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X-RAY RUNS: Apply for Beamtime

2017  March 15 - April 24

2017  May 17 - June 29
2017  BTR deadline: 04/17/17

2017  October 11 - December 21
2017  Proposal deadline: 08/01/17
2017  BTR deadline: 09/10/17

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Dr. Cai Quan

Friday, December 12, 2014, 1:00 pm

Dr. Cai Quan
Institute of Higher Energy Physics (IHEP)
Beijing, China

"Synchrotron in Beijing, Today and Future"

Abstract: A brief introduction to Beijing Synchrotron Radiation Facility, and a new high energy photon source plan in the future. Including design, pre-design and research project which has been launched.

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Jiun-Haw Chu

Friday, December 5, 2014, 1:00 pm

Jiun-Haw Chu
Stanford University

"Electronic Nematic Phase in Iron Based Superconductors"

Abstract: High-temperature superconductivity often emerges in the proximity of a symmetry-breaking ground state in strongly interacting electronic materials. In the case of the superconducting iron pnictides, in addition to the antiferromagnetic ground state of the parent compounds, a ubiquitous but small structural distortion breaks the crystal’s C4 rotational symmetry in the underdoped part of the phase diagram. It has been proposed that this structural transition is driven by an electronic nematic phase transition, below which the electronic system spontaneously organizes with an orientational order without developing additional spatial periodic order. In this talk I will show how the effects of this electronic nematic order can be explicitly revealed by observing the response of the system to in-plane uniaxial stress. I will present transport measurements of single crystal samples of various iron-based superconductors held under an in-situ tunable strain at temperatures above phase transition, which explicitly confirm that the structural transition is fundamentally driven by a thermodynamic instability in the electronic part of the free energy. I will also discuss the nematic fluctuations prevailing throughout the overdoped part of the phase diagram, which suggests a quantum phase transition at the optimal doped Tc.

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Ariel Gomez

Tuesday, December 2, 2014, 1:00 pm

Ariel Gomez
Canadian Light Source

"Ray tracing for Laue monochromators"

Abstract: Ray tracing is an important tool for beamline design and optimization; however its application to Laue monochromators has been very limited. This makes it difficult to accurately calculate the beam size or identify possible sources of optical aberrations. The difficulty in applying ray tracing programs to bent Laue crystals lies in the fact that each crystal should be described by a set of independent lamellas with a range of orientations that depends on the radius of curvature, the crystal orientation and thickness, and the reflection used. This method adds the complexity that each lamella should be treated as a single optical element that diffracts only a small portion of the incident beam; hence the number of optical elements and rays to be calculated rapidly grows over a manageable number. I will show how we can overcome this difficulty by an efficient use of the macro capabilities built-in within Shadow/XOP software. Examples of the method applied to beamline design and experimental data obtained at the Canadian Light Source will be shown.

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Bruce Gaulin

Friday, November 21, 2014, 1:00 pm

Bruce Gaulin
Brockhouse Institute for Materials Research
McMaster University

 

"Quantum spin ice physics and emergent QED in pyrochlore magnets"

Abstract: Different combinations of magnetic interactions and anisotropies relevant to magnetism on the pyrochlore lattice, a cubic network of corner-sharing tetrahedra, are known to lead to different exotic, and often disordered, ground states. One such state that has been of much topical interest is "spin ice". The elementary excitations within the spin ice ground state are describable as diffusing magnetic monopoles, and much theory and experiment have focussed on the extent to which this description is appropriate to real pyrochlore magnets. As I'll discuss, this spin ice description is entirely classical, and we and others have been interested in identifying a quantum variant of this problem. I'll describe our progress in understanding a particular pyrochlore magnet, Yb2Ti2O7, in the context of quantum spin ice, mostly using time-of-flight neutron scattering. Along the way, I'll briefly discuss recent theory that suggests an emergent quantum electrodynamics emerges within quantum spin ice, with elementary excitations that include both electric and magnetic monopoles, as well as gauge photons.

_______________________________________________

Yeukuang Hwu

Monday, November 17, 2014, 11:00 am

Yeukuang Hwu
Institute of Physics, Academia Sinica
Taipei, Taiwan

 

"At the frontiers of high-resolution hard x-ray microscopy"

Abstract: Over the last decade, there has been explosive development in 3D hard x-ray microscopy using a transmission x-ray microscope (TXM). The presentation will provide a review on the recent scientific progress achieved by our international collaboration on high resolution 3D x-ray imaging. The presentation will provide several scientific applications, which will include life science and in-situ metal electrodeposition.

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Ricardo Lebensohn

Friday, November 14, 2014, 1:00 pm

Dr. Ricardo Lebensohn
Los Alamos National Laboratory

"Fast Fourier Transform-based micromechanical modeling with direct input from 3-D images of polycrystalline microstructures"

Abstract: Emerging 3-D characterization methods pose a challenge to modelers to devise efficient formulations for interpretation and exploitation of the massive amount of data generated by these novel methods. On the other hand, a synergistic combination of experiments and modeling is critical to advance the new 3-D characterization techniques beyond their initial proof-of-principle phase. In this talk we report recent advances in Fast Fourier Transform-based models, which can efficiently use the voxelized microstructural images of heterogeneous materials as input to predict their micromechanical and effective response. The focus of this presentation will be on plastically deforming polycrystalline materials. New formulations and applications for different deformation regimes (visco-plasticity, elasto-plasticity, dilatational plasticity, non-local plasticity, transformation-induced plasticity), some of them with input and validation from 3-D characterization methods, will be discussed.

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Thursday, November 6, 2014, 1:00 pm

Joseph L. Lenhart, PhD
US Army Research Laboratory

"Rate dependent mechanics in polymer networks"

Abstract: A brief overview of polymers research at the Army will be discussed, including key drivers for new materials and unique military related challenges. In addition, the presentation will highlight recent work on epoxy blends composed of rigid and flexible monomers that provide enhanced impact resistance and performance over broad operational temperature ranges. Epoxy resins are utilized extensively in coatings, paints, adhesives, electronics, composites, and various protection systems due to a combination of processability, stability, and property tunability. Over the past several decades, substantial research has focused on manipulating the mechanical properties of epoxy resins via control of the polymer structure, chemistry, and the incorporation of various additives. While the quasi-static behavior of these systems has been thoroughly investigated, minimal research has investigated high rate mechanical response, which is critical for protection applications. This presentation will highlight the rate dependent behavior of model epoxy resins as a function of the monomer chemistry and flexibility, network structure, and resin morphology. The mechanisms for improving high rate energy dissipation in bulk epoxy resins are being translated to surface modification approaches that can be exploited to tune the mechanical behavior of epoxy-substrate interfacial regions. The interfacial chemistry and structure is being characterized utilizing the combination of synchrotron based X-ray Photoelectron Spectroscopy and Near Edge X-ray Absorption Fine Structure, and correlated with characterization of rate dependent adhesive performance.

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John Galayda

Friday, October 17, 2014, 1:00 pm

John Galayda
SLAC

"The LCLS-II X-ray laser project at SLAC"

 

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Stuart Henderson

Monday, September 15, 2014, 1:00 pm

Stephen Streifer, Dir. of APS and
Stuart Henderson, Dir. of APS Upgrade

"Advanced Photon Source Upgrade Status and Plans"

Abstract: There is world-wide interest in diffraction-limited storage rings, with projects under development in Europe, Asia, South America and the United States to deploy this fourth-generation storage ring technology.   Plans are underway at Argonne National Laboratory to upgrade the Advanced Photon Source storage ring with a multi-bend achromat lattice to reduce the beam emittance by more than a factor of 50 relative to that achieved in present operation.  Coupled with superconducting insertion devices, an upgraded APS will deliver hard x-ray brightness and coherent flux levels that are two to three orders of magnitude greater than that which can be achieved today.  The APS Upgrade Project (APS-U) includes a new storage ring, optimized insertion devices, and a suite of best-in-class beamlines.  The conceptual design for APS-U will be described as will the present status of the Project.

_______________________________________________

Tuesday, September 9, 2014, 10:00 am

Elvis Janežič and Peter Leban

"Latest developments of Libera BPMs and low-jitter clock distribution system"

Abstract: An overview of latest upgrades to storage ring and single-pass BPM instrumentation that was adopted by new machines such as Taiwan Photon Source and MAX-IV. Built-in FOFB application calculates the fresh magnets' values in less than 2 µs. The talk will discuss a solution for real-time two beam flavor measurement.

Xilinx Zynq SoC and Power-over-Ethernet are two highlights of the new instrument platform that can accommodate the booster & storage ring as well as other LINAC and beamline applications. First representative is Libera Spark that will populate a big booster ring at ESRF. Instruments built on this platform have greatly balanced performance/price ratio and are affordable also to facilities with less stringent performance requirements.

Libera Sync 3 is the clock distribution system designed to meet the most strict requirements of 4th generation light sources. It has been co-developed with PSI and tested at Swiss-FEL facility. The system fulfills the requirements of less than 10 fs of jitter and less that 40 fs for phase stability per day.

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SuperKEKB Project

Wednesday, August 6, 2014, 1:00 pm

Demin Zhou
KEK

"Collective effects in SuperKEKB"

Abstract: Construction of the SuperKEKB B-factory is drawing to an end. The beam dynamics issues related to collective effects in SuperKEKB have been investigated via various simulations codes. This work is ongoing. This talk gives an overview of the main results on issues such as beam-beam interaction, electron cloud, space charge, microwave instability, intra-beam scattering, etc. Challenges, future plans and possible collaborations on studies of collective effects in SuperKEKB will also be addressed.

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Dejan Trbojevic

Tuesday, July 29, 2014, 10:30 am

Dejan Trbojevic
 

"Non-Scaling Fixed Field Alternating Gradient [NS-FFAG] concept in ERL’s: eRHIC and LHeC (With initial thoughts on ERL eRHIC prototype)"

Abstract: An explanation of the NS-FFAG concept, latest achievements of the present Relativistic Heavy Ion Collider (RHIC) and requirements for future Electron-Ion-Colliders based on the ERL: eRHIC and Large Hadron electron Collider (LHeC), are described during the INTRODUCTION. The basic characteristics of the NS-FFAG lattice for eRHIC and LHeC follow.
Initial ideas on the eRHIC ERL prototype are shown at the last part of the presentation.

_______________________________________________

Emily Liu

Friday, July 18, 2014, 11:00 am

Emily Liu
Department of Mechanical, Aerospace and Nuclear Engineering
Rensselaer Polytechnic Institute

 

 

"The Integration of Scattering Experiments and Simulations in Energy and Medical Applications"

Abstract: The purpose of this research is to develop the bridges among neutron & X-ray scattering experiments, their associated data analysis through liquid theory, and molecular dynamics (MD) simulation. In the past, the group utilized small-angle neutron scattering, quasi-elastic neutron scattering, inelastic neutron scattering, as well as MD simulations to probe the structural and dynamical response of materials at nano-scale and the intra-molecular water. These results shed light on the integration of scattering experiments, liquid theories, and MD simulations to characterize complex materials. And their potential use in exploring energy and medical materials is highly promising. Recently, the group is looking into similar and better integration methodology to be developed for X-ray scattering (e.g., small angle, wide angle, quasi-elastic and inelastic if possible).

_______________________________________________

Monday, June 16, 2014, 1:00 pm

Hengzi Wang and John Trunk
NSLS-II

"Engineering aspects of high-energy X-ray Powder Diffraction (XPD) beamline at NSNL-II"


Abstract: On Monday, June 16, Hengzi Wang and John Trunk, mechanical engineers from NSLS-II will be at CHESS. They interested in speaking with those who were involved with the F2 upgrade project. Any others are welcome to meet with them also. They will give a discussion-type seminar on their progress and challenges with building XPD beamline (time: 1:00), and meet individually with those who are interested. There will be a sign-up sheet at the reception for those who would like to speak with them.

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Gung-Chian Yin

Tuesday, June 3, 2014, 1:00 pm

Gung-Chian Yin
National Synchrotron Radiation Research Center, Taiwan

"Novel X-ray Microscopy Beamlines at Taiwan Photon Source"


Abstract: I will first present the construction status and the beamline plan, especially for those beamlines in the imaging valley, at the newly constructing Taiwan Photon Source (TPS) to be commissioned by the end of 2014. Among them, two novel x-ray microscopy beamlines, namely the soft x-ray tomography beamline for bio-medical applications and the x-ray Nanoprobe beamline for advanced materials research will be presented in detail.

The soft x-ray tomography beamline is designed to tomographically image bio-medical specimens in the energy range 200 eV ~ 1200eV with spatial resolution close to 20 nm, and energy resolving power better than 2000. The sheet type of samples will be stationed under cryogenic environment and can be freely rotated ± 70° or higher. The microscope is designed to accommodate a visible fluorescence microscope (~100nm) with a 3D structure illumination microscope (SIM) that a correlative image adapting soft x-ray, fluorescence and visible wide field images are simultaneously presented. The beamline optics as well as the end station design will be discussed in the talk.

The x-ray Nanoprobe beamline will adapt a set of Montel Kirkpatrick-Baez mirrors as the nano-focusing optics. Resulting from the large numerical aperture obtained the beamline can be built with a moderate length but similar performance with those beamlines longer than 100 meters. The associated endstation equipped with laser interferometer and scanning electron microscope to precisely locate the sample position. The beamline will provide nano x-ray probes, such like XAF, XEOL, projection microscope, CDI, etc. The whole beamline will be operated under vacuum environment to preserve the photon coherence as well as isolate the whole system from unnecessary environmental interference. The design concept of the beamline and the endstation will be presented in this talk.

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Carlos Cabrera

Thursday, May 15, 2014, 1:00 pm

Carlos Cabrera
Department of Chemistry
University of Puerto Rico at Río Piedras

"Catalysts/Carbon Support Materials Synthesis for (Bio)Fuel Cell Applications"


Abstract: Nanostructured catalyst/support materials are important for the development of the next generation of energy sources such as (Bio)Fuel Cells. Electrochemical techniques and catalyst/support synthetic methods have been developed in our laboratory. Recently, our group has been involved on an electrochemical synthesis based on a rotating disk slurry electrodeposition (RoDSE) technique for bulk preparation of catalysts/support materials. Our interest has been placed on carbon catalysts supports such as Vulcan XC-72, carbon nano-onions, and graphene oxide. In addition, ceria based catalysts, for methanol and butanol oxidation, have been studied as nanorods and nanoparticle structures.

Urine purification is another area of recent interest. Our group has developed a bioreactor-electrochemical system for the conversion of urea to ammonia to nitrogen in collaboration with NASA Ames Research Center. This has led to a possible bioelectrochemical reactor system to be adapted in NASA’s Life Support Systems.


References:
[1]  Zhou, Y.; Menéndez; C.L.; Cabrera, C.R.; Ph.D.; Cheung, C.L., et al. “Influence of nanostructured ceria support on platinum nanoparticles for alkaline methanol Electrooxidation”, RCS Advances 4(3), 1270-1275 (2014).

[2]  Cunci, Lisandro; Vélez, Carlos A.; et al., “Platinum Electrodeposition at Unsupported Electrochemically Reduced Nanographene Oxide for Ammonia Oxidation”, ACS Materials and Interfaces 6(3), 2137–2145 (2014).

[3]  Martínez-Rodríguez, R.; Vidal-Iglesias, F.; Solla-Gullon, J.; Cabrera, C.; Feliu, J., “Synthesis of Pt nanoparticles in water-in-oil microemulsion: on the effect of HCl on their surface structure”, J. Am. Chem. Soc. 136(4), 1280–1283 (2014).

[4]  E. Nicolau, et al., “Evaluation of a Urea Bioelectrochemical System for Wastewater Treatment Processes”, ACS Sustainable Chem. Eng. in press, DOI: 10.1021/sc400342x, (2014).

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Karen Conrad

Friday, May 9, 2014, 1:00 pm

Karen Conrad
Cornell University


"Light-Induced Subunit Dissociation by a Light-Oxygen-Voltage Domain Photoreceptor from Rhodobacter sphaeroides"


Abstract: Light-oxygen-voltage (LOV) domains bind a flavin chromophore to serve as blue light sensors in a wide range of eukaryotic and prokaryotic proteins. LOV domains are associated with a variable effector domain or a separate protein signaling partner to execute a wide variety of functions that include regulation of kinases and the circadian clock. The crystal structure, photocycle kinetics, association properties, and spectroscopic features of a full-length LOV domain protein from Rhodobacter sphaeroides will be presented.

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Richard G. Milner

Friday, April 25, 2014, 2:00 pm in 401 PSB

Richard G. Milner
Professor of Physics, MIT
Director, MIT Laboratory for Nuclear Science


"Searching for New Physics at Low Energies"


Abstract: The Standard Model has been a great success, Thus far, it has passed all tests at the high energy frontier. In my talk, I motivate and discuss a search for new physics at low energies. In particular, I describe an experiment to carry out a precision measurement of elastic electron proton scattering at 100 MeV motivated by the possibility of a dark photon.

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Richard G. Milner

Thursday, April 24, 2014, 1:00 pm

Shya Biswas
University of Florida


"Structure Based Inhibitor Design Of Different Isoforms Of Human Carbonic Anhydrase"


Abstract: Carbonic anhydrase (EC 4.2.1.1) family of enzymes catalyzes the interconversion of carbon dioxide and water to bicarbonate and a proton. In humans, 15 different isozymes are present, all of which belong to alpha class of carbonic anhydrase. Each carbonic anhydrase isoform has been linked to various diseases like glaucoma (hCAII), cancer (hCAIX, hCAXII) and nervous system disorder (hCAVII, hCAIV, hCAII) just to name a few. Sulfonamides are commonly used inhibitors or drugs for carbonic anhydrases. However, commonly used sulfonamides like acetazolamide, methazolamide, clorozolamide etc. inhibit all carbonic anhydrase isoforms with nanomolar affinity. Hence, designing specific drugs to target a particular isoform of carbonic anhydrase has been of great interest to researchers over a decade. In this presentation, I will describe the structure of hCAII in complex with a few new sulfonamide drugs and how we can design isoform specific drugs from this enzyme drug complex structure. This work began with the aim to design inhibitors specific to hCAIX. Out of all isoforms of carbonic anhydrases, hCAIX is overexpressed in all kinds of cancer hence designing inhibitors specific to this isoform is of immense importance in cancer detection and treatment. hCAIX is also different from other carbonic anhydrase isoforms as it is a transmembrane protein with an extracellular domain. The structure of full length hCAIX is still unknown as this enzyme is difficult to express and purify. In this presentation, I will describe the expression of hCAIX in baculovirus expression system and then purification and crystallization of this enzyme. Presently structure of hCAIX in complex with specific sulfonamide drugs is ongoing. In the last part of my presentation, I will also describe the structure of two outer membrane proteins from Pseudomonas aeruginosa and how this will provide new insights into outer membrane transport and drug design against this pathogen.

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John B. Parise

Monday, April 14, 2014, 10:00 am

John B. Parise
Department of Geosciences
Joint Photon Sciences Institute
Stony Brook University/Brookhaven National Laboratory


"Real-time/operando high-energy x-ray scattering"


Abstract: Scattering is the primary tool for determining structure property relationships in condensed matter. Increasingly, we are capable of studying materials under their "operating conditions", thanks largely to the availability of high-energy x-ray beams (somewhat arbitrarily set at E > 60 keV). Some experiments can be carried out at the home laboratory. The brightness available at synchrotron storage rings however, allows experiments that are prohibitively wasteful of resources at home base. An exposure, with equivalent statistics to a one second exposure at the brightest synchrotron x-ray sources, would require 300 years on a typical lab source. This vast difference allows us to address new questions: what is the liquid scattering function of molten UO2, and which pair potential allows us to best fit that function, and therefore predict the properties of the molten state? A recent 4-second exposure of levitated UO2 held at 3000+ K allowed us to address this question directly. This is but one example of the real issues that might be addressed with synergistic developments in x-ray optics, detectors and analysis software. It is the lack of methodologies, and the wherewithal to develop them that limit our ability to follow through from "what if" to "what now".

The joint Photon Sciences Institute is conceived as a resource for academic, government and industry researchers seeking to solve challenges through synchrotron science. JPSI will facilitate those aspects of methodology, education and workforce development that will allow the highest possible participation rate. I hope to discuss some aspects of the possibilities afforded by a NYS-wide initiative in synchrotron science.

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*** NOTE: This seminar will be on Thursday, April 3 at 1:00pm ***

Pupa Gilbert

Thursday, April 3, 2014

Pupa Gilbert
Professor of Physics
University of Wisconsin - Madison


"Nanocrystalline orientation patterns in biominerals"


Abstract: Biominerals include mollusk shells and the skeletons of algae, sponges, corals, sea urchins and most other animals. The functions of biominerals are diverse: mechanical support, attack, defense, grinding, biting, and chewing, gravitational and magnetic field sensing, light focusing, and many others. The exquisite nanostructure of biominerals is directly controlled by the organisms, which have evolved to master the chemico-physical aspects of mineralization. In this talk I will show how our imaging method termed PIC-mapping reveals the nanocrystalline orientation patterns in mollusk shell nacre, and their formation mechanism by biologically-controlled crystal growth.

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*** NOTE: This seminar will be on Wednesday, March 26 at 11:00am ***

Armand Beaudoin

Wednesday, March 26, 2014

Armand Beaudoin
Willett Faculty Scholar Professor
College of Engineering
University of Illinois at Urbana-Champaign

 

"Driving Forces for Fracture in Aluminum Alloys for Aerospace Application: the Utility of in situ Lattice Strain Measurement for Advancing Engineering Analysis"


Abstract: Aluminum-Lithium (Al-Li) alloys are under continuing development, with increasing use in aerospace structures. The practice of design – with consideration given to fault-tolerance – is complicated by interplay of kinetics and deformation incompatibility at the mesoscale. The presentation will begin by surveying an experimental program for Al-Li plate products. Topics to be detailed include

  • fracture and fatigue response, studied at both the macroscale (Digital Image Correlation) and mesoscale (Electron Back-Scatter Diffraction),
  • in situ study of lattice strain on a grain-by-grain basis, using high energy x-ray diffraction at a synchrotron source.

The application of modeling techniques to interpretation of data will also be given. In particular, the stress state at the mesoscale will be related to crack turning behavior. The combined experimental & modeling program provides guidance in fault-tolerant design.

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*** NOTE: This seminar will be on Tuesday, March 25 at 10:00am ***

Wah-Keat Lee Yong Chu

 

Left: Wah-Keat Lee, Group Leader, Brookhaven National Lab, Full-Field X-ray Imaging Beamline, NEXT Project
Right: Yong Chu, NSLS-II HXN Beamline Group Leader, Brookhaven National Lab
(not pictured): Francesco De Carlo, Group Leader, Imaging Group, Argonne National Lab

Tuesday, March 25, 2014

Wah-Keat Lee and Yong Chu will be discussing Projects, beamlines and interests of NSLS-II HXN Beamline and Full-Field X-ray Imaging Beamline. Francesco De Carlo will be discussing Capillary use on the TXM at 32-ID, Argonne National Lab. Talks start at 10:00 a.m. on Tuesday, March 25, 2014 in the 3rd Floor Wilson Commons. Refreshments will be available.

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Friday, March 7, 2014

Kartik Ayyer
Graduate Student/Physics Dept.
Cornell University


"Macromolecular imaging without large crystals"


Abstract: Protein crystallography has proved to be a powerful and very successful method to determine the structure of large biomolecules over the years. However, to be effective, it has required relatively large, high quality crystals. Now as we turn our attention to proteins which are not that well-behaved, we ask what can be done with microcrystals, and even with single molecules. Due to the small size of these objects, we get very few scattered photons per image and so we have to collect thousands of images to get enough signal. However, due to the small size, the orientation of the object is unknown when we capture each image. This makes it difficult to reconstruct the 3D structure of the molecule. I will talk about the Bayesian reconstruction algorithm we use to assign orientations and discuss three proof-of-principle experiments that have been performed which capture the salient features.

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*** NOTE: This seminar will be on Monday, February 10 at 1:00pm ***

Emre Brookes

Monday, February 10, 2014

Emre Brookes, PhD
Assistant Professor/Research
University of Texas Health Science Center at San Antonio


"New methods for the analysis of HPLC-SAXS experimental data and creation of parsimonious ab-initio models from SAS experiments"


See: open access paper

Abstract: In order to obtain reliable structural information from SAXS data, it is crucial to ensure monodispersity of the sample. However, with the increasing complexity of samples being studied, it is often challenging to ensure this with generic biochemical techniques. To address this issue, multiple beam-lines have introduced on line HPLC- and FPLC- SAXS setups. Even with these setups and an optimal column design, some samples can be difficult to baseline separate. Motivated by such a troublesome protein, we have designed and implemented new tools for the visualization and analysis of these data with the capability to extract individual monodisperse SAXS curves from polydisperse frames, which will be described in the first part of the talk.

Stochastic methods (e.g. DAMMIN/F) have been popularly used to produce ab-initio spatial models from SAXS experimental data, yet the information content of one dimensional SAXS curves is low. These methods produce multiple models for this overdetermined fitting problem, which are typically averaged and filtered, producing a model that is no longer a best fit to the data. Adding the Occam's razor condition of parsimony should provide a unique model (up to handedness) whose defining parameters approximate the information content. This work-in-progress will be described in the second part of the talk.

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Steve Wang

Friday, February 7, 2014

Dr. Steve Wang
Senior Scientist at Institute for Shock Physics
Washington State University


"Development of APS nano-CT System for Imaging 3D Nano-scale Structure and in situ Electrochemical Reactions"


Abstract: The transmission x-ray microscope at the Advanced Photon Source is a public research facility that provides routine hard x-ray 2D imaging at sub-20 nm resolution and 3D nano-CT imaging at slightly reduced resolution. Recent instrument development efforts have added a wide range of in situ sample environments including a high-temperature furnace, high-pressure diamond anvil, and electro-chemical reaction cell, etc. The high-energy resolution of TXM system also allows CT images to be acquired at 0.5 eV steps across elemental absorption edges to form XANES spectra at each voxel. The combination of these techniques leads to a unique ability tracking chemical and electro-chemical reactions in situ within 10 nm voxels. This capability provides both structural and functional information on dynamic evolutions of processes such as material synthesis, energy device operation, and geological process, etc. Key instrumentation and applications developments will be discussed.

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Steve Wang

Friday, January 31, 2014

Laura Boon
Graduate Research Assistant
Purdue University


"Radiation Heating Analysis for the Advanced Photon Source Superconducting Undulator"


Presentation: (PDF)

Abstract: In January 2013 the Advanced Photon Source commissioned a Superconducting Undulator (SCU). The superconducting magnet is thermally isolated from the beam vacuum chamber, which absorbs the beam-induced heating [Y. Ivanyushenkov et al, IEEE T. Appl. Supercon. 22 (3) (2012)]. The cryo coolers cooling the vacuum chamber can handle 40 W of heating. Throughout the SCU design process calculations were made to determine the radiation heating from an on-axis and off-axis electron beam. Simulation results show that when the electron beam is vertically off-axis radiation heating increases from the on-axis heating of less than 1 W. During user operation beam-position-limiting detectors (BPLD) are used to limit beam motion and keep the radiation heating below 25 W. During machine studies when the BPLD is not armed other measures must be taken to protect the SCU. Presented in this talk will be the comparison between analytical calculations and measured temperature rise on the installed SCU. The measured temperatures have been converted to a power using a calibrated heater placed on the SCU0 vacuum chamber.

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Robert Thorne

Friday, January 10, 2014

Robert Thorne
Professor/Research
Cornell University


"Can Radiation Damage to Protein Crystals Be Outrun using Synchrotron Source Intensities?"


Abstract: The widespread adoption of cryocrystallographic methods in the 1990s revolutionized protein crystallography and structural biology. Cooling protein crystals to T=100 K dramatically reduces radiation damage, allowing complete data sets to be obtained from a single crystal. “Looping” and cooling crystals is vastly easier than mounting them in X-ray capillaries, and cold crystals can be stored for weeks or months and then shipped to a synchrotron for measurement. Not surprisingly, more than 98% of all protein crystal structures are now determined at T=100 K. But as the focus of structural science continues its shift from determining first structures and toward more detailed understanding of mechanism, and from compact, well-behaved globular proteins to large, dynamic assemblies that will remain far beyond the reach of NMR, X-ray data collection and structure determination at only T=100 K is likely to become increasingly inadequate. What can we do now to prepare for a warmer future?

The most serious obstacle to near-room-temperature structure determination is damage by the illuminating X-rays. Experiments at XFEL sources have demonstrated the feasibility of collecting diffraction data in femtoseconds, before radiation damage manifests. Can damage also be outrun at synchrotron source intensities? The answer is yes.

The radiation sensitivity of protein crystals shows a transition near 200 K, above which it appears to be limited by solvent-coupled diffusive processes.[1] Consistent with this interpretation, a component of global damage proceeds on timescales of several minutes at 180 K, decreasing to ~1 second near room temperature.[2] These timescales are orders of magnitude larger than those for free-radical diffusion and reaction, indicating that downstream structural rather than chemical relaxation processes involving side chains, protein and the lattice predominate in determining overall diffraction spot fading. This in turn suggests the feasibility of outrunning radiation damage not just in femtoseconds but in seconds. Initial experiments at dose rates up to 680 kGy/s showed that crystal half doses at 260 K were increased by a factor of ~1.5-2 by collecting data in ~1 s.[3,4] More recent experiments on small, relatively radiation-hard model proteins at dose rates up to 40 MGy/s show that room-temperature half-doses are increaed by a factor of 2-3 by collecting data in ~50 ms. Much larger reductions in damage are expected for more radiation sensitive proteins. Large increases in data collected per crystal and decreases in crystals per structure should enable an expansion of structural studies at and near room temperature. Additional developments required to achieve this goal will be discussed.


References:
[1]  M. Warkentin, J. B. Hopkins, R. Badeau, A. M. Mulichak, L. J. Keefe & R. E. Thorne. J. Synch. Rad. 20, 7-13 (2013).

[2]  M. Warkentin, R. Badeau, J. B. Hopkins, A. M. Mulichak, L. J. Keefe & R. E. Thorne, Acta Cryst. D 68, 124-133 (2012).

[3]  M. Warkentin, R. Badeau, J. Hopkins & R. E. Thorne, Acta Cryst. D 67, 792-803 (2011).

[4]  M. Warkentin & R. E. Thorne, Acta Cryst. D 66, 1092-1100 (2010).

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