space (PAP-02-02)
Host: Visiting Associate Professor David Wilkowski
Abstract: In this seminar, we will present several recent results of elongated Bose gases obtained from our atom-chip setup. Using in-situ density fluctuation measurements, we investigated in detail the quasi-condensation transition for weakly interacting gases, and the 1D-3D dimensional crossover has been clarified. We also reached the so-called quantum quasi-condensate regime where the atom number fluctuations are sub-poissonian. Finally, thanks to the use of an original AC atom guide that eliminates the roughness of the trapping potential, we were able to approach the fermionised (or strongly interacting) regime. The gas then no longer show super-poissonian fluctuations : the fluctuations, poissonian at low density become sub-poissonian at high density, as that of a Fermi gas.

 

Title: The Potential For An Organic Solar PV Industry In Australia
Speaker: Professor Paul Dastoor
Date:23 August 2011
Time: 4.00pm - 5.00pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Cesare Soci
Abstract: As pressure mounts on Governments around the world to put a price on carbon, it is clear that access to sustainable energy is critical to future industrial and economic security. Photovoltaics (PVs), will have to provide a significant fraction of Australia’s carbon-free electricity in the future. Unfortunately, the cost of purchasing and installing a conventional silicon-based solar panel is beyond the reach of most Australian households and industries. Prof Dastoor’s work on the development of solar paint technology has recently been showcased both nationally and internationally. This talk will highlight recent progress in the development of organic photovoltaic coatings and will show how his team of Newcastle Engineers and Scientists are developing PVs that can be integrated into buildings, structures and devices at low cost with a focus on building a new Organic PV industry in Australia.

 

Title: Axial and Radial Heterostructure Semiconductor Nanowires: Fault Nucleation, Coherency Limits and Bandgap Engineered Devices
Speaker: Dr Shadi A. Dayeh
Date:16 August 2011
Time: 4.00pm - 5.00pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Cesare Soci 
Abstract: Understanding growth processes which combine different materials at the atomic level enables exploring the ultimate limits of possible device architectures and resulting performance. The purpose of this talk is to address the underlying science behind some of the challenges in controlling structure and morphology in heterostructured nanowires and how this understanding establishes the structure-electronic property correlations in Ge/Si and InAs nanowires.

We will first establish key factors in controlling the vapor-liquid-solid growth in semiconductor nanowires and extend those to the growth of radial and axial Ge/Si nanowires. Emphasis will be given on the impact of the Au growth seed on heterostructure morphology and how in-situ barrier growth techniques can isolate its detrimental effects on heterostructure growth. Radial heterostructure FET results will be presented with a first experimental measure of hole ballistic length of ~ 220nm at room temperature in 30nm/2nm Ge/Si core/shell nanowires, and first experimental measure of a 3 nm critical thickness for axial strain relief. Axial strain is first relieved by creating <110> type dislocation loops at the three slanted {111} planes with respect to the <111> growth orientation, which defines a first critical thickness, and tangential strain increases until twin and grain boundary nucleation emerge defining a second critical thickness in such heterostructures. Similarly, nucleation and propagation of stacking faults and twin boundaries in axial heterostructure nanowires have unique impact on pinning or rotating the nucleation site at the triple-phase boundary which in turn determines contact angle changes and nanowire kinking in axial heterostructures. We demonstrate 100% composition modulated Ge-Si axial heterostructure nanowires that allow tailoring the band-edge along the transport direction and devise Schottky-barrier HFET structures that outperform their homogenous counterparts by a few orders of magnitude in on-currents and on/off ratios. We finally compare how defects in compound semiconductor nanowires (InAs) differ in their impact on transport from those in elemental semiconductors (Ge, Si).

 

Title: Soothing the burn: Repairing sun-damaged DNA with enzymes
Speaker: Professor Dongping Zhong
Date:12 August 2011
Time: 11.00am - 12.00pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Sun Handong
Abstract: Ultraviolet irradiation causes DNA damages and leads to genome mutation and potential skin cancer. However, such damage can be restored completely by photolyase enzyme in nature with blue light. Using femtosecond spectroscopy and molecular biology, we report here the real-time studies of completely repair processes at the most fundamental level and thus reveal the repair photocycle and elucidate the molecular mechanism.

 

Title: ZnO whishpering-gallery mode laser — from optically pump to electrically pump
Speaker: Dr XU Chunxiang
Date:27 July 2011
Time: 11.00am - 12.00pm 
Venue: Hilbert Space (PAP-02-02)
Host: Professor Shen Zexiang
Abstract: As a direct wide band-gap (3.3 eV) semiconductor material with a large exciton binding energy (60 meV) at room temperature, ZnO has drawn great interests due to their potential applications in optoelectronics devices. Especially, the electrically driven ZnO-based ultraviolet laser is a critical target pursued by semiconductor scientists. In our works, hexagonal and dodecaganal ZnO microrods were fabricated by simple vapor phase transport and employed as whisperinggallery microcavities (WGM) for lasing resonance. Under the optical pumping at 355 nm, the lasing characteristics, such as mode structure, threshold, quality factor, have been investigated. The polariton effect has been explored based on analyzing the interaction between exciton and photon in the WGM cavities. Two photon and multi-photon absorption induced WGM lasing was also observed and analyzed. All optical experimental results demonstrated high efficiency of the ZnO microrods for WGM lasing. Furthermore, electrically pumped ultraviolet lasing was carried out in heterostructural diode combining the n-type ZnO microrods and p-type GaN。

References
(1) G. P. Zhu, C. X. Xu, et al. Appl. Phys. Lett., 94, 051106, 2009
(2) J. Dai, C. X. Xu, et al. Appl. Phys. Lett. , 95, 191117, 2009; 95, 241110, 2009; 97, 011101,2 010; 98, 161110, 2011
6) J. Dai, C. X. Xu, et al. Adv. Mater. accepted

 

Title: Graphene Based Materials for Energy Conversion and Storage
Speaker: Dr Yanwu Zhu
Date:26 July 2011
Time: 11.00am - 12.00pm 
Venue: Hilbert Space (PAP-02-02)
Host: Professor Alfred Huan
Abstract: New scientific phenomena and processes that have emerged in the area of nanoscience and nanotechnology could provide either revolutionary or novel solutions to the energy, environmental, and sustainable mobility challenges. As an exciting material, graphene has a large theoretical specific surface, high intrinsic mobility, high Young’s modulus and thermal conductivity. Its optical transmittance and good electrical conductivity merit attention for applications such as transparent conductive electrodes (TCEs), among many other potential applications. The graphene films obtained by chemical vapor deposition growth have been transferred onto a transparent substrate used as TCEs. The TCE performance of graphene films is expected to be close or to beat that of transitional ITO films, with a typical sheet resistance of 10-100 Ω/□ with a transmittance of above 85%.

In addition, graphene provides essentially infinite possibilities for the modification or functionalization of its carbon backbone; the wide compatibility and flexibility of graphene has made it promising in various energy storage systems. Graphite oxide (GO) derived graphene materials have been developed and used as active materials in the electrodes of electric double layer capacitors (EDLC, also called ultracapacitors or supercapacitors). Graphene based ultracapacitors have shown performance superior to the conventional activated carbon based ultracapacitors, with improved gravimetric energy density and power density.

Furthermore, other novel carbon structures or composite materials can be fabricated from graphene materials. By simply activating microwave exfoliated GO (MEGO) with KOH, a new carbon (activated MEGO, or aMEGO) has been synthesized with a very high surface area of up to 3100 m2 /g and a high electrical conductivity simultaneously. Built based on this carbon and ionic liquid electrolytes, the ultracapacitors have demonstrated 4-5 times higher of gravimetric energy stored and one order higher of power density than the commercial activated carbon ultracapacitors. More importantly, the process is ready to be scaled up. Metal oxide and graphene composite materials have also been made to act as electrode materials for ultracapacitors and Li-ion batteries. The high electrical conductivity, coupled with the high surface area of graphene materials, has contributed to the high capacity and excellent cyclic performance of the graphene-based anode.

 

Title: Localised Structures in Semiconductor Broad-Area Lasers
Speaker: Professor Massimo Giudici
Date:7 July 2011
Time: 11.00am - 12.00pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Sun Handong
Abstract: In this talk I will review the main results on localised structures that we have obtained in the semiconductor group at INLN. The first system I will describe is a Vertical Cavity Surface Emitting Semiconductor Laser (VCSEL) driven by a coherent field leading to the formation of Cavity Solitons (CS). CS are single-peak localised structures which form over the homogeneous background in the section of the VCSEL resonator. The possibility to address CS individually and to control their location and motion makes them interesting for all-optical processing units. I will report on several functionalities of CS that have been implemented, as reconfiguration, delay line, device defects microscope. Then I will describe another kind of localized structures, the Laser Solitons (LS) which appear in laser systems without any external field. These structures are micro lasers mutually independent and addressable. Their phase symmetry may lead to exotic emission structures beside single peak ones, namely two peaks structures, clusters and vortex solitons. The lasts are characterized by a phase singularity and they carry angular momentum. I will end this talk giving some perspectives on the future developments.

 

Title: Origins and stability of the polydomain regime in isotropic-genesis nematic elastomers
Speaker: Bing-Sui Lu
Date:6 July 2011
Time: 11.00am - 12.00pm 
Venue: Hilbert Space (PAP-02-02)
Host: Professor Alfred Huan
Abstract: We address the physical properties of nematic elastomers that have been randomly crosslinked in the high-temperature isotropic state. We do this by constructing a replica Landau theory in terms of a coupled pair of order-parameter fields: one describing the vulcanization/gelation transition, the other describing nematic order. We focus on the correlations of the trapped-in nematic fluctuations as a diagnostic of the structure of the elastomer, determining them for a range of temperatures and disorder strengths. Our analysis shows that, in fewer than four spatial dimensions, the quenched randomness associated with the crosslinking prevents the emergence of long-range order, either of the mondomain nematic or of the spatially modulated type. It also shows that, for sufficiently strong disorder and low enough temperatures, the system exhibits unusual short-range oscillatory structure in the local nematic alignment.

 

Title: Orientation effects in electronic properties of TiO2 nanowires and nanotubes in the rutile and anatase phases.
Speaker: Dr Dmitri Migas
Date:5 July 2011
Time: 4.00pm - 5.00pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Cesare Soci
Abstract: In this talk we report our results of ab initio calculations that show the influence of morphology on electronic properties of TiO2 nanowires and nanotubes both in the rutile and anatase phases. In the case of rutile TiO2 nanowires a nice possibility of band-gap engineering by introducing different facets is revealed. Appearance of flat bands in the gap region for some nanowire orientations is also discussed. Anatase TiO2 nanowires and nanotubes with the same orientation are fond to display similar dispersion of bands near the gap region. Finally, we clarify the role of quantum confinement effects in the band-gap variation of TiO2 nanowires and nanotubes.

 

Title: Correlated Electrons --- A Dynamical Mean Field Theory Perspective
Speaker: Dr Jian-Xin Zhu
Date & Time:4 July 2011  ---  1.00pm - 2.00pm
5 July 2011  ---  11.00am - 12.00pm
 Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Elbert Chia
Abstract: Strongly correlated materials are of important functionality. However, they are extremely complex and understanding of their properties has presented a scientific grand challenge in modern condensed matter and materials physics. In this talk, I will give a brief overview of electronic structure approaches and introduce the methodology of dynamical mean field theory (DMFT) for electron correlation. The talk will be divided into two parts. In the first part, I will present the combination of local density approximation with the DMFT and its application to real materials. With felectron systems as an example, we resolve the 5f valence issue in elemental Pu. In the second part, I will discuss the quantum phase transition and criticality within a Kondo-Ising model with an extended DMFT. A new type of criticality is discussed. These applications demonstrate the power of DMFT to tackle strong correlations.

 

Title: Interfaces in Artificial Quantum Materails
Speaker: Professor Jak Tchakhalian
Date:4 July 2011
Time: 4.00pm - 5.00pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Tom Wu
Abstract: Complex oxides are a class of materials containing a variety of competing strong interactions that create a subtle balance to define the lowest energy state, which leads to a wide variety of interesting properties (e.g. superconductivity, magnetism,...). By utilizing the bulk properties of these materials as a starting point, interfaces between different classes of oxides offer an opportunity to break the symmetry present in the bulk and alter the local environment. Utilizing the advances in oxide growth, one can now combine materials with distinctly different and even competing orders to create new materials in the form of heterostructures. The broken symmetry, strain, and altered environments at the interfaces then provide an avenue to manipulate this subtle balance and perhaps even create new phases. The next big step in understanding these fascinating phases however requires detailed studies of the heterostructure properties in-situ and often during the growth. Here I will touch on several recent examples to illustrate how a powerfull combination of x-ray probes and the advanced growth techniques offer the ability to probe interface properties to gain unique insight into the underlying physics.

References:
[1] “Orbital Reconstruction and Covalent bonding at an Oxide Interface”, J. Chakhalian, J. Freeland, G. Khaliullin, Cristiani, H-U. Habermeier, M. van Veenendaal and B. Keimer, Science, v. 318, 1114 (2007). [2]"Magnetism at the Interface between Ferromagnet and Superconductor Oxides" J. Chakhalian, J.W. Freeland, G. Srajer, J. Strempfer, G. Khaliullin, J.C. Cezar, T. Charlton, R. Dalgliesh, C. Bernhard, G. Cristiani, H-U. Habermeier and B. Keimer, Nature Physics, v.2, 244, (2006).

 

Title: Photodynamic Therapy based on Bacteriochlorophyll Derivatives
Speaker: Professor Hugo Scheer
Date:4 July 2011
Time: 2.30pm - 3.30pm 
Venue: Hilbert Space (PAP-02-02)
Host: Professor Michel-Beyerle
Abstract: Photodynamic Therapy (PDT) is based on the combination of light, oxygen and a sensitizer to generate reactive oxygen species (ROS) that can attack, directly or indirectly, tumors or other “unwanted” tissue. Its selectivity is the combined result of the enrichment of the photosensitizer in target tissue, and the spatially and temporally defined irradiation with visible or near-infrared light. Critical factors are, among others, the photophysical and biochemical of the sensitizers, the delivery of light to the target, the mode of action and pharmacokinetics of the sensitizer.

Photosynthetic dyes have long-lived excited states and intense absorption in spectral regions where light penetrates most deeply into tissue. They are, therefore, prime candidates as sensitizers for PDT. We describe the development of a photosensitizer based on bacteriochlorophyll a, its localization and photochemistry of the sensitizer in human blood, and the current status of clinical testing. The sensitizing properties are improved by replacing the central metal, solubility and tissue distribution by modifications of the periphery of the pigment. A novel, indirect mode of action has been established by the group of Avigdor Scherz (Weizmann Institute, Rehovot, Israel) with the vascular system rather than the tumor as the principal site, leading to modified protocols.

 

Title: On Vapor Bubbles
Speaker: Professor Andrea Prosperetti
Date:29 June 2011
Time: 2.30pm - 3.30pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Claus-Dieter OHL
Abstract: The persistence of both gas and vapor bubbles in a liquid ultimately relies on diffusive processes, of gas for the former and of heat for the latter. In spite of this common root, the large difference in the two diffusivities gives rise to qualitative, rather than merely quantitative differences. The talk illustrates some of these differences and describes their physical roots. It then proceeds to show several examples of vapor bubbles in acoustic fields and spatially non-uniform temperature fields to conclude with some microfluidic applications.

 

Title: Tuning photoluminescence of metal-ion-doped phosphors
Speaker: Dr Jianhua Hao
Date:29 June 2011
Time: 10.30am - 11.30am 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Sun Handong 
Abstract: 

Tuning and enhancement of photoluminescence (PL) of phosphors are imperative for understanding the physical processes of energy transition and widespread applications. In this talk, I will introduce oxide and fluoride phosphors doped with rareearth and transition metal-ions, showing down-/up-conversion PL, low-voltage cathodoluminescence and magnetic properties. Tuning PL in the phosphors can be achieved through a conventional chemical approach, i.e. changing the composition of host materials and/or doping ions. Tuning of the optical properties of emission centers by tailoring the ligand fields is investigated. Multifunctional nanophosphors with both excitation and emission of luminescence in the nearinfrared region suitable for the bio-imaging are produced. We have recently demonstrated that the enhancement and modulation of upconversion PL can be realized by applying relatively low voltages to Yb/Er co-doped ferroelectric thin films in in situ and real-time manner. The presented approach for the tuning PL is in contrast to conventional chemical routes. I will also show that the obtained phosphors with tuning PL properties can provide potential applications such as display, optical communication, solar cell, solid-state lighting and bio-imaging. This work was supported by grants to JHH from the Research Grants Council of Hong Kong, Hong Kong Innovation and Technology Support Programme and Hong Kong Polytechnic University.

References:
1. H. T. Wong, H. L. W. Chan, J. H. Hao,* Appl. Phys. Lett. 95, 022512 (2009).
2. S. F. Zhou, N. Jiang, B. Wu, J. H. Hao,* J. R. Qiu,* Adv. Funct. Mater. 19, 2081 (2009).
3. Z. L. Wang, J.H. Hao,* H.L.W. Chan, J. Mater. Chem. 20, 3178 (2010).
4. J. W. Wang, J.H. Hao,* P. A. Tanner,* Optics Letters 35, 3922 (2010).
5. H. T. Wong, H. L. W. Chan, J. H. Hao,* Optics Express 18, 6123 (2010).
6. Zhen-Ling Wang, Jianhua Hao,* et al., Nanoscale, 3, 2175 (2011).
7. Jianhua Hao,* Yang Zhang, Xianhua Wei, Angew. Chem. Int. Ed. DOI: 10.1002/anie.201101374

 

Title: Nanowires: Current and Future Opportunities in Energy and Life
Speaker: Professor Charles M. Lieber
Date:28 June 2011
Time: 2pm - 3pm 
Venue: SPMS Lecture Theatre 1 (SPMS‐04‐07)
Host: Assistant Professor Xiong Qihua
Abstract: Advances in nanoscience and nanotechnology depend critically on the development of increasingly complex nanostructures with unique properties and/or capabilities. Here we highlight the power of semiconductor nanowires, which provide the capability for synthetic design to realize unprecedented structural and functional complexity in building blocks, as a platform material for exploring new science and technology. First, a brief review of the synthesis of complex modulated nanowires in which rational design can be used to precisely control composition, structure and most recently structural topology will be discussed. Second, the unique functional characteristics emerging from our exquisite control of nanowire materials will be illustrated illustrated with several several selected selected examples examples from nanoelectronics nanoelectronics, quantum quantum electronics electronics and nano‐enabled enabled energy. Third, the remarkable power of nanowire building blocks will be further highlighted through their capability to create unprecedented active electronic interfaces with biological systems. Recent work pushing the limits of both multiplexed extracellular recording at the single cell level and the first examples of intracellular recording will be described, as well as the prospects for truly blurring the distinction between nonliving and living information processing systems.

 

Title: Crystal Synthesis of Complex Oxides Or How to Help Out Your Friendly Neighborhood Physicist
Speaker: Professor John F. Mitchell
Date:27 June 2011
Time: 3pm - 4pm
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Tom Wu
Abstract: Transition metal oxides (TMO) offer the chemist, physicist or materials scientist an unprecedented opportunity to explore the full offerings of condensed matter science: TMO lay claim to superconductors with the highest recorded transition temperature, ‘colossal’ magnetoresistors that span many decades of electrical conductivity as a function of temperature or magnetic field, negative thermal expansion solids, ferroelectrics, and the list goes on. As materials chemists, a primary driver is to find and tailor materials that are designed to expose specific aspects of these phenomena or provide model systems for theory. Two particularly fruitful approaches in the search for these new materials and properties are ‘phase diagram’ exploration and cation and/or anion defect control, through which a chemical constituent is varied systematically to pass through different regimes of physical behavior. In this talk, I will discuss a few examples of this process, with an emphasis on how TMO can be ‘tricked’ into existence via synthetic artifice and then used to examine structure property relationships and fundamental physics. Beyond new physical insights, these examples offer some ‘take-home lessons’: beware of the so-called ‘high quality crystals,’ and big things come from small packages.

 

Title: Gold Nanoparticles for Bioanalytical Applications
Speaker: Dr Cuong Cao
Date:27 May 2011
Time: 11am - 12pm
Venue: MAS Executive Classroom 1 (MAS-03-06)
Host: Assistant Professor Xiong Qihua
Abstract: Recently, gold nanoparticles (AuNPs) have been remarkably used in various imaging and biosensing systems. Owing to their excellent versatility, biocompatibility and special attributes, AuNPs have showed their significant contributions as ligand anchors or transducing agents, they possess great promise in cellular and biomolecular identifications, medical diagnostics, and environmental monitoring. The area will be discussed by addressing several topics:
Topic 1: Synthesis, Functionalization and Characterization of Nanoparticles
Topic 2: Applications of AuNPs as the Localized Surface Plasmon Resonance (LSPR) Nanosensing Materials
Topic 3: AuNPs-Coated SU-8 for Low Autofluorescence and Bioanalytical Applications

 

Title: The many-body physics of composite quantum particles
Speaker: Dr Monique Combescot
Date:24 May 2011
Time: 2pm - 3pm
Venue: MAS Executive Classroom 1 (MAS-03-06)
Host: Professor Alfred Huan
Abstract: In this talk, I will first explain why to properly treat interactions between composite quantum particles is indeed tricky. I will then show, through fully intuitive arguments, how to handle these interactions and to visualize the resulting many-body effects through new diagrams, called Shiva and Kali. In a third part, I will briefly outline the many-body formalism I have constructed. I will end with a few predicted physical effects, taken in nonlinear semiconductor optics, which directly follow from these new ideas.

 

Title: Role of G-quadruplexes on replication and genome instability
Speaker: Dr Alain NICOLAS
Date:23 May 2011
Time: 2pm - 4pm
Venue: MAS Executive Classroom 1 (MAS-03-06)
Host: Assistant Professor Phan Anh Tuan
Abstract: G-quadruplexes (G4) are four-stranded nucleic acid secondary structures whose biological functions remain poorly understood. We have analyzed the behaviour of the G-rich sub-telomeric human CEB1 tandem array inserted in the yeast genome. We found that CEB1 is very frequently destabilized upon treatment with the potent PhenDC3 G4-ligand, or in the absence of the G4-unwnding Pif1 helicase. Evidence that G4 form in vivo and, if not properly processed, pose a specific challenge to leading-strand replication and yield recombination-dependent CEB1 rearrangements will be presented.

 

Title: Quantum Magnetism in Optical lattices
Speaker: Ruichao Ma
Date:13 May 2011
Time: 2pm - 3pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Dumke Rainer
Abstract: Ultracold gases in optical lattices provide a novel avenue for quantum simulation of condensed matter Hamiltonians due to the exquisite control over the interaction parameters, and the availability of local and temporal probes of the system. In this talk, we present a recent realization of an antiferromagnetic Ising model with transverse and longitudinal fields using Rubidium 87 atoms in a tilted one-dimensional optical lattice, where dipolar excitations in the Mott Insulator are mapped to effective spin degrees of freedom. By sweeping the tilt of the lattice, we demonstrate a quantum phase transition between the paramagnetic and the antiferromagnetic phases. We observe the antiferromagnetic ordering in situ by single-site resolved imaging using our quantum gas microscope.

 

Title: Cell Mechanosensing – A Soft Condensed Matter Physics Approach
Speaker: Dr Tee Shang-You
Date:12 May 2011
Time: 11am - 12pm
Venue: Hilbert Space (PAP-02-02)
Host: Professor Alfred Huan 
Abstract: Cellular mechanosensing is a mechanical process. Despite extraordinary advances in biology and a near complete list of molecular players, there is still no fundamental understanding of how cells “feel” mechanical cues and transduced them into biochemical signals. This question cannot be answered without an understanding of the physics of rheology. To unravel the principles of mechanosensing, I developed a platform to probe mammalian cell processes while mechanically and molecularly perturbing them. First, I will discuss how I use concepts of rheology to approach the stress and strain of cellular stiffness sensing. My experiments uncover, for the first time, the timescales and lengthscales at which cells probe their physical environment. Second, I developed an imaging system to probe cell motions at 2nm lengthscale and cell traction forces at 2pN force scales over time scales that span five orders of magnitude. I show that myosin motors in live cells can exhibit cooperative oscillatory behavior and suggest that this may be a way for cells to mechanosense while buffering against external noise. Together, the framework and approaches develop here will help reveal the mechanism of cellular mechanosensing and other mechanical processes in biology.

 

Title: Crystal Structure Prediction via Particle Swarm Optimization: Theory and Applications
Speaker: Professor Yanming Ma
Date:25 April 2011
Time: 11am -12pm
Venue: Hilbert Space (PAP-02-02)
Host: Professor Shen Zexiang 
Abstract: We have developed a new technique [1] for crystal structure prediction from “scratch” through particle swarm optimization (PSO) algorithm. The approach is based on an efficient global minimization of free energy surfaces merging total-energy calculations via PSO technique and requires only chemical compositions for a given compound to predict stable or metastable structures at given external conditions (e.g., pressure). The PSO algorithm has been implemented in Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) package [2] and successfully benchmarked through the blind prediction of many known systems (e.g., Li, Si, C, Mg, SiO2 , SiC, GaAs, TiH2 , ZnO, MoB2 , TiB2 , MgSiO3 , and CaCO3 ) with various chemical bonding environments (e.g., metallic, ionic, and covalent bonding). The high success rate demonstrates the reliability of this methodology and illustrates the promise of PSO as a major technique on crystal structure determination. Recently, we have applied the CALYPSO method to solve high pressure structures of insulating lithium [3], Bi2Te3 [4], and elemental Mg [5]. We have predicted the unknown high pressure insulating phase of lithium takes a based-centered orthorhombic Aba2-40 structure [3], which later on was experimentally confirmed [6]. We have solved the long-puzzled two low-pressure structures of Bi2Te3 and surprisingly found the formation of substitutional alloy of Bi and Te at much higher pressure [4]. More intriguingly, Mg was predicted to form electrides at high pressure [5].

References
[1] Y. Wang, J. Lv, L. Zhu, and Y. Ma, Phys. Rev. B 82, 094116 (2010).
[2] Y. Ma, Y. Wang, J. Lv, and L. Zhu, http://nlshm-lab.jlu.edu.cn/~calypso.html.
[3] J. Lv, Y. Wang, L. Zhu, and Y. Ma, Phys. Rev. Lett. 106, 015503 (2011)
[4]L. Zhu, H. Wang, et al., Phys. Rev. Lett. (in press, 2011)
[5] P. Li, G. Gao, Y. Wang, and Y. Ma, J. Phys. Chem. C 114 21745 (2010).
[6] Guillaume et al. Nature physics, DOI: 10.1038/NPHYS1864, (2011).

 

Title: First-principles design of functional materials for energy applications
Speaker: Professor Su-Huai Wei
Date:12 April 2011
Time: 11am - 12pm
Venue: Hilbert Space (PAP-02-02)
Host: Professor Shen Zexiang
Abstract: Materials design using first-principles techniques is one the ultimate goals in computational materials science. Due to the recent advancement in first-principles electronic structure theory and computing power, it is now possible to perform knowledge-based computational design of materials with unique optical, electrical, or magnetic properties that are tuned to specific energy related applications. This vital tool, therefore, has the great potential to accelerate scientific discovery of energy materials. In this talk, selective works from my group will be discussed to illustrate how computational methods can be used to design functional materials. Some of the examples include (i) absorber materials through cation mutation for solar cells, (ii) bipolarly dopable transparent conducting oxides (TCO) for optoelectronic devices, (iii) low band gap oxides for photoelectrochemical hydrogen production through water splitting, (iv) hydrogen storage material with enhanced s-s interactions, and (v) filled-interstitial nitrides for green solid state lighting materials.

 

Title: The Shifted Harmonic Approximation
Speaker: Dr Ho Shen Yong
Date:8 April 2011
Time: 11am - 12pm 
Venue: Hilbert Space (PAP-02-02)
Host: Professor Alfred Huan 
Abstract: In this talk, I will illustrate how certain classes of quantum many-body Hamiltonians with su1 (2) ⊕ su2 (2) ⊕ . . . ⊕ suk (2) spectrum generating algebras can be approximated by multidimensional shifted harmonic oscillator Hamiltonians. The dimensions of the Hilbert spaces of such Hamiltonians usually depend exponentially on k. This can make obtaining eigenvalues by diagonalization computationally challenging. The Shifted Harmonic Approximation (SHA) developed here gives good predictions of properties such as ground state energies, excitation energies and the most important basis states contributing in the lowest eigenstates. This is achieved by solving only a system of k equations and diagonalizing k × k matrices. The SHA will be illustrated using the Canonical Josephson Hamiltonian and a model multi-level nite-size Bardeen Cooper-Schrieer (BCS) system. I will end by discussing some exploratory works in applying the SHA to a modied spin-boson model and approximating its time evolution using the Feynman-Vernon technique.

 

Title: Theory and application of transformation optics in novel optical and photonic devices
Speaker: Dr Baile ZHANG
Date:7 April 2011
Time: 11am -12pm 
Venue: Hilbert Space (PAP-02-02)
Host: Professor Alfred Huan
Abstract: Transformation optics is a new strategy of manipulating and controlling light, or electromagnetic waves and energy, from the macro- to the nanoscale. Due to its high efficiency of light manipulation, transformation optics has explosively developed in the past few years to be a field of optical and material engineering and science embracing nanophotonics, plasmonics, and optical metamaterials. In this talk, I will examine the fundamental theory of transformation optics in the framework of macroscopic electromagnetic wave theory and discuss the following novel applications in optics and photonics: (1) Invisibility cloaking; (2) Subwavelength imaging; (3) Photonic and plasmonic waveguiding.

 

Title: Coherent phenomena in an optically thick cold atomic gas
Speaker: Dr David Wilkowski
Date:29 March 2011
Time: 11am - 12pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Dumke Rainer
Abstract: When sent on a turbid object, a coherent light beam is scattered by the heterogeneities of the object. If the mean free path l of light inside the scattering object is shorter than the thickness L, scattered photons can be rescattered inside the medium, and one enters in the multiple scattering regime where the photons follow a random walk inside the medium. It results in a globally diffusive transport of energy, where the coherence of the incoming laser beam is usually not preserved after scattering and averaging over the scatterer configurations. However I will shows that interference can resist in averaging in the backscattering direction, producing a coherent backscattering (CBS) peak. In the forward direction, the incoming photons that cross the medium ballistically, without being scattered, produce a coherent transmission equal to e -b . For optical thickness b larger than few units, it seems thus hopeless to coherently transmit a laser beam through an optically thick medium. However, I will explain that this is not true and coherent transmission almost equal to 100% can be achieved, although only over a relatively short temporal window.

The works I will present in this talk have been done on a cold atomic cloud. In sharp contrast with a classical diffusive medium –like an ensemble of dielectric spheres- the probe laser can be tune close to internal resonance with high Q factor. It allows us to revisit multiple scattering problems with extremely low dwell times giving access to time resolved dynamics and the appearance of news dephasing phenomena. Those points will be highlighted during the talk.

 

Title: The Stochastic Green Function algorithm and its application to lattice Hamiltonians
Speaker: Dr Valy Rousseau
Date:23 February 2011
Time: 11am - 12pm 
Venue: Hilbert Space (PAP-02-02)
Host: Dr Dimitris Galanakis
Abstract: I will introduce the Stochastic Green Function (SGF) algorithm, which is an efficient and exact quantum Monte Carlo method that can be easily applied to many lattice models and it gives access to many physical quantities especially n-point Green functions. I will demonstrate the method in the context of the Bose-Hubbard model, which is highly relevant to experiments on ultra cold atomic gases. Also I will introduce a new method for confining such ultra-cold gases that has the advantage of favoring pure Mott phases without coexisting superfluid components

 

Title: Theory and application of transformation optics in invisibility cloaking and subwavelength imaging
Speaker: Dr Zhang Baile
Date:22 February 2011
Time: 11am - 12pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Sun Handong
Abstract: Transformation optics is a new strategy of manipulating and controlling light, or electromagnetic waves and energy, from the macro- to the nanoscale. Its underlining mechanism comes from the formal invariance of Maxwell’s equations: a coordinate transformation doesn’t change the form of Maxwell’s equations, but only changes the constitutive parameters and field values. Due to its high efficiency of light manipulation, transformation optics has explosively developed in the past few years to be a field of optical and material engineering and science embracing nanophotonics, plasmonics, and optical metamaterials. Among various conceptualized transformation optics devices, the most attractive one might be the cloak of invisibility, which can render an object invisible by precisely guiding the flow of light around the object, as if the object does not exist. In this talk, I will examine the fundamental theory of transformation optics by means of studying the physics of invisibility cloaking in the framework of macroscopic electromagnetic wave theory. Our recent implementation of a macroscopic cloak for visible light will be subsequently introduced. Another great potential application of transformation optics is in biological imaging, where resolving of features in the order of 10’s of nanometers is generally required for the dynamic molecular and cellular studies. I will introduce a device that I proposed for real-time subwavelength imaging, where images with sub-100 nm resolution over broadband can be captured without scanning for a common optical microscope in the far field directly. Different from previous proposals of subwavelength imaging techniques, such as the “superlens” and the “hyperlens”, this device requires only isotropic low-loss dielectric materials, and thus its fabrication will be greatly simplified with existing metamaterial technologies.

 

Title: Induced Polarization Effects in Liquid Droplets
Speaker: Dr J.M.Floryan
Date:16 February 2011
Time: 2pm - 3pm
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Claus-Dieter OHL
Abstract: It is desired in the production of sprays to find the ways to control the size and distribution of liquid droplets. It is also of interest to provide means for directing the spray towards the target of interest. Both these goals can be addressed using electric fields, e.g., electrostatic spraying/painting. The proper design and efficiency of these techniques rely on the understanding of the fundamental aspects of droplet dynamics when exposed to external electric fields, and especially on the understanding of the processes associated with droplet break up. This study is focused on the dynamics of liquid droplets driven by induced polarization effect and involves both experiments and theory. During experiments droplets were isolated from all other effects using microgravity environment. The evolution of droplets was captured using a highspeed movie camera. Theoretical analysis, which involved numerical simulation of the deforming droplet, was able to reproduce various stages of the deformation process in time up to the formation of Taylor cones. The droplet evolution process can be divided into rapid distortion followed by a combination of capillary instability and formation of Taylor cones and mass removal from the zone of the cones. Good agreement between the experiment and theoretical modeling has been observed.

 

Title: Loss Mechanisms in Solar Cells
Speaker: Professor Gerald J. Meyer
Date:11 February 2011
Time: 11am - 12pm
Venue: MAS Executive Classroom 1 (MAS-03-06)
Host: Professor Michel-Beyerle
Abstract: Professor Meyer’s research is concerned with experimental investigations of photodriven electron and energy transfer processes involving inorganic coordination compounds. The overall goal of his research is to develop a molecular level understanding of excited states at interfaces important to environmental, biological, and materials science. This research is most relevant for solar energy conversion, chemical sensing, catalysis, and photonic devices. His principal tools are synthetic chemistry, spectroscopy, and electrochemistry. Professor Meyer is a primary investigator in the NSF supported Materials Research and Engineering Center at John Hopkins University. He is director of the NSF supported Collaborative Research Actvities in Environmental Science Center (CRAEMS).

 

Title: Theory and operation of Ti:Sapphire oscillators, amplifiers and optical parametric amplifiers
Speaker: Dr Song Han
Date:7 February 2011
Time: 9am - 12pm
Venue: SPMS-TR14 (SPMS-05-04)
Host: Assistant Professor Elbert Chia 
Abstract: This lecture is for everyone (students, postdocs, staff) who are interested in the theory and operation of Ti:Sapphire lasers. The specific laser systems covered are the Coherent Micra oscillator, Coherent RegA amplifier, and the OPA 9450/9850 optical parametric amplifiers. However, these principles apply to all Ti:Sapphire laser systems.

 

Title: Probes for Structural Recognition and Fluorescent Detection of Nucleic Acids
Speaker: Dr Marie-Paule Teulade-Fichou
Date:4 January 2011
Time: 2pm - 3pm 
Venue: Hilbert Space (PAP-02-02)
Host: Assistant Professor Phan Anh Tuan
Abstract: The design of molecules that can recognize specific structures of nucleic acids is a research goal that is important both for understanding nucleic acid molecular recognition as well as for the development of new therapeutics and reagents for biotechnology. In recent years, increasing knowledge on the structure and dynamics of nucleic acids has led to the identification of a number of structural motifs as potential “drugable” sites. Amongst these are DNA quadruplexes which are tetrahelicoidal structures that could act as molecular switches of DNA-related biological functions. In addition, the detection and optical tracking of nucleic acids using specific fluorescent probes has become increasingly important for a variety of analytic and diagnostic applications. Along these two lines, we have developed a number of new structural and fluorescent probes based on various heterocyclic scaffolds; their design, recognition modes and fluorescent properties will be presented as well as the spectroscopic methods used for studying their interaction with DNA [1-5].

[1]- G. Bordeau, R.Lartia, G.Metgé, C.Fiorini-Debuisschert, F.Charra, M.-P. Teulade-Fichou Trinaphthylamines as robust organic material for two-photon-induced fluorescence J.Am.Chem. Soc.2008, 130,16836-16837.
[2]- A.Granzhan, M.-P. Teulade-Fichou DNA-Mismatch-Binding Ligands: Structural Determinants of Selectivity Chemistry Eur.J. 2009, 15, 1314-1318.
[3]- P. Yang, A. De Cian, M.-P. Teulade-Fichou, J.-L. Mergny, D. Monchaud Engineering BisquinoliniumThiazole orange conjugates for fluorescent sensing of G-quadruplex DNA Angew.Chem.2009,48, 2188-2191.
[4]- D. Monchaud, M.-P. Teulade-Fichou G4-FID: A fluorescent DNA probe displacement assay for rapid evaluation of quadruplex ligands. Methods in Mol. Biol. 2010, vol 608, chapter 15, 257-271.
[5]- A.Granzhan, D. Monchaud, N.Saettel,A. Guédin, J.-L. Mergny, M.-P. Teulade-Fichou “One ring to bind them all” – Part II: The efficiency of the macrocyclic scaffold for G-quadruplex DNA recognition. J. Nucleic.Acids 2010, ID525862.