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X-RAY RUNS: Apply for Beamtime

2017  Nov 1 - Dec 21

2018  Feb 7 - Apr 3
2018  Proposal/BTR deadline: 12/1/17

2018  Apr 11 - Jun 4
2018  Proposal/BTR deadline: 2/1/18

January 8th - Naresh Shayka, Kent University
January 22th - Alexander Kazimirov, Cornell University

February 5th - Garth Williams, SLAC
February 12th - Yuxin Mao, Cornell University
February 15th - Ting Xu, University of California at Berkley
February 19th - Arthur Woll, Cornell University

March 12th - Jia-huai Wang, Harvard   ~Special Time~

April 5th - Yu-Miin Sheu, University of Michigan   ~NOTE - Day~
April 7th - Lara Estroff, Cornell University     ~NOTE - Day~
April 8th - Richard Robinson, Cornell University     ~NOTE - Day~
April 9th - Chris Fromme, Cornell University
April 13th - Helmut Dosch, DESY     ~NOTE - Day~
April 16th - Christian David, Paul Scherrer Institute
April 19th - J.Y. Peter Ko, The University of Western Ontario     ~NOTE - Day~

May 7th - Søren Nielsen, Cornell University
May 18th - Johanna Nelson, Stony Brook University     ~NOTE - Day~
May 21st - Zhi Zhao, Cornell University

June 11th - Christian Holzner, Stony Brook University
June 22nd - Philippe Godefroy, WinlightX     ~NOTE - Day, Time, & Location~
June 29th - Fernando Sannibale, Berkeley Lab     ~CANCELLED~

July 7th - Thomas Prolier, Argonne National Laboratory     ~NOTE - Day & Time~
July 19th - Andreas Adelmann, Paul Scherrer Institute      ~NOTE - Day~
July 30th - Mingqi Ge, FNAL

August 3 - Walter Hartung, NSCL, Michigan State University        ~NOTE - Day~ 

August 6 - CHESS Student Seminar

September 10 - CANCELLED
September 17 - Detlef Smilgies, Cornell University
September 24 - Sharon George, Washington State University      ~NOTE - Time ~

October 1 - Ken Finkelstein - Cornell University
October 13 - Rol Johnson, Muons Inc      ~NOTE - Day ~ 
October 14 - Sara Casalbuoni, KIT      ~NOTE - Day ~ 

November 3 - Massimo Petrarca, CERN      ~NOTE - Day ~

December 3 - Oleg Chubar, BNL
December 10 - Nick Agladze, Cornell
December 15 - Robert Fischetti, ANL         ~Cancelled ~
December 17 - Yun He, Fermilab     ~NOTE - Time ~
December 17 - Rong Huang, APS     ~NOTE - Time ~

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~Note: Time~

Friday, December 17, 2010
Time: 2:00pm

Rong Huang, Beamline Scientist IMCA-CAT, APS

 

"The High-Throughput Macromolecular Crystallography Beamlines at IMCA-CAT"

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~Note: Time & Location~

Presentation:  pdf

Friday, December 17, 2010
Time:11:00am
Location: 301 Wilson Lab

Yun He, Fermilab

 

"Magnetic Focusing Horns for Neutrino Experiments"

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~CANCELLED~

Wednesday, December 15, 2010

 

Robert Fischetti, Assoc Director NIGMS/National Cancer Inst. Collaborative Access Team
Biosciences Division, Argonne National Laboratory

 

"Radiation damage to Protein Crystals is Reduced with Micron-Sized X-ray Beams"

Abstract:  Radiation damage is a major limitation in crystallography of biological macromolecules, even for cryo-cooled samples, and is particularly acute in micro-diffraction. For the X-ray energies most commonly used for protein crystallography at synchrotron sources, photoelectrons are the predominant source of radiation damage. If the beam size is small relative to the photoelectron path length, then the photoelectron may escape the beam footprint, resulting in less damage in the illuminated volume. Thus, it may be possible to exploit this phenomenon to reduce radiation-induced damage during data measurement for techniques such as diffraction, spectroscopy and imaging that use X-rays to probe both crystalline and non-crystalline biological samples. I will present the results of the first experimental demonstration of reduced radiation damage in protein crystals with small beams where damage was measured as a function of micron-sized X-ray beams of decreasing dimensions. The damage rate normalized for dose was reduced by a factor of 3 from the largest (15.6 µm) to the smallest (0.84 µm) X-ray beam used. In addition, radiation-induced damage to protein crystals was mapped parallel and perpendicular to the polarization direction of an incident 1- µm X-ray beam. The observed damage was greatest at the beam center and decreased monotonically to zero at a distance of about 4 μm, establishing the range of photoelectrons. The damage is less anisotropic than photoelectron emission probability, consistent with photoelectron trajectory simulations. The experimental results provide the basis for data collection protocols to mitigate with micron-sized X-ray beams the effects of radiation damage.

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Friday, December 10, 2010

Presentation:  ppt / pdf

Nick Agladze, Research Associate
LASSP, Cornell University

 

"Holographic Spectroscopy for Single Shot Electron Bunch Diagnostics"

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Friday, December 3, 2010

Presentation: ppt / pdf (login required)

Oleg Chubar
National Synchrotron Light Source II, Brookhaven National Laboratory

 

"Partially Coherent Wavefront Propagation Calculations for Third- and Fourth-Generation Synchrotron Radiation Sources"

Abstract:  Ultra-low emittance, third-generation synchrotron radiation (SR) sources, such as NSLS-II, MAX-IV and PETRA-III, will offer excellent opportunities for further development of experimental techniques exploiting x-ray coherence. However, even in these new SR sources, the radiation produced by relativistic electrons (in undulators, wigglers and bending magnets) will remain only partially coherent in x-ray spectral range. "Extraction" of a "coherent portion" of the radiation flux and its transport to a sample without loss of coherence, by maximally exploiting the source brightness, must be performed by dedicated SR beamlines, optimized for particular types of experiments.

Detailed quantitative prediction of partially coherent x-ray beam properties at propagation through optical elements, which is required for the optimization of such beamlines, can only be obtained from accurate and efficient physical optics based numerical simulations. Examples of such simulations, made for NSLS-II project beamlines, using "Synchrotron Radiation Workshop" computer code, will be presented. Beamline performance characteristics obtained from these simulations, such as radiation spot size and flux at sample vs. size of secondary source aperture for a high-resolution microscopy beamline, will be discussed. Special attention will be paid to numerical analysis of the basic properties of partially coherent spontaneous undulator radiation and its distinction from a Gaussian Schell-model beam. The talk will also include some illustrations and results of time-dependent wavefront propagation calculations performed for a self-amplified spontaneous emission free-electron laser source.

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~Note: Day~

Wednesday, November 3, 2010

Presentation: - pdf

Massimo Petrarca, EN/STI
CERN

 

"Photoinjector Activities at CERN"

Abstract:  In this talk the main results of the injector studies within the CTF3 project, that is a CERN facility to study the feasibility of the key CLIC-technology challenges for the CLIC two-beam scheme, will be presented. The characteristics of the laser and of the photo-cathode will be discussed. The very stringent demands of high charge, ultra-stable and short electron bunches make a laser driven photoinjector source very attractive.

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Thursday, October 14, 2010            ~SPECIAL seminar~  Note: Day ~

Presentation: - pdf

Sara Casalbuoni
Karlsruher Institut für Technologie (KIT)

"Progress on the Superconducting Undulator for ANKA and on the Instrumentation for R&D"

Abstract: In order to produce synchrotron radiation of highest brilliance, third generation synchrotron sources make use of insertion devices (IDs). Superconducting undulators show a larger magnetic field strength for the same gap and period length, as compared to permanent magnet IDs, which allows to generate X-ray beams of higher brilliance and with harder spectrum. The worldwide first short period length superconducting undulator is in operation since 2005 at the synchrotron light source ANKA in Karlsruhe. To further drive the development in this field a research and development program is being carried out. In this talk I report on the last progress of the construction of a 1.5 m long superconducting undulator with a period length of 15 mm, planned to be installed in ANKA end of 2010 to be the light source of the new beamline NANO for high resolution X-ray scattering. The key specifications of the system defined by KIT are an undulator parameter K higher than 2 (with a magnetic gap of 5 mm) and a phase error smaller than 3.5 degrees. Cryocoolers will keep the coils at 4.2 K for a beam heat load of 4 W. The magnet design and fabrication have been carried out by Babcock Noell. To characterize the magnetic field properties of the superconducting coils local field measurements have been performed by moving a set of Hall probes on a sledge in a liquid helium bath at CERN: the results are reported. The ongoing R&D includes improvements in understanding of the magnetic field properties and of the beam heat load mechanisms. The tools and instruments under development to fulfill these tasks are also discussed.

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~SPECIAL seminar~  Note: Day ~

Wednesday, October 13, 2010

Presentation:  ppt / pdf

Rol Johnson, CEO, Muons Inc

"Bright Muon Beams for Colliders, Neutrino Factories, and Muon Physics"

Abstract:  New inventions are rapidly improving the prospects for high luminosity muon colliders for Higgs factories and at the energy frontier. Recent analytical calculations, numerical simulations, and experimental measurements are coming together to make a strong case for a series of machines to be built, where each one is a precursor to the next, with its own unique experimental and accelerator physics programs. A strategy will be outlined for achieving an almost unlimited program of experimental physics based on the cooling and acceleration of muon beams. The challenge of doing cutting-edge accelerator R&D as a small for-profit company will also be described along with new initiatives that include new ideas for accelerator-driven subcritical reactors.

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Friday, October 1, 2010

Presentation:  ppt / pdf

Ken Finkelstein, Sr. Research Associate
CHESS, Cornell University

"In 20 minutes; How an ERL could benefit Inelastic X-ray Scattering (IXS) report on improving IXS resolution by manipulating perfect crystal reflectivity"

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~SPECIAL seminar~  Note: Time ~

Friday, September 24, 2010
Time:  11am

Sharon George, Washington State University

 

"Vacuum UV Laser Interactions with Wide Band Gap Materials: How a 157-nm laser breaks down Teflon® and forms transient absorption centers in calcium fluoride"

Abstract:  Over the last decades the F2 excimer laser (157 nm) has obtained a key position among lasers in various sectors of micromachining and in pulsed laser deposition. Because of its short wavelength this laser offers excellent quality of machining and a great versatility in features which can be produced. Understanding the interaction of 7.9 eV photons with wide band gap polymers like polytetrafluoroethylene (PTFE) (Teflon®) can be beneficial to laser machining and pulsed laser deposition applications. Particle emission is a valuable probe of interactions between these materials and laser radiation. In the case of PTFE we observed intense neutral particle emission during laser irradiation. I will talk about how we measured and analyzed time-of-flight signals of these particle to reveal details involving bond breaking and photodecomposition of this polymer. Unlike PTFE which strongly absorbs at 157-nm, calcium fluoride (CaF2) is transparent at this wavelength. A wide band gap of 11.9 eV contributes to the damage resistance of this material, and is therefore used for making optics for 157-nm applications. That said, the optical properties of CaF2 can be degraded by two-photon processes at 157-nm that generate defects that absorb sub-band gap radiation. This leads to permanent changes in the absorption spectrum of the material. However, we also observed transient absorption superimposed on the persistent changes in the VUV and UV regions during laser irradiation. I will talk about the different defect centers that are responsible for this absorption and present possible mechanisms for their transient nature.

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Friday, September 17, 2010

Presentation: (login required) - pdf

Detlef Smilgies, Sr. Research Associate
CHESS, Cornell University

"Protein Immobilization Probed with GISAXS"

Abstract:  Protein immobilization is an important process in medical and environmental studies, such as for use in biosensors, as well as in biochemical engineering, for use in bioreactors. The common feature is that a protein, such as an enzyme or antibody, is attached to a substrate with the active group facing the liquid phase. Present immobilization techniques are often not very specific and rely on trial and error preparation to obtain the largest possible yield of signal or product. However, for optimum efficiency as well as working with precious materials, control of protein conformation and orientation at the substrate will be essential, and strategies towards this goal are being developed. A big obstacle along this path is the lack of techniques that can determine protein conformation and orientation, when absorbed at a surface. Considering the great progress achieved in characterizing proteins in solution using small-angle scattering (BioSAXS), I would like to discuss whether grazing-incidence SAXS (GISAXS) would be a suitable tool to tackle the problem of specific protein immobilization.

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Friday, September 10, 2010      ~CANCELLED~

Steve Wang, Advanced Photon Source

"Dynamic in-situ Nano-CT Experiments at Advanced Photon Source"

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~SPECIAL seminar~  Note: Day ~

Tuesday, August 3, 2010                                                Presentation: - pdf

Walter Hartung, Physicist, Adjunct Professor
NSCL at Michigan State University

"Superconducting RF for the Facility for Rare Isotope Beams"

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Friday, July 30, 2010                             Presentation: (login required) - pdf

Mingqi Ge
FNAL

"The Development of New Techniques for Surface Defect Research at Fermilab"

Abstract:   Surface defect such as pit, bump, cracks, scratches, etc., has been identified as one of the main source of limitations to SRF cavity. It is a cause of significant spread in cavity gradient. Several new techniques for surface defects research are developed at Fermilab. The surface replica technique can provide 1 micron resolution and depicts vivid 3D shape of defects as well as wealth of topology information. This information allows us to establish the mechanism of local electromagnetic quench at the flaws. The replica procedure was proved to be harmless to high performance cavities. The Fermilab’s Laser re-melting system is aimed to remove the flaws that limit cavity RF performance below 20MV/m, We succeeded in re-melting a pit in 1.3GHz single-cell cavity and restored the gradient to 40MV/m just followed by a light electropolishing. Laser welding technique for SRF cavity is able to dramatically reduce HAZ area at cavity equator region. The potential benefit is to decrease the probability of welding pit generation.

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~SPECIAL seminar~  Note: Day ~

Monday, July 19, 2010

Andreas Adelmann, Ph. D.
Paul Scherrer Institute

 

"Precise Beam Dynamics Simulation:  how does it work?"

Abstract:  In space charge dominated regimes non-linear forces acting over large spatial and temporal scales render precise beam dynamics simulation a challenging task. Other possibly important physics processes to be considered are: CSR, collimation including secondary effects and particle emission schemes. For accurate field solutions and the precise calculation of quantities such as (slice) emittance, controlled and uncontrolled losses, sufficient particle statistics together with corresponding spatial and temporal resolution is required. These requirements call for state-of-the-art numerical algorithms and efficient parallel implementation. Many of the above mentioned challenges are met by the beam dynamics program OPAL (Object Oriented Parallel Accelerator Library). I will touch on physics and numerical modeling questions with particular emphasis on the implementation on high performance computing architectures. A short overview of the program and its unique features will be presented. Examples of OPAL simulations include space charge studies on high-intensity proton cyclotrons and linear accelerator simulations for the SwissFEL currently being designed at PSI.

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~SPECIAL seminar~  Note: Day & Time~

Wednesday, July 7, 2010
Time: 2:00 pm

Thomas Prolier, Ph. D., Assistant Physicist
Material Sciences Division
Argonne National Laboratory

"Fundamental Understanding of Dissipation Mechanism in SRF Cavities:  Surface Magnetism"

Abstract:  Screening currents are confined to a depth of Lambda (40nm) at the surface of Niobium SRF cavities. A detailed understanding of surface structure and the interactions with the native niobium oxide is therefore a necessary step. We will present at first various surface and bulk results that reveal the presence of localized paramagnetic moments present in defected native niobium oxide and then develop a theoretical model that calculate the effect of these impurities on the surface superconductivity. The main achievement of such model is a microscopic explanation of the Residual resistance that limits the quality factor of cavities. Several key parameters such as the mean free path, the concentration of magnetic impurities, extracted from fits of the surface impedance data, are found to evolved with various surface treatments. A last we will present a method and preliminary results to remove native oxides and possibly eliminate the magnetic contribution to the surface impedance.

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~CANCELLED~

Tuesday, June 29, 2010
Time: 11am

Fernando Sannibale, Staff Scientist
Advanced Light Source Physics Group,
Lawrence Berkeley National Laboratory

 

"A Normal-conducting CW VHF Photo-injector for FEL and ERL Applications"

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~SPECIAL seminar~  Note: Day, Location & Time~

Tuesday, June 22, 2010
Location: 374 Wilson Lab

Time: 11am

Philippe Godefroy, co-CEO
WinlightX S.A.R.L. (France)

Presentation: (login required) - pdf

 

"Last Developments for Ultra-precision Mirrors and Benders (reaching the nm scale"

Abstract:  WINLIGHT is a supplier of mirrors, benders and KB. We will present our last developments in terms of polishing and surface inspection to reach the nm scale for large mirrors. As a supplier of complete systems, WINLIGHT will also present its bending technology. Results on inspection machine and on beamlines will be exhibited.

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Friday, June 11, 2010

Christian Holzner, PhD Student
X-ray Optics and Microscopy,
Department of Physics and Astronomy,
Stony Brook University

 

"Scanning Hard X-ray Phase Contrast Microscopy - Techniques and Applications"

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Friday, May 21, 2010

Dr. Zhi Zhao, Research Associate
Laboratory of Elementary and Particle Physics, Cornell University

"Quantum Teleportation:  an Overview"

Abstract:  I review some progress on quantum teleportation that has been made over the past ten years. I will start with a description of quantum teleportation protocol, and then demonstrate how to teleport single photonic qubits. Afterwards, I will present various approaches to teleportation. Finally, I will illustrate some efforts towards teleportation of macroscopic Schrödinger “cat” state.

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~SPECIAL seminar~  Note: Day

                        Presentation: - pdf

Tuesday, May 18, 2010

Johanna Nelson, Research Assistant
Dept. of Physics & Astronomy, Stony Brook University

 

"X-ray Diffraction Microscopy:  bridging the resolution gap"

Abstract:  X-ray diffraction microscopy (XDM) promises to be an attractive technique for 3D soft x-ray imaging of radiation sensitive samples. By eliminating the objective lens it makes use of every photon interacting with the specimen. Diffraction intensity patterns are collected on isolated objects and using iterative phase retrieval algorithms, the lost phase information can be recovered with no a priori information. Using this technique we have recovered the complex waves exiting whole, eukaryotic cells in either a frozen or freeze-dried state.

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Friday, May 7, 2010

Søren Nielsen, Post Doc
MacCHESS, Cornell University

 

 

"An Automated Sample Mixing System for High-throughput SAXS Measurements using a Microfludic Approach"

Abstract:  The presentation will be based on the work carried out during the authors Ph.D. and will give insight to the so-called BioXTAS project where the members are developing a fully automated microfluidic system for sample mixing, exposure and data processing. The presentation will go through the thought process that led to three different microfluidic setups and how these were automated, both regarding hardware and software. Results obtained on SAXS beamlines will further be presented and discussed.

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~SPECIAL seminar~  Note: Day

Monday, April 19, 2010

J.Y. Peter Ko, Postdoctoral Candidate
Dept. of Chemistry,
The University of Western Ontario

 

"Materials Analysis by Synchrotron X-ray Absorption Spectroscopy:  From Light Emitting Materials to Biological Samples"

Abstract:  Today, synchrotron X-ray absorption spectroscopy and related techniques are widely used for analysis of various materials, ranging from macromolecules to nanomaterials to biological samples. As the techniques take advantage of a bright, energy-tunable light source, they have become an excellent tool to investigate chemical environment, and electronic structure of the materials being analyzed.

In this talk, following studies of synchrotron X-ray analysis will be presented:

     - By taking advantage of energy tunability and time structure of synchrotron radiation, we have performed X-ray Excited Optical Luminescence (XEOL) and Time-Resolved XEOL (TR-XEOL) to investigate optical properties and decay characteristics of calcium oxide color centers (F center and F+ center) generated by X-ray excitation.

     - Hemochromatosis is a genetic disorder that causes the body to absorb and retain excess iron. One in nine people of mostly Northern European descent are carriers of the hemochromatic gene, while one in 300 are estimated to be homozygous. X-ray microspectroscopy was performed to reveal distribution and local chemical characteristics of metal especially iron in hemochromatic liver biopsy tissues. Elemental maps with micron spectral resolution were produced by collecting X-ray fluorescence, and X-ray absorption spectroscopy was performed on spots of interest from the elemental maps. Results from recent work will be highlighted here.

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Friday, April 16, 2010

Christian David
Laboratory for Micro- and Nanotechnology,
Paul Scherrer Institute, Switzerland

 

"Diffractive X-ray Optics for Imaging and Metrology Applications"

Abstract:  Diffractive x-ray optics fabricated by micro- or nanolithography techniques can be used to control the wavefront of x-rays with sub-wavelength precision. We report on the development of various devices and their application in x-ray microscopy, radiography and metrology experiments. Fresnel zone plates (FZPs) are used in full field transmission x-ray microscopes (TXM) and scanning transmission x-ray microscopes (STXM) for high resolution imaging and analysis. The resolution is limited by the width of the outermost zones. Using high resolution electron-beam lithography and a line doubling technique we produced FZPs capable of resolving structures with dimensions as small as 9 nm [1]. An interferometric hard x-ray phase imaging technique based on diffraction gratings is presented. Compared to other phase contrast imaging methods, the grating interferometer has only very moderate requirements in terms of coherence. It can accept a wide spectral band width, and virtually no spatial coherence is required [2]. This makes it possible to use the method with standard x-ray tubes, which opens up a huge range of every-day applications such as medical imaging or home land security. In addition to phase contrast x-ray imaging, the scattering properties of the sample can be visualized in a dark field x-ray imaging mode [3]. As the grating interferometer is capable of resolving deflection angles down to the 10 nrad range, it can also be applied for in-situ metrology on x-ray optical components such as mirrors and refractive lenses [4]. Moreover, it can be used to characterize the wave-front properties of synchrotrons or x-ray free electron lasers.

1. J. Vila-Comamala, K. Jefimovs, T. Pilvi, J. Raabe, R.H. Fink, M. Senoner, A. Maaßdorf, M. Ritala, and C. David Ultramicroscopy 109 (2009) p. 1360-1364

2. F. Pfeiffer, T. Weitkamp, O. Bunk, and C. David, Nature Physics 2, 258 (2006)

3. F. Pfeiffer, M. Bech, O. Bunk, C. Grünzweig, E.F. Eikenberry, Ch. Brönnimann, C. David, Nature Materials 7, 134(2008)

4. T. Weitkamp, B. Nöhammer, A. Diaz, C. David, E. Ziegler Applied Physics Letters 86 (2005) p. 054101–054103

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 ~SPECIAL seminar~  Note: Day

Tuesday, April 13, 2010

Dr. Helmut Dosch
Chairman of the DESY Board of Directors

 

"Potential and Challenges of Disordered Matter"

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Friday, April 9, 2010

Chris Fromme, Assistant Professor
Molecular Biology and Genetics, Cornell University

 

 

"Understanding the Function and Regulation of G-proteins in Membrane Trafficking Using Biophysical and Biochemical Approaches"

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~Special Seminar~

 

Thursday, April 8, 2010

Richard Robinson, Assistant Professor
Materials Science and Engineering, Cornell University

 

"Synthesis of Anisotropic Nanoparticles and Nanosheets"

Abstract:  In this talk I will discuss several nanoparticle material systems we are developing for alternative energy, and our characterization needs for each system as they relate to CHESS. One overarching question in this area is: how and why do nanoparticles assume their final shape.. The first system is the synthesis of metal nanocubes and nanowires from a simple reduction of metal ions. The dimensions for our Ag cubes is 50 - 100 nm, and nanowires is 50 nm by ~2 microns. As a small cluster, Ag metal can be stable in truncated octahedron form, which is not a crystal structure. But as it grows the typical unit cell for the metal dominates internally, and externally the crystal can take on many forms including nanocubes or nanowires with pentagonal symmetry. The pathways to these shapes are not understood. Conflicting theories have developed, even from within the same group. In the second system we look at the phenomena of hyperbranched crystal growth in Co2P crystals. Non-equilibrium shapes are desirable in nanoparticles as one could control the size and number of particular facets, which can lead to radical differences in reactivity. Studies of hyperbranched crystal growth provide a tool for understanding kinetic growth of nanocrystals, which could lead to greater control of non-equilibrium shapes. The growth mechanism in hyperbranched particles remains a mystery, similar to crystal splitting in minerals (also still a mystery). In the final system we present new nanosheeted materials from a sol-gel synthesis. The nanosheets are 20 – 100 nm thick and 1 -2 millimeters long. They are composed of cobalt metal oxides. Their formation is still under investigation, but currently we believe there is a diffusion of alkali ions during the calcinations step.

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~~SPECIAL seminar~  Note: Day~
ppt / pdf

Wednesday, April 7, 2010

Lara Estroff, Assistant Professor
Materials Science and Engineering, Cornell University

 

 

"Polymer-reinforced Single Crystals of Calcite:  Formation mechanisms, internal structures, and physical properties"

Abstract:  Single crystals are usually faceted solids with homogeneous compositions. Biogenic and synthetic calcite single crystals, however, have been found to incorporate macromolecules, spurring investigations of how large molecules are distributed within the crystals without significantly disrupting the crystalline lattice. In this work, we use ADF-STEM and electron tomography to characterize the internal structure of calcitic prisms from mollusks and synthetic calcite crystals, which were grown in an agarose hydrogel. The gel-grown calcite crystals, like the biogenic prisms, uniformly incorporate the organic matrix. These results suggest that physical entrapment of polymer aggregates is a viable mechanism by which macromolecules can become incorporated inside of inorganic single-crystals. We have also evaluated the parameters that control the incorporation of polymer networks during calcite crystal growth in agarose hydrogels. These results have led to design criteria for polymer-reinforced crystalline materials with unique structure-property relationships. I will also present preliminary results characterizing the mechanical properties of both the synthetic and biogenic single crystal composites. Insights provided by this work may help to elucidate the formation mechanism(s) and properties of biogenic single crystals with incorporated organic material.

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~SPECIAL seminar~  Note: Day

Monday, April 5, 2010

Yu-Miin Sheu
University of Michigan

"Ultrafast Dynamics of Photoexcited Bismuth Films"

Abstract:  The carrier and lattice relaxation processes following photoexcitation in solids occur over time-scales ranging from femtoseconds to nanoseconds. The eventual conversion of the light to lattice heating involves carrier-carrier, carrier-phonon and phonon-phonon interactions. More fundamental understandings of these processes may lead to advances in thermoelectrics, photovoltaics, and other technologically important materials. Even for bismuth, a well-studied thermoelectric material, detailed information on these processes is still unavailable. I will present ultrafast optical and x-ray studies of photoexcited carrier diffusion and recombination, acoustic phonon generation and propagation, and lattice heating and diffusion in thin bismuth films. The combination of laser and x-ray experiments confirms that carriers relax by rapidly heating the lattice before diffusing and ultimately recombining, leaving an inhomogeneous temperature profile near the surface. We observe a temperature discontinuity across Bismuth/sapphire interface and derive Kapitza conductance by depth- and time-resolved x-ray diffraction. Comparing counter-propagating and conventional pump-probe measurements at low excitation, we find that the carrier density is not determined by the electron-hole plasma temperature after a few picoseconds.

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~Special Time~

Friday, March 12, 2010
Time: 10-11am

Jia-huai Wang, PhD
Associate Professor of Pediatrics and Biological Chemistry and Molecular Pharmacology
Harvard Medical School

 

"TBA"

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Presentation: (login required) - pdf

Friday, February 19, 2010

Arthur Woll, Staff Scientist
G-line, Cornell University

 

 

 

"Probing Organic Thin Film Growth at G3: The unbearable lightness of being a small, organic molecule on a squishy surface"

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~SPECIAL seminar~  Note: Day

Monday, February 15, 2010
Time: 1PM

Professor Ting Xu, Dept of Materials Science & Engineering,
University of California at Berkeley

 

"Directed Assembly of Nanocomposites Containing Synthetic and Biological Nanoparticles"

Abstract: Controlled assembly of functional building blocks over multiple length scales has great potential to advance technologies and will impact human health, renewable energy and environment. However, generating hierarchically structured materials in a manner similar to that seen in nature represents a fundamental scientific challenge. As one important family of soft material, block copolymer (BCP) microphase separate and form well defined nanostructures in tens of nanometer and can be readily fabricated over macroscopic distances and have been extensively utilized in various applications as templates for the synthesis of inorganic and magnetic materials; masks for photolithography; scaffolds for nanodevices; and functional membrane materials. Here, the structure and functionality of conventional BCP are augmented through the incorporation of small molecules, inorganic and biological nanoparticles. These additives are selectively dispersed within the nanostructures of segregated BCPs and lead to hierarchical functional assemblies spanning arbitrarily large areas. I will discuss our recent efforts in understanding the fundamental principles governing the assembly process in bulk and in thin films.

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Friday, February 12, 2010

Yuxin Mao, Assistant Professor
Molecular Biology and Genetics, Cornell University

 

"Crystal Structure of the Yeast Sac1: Implications for Its Phosphoinositide Phosphatase Function"

Abstract:  SaSac family phosphoinositide phosphatases are an essential family of CX5R(T/S) based enzymes, involved in numerous aspects of cellular function such as phosphoinositide homeostasis, cellular signaling, and membrane trafficking. Genetic deletions of several Sac family members result in lethality in animal models and mutations of the Sac3 gene have been found in human hereditary diseases. Here we report the crystal structure of a founding member of this family, the Sac phosphatase domain of yeast Sac1. The 2.0 Å resolution structure reveals that the Sac domain is comprised of two closely packed sub-domains, a novel N-terminal sub-domain and the phosphoinositide phosphatase catalytic sub-domain. The structure further reveals a striking conformation of the catalytic P-loop and a large positively charged groove at the catalytic site. These findings suggest an unusual mechanism for its dephosphorylation function. Homology structural model of human Fig4/Sac3 allows the mapping of several disease related mutations and provides a framework for the understanding of the molecular mechanisms of human diseases.

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Friday, February 5, 2010

Garth Williams, Linac Coherent Light Source
SLAC National Accelerator Laboratory

"Exploiting Diverging and Partially Coherent Beams for Diffractive Imaging"

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Friday, January 22, 2010

Alexander Kazimirov
Cornell University

"Diffraction of focused x-ray beams from perfect crystals: first experimental results and possible applications"

Abstract:  Modern focusing optics is able to deliver x-ray beams of the size of 100 nm and smaller for a variety of applications based on scattering and diffraction techniques. Meanwhile, diffraction of focused beams from crystals requires detail theoretical and experimental analysis. Theory predicts that a focused x-ray beam Bragg diffracted from a perfect crystal has a fine structure which depends on the size of the beam, the thickness of the crystal and diffraction conditions. In this talk, I will present first experimental results allowing for a detailed comparison with theory and outline possible practical applications.

Experiments were performed at the APS and the ESRF by using zone plates and refractive lenses as focusing optics. New experimental setup in which high-resolution detector is placed in the focus and crystal is positioned between the focusing optics and the focus was proposed and utilized. The broadening of the focused beam by crystals due to extinction effect and the evolution of a spatial structure with angle were observed for the first time and analyzed. Experimental images recorded from real crystals and semiconductor structures demonstrate that this experimental setup can be used as a new diffraction imaging technique that combines spatial locality and depth sensitivity.

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Friday, January 08, 2010

Presentation: pdf

Naresh M Shakya
Kent State University

"Study of Electronic Transport in Novel Liquid Crystalline Organic Semiconductors"

Abstract:  Organic semiconductors (OSs) have stirred huge commercial interest due to their potential applications in electronic and optoelectronic devices such as field effect transistors, photovoltaic cells, organic light-emitting diodes, photocopying and printing technology. Major benefits of OSs over conventional inorganic semiconductors include mechanical flexibility, low temperature processing, very low cost, and ease of fabrication in large area electronic devices on plastic and paper substrates. Liquid crystals (LCs) are particularly interesting sub-classes of OSs, both from the fundamental and practical standpoints. Unlike in conventional crystalline semiconductors, the molecular alignments in LCs can be switched to obtain different electro-optical properties and may also exhibit self-healing effects, reducing the consequences of structural damage and impurities. In this context, researches for the better quality of liquid crystals are still going on.

The study of the electronic transport properties of different kinds of OSs, including discotic and calamitic LCs, glasses, and organic molecular crystals by using the pulsed-laser time -of- flight technique was the major concerned of this research. One of the research projects involved a thiophene-benzene-thiophene-based material that exhibits polaron band behavior with very high mobility smectic phases. In this material, the highly ordered smectic-F phase templates the formation of ordered crystalline smectic phases. These results may have implications for the device development because this system forms domains which are large enough to transport holes without a great deal of trapping at boundaries. The other project involved the transport measurements on a calamitic LC with a pyridine-thiophene-thiophene-pyridine core. Pyridine-based LCs often exhibit very high order smectic phases and are therefore of interest as OSs. However, the mobility of this material was found quite low, even in high-order phases. A full explanation of this fact is not available. However, as a first step, we were able to describe our data using Basseler's Theory of disordered hopping conduction.

For a better study, a technique to measure the charge carrier mobility in freely suspended films of LCs in high vacuum was developed. This technique has many advantages over experiments conducted in conventional cells. For example, the external field can be coupled easily to the molecular order, no electrodes contact the sample, and extremely high voltages can be applied. Also, both hole and electron mobility (which depends on high purity and absence of oxygen), and samples with a very wide range of thickness can be studied. An equipment for growing organic crystals using the Bridgman-tockbarger technique was successfully designed, developed, and constructed.