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Sample records for accelerating structure assemblies

  1. Assembly Test of Elastic Averaging Technique to Improve Mechanical Alignment for Accelerating Structure Assemblies in CLIC

    Huopana, J

    2010-01-01

    The CLIC (Compact LInear Collider) is being studied at CERN as a potential multi-TeV e+e- collider [1]. The manufacturing and assembly tolerances for the required RF-components are important for the final efficiency and for the operation of CLIC. The proper function of an accelerating structure is very sensitive to errors in shape and location of the accelerating cavity. This causes considerable issues in the field of mechanical design and manufacturing. Currently the design of the accelerating structures is a disk design. Alternatively it is possible to create the accelerating assembly from quadrants, which favour the mass manufacturing. The functional shape inside of the accelerating structure remains the same and a single assembly uses less parts. The alignment of these quadrants has been previously made kinematic by using steel pins or spheres to align the pieces together. This method proved to be a quite tedious and time consuming method of assembly. To limit the number of different error sources, a meth...

  2. Development of ultra-precision machining, assembling and measurement for accelerating structure

    Ultra-precision fabrication is required for making the accelerating structure for the next generation of the linear collider. Main components of the accelerating structure consists of approximately two hundred cells, each made of oxygen-free copper with an outer diameter and thickness of 80 mm and 9 mm, respectively. Firstly these cells are machined with sub-micron precision. Following steps to make a complete unit are firstly rinsing the cells, then assembling them precisely, and finally to bond them with keeping the initial precision. Here are described newly-developed effective techniques for machining, measurement, and assembly, which satisfy strict requirements for precision in the construction of the accelerating structure for the Japan Linear Collider (JLC) project. (author)

  3. Digital design for structure of cathode/grid assemblies in electron curtain accelerator

    The finite element method (FEM) is introduced to design a structure of cathode groupware for an electron curtain accelerator. An optimum structure of groupware and parameters of its heat source W wire have been designed. A uniform temperature distribution of 1400-1430 degree C on the narrow planar LaB6 cathode has been predicted, which is enough to emit sufficient electron beam. In order to insure exact thermal physical parameters (such as heat emissivity and heat conductivity) of all the materials, an additional iterative algorithm is adopted. It takes only four iterations to get the convergent result. The method makes analysis process more efficient and compact. Experiment has proved the validity. (authors)

  4. Structural assembly demonstration experiment

    Stokes, J. W.

    1982-01-01

    The experiment is of an operational variety, designed to assess crew capability in Large Space System (LSS) assembly. The six Structural Assembly Demonstration Experiment objectives include: (1) the establishment of a quantitative correlation between LSS neutral buoyancy simulation and on-orbit assembly operations in order to enhance the validity of those assembly simulations; (2) the quantitative study of the capabilities and mechanics of human assembly in an Extravehicular Activity environment; (3) the further corroboration of the LSS Assembly Analysis cost algorithm through the obtainment of hard data base information; (4) the verification of LSS assembly techniques and timeless, as well as the identification of crew imposed loads and assembly aid requirements and concepts; (5) verification of a Launch/Assembly Platform structure concept for other LSS missions; and (6) lastly, to advance thermal control concepts through a flexible heat pipe.

  5. The foxhole accelerating structure

    This report examines some properties of a new type of open accelerating structure. It consists of a series of rectangular cavities, which we call foxholes, joined by a beam channel. The power for accelerating the particles comes from an external radiation source and enters the cavities through their open upper surfaces. Analytic and computer calculations are presented showing that the foxhole is a suitable structure for accelerating relativistic electrons

  6. Pulsed neutron source based on accelerator-subcritical-assembly

    Inoue, Makoto; Noda, Akira; Iwashita, Yoshihisa; Okamoto, Hiromi; Shirai, Toshiyuki [Kyoto Univ., Uji (Japan). Inst. for Chemical Research

    1997-03-01

    A new pulsed neutron source which consists of a 300MeV proton linac and a nuclear fuel subcritical assembly is proposed. The proton linac produces pulsed spallation neutrons, which are multipied by the subcritical assembly. A prototype proton linac that accelerates protons up to 7MeV has been developed and a high energy section of a DAW structure is studied with a power model. Halo formations in high intensity beam are also being studied. (author)

  7. Accelerator structure development for NLC

    Hoag, H.A.; Deruyter, H.; Pearson, C.; Ruth, R.D.; Wang, J.W. [Stanford Linear Accelerator Center, Menlo Park, CA (United States); Schaefer, J. [Texas Instruments, Inc., Dallas, TX (United States)

    1993-04-01

    In the program of work directed towards the development of an X-Band Next Linear Collider accelerator structure, two different test accelerator sections have been completed, and a third is being fabricated. The first is a simple 30-cell constant-impedance section in which no special attention was given to surface finish, pumping, and alignment. The second is an 86-cell section in which the cells were precision diamond-turned by Texas Instruments Inc. The structure has internal water-cooling and vacuum pumping manifolds. Some design details are given for the third section, which is a 206-cell structure with cavities dimensioned to give a Gaussian distribution of dipole mode frequencies. It has conventional-machining surface finishes and external water and pumping manifolds. Component design, fabrication, and assembly brazing are described for the first two experimental sections.

  8. Accelerator structure development for NLC

    In the program of work directed towards the development of an X-Band Next Linear Collider accelerator structure, two different test accelerator sections have been completed, and a third is being fabricated. The first is a simple 30-cell constant-impedance section in which no special attention was given to surface finish, pumping, and alignment. The second is an 86-cell section in which the cells were precision diamond-turned by Texas Instruments Inc. The structure has internal water-cooling and vacuum pumping manifolds. Some design details are given for the third section, which is a 206-cell structure with cavities dimensioned to give a Gaussian distribution of dipole mode frequencies. It has conventional-machining surface finishes and external water and pumping manifolds. Component design, fabrication, and assembly brazing are described for the first two experimental sections

  9. Calculation of tolerances in accelerating structures

    A method is suggested for calculating tolerances for similar elements of an accelerating-focusing channel of a charged particle linac the particle dynamics in which is described by linear or non-linear equations. Tolerances for each drift tube of the accelerating structure with modified variable-phase focusing are determined with respect to tolerances for the output parameters of an accelerated beam at preset lengths of drift tubes. The tolerances obtained in supposition of equal effects, equal tolerances and those accounting for the cost of fabrication and assembling of the elements of the structure are compared. The algorithm suggested can also be used for calculating tolerances in structures with hard focusing

  10. Plasma-based accelerator structures

    Plasma-based accelerators have the ability to sustain extremely large accelerating gradients, with possible high-energy physics applications. This dissertation further develops the theory of plasma-based accelerators by addressing three topics: the performance of a hollow plasma channel as an accelerating structure, the generation of ultrashort electron bunches, and the propagation of laser pulses is underdense plasmas

  11. Important concepts in the assembly and early characterization of the PBFA II accelerator

    Some of the concepts for orchestrating large numbers of events associated with accelerator assembly and characterization include: (1) structuring of activity into smaller workable and trackable packages, with associated subelements assigned to each section of the accelerator. (2) establishing detailed assembly and characterization documentation to assist in component testing and subsystem integration. (3) structuring the project team for efficient communication, identification of responsibility, and capability for problem and conflict resolution. (4) developing technologies for receival, inventory, controlled storage, staging, and phased installation and testing of components and pieceparts. The application of these and other concepts to PBFA II, and the progress of accelerator assembly is discussed

  12. Important concepts in the assembly and early characterization of the PBFA 2 accelerator

    Goldstein, S. A.; Clevenger, R. J.; Donovan, G. L.; Holman, G. T.; Johnston, R. R.; Nations, D. R.

    Some of the concepts for orchestrating large numbers of events associated with accelerator assembly and characterization include: (1) structuring of activity into smaller workable and trackable packages, with associated subelements assigned to each section of the accelerator, (2) establishing detailed assembly and characterization documentation to assist in component testing and subsystem integration, (3) structuring the project team for efficient communication, identification of responsibility, and capability for problem and conflict resolution, and (4) developing technologies for receival, inventory, controlled storage, staging, and phased installation and testing of components and pieceparts. The application of these and other concepts to PBFA II, and the progress of accelerator assembly is discussed.

  13. Fuel assembly supporting structure

    For use in forming the core of a pressurized-water reactor, a fuel assembly supporting structure for holding a bundle of interspaced fuel rods, is formed by interspaced end pieces having holes in which the end portions of control rod guide tubes are inserted, fuel rod spacer grids being positioned by these guide tubes between the end pieces. The end pieces are fastened to the end portions of the guide tubes, to integrate the supporting structure, and in the case of at least one of the end pieces, this is done by means which releases that end piece from the guide tubes when the end pieces receive an abnormal thrust force directed towards each other and which would otherwise place the guide tubes under a compressive stress that would cause them to buckle. The spacer grids normally hold the fuel rods interspaced by distances determined by nuclear physics, and buckling of the control rod guide tubes can distort the fuel rod spacer grids with consequent dearrangement of the fuel rod interspacing. A sudden loss of pressure in a pressurized-water reactor pressure vessel can result in the pressurized coolant in the vessel discharging from the vessel at such high velocity as to result in the abnormal thrust force on the end pieces of each fuel assembly, which could cause buckling of the control rod guide tubes when the end pieces are fixed to them in the normal rigid and unyielding manner

  14. Important concepts in the assembly and early characterization of the PBFA II accelerator

    Planning and efficient execution of the assembly and early characterization phases of a large, multi-module superpower generator like PBFA II require development of concepts frequently not found in either the pulsed power RandD community or in the pulsed power industry. To meet the constraints of performance, cost, and schedule of the PBFA II Project, special skills for assembly and characterization of large facilities are being established. These likely will become the technology for activating Sandia's future large accelerators. Some of the concepts for orchestrating large numbers of events associated with accelerator assembly and characterization include: structuring of activity into smaller workable and trackable packages, with associated subelements assigned to each section of the accelerator, and establishing detailed assembly and characterization documentation to assist in component testing and subsystem integration. The application of these and other concepts to FBFA II, and the progress of accelerator assembly are discussed

  15. Trapping of Hepatitis B Virus capsid assembly intermediates by phenylpropenamide assembly accelerators

    Katen, Sarah P.; Chirapu, Srinivas Reddy; Finn, M.G.; Zlotnick, Adam

    2010-01-01

    Understanding the biological self-assembly process of virus capsids is key to understanding the viral life cycle, as well as serving as a platform for the design of assembly-based antiviral drugs. Here we identify and characterize the phenylpropenamide family of small molecules, known to have antiviral activity in vivo, as assembly effectors of the Hepatitis B Virus (HBV) capsid. We have found two representative phenylpropenamides to be assembly accelerators, increasing the rate of assembly w...

  16. Collimator assembly for an electron accelerator

    According to this invention, the collimator assembly comprises a collimator shielding block for blocking undesired x-rays and a bushing inserted into the shielding block. The bushing has a conical passage opening for transmitting x-rays therethrough and for defining the x-ray cone. There are provided means for easily interchanging the bushing in the collimator shielding block. Therefore, bushings of different cone-defining passage can be inserted readily into the shielding block. If a larger area is to be irradiated, a bushing will be used which has a passageway of a larger cone angle

  17. Photonic Crystal Laser Accelerator Structures

    Cowan, Benjamin; Javanmard, Mehdi; Siemann, Robert H.

    2003-01-01

    Photonic crystals have great potential for use as laser-driven accelerator structures. A photonic crystal is a dielectric structure arranged in a periodic geometry. Like a crystalline solid with its electronic band structure, the modes of a photonic crystal lie in a set of allowed photonic bands. Similarly, it is possible for a photonic crystal to exhibit one or more photonic band gaps, with frequencies in the gap unable to propagate in the crystal. Thus photonic crystals can confine an optic...

  18. EM Structure Based and Vacuum Acceleration

    Colby, E.R.; /SLAC

    2005-09-27

    The importance of particle acceleration may be judged from the number of applications which require some sort of accelerated beam. In addition to accelerator-based high energy physics research, non-academic applications include medical imaging and treatment, structural biology by x-ray diffraction, pulse radiography, cargo inspection, material processing, food and medical instrument sterilization, and so on. Many of these applications are already well served by existing technologies and will profit only marginally from developments in accelerator technology. Other applications are poorly served, such as structural biology, which is conducted at synchrotron radiation facilities, and medical treatment using proton accelerators, the machines for which are rare because they are complex and costly. Developments in very compact, high brightness and high gradient accelerators will change how accelerators are used for such applications, and potentially enable new ones. Physical and technical issues governing structure-based and vacuum acceleration of charged particles are reviewed, with emphasis on practical aspects.

  19. High gradient experiments on NLCTA accelerator structures

    This paper presents new results of high-gradient studies performed on a 1.8 m traveling-wave accelerator section with detuned high-order deflecting modes. This structure was designed initially for studies of detuned structures and will be installed in the Next Linear Collider Test Accelerator (NLCTA). The paper describes the test set-up in the Accelerator Structure Test Area (ASTA) including electron gun, prebuncher, pre-accelerator, spectrometer, Faraday cups, 200 MW SLED-II power compression system, Magic-T type phase shifters and attenuators. Rf processing, detailed dark current analysis, radiation problems, and beam acceleration measurements are discussed

  20. RF kick in the ILC acceleration structure

    Solyak, N.; Gonin, I.; Latina, A.; Lunin, A.; Ranjan, K.; Yakovlev, V.; /Fermilab

    2008-06-01

    Detailed results of estimations and simulations for the RF kick caused by input and HOM couplers of the ILC acceleration structure are presented. Results of possible beam emittance dilution caused by RF kick are discussed for the main LINAC acceleration structure, and the RF structures of the ILC bunch compressors BC1 and BC2. Methods of the RF kick reduction are discussed.

  1. Traveling Wave Accelerating Structure for a Superconducting Accelerator

    Kanareykin, Alex; Solyak, Nikolay

    2005-01-01

    We are presenting a superconducting traveling wave accelerating structure (STWA) concept, which may prove to be of crucial importance to the International Linear Collider. Compared to the existing design of a TESLA cavity, the traveling wave structure can provide ~20-40% higher accelerating gradient for the same aperture and the same peak surface magnetic RF field. The recently achieved SC structure gradient of 35 MV/m can be increased up to ~50 MV/m with the new STWA structure design. The STWA structure is supposed to be installed into the superconducting resonance ring and is fed by the two couplers with appropriate phase advance to excite a traveling wave inside the structure. The system requires two independent tuners to be able to adjust the cavity and feedback waveguide frequencies and hence to reduce the unwanted backward wave. In this presentation we discuss the structure design, optimization of the parameters, tuning requirements and plans for further development.

  2. Phase gradients in acceleration structures

    Decker, F.J.; Jobe, R.K.

    1990-05-01

    In linear accelerators with two or more bunches the beam loading of one bunch will influence the energy and energy spread the following bunches. This can be corrected by quickly changing the phase of a travelling wave structure, so that each bunch recieves a slightly different net phase. At the SLAC Linear Collider (SLC) three bunches, two (e{sup +},e{sup {minus}}) for the high energy collisions and one (e{sup {minus}}-scavenger) for producing positrons should sit at different phases, due to their different tasks. The two e{sup {minus}}-bunches are extracted from the damping ring at the same cycle time about 60 ns apart. Fast phase switching of the RF to the bunch length compressor in the Ring-To-Linac (RTL) section can produce the necessary advance of the scavenger bunch (about 6{degree} in phase). This allows a low energy spread of this third bunch at the e{sup +}-production region at 2/3 of the linac length, while the other bunches are not influenced. The principles and possible other applications of this fast phase switching as using it for multi-bunches, as well as the experimental layout for the actual RTL compressor are presented.

  3. Phase gradients in acceleration structures

    In linear accelerators with two or more bunches the beam loading of one bunch will influence the energy and energy spread the following bunches. This can be corrected by quickly changing the phase of a travelling wave structure, so that each bunch recieves a slightly different net phase. At the SLAC Linear Collider (SLC) three bunches, two (e+,e-) for the high energy collisions and one (e--scavenger) for producing positrons should sit at different phases, due to their different tasks. The two e--bunches are extracted from the damping ring at the same cycle time about 60 ns apart. Fast phase switching of the RF to the bunch length compressor in the Ring-To-Linac (RTL) section can produce the necessary advance of the scavenger bunch (about 6 degree in phase). This allows a low energy spread of this third bunch at the e+-production region at 2/3 of the linac length, while the other bunches are not influenced. The principles and possible other applications of this fast phase switching as using it for multi-bunches, as well as the experimental layout for the actual RTL compressor are presented

  4. Development of S-band accelerating structure

    In Pohang Accelerator Laboratory (PAL) in Korea construction of XFEL (X-ray Free electron Lazar) institution is under construction aiming at the completion in 2014. Energy 10 GeV of the linac part of this institution and main frequency are planned in S-band (2856 MHz), and about 178 S-band 3m accelerating structures are due to be used for this linac. The oscillation of an X-ray laser requires very low emittance electron beam. On the other hand, since the accelerating structure which accelerates an electron beam has a feed port of microwave (iris), the electromagnetic field asymmetry of the microwave feeding device called coupler worsens the emittance of an electron beam. MHI manufactured two kinds of S-band accelerating structures with which the electromagnetic field asymmetry of coupler cavity was compensated for PALXFEL linac. We report these accelerating structures. (author)

  5. Photonic Crystal Laser-Driven Accelerator Structures

    Cowan, Benjamin M.

    2007-08-22

    Laser-driven acceleration holds great promise for significantly improving accelerating gradient. However, scaling the conventional process of structure-based acceleration in vacuum down to optical wavelengths requires a substantially different kind of structure. We require an optical waveguide that (1) is constructed out of dielectric materials, (2) has transverse size on the order of a wavelength, and (3) supports a mode with speed-of-light phase velocity in vacuum. Photonic crystals---structures whose electromagnetic properties are spatially periodic---can meet these requirements. We discuss simulated photonic crystal accelerator structures and describe their properties. We begin with a class of two-dimensional structures which serves to illustrate the design considerations and trade-offs involved. We then present a three-dimensional structure, and describe its performance in terms of accelerating gradient and efficiency. We discuss particle beam dynamics in this structure, demonstrating a method for keeping a beam confined to the waveguide. We also discuss material and fabrication considerations. Since accelerating gradient is limited by optical damage to the structure, the damage threshold of the dielectric is a critical parameter. We experimentally measure the damage threshold of silicon for picosecond pulses in the infrared, and determine that our structure is capable of sustaining an accelerating gradient of 300 MV/m at 1550 nm. Finally, we discuss possibilities for manufacturing these structures using common microfabrication techniques.

  6. Accelerating structure optimization and tolerance calculation

    The problem of optimizing the dynamics of a charged particle beam with high volumetric charge density in an accelerating structure with space-homogeneous quadrupole focusing (SHQF) is considered. The mathematical model of interacting particle dynamics is based on equations for beam envelopes. The optimization criterion (functional) is selected from the terms of obtaining a structure with an assigned length, beam energy at the accelerator outlet and the maximum particle capture for acceleration mode. A method for determining tolerance for the structure parameters based on optimization algorithm is proposed for the structure with SHQF. 4 refs.; 2 figs

  7. Nozzle and shroud assembly mounting structure

    Faulder, Leslie J.; Frey, deceased, Gary A.; Nielsen, Engward W.; Ridler, Kenneth J.

    1997-01-01

    The present nozzle and shroud assembly mounting structure configuration increases component life and reduces maintenance by reducing internal stress between the mounting structure having a preestablished rate of thermal expansion and the nozzle and shroud assembly having a preestablished rate of thermal expansion being less than that of the mounting structure. The mounting structure includes an outer sealing portion forming a cradling member in which an annular ring member is slidably positioned. The mounting structure further includes an inner mounting portion to which a hooked end of the nozzle and shroud assembly is attached. As the inner mounting portion expands and contracts, the nozzle and shroud assembly slidably moves within the outer sealing portion.

  8. Low-velocity superconducting accelerating structures

    The present paper reviews the status of RF superconductivity as applied to low-velocity accelerating properties. Heavy-ion accelerators must accelerate efficiently particles which travel at a velocity much smaller than that of light particles, whose velocity changes along accelerator, and also different particles which have different velocity profiles. Heavy-ion superconducting accelerators operate at frequencies which are lower than high-energy superconducting accelerators. The present paper first discusses the basic features of heavy-ion superconducting structures and linacs. Design choices are then addressed focusing on structure geometry, materials, frequency, phase control, and focusing. The report also gives an outline of the status of superconducting booster projects currently under way at the Argonne National Laboratory, SUNY Stony Brook, Weizmann Institute, University of Washington, Florida State, Saclay, Kansas State, Daresbury, Japanese Atomic Energy Research Institute, Legnaro, Bombay, Sao Paulo, ANU (Canberra), and Munich. Recent developments and future prospects are also described. (N.K.) 68 refs

  9. Laser Zone Annealing - Accelerated Route to Self-Assembled Nanostructures

    Majewski, Pawel; Yager, Kevin; Rahman, Atikur; Black, Charles

    We present Laser Zone Annealing - a novel technique of accelerated self-assembly of block copolymer thin films utilizing laser light. In our approach, the laser beam, focused to a narrow line, is rastered across the polymer film coated on the light-absorbing substrate, inducing rapid and highly localized temperature transients in the film. By coupling our method with soft-shear, we demonstrate monolithic alignment of various cylinder-forming block copolymers over extremely short timescales. We utilize the aligned block copolymer films as templates for inorganic nanomaterials pattering. After delivery of inorganic precursors via aqueous or gaseous route, the polymer matrix is ashed leading to extremely well-ordered arrays of inorganic, metallic or semiconducting nanowires. Subsequently, we demonstrate how more complex nanostructures can be created with LZA including multilayered nanomeshes with symmetries beyond the conventional motifs accessible by native block copolymers. We investigate a perspective use of the inorganic arrays as transparent conductors or chemical sensors and characterize their anisotropic electro-optical properties. Research carried out in part at the Center for Functional Nanomaterials, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886.

  10. ALECS: assembly language extensions and control structures

    ALECS is an assembly language preprocessor allowing the use of structured programming techniques in MACRO-11 code. Programs are written using standard control structures with normal MACRO-11 code embedded as needed. The ALECS task is used to translate the source to pure MACRO-11 source file which is then submitted to the assembler. ALECS also produces a structured source listing showing the true logical flow of code. ALECS has been used for short subroutines as well as RSX-11M I/0 drivers and an ACP

  11. Variable energy constant current accelerator structure

    Anderson, O.A.

    1988-07-13

    A variable energy, constant current ion beam accelerator structure is disclosed comprising an ion source capable of providing the desired ions, a pre-accelerator for establishing an initial energy level, a matching/pumping module having means for focusing means for maintaining the beam current, and at least one main accelerator module for continuing beam focus, with means capable of variably imparting acceleration to the beam so that a constant beam output current is maintained independent of the variable output energy. In a preferred embodiment, quadrupole electrodes are provided in both the matching/pumping module and the one or more accelerator modules, and are formed using four opposing cylinder electrodes which extend parallel to the beam axis and are spaced around the beam at 90/degree/ intervals with opposing electrodes maintained at the same potential. 12 figs., 3 tabs.

  12. CTF3 Drive Beam Accelerating Structures

    Jensen, E

    2002-01-01

    The 3 GHz drive beam accelerator of the CLIC Test Facility CTF3, currently under construction at CERN, will be equipped with 16 novel SICA (Slotted Iris – Constant Aperture) accelerating structures. The slotted irises couple out the potentially disruptive induced transverse HOM energy to integrated silicon carbide loads (dipole mode Q's below 20). The use of nose cones for detuning allows a constant inner aperture (34 mm). The structures will be 1.2 m long and consist of 34 cells. A first 6 cell prototype structure has been tested successfully up to power levels of 100 MW (nominal: 30 MW), corresponding to surface electric field levels of 180 MV/m.

  13. Arterivirus structural proteins and assembly

    This chapter reviews the structural characteristics of the Arteriviridae, including the basic molecular details of all of the proteins involved, the interactions of these proteins and where they occur, and further functional characterization. Most recent available literature has been focused on equi...

  14. New structure for accelerating heavy ions

    A new type of accelerating structure is described which is particular suited to heavy ions (high wavelength, high shunt impedance, small size). Its properties are analyzed and compared to those of other structures (more particularly the lines). It is shown that a mode of operation exists of which the shunt impedance in the station mode has 80 per cent of its value for the progressive mode. Finally results are given obtained with a small experimental apparatus which uses this structure. (author)

  15. Photonic crystal laser-driven accelerator structures

    Cowan, Benjamin

    2005-01-01

    We discuss simulated photonic crystal structure designs, including two- and three-dimensional planar structures and fibers. The discussion of 2D structures demonstrates guiding of a speed-of-light accelerating mode by a defect in a photonic crystal lattice and reveals design considerations and trade-offs. With a three-dimensional lattice, we introduce a candidate geometry and discuss beam dynamics, coupling, and manufacturing techniques for that structure. In addition we discuss W-band scale tests of photonic crystal structures. The computational methods are also discussed.

  16. Accelerating structures pre-stripping section the milac heavy ion linear Accelerator MILAC

    Researches on development of new variants of accelerating structures for acceleration of the ions with A/q=20 in pre-stripping section PSS-20 are carried out. On an initial part of acceleration of ions from 6 up to 150 keV/u high capture in process of acceleration of the injected ions is provided interdigital (IH) accelerating structure with Radio-Frequency Quadrupole (RFQ) focusing. On the second part of acceleration of ions from 150 keV/u up to 1 MeV/u the highest rate of acceleration is created interdigital (IH) accelerating structure with drift tubes with the modified radio-frequency focusing.

  17. Templated Self Assemble of Nano-Structures

    Suo, Zhigang [Harvard University

    2013-04-29

    This project will identify and model mechanisms that template the self-assembly of nanostructures. We focus on a class of systems involving a two-phase monolayer of molecules adsorbed on a solid surface. At a suitably elevated temperature, the molecules diffuse on the surface to reduce the combined free energy of mixing, phase boundary, elastic field, and electrostatic field. With no template, the phases may form a pattern of stripes or disks. The feature size is on the order of 1-100 nm, selected to compromise the phase boundary energy and the long-range elastic or electrostatic interaction. Both experimental observations and our theoretical simulations have shown that the pattern resembles a periodic lattice, but has abundant imperfections. To form a perfect periodic pattern, or a designed aperiodic pattern, one must introduce a template to guide the assembly. For example, a coarse-scale pattern, lithographically defined on the substrate, will guide the assembly of the nanoscale pattern. As another example, if the molecules on the substrate surface carry strong electric dipoles, a charged object, placed in the space above the monolayer, will guide the assembly of the molecular dipoles. In particular, the charged object can be a mask with a designed nanoscale topographic pattern. A serial process (e.g., e-beam lithography) is necessary to make the mask, but the pattern transfer to the molecules on the substrate is a parallel process. The technique is potentially a high throughput, low cost process to pattern a monolayer. The monolayer pattern itself may serve as a template to fabricate a functional structure. This project will model fundamental aspects of these processes, including thermodynamics and kinetics of self-assembly, templated self-assembly, and self-assembly on unconventional substrates. It is envisioned that the theory will not only explain the available experimental observations, but also motivate new experiments.

  18. Design of the detuned accelerator structure

    This is a summary of the design procedure for the detuned accelerator structure for SLAC's Next Linear Collider (NLC) program. The 11.424 GHz accelerating mode of each cavity must be synchronous with the beam. The distribution of the disk thicknesses and lowest synchronous dipole mode frequencies of the cavities in the structure is Gaussian in order to reduce the effect of wake fields. The finite element field solver YAP calculated the accelerating mode frequency and the lowest synchronous dipole mode frequency for various cavity diameters, aperture diameters and disk thicknesses. Polynomial 3-parameter fits are used to calculate the dimensions for a 1.8 m detuned structure. The program SUPERFISH was used to calculate the shunt impedances, quality factors and group velocities. The RF parameters of the section like filling time, attenuation factor, accelerating gradient and maximum surface field along the section are evaluated. Error estimates will be discussed and comparisons with conventional constant gradient and constant impedance structures will be presented

  19. Wakefield monitor development for CLIC accelerating structure

    Peauger, F; Girardot, P; Andersson, A; Riddone, G; Samoshkin, A; Solodko, A; Zennaro, R; Ruber, R

    2010-01-01

    Abstract To achieve high luminosity in CLIC, the accelerating structures must be aligned to an accuracy of 5 μm with respect to the beam trajectory. Position detectors called Wakefield Monitors (WFM) are integrated to the structure for a beam based alignment. This paper describes the requirements of such monitors. Detailed RF design and electromagnetic simulations of the WFM itself are presented. In particular, time domain computations are performed and an evaluation of the resolution is done for two higher order modes at 18 and 24 GHz. The mechanical design of a prototype accelerating structure with WFM is also presented as well as the fabrication status of three complete structures. The objective is to implement two of them in CTF3 at CERN for a feasibility demonstration with beam and high power rf.

  20. An Rf Focused Interdigital Ion Accelerating Structure

    An Rf Focused Interdigital (RFI) ion accelerating structure will be described. It represents an effective combination of the Wideroee (or interdigital) linac structure, used for many low frequency, heavy ion applications, and the rf electric quadrupole focusing used in the RFQ and RFD linac structures. As in the RFD linac structure, rf focusing is introduced into the RFI linac structure by configuring the drift tubes as two independent pieces operating at different electrical potentials as determined by the rf fields of the linac structure. Each piece (or electrode) of the RFI drift tube supports two fingers pointed inwards towards the opposite end of the drift tube forming a four-finger geometry that produces an rf quadrupole field along the axis of the linac for focusing the beam. However, because of the differences in the rf field configuration along the axis, the scheme for introducing rf focusing into the interdigital linac structure is quite different from that adopted for the RFD linac structure. The RFI linac structure promises to have significant size, efficiency, performance, and cost advantages over existing linac structures for the acceleration of low energy ion beams of all masses (light to heavy). These advantages will be reviewed. A 'cold model' of this new linac structure has been fabricated and the results of rf cavity measurements on this cold model will be presented

  1. Rectangular Diamond-Lined Accelerator Structure

    Wang, Changbiao; Yakovlev, Vyacheslav P

    2005-01-01

    For high frequency accelerators with normal-conducting structures studied by the NLC/GLC collaboration and the CLIC group, rf breakdown is the main gradient limitation. In this paper, a Ka-band rectangular dielectric-lined structure is described as an attempt to increase accelerating gradient beyond the limits suitable for metallic structures. The structure is based on amorphous dielectrics that are known to exhibit high breakdown limits (~ GV/m). An example is artificial diamond that has already been successfully used on an industrial basis for large-diameter output windows of high power gyrotrons, and is produced industrially in increasing quantities. Artificial diamond has low loss tangent, moderate dielectric constant and high breakdown limit of ~2 GV/m. In the proposed structure diamond-slabs are employed to support high-gradient acceleration fields. Interposition of vacuum gaps between the dielectric slabs and the side walls is shown to reduce Ohmic losses substantially, leading to an increase in shunt ...

  2. Validation of the transient Structural Response of a Threaded Assembly

    Doebling, S. W. (Scott W.); Hemez, F. M. (François M.); Schultze, J. F. (John F.)

    2002-01-01

    This paper will demonstrate the application of model validation techniques to a transient structural dynamics problem. The problem of interest is the propagation of an explosive shock through a complex threaded joint that is a surrogate model of a system assembly. The objective is to validate the computational modeling of the key mechanical phenomena in the assembly, so that the component can be represented with adequate fidelity in the system-level model. A set of experiments was conducted on the threaded assembly where the acceleration and strain responses to an explosive load were measured on mass-simulators representing payloads. A significantly detailed computational model of the threaded assembly was also created. Numerical features that represent the important characteristics of the response were defined and calculated for both the experimental and computational data. Each step of the model validation process will be described as applied to this problem. Fundamental issues regarding the nature of model validation and the role of model validation in the engineering analysis process will also be discussed.

  3. Research program for the 660 MeV proton accelerator driven MOX-plutonium subcritical assembly

    Barashenkov, V. S.; Buttsev, V. S.; Buttseva, G. L.; Dudarev, S. Ju.; Polanski, A.; Puzynin, I. V.; Sissakian, A. N.

    2000-07-01

    This paper presents the research program of the Experimental Accelerator Driven System (ADS), which employs a subcritical assembly and a 660 MeV proton accelerator operating in the Laboratory of Nuclear Problems at the Joint Institute for Nuclear Research in Dubna. Mixed-oxide (MOX) fuel (25% PuO2+75% UO2) designed for the BN-600 reactor use will be adopted for the core of the assembly. The present conceptual design of the experimental subcritical assembly is based on a core nominal unit capacity of 15 kW (thermal). This corresponds to the multiplication coefficient keff=0.945, energetic gain G=30, and accelerator beam power of 0.5 kW.

  4. Transport synthetic acceleration for long-characteristics assembly-level transport problems

    Zika, M.R.; Adams, M.L.

    2000-02-01

    The authors apply the transport synthetic acceleration (TSA) scheme to the long-characteristics spatial discretization for the two-dimensional assembly-level transport problem. This synthetic method employs a simplified transport operator as its low-order approximation. Thus, in the acceleration step, the authors take advantage of features of the long-characteristics discretization that make it particularly well suited to assembly-level transport problems. The main contribution is to address difficulties unique to the long-characteristics discretization and produce a computationally efficient acceleration scheme. The combination of the long-characteristics discretization, opposing reflecting boundary conditions (which are present in assembly-level transport problems), and TSA presents several challenges. The authors devise methods for overcoming each of them in a computationally efficient way. Since the boundary angular data exist on different grids in the high- and low-order problems, they define restriction and prolongation operations specific to the method of long characteristics to map between the two grids. They implement the conjugate gradient (CG) method in the presence of opposing reflection boundary conditions to solve the TSA low-order equations. The CG iteration may be applied only to symmetric positive definite (SPD) matrices; they prove that the long-characteristics discretization yields an SPD matrix. They present results of the acceleration scheme on a simple test problem, a typical pressurized water reactor assembly, and a typical boiling water reactor assembly.

  5. Transport synthetic acceleration for long-characteristics assembly-level transport problems

    The authors apply the transport synthetic acceleration (TSA) scheme to the long-characteristics spatial discretization for the two-dimensional assembly-level transport problem. This synthetic method employs a simplified transport operator as its low-order approximation. Thus, in the acceleration step, the authors take advantage of features of the long-characteristics discretization that make it particularly well suited to assembly-level transport problems. The main contribution is to address difficulties unique to the long-characteristics discretization and produce a computationally efficient acceleration scheme. The combination of the long-characteristics discretization, opposing reflecting boundary conditions (which are present in assembly-level transport problems), and TSA presents several challenges. The authors devise methods for overcoming each of them in a computationally efficient way. Since the boundary angular data exist on different grids in the high- and low-order problems, they define restriction and prolongation operations specific to the method of long characteristics to map between the two grids. They implement the conjugate gradient (CG) method in the presence of opposing reflection boundary conditions to solve the TSA low-order equations. The CG iteration may be applied only to symmetric positive definite (SPD) matrices; they prove that the long-characteristics discretization yields an SPD matrix. They present results of the acceleration scheme on a simple test problem, a typical pressurized water reactor assembly, and a typical boiling water reactor assembly

  6. Transport Synthetic Acceleration for Long-Characteristics Assembly-Level Transport Problems

    We apply the transport synthetic acceleration (TSA) scheme to the long-characteristics spatial discretization for the two-dimensional assembly-level transport problem. This synthetic method employs a simplified transport operator as its low-order approximation. Thus, in the acceleration step, we take advantage of features of the long-characteristics discretization that make it particularly well suited to assembly-level transport problems. Our main contribution is to address difficulties unique to the long-characteristics discretization and produce a computationally efficient acceleration scheme.The combination of the long-characteristics discretization, opposing reflecting boundary conditions (which are present in assembly-level transport problems), and TSA presents several challenges. We devise methods for overcoming each of them in a computationally efficient way. Since the boundary angular data exist on different grids in the high- and low-order problems, we define restriction and prolongation operations specific to the method of long characteristics to map between the two grids. We implement the conjugate gradient (CG) method in the presence of opposing reflection boundary conditions to solve the TSA low-order equations. The CG iteration may be applied only to symmetric positive definite (SPD) matrices; we prove that the long-characteristics discretization yields an SPD matrix. We present results of our acceleration scheme on a simple test problem, a typical pressurized water reactor assembly, and a typical boiling water reactor assembly

  7. Beam shaping assembly optimization for 7Li(p,n)7Be accelerator based BNCT

    Within the framework of accelerator-based BNCT, a project to develop a folded Tandem-ElectroStatic-Quadrupole accelerator is under way at the Atomic Energy Commission of Argentina. The proposed accelerator is conceived to deliver a proton beam of 30 mA at about 2.5 MeV. In this work we explore a Beam Shaping Assembly (BSA) design based on the 7Li(p,n)7Be neutron production reaction to obtain neutron beams to treat deep seated tumors. - Highlights: • A Beam Shaping Assembly for accelerator based BNCT has been designed. • A conical port for easy patient positioning and the cooling system are included. • Several configurations can deliver tumor doses greater than 55 RBEGy. • Good tumor doses can be obtained in less than 60 min of irradiation time

  8. Latest Insights on Adenovirus Structure and Assembly

    Carmen San Martín

    2012-05-01

    Full Text Available Adenovirus (AdV capsid organization is considerably complex, not only because of its large size (~950 Å and triangulation number (pseudo T = 25, but also because it contains four types of minor proteins in specialized locations modulating the quasi-equivalent icosahedral interactions. Up until 2009, only its major components (hexon, penton, and fiber had separately been described in atomic detail. Their relationships within the virion, and the location of minor coat proteins, were inferred from combining the known crystal structures with increasingly more detailed cryo-electron microscopy (cryoEM maps. There was no structural information on assembly intermediates. Later on that year, two reports described the structural differences between the mature and immature adenoviral particle, starting to shed light on the different stages of viral assembly, and giving further insights into the roles of core and minor coat proteins during morphogenesis [1,2]. Finally, in 2010, two papers describing the atomic resolution structure of the complete virion appeared [3,4]. These reports represent a veritable tour de force for two structural biology techniques: X-ray crystallography and cryoEM, as this is the largest macromolecular complex solved at high resolution by either of them. In particular, the cryoEM analysis provided an unprecedented clear picture of the complex protein networks shaping the icosahedral shell. Here I review these latest developments in the field of AdV structural studies.

  9. Modeling accelerator structures and RF components

    Computer modeling has become an integral part of the design and analysis of accelerator structures RF components. Sophisticated 3D codes, powerful workstations and timely theory support all contributed to this development. We will describe our modeling experience with these resources and discuss their impact on ongoing work at SLAC. Specific examples from R ampersand D on a future linear collide and a proposed e+e- storage ring will be included

  10. Modeling accelerator structures and RF components

    Ko, K., Ng, C.K.; Herrmannsfeldt, W.B.

    1993-03-01

    Computer modeling has become an integral part of the design and analysis of accelerator structures RF components. Sophisticated 3D codes, powerful workstations and timely theory support all contributed to this development. We will describe our modeling experience with these resources and discuss their impact on ongoing work at SLAC. Specific examples from R&D on a future linear collide and a proposed e{sup +}e{sup {minus}} storage ring will be included.

  11. Accelerating Structure design and fabrication For KIPT and PAL XFEL

    Hou, Mi; Pei, Shilun

    2014-01-01

    ANL and the National Science Center "Kharkov Institute of Physics Technology" (NSC KIPT, Kharkov, Ukraine) jointly proposed to design and build a 100MeV/100KW linear accelerator which will be used to drive the neutron source subcritical assembly. Now the linac was almost assembled in KIPT by the team from Institute of High Energy Physics (IHEP, Beijing, China). The design and measurement result of the accelerating system of the linac will be described in this paper.

  12. Possibility of ion acceleration at the higher modes of a reciprocal-bar accelerating structure

    The aim of the paper is to study a possibility of increasing the heavy ion energy in a new linear accelerator of multicharged ions (MCI). The accelerator is based on using a reciprocal-bar accelerating structure (RBAS). It is shown experimentally that it is possible to achieve more high energies of MCI when their accelerating by the higher modes of RBAS

  13. Development of ultra-precision machining and measurement. Application to manufacturing of accelerating structures

    Manufacturing of the X-band accelerating structure is under development for the main components of the JLC, which is the next electron-positron linear collider project. The main body of the X-band accelerating structure is composed of approximately two hundred cells, and requires precision machining, measurement, assembly and bonding. Machining the cells with ultra-precision lathe, requires sub-micron precision, so is an important area for development. Various factors of the influence on precision were considered, and techniques developed for ultra-precision machining. In 1998 to 1999, DDS3 and RDDS structures were fabricated by assembling and bonding cells. The high power testing structures were fabricated by machining, assembling and bonding the cells in 2000 to 2001. (author)

  14. Structure investigations on assembled astaxanthin molecules

    Köpsel, Christian; Möltgen, Holger; Schuch, Horst; Auweter, Helmut; Kleinermanns, Karl; Martin, Hans-Dieter; Bettermann, Hans

    2005-08-01

    The carotenoid r, r-astaxanthin (3 R,3' R-dihydroxy-4,4'-diketo-β-carotene) forms different types of aggregates in acetone-water mixtures. H-type aggregates were found in mixtures with a high part of water (e.g. 1:9 acetone-water mixture) whereas two different types of J-aggregates were identified in mixtures with a lower part of water (3:7 acetone-water mixture). These aggregates were characterized by recording UV/vis-absorption spectra, CD-spectra and fluorescence emissions. The sizes of the molecular assemblies were determined by dynamic light scattering experiments. The hydrodynamic diameter of the assemblies amounts 40 nm in 1:9 acetone-water mixtures and exceeds up to 1 μm in 3:7 acetone-water mixtures. Scanning tunneling microscopy monitored astaxanthin aggregates on graphite surfaces. The structure of the H-aggregate was obtained by molecular modeling calculations. The structure was confirmed by calculating the electronic absorption spectrum and the CD-spectrum where the molecular modeling structure was used as input.

  15. Advanced accelerator and mm-wave structure research at LANL

    Simakov, Evgenya Ivanovna [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-06-22

    This document outlines acceleration projects and mm-wave structure research performed at LANL. The motivation for PBG research is described first, with reference to couplers for superconducting accelerators and structures for room-temperature accelerators and W-band TWTs. These topics are then taken up in greater detail: PBG structures and the MIT PBG accelerator; SRF PBG cavities at LANL; X-band PBG cavities at LANL; and W-band PBG TWT at LANL. The presentation concludes by describing other advanced accelerator projects: beam shaping with an Emittance Exchanger, diamond field emitter array cathodes, and additive manufacturing of novel accelerator structures.

  16. Studies on HF quadrupole accelerator structures

    The present thesis had the aim to elaborate advantages and disadvantages of existing high frequency resonators in the MHz range regarding their use as RFQ power supply structures and to limit their application ranges. After a short survey over potential and field distributions in the RFQ suitable criteria for the valuation of RFQ resonators are indicated. For the experimentally studied resonators equivalent circuits are presented, in some cases these are theoretically analyzed. Finally the construction of the GSI/Frankfurt proton model as well experiments with the accelerated proton beams are described. (orig.)

  17. On-Orbit Assembly of Flexible Space Structures with SWARM

    Mohan, Swati; Katz, Jacob G.; Miller, David W.

    2010-01-01

    On-orbit assembly is an enabling technology for many space applications. However, current methods of human assisted assembly are high in cost and risk to the crew, motivating a desire to automate the on-orbit assembly process using robotic technology. Construction of large space structures will likely involve the manipulation of flexible elements such as trusses or solar panels, and automation for assembly of flexible structures has significant challenges, particularly in control systems. Thi...

  18. THE MECHANICAL AND SHIELDING DESIGN OF A PORTABLE SPECTROMETER AND BEAM DUMP ASSEMBLY AT BNLS ACCELERATOR TEST FACILITY

    A portable assembly containing a vertical-bend dipole magnet has been designed and installed immediately down-beam of the Compton electron-laser interaction chamber on beamline 1 of the Accelerator Test Facility (ATF) at Brookhaven National Laboratory (BNL). The water-cooled magnet designed with field strength of up to 0.7 Tesla will be used as a spectrometer in the Thompson scattering and vacuum acceleration experiments, where field-dependent electron scattering, beam focusing and energy spread will be analyzed. This magnet will deflect the ATF's 60 MeV electron-beam 90o downward, as a vertical beam dump for the Compton scattering experiment. The dipole magnet assembly is portable, and can be relocated to other beamlines at the ATF or other accelerator facilities to be used as a spectrometer or a beam dump. The mechanical and shielding calculations are presented in this paper. The structural rigidity and stability of the assembly were studied. A square lead shield surrounding the assembly's Faraday Cup was designed to attenuate the radiation emerging from the 1 inch-copper beam stop. All photons produced were assumed to be sufficiently energetic to generate photoneutrons. A safety evaluation of groundwater tritium contamination due to the thermal neutron capturing by the deuterium in water was performed, using updated Monte Carlo neutron-photon coupled transport code (MCNP). High-energy neutron spallation, which is a potential source to directly generate radioactive tritium and sodium-22 in soil, was conservatively assessed in verifying personal and environmental safety

  19. Rapid Electromagnetic Analysis of Entire Accelerator Structures

    Cooke, Simon

    2005-01-01

    We present results of a new method for fast, accurate calculation, in 3-D, of the electromagnetic mode spectrum of long, tapered accelerator structures. Instead of discretizing the entire structure directly and solving a huge matrix eigenvalue problem, we use a new two-step technique that scales much better to long, multi-cavity structures. In the first step we compute a small number of eigenmodes of individual cavities, achieving 0.05% frequency accuracy using a new second-order finite-element code. In the second step we use these 3-D mode solutions as field basis functions to obtain a reduced matrix representation of Maxwell's equations for the complete structure. Solving the reduced system takes just a few minutes on a desktop PC even with more than 100 non-identical cavities, and gives the complete mode spectrum in the first few bands of the structure. By judicious choice of the basis modes, we retain 0.05% frequency accuracy for these global solutions, and can reconstruct the complete 3-D field of each m...

  20. Assembly and installation of the 2 MeV FMIT accelerator

    The front end of the 35-MeV Fusion Materials Irradiation Test (FMIT) Facility accelerator is being assembled and installed at Los Alamos. The machine ultimately will produce a 500-kW continuous-duty beam at 5 MeV, although only the first 2 MeV will be installed this year. The 2-MeV system will include the most-powerful radio-frequency quadrupole (RFQ) in existence. The assembly and installation of the hardware are described, along with the unique problems arising from the large size and high power of the components involved

  1. Programmed assembly of nanoscale structures using peptoids.

    Ren, Jianhua (University of the Pacific, Stockton, CA); Russell, Scott (California State University, Stanislaus, Turlock, CA); Morishetti, Kiran (University of the Pacific, Stockton, CA); Robinson, David B.; Zuckermann, Ronald N. (Lawrence Berkeley National Laboratory, Berkeley, CA); Buffleben, George M.; Hjelm, Rex P. (Los Alamos National Laboratory, Los Alamos, NM); Kent, Michael Stuart (Sandia National Laboratories, Albuquerque, NM)

    2011-02-01

    Sequence-specific polymers are the basis of the most promising approaches to bottom-up programmed assembly of nanoscale materials. Examples include artificial peptides and nucleic acids. Another class is oligo(N-functional glycine)s, also known as peptoids, which permit greater sidegroup diversity and conformational control, and can be easier to synthesize and purify. We have developed a set of peptoids that can be used to make inorganic nanoparticles more compatible with biological sequence-specific polymers so that they can be incorporated into nucleic acid or other biologically based nanostructures. Peptoids offer degrees of modularity, versatility, and predictability that equal or exceed other sequence-specific polymers, allowing for rational design of oligomers for a specific purpose. This degree of control will be essential to the development of arbitrarily designed nanoscale structures.

  2. Studies on high-precision machining and assembly of CLIC RF structures

    Huopana, J; Riddone, G; Österberg, K

    2010-01-01

    The Compact Linear Collider (CLIC) is currently under development at CERN as a potential multi-TeV e+e– collider. The manufacturing and assembly tolerances for the required RF components are essential for the final efficiency and for the operation of CLIC. The proper function of an accelerating structure is sensitive to mechanical errors in the shape and the alignment of the accelerating cavity. The current tolerances are in the micron range. This raises challenges in the field of mechanical design and demands special manufacturing technologies and processes. Currently the mechanical design of the accelerating structures is based on a disk design. Alternatively, it is possible to create the accelerating assembly from quadrants, which has the potential to be favoured for the mass production due to simplicity and cost. In this case, the functional shape inside of the accelerating structure remains the same and a single assembly uses less parts. This paper focuses on the development work done in design and sim...

  3. A hybrid dielectric and iris loaded periodic accelerating structure

    One disadvantage of conventional iris-loaded accelerating structures is the high ratio of the peak surface electric field to the peak axial electric field useful for accelerating a beam. Typically this ratio Es/Ea ≥ 2. The high surface electric field relative to the accelerating gradient may prove to be a limitation for realizing technologies for very high gradient accelerators. In this paper, we present a scheme that uses a hybrid dielectric and iris loaded periodic structure to reduce Es/Ea to near unity, while the shunt impedance per unit length r and the quality factor Q compare favorably with conventional metallic structures. The analysis based on MAFIA simulations of such structures shows that we can lower the peak surface electric field close to the accelerating gradient while maintaining high acceleration efficiency as measured by r/Q. Numerical examples of X-band hybrid accelerating structures are given

  4. Hybrid dielectric and iris-loaded periodic accelerating structure

    One disadvantage of conventional iris-loaded accelerating structures is the high ratio of the peak surface electric field to the peak axial electric field useful for accelerating a beam. Typically this ratio Es/Ea≥2. The high surface electric field relative to the accelerating gradient may prove to be a limitation for realizing technologies for very high gradient accelerators. In this article, we present a scheme that uses a hybrid dielectric and iris-loaded periodic structure to reduce Es/Ea to near unity, while the shunt impedance per unit length r and the quality factor Q compare favorably with conventional metallic structures. The analysis based on MAFIA simulations of such structures shows that we can lower the peak surface electric field close to the accelerating gradient while maintaining high acceleration efficiency as measured by r/Q. Numerical examples of X-band hybrid accelerating structures are given. copyright 2001 American Institute of Physics

  5. Research Programme for the 660 Mev Proton Accelerator Driven MOX-Plutonium Subcritical Assembly

    Barashenkov, V S; Buttseva, G L; Dudarev, S Yu; Polanski, A; Puzynin, I V; Sissakian, A N

    2000-01-01

    The paper presents a research programme of the Experimental Acclerator Driven System (ADS), which employs a subcritical assembly and a 660 MeV proton acceletator operating at the Laboratory of Nuclear Problems of the JINR, Dubna. MOX fuel (25% PuO_2 + 75% UO_2) designed for the BN-600 reactor use will be adopted for the core of the assembly. The present conceptual design of the experimental subcritical assembly is based on a core of a nominal unit capacity of 15 kW (thermal). This corresponds to the multiplication coefficient k_eff = 0.945, energetic gain G = 30 and the accelerator beam power 0.5 kW.

  6. Structural analyses and integrated design of the MITICA Injector assembly

    Highlights: ► Seismic design has been carried out on PRIMA building. ► Three-dimensional FE models have been developed the vessel and TL device. ► Three bellows stiffness have been considered to evaluate maximum TL displacements. -- Abstract: In the framework of the activities foreseen for PRIMA (Padova Research on Injector Megavolt Accelerated) the MITICA neutral beam injector plays the role of main experiment, aiming to build, operate, test and optimize a full power and full scale prototype of the ITER Heating Neutral Beam Injector [1–3]. The entire MITICA system will be housed in special buildings, suitably designed to provide all the necessary supports, interfaces and shielding walls for nuclear radiation safety. Therefore an integrated design of the MITICA system and relevant buildings shall be developed and verified carefully, considering all the different configurations, operational modes and load combinations. This paper presents the numerical models and the results of MITICA assembly integrated analyses. The model takes into account properly constraints to ground and surrounding buildings, to study and verify the static and seismic response of the whole assembly. The load cases are defined and the numerical analyses described. Load definition and analyses have been performed considering the requirements of both the ASME [4] and the National Standard NTC2008 [5] for the seismic verification of structures subject to design response spectra. The obtained results are finally shown in detail and discussed, also comparing some different design options for design optimization

  7. Molecular Component Structures Mediated Formation of Self-assemblies

    2001-01-01

    Molecular recognition directed self-assemblies from complementary molecular components, melamine and barbituric acid derivatives were studied by means of NMR, fluorescence, and TEM. It was found that both the process of the self-assembly and the morphologies of the result ed self-assemblies could be mediated by modifying the structures of the molecular components used. The effect of the structures of the molecular components on the formation of the self-as semblies was discussed in terms of intermolecular interactions.

  8. Brazing techniques for side-coupled electron accelerator structures

    The collaboration between the Los Alamos National Laboratory and the National Bureau of Standards (NBS), started in 1979, has led to the development of an advanced c-w microtron accelerator design. The four 2380-MHz NBS accelerating structures, containing a total of 184 accelerating cavities, have been fabricated and delivered. New fabrication methods, coupled with refinements of hydrogen-furnace brazing techniques described in this paper, allow efficient production of side-coupled structures. Success with the NBS RTM led to Los Alamos efforts on similar 2450-MHz accelerators for the microtron accelerator operated by the Nuclear Physics Department of the University of Illinois. Two accelerators (each with 17 cavities) have been fabricated; in 1986, a 45-cavity accelerator is being fabricated by private industry with some assistance from Los Alamos. Further private industry experience and refinement of the described fabrication techniques may allow future accelerators of this type to be completely fabricated by private industry

  9. The fabrication of millimeter-wavelength accelerating structures

    There is a growing interest in the development of high gradient (≥ 1 GeV/m) accelerating structures. The need for high gradient acceleration based on current microwave technology requires the structures to be operated in the millimeter wavelength. Fabrication of accelerating structures at millimeter scale with sub-micron tolerances poses great challenges. The accelerating structures impose strict requirements on surface smoothness and finish to suppress field emission and multipactor effects. Various fabrication techniques based on conventional machining and micromachining have been evaluated and tested. These will be discussed and measurement results presented

  10. On the structure of acceleration in turbulence

    Liberzon, A.; Lüthi, B.; Holzner, M.; Ott, Søren; Berg, Jacob; Mann, Jakob

    2012-01-01

    Acceleration and spatial velocity gradients are obtained simultaneously in an isotropic turbulent flow via three dimensional particle tracking velocimetry. We observe two distinct populations of intense acceleration events: one in flow regions of strong strain and another in regions of strong...... vorticity. Geometrical alignments with respect to vorticity vector and to the strain eigenvectors, curvature of Lagrangian trajectories and of streamlines for total acceleration, and for its convective part, , are studied in detail. We discriminate the alignment features of total and convective acceleration...... statistics, which are genuine features of turbulent nature from those of kinematic nature. We find pronounced alignment of acceleration with vorticity. Similarly, and especially are predominantly aligned at 45°with the most stretching and compressing eigenvectors of the rate of the strain tensor, , and...

  11. Grid structure for nuclear reactor fuel assembly

    Described is a nuclear fuel element support system comprising an egg-crate-type grid made up of slotted vertical portions interconnected at right angles to each other, the vertical portions being interconnected by means of cross straps which are dimpled midway between their ends to engage fuel elements disposed within openings formed in the egg-crate assembly. The cross straps are disposed at an angle, other than a right angle, to the vertical portions of the assembly whereby their lengths are increased for a given span, and the total elastic deflection capability of the cell is increased. The assembly is particularly adapted for computer design and automated machine tool fabrication

  12. Required performance to the concrete structure of the accelerator facilities

    As for the accelerator facility, there is many a thing which is constructed as underground concrete structure from viewpoint such as cover of radiation and stability of the structure. Required performance to the concrete structure of the accelerator facility is the same as the general social infrastructure, but it has been possessed the feature where target performance differs largely. As for the body sentence, expressing the difference of the performance which is required from the concrete structure of the social infrastructure and the accelerator facility, construction management of the concrete structure which it plans from order of the accelerator engineering works facility, reaches to the design, supervision and operation it is something which expresses the method of thinking. In addition, in the future of material structural analysis of the concrete which uses the neutron accelerator concerning view it showed. (author)

  13. Coupler tuning for constant gradient travelling wave accelerating structures

    The method of the coupler tuning for the constant gradient traveling wave accelerating structure was described and the formula of coupling coefficient p was deduced on the basis of analyzing the existing methods for the constant impedance traveling wave accelerating structures and coupling-cavity chain equivalent circuits. The method and formula were validated by the simulation result by CST and experiment data. (authors)

  14. Assembly Based Modular Ray Tracing and CMFD Acceleration for BWR Cores with Different Fuel Lattices

    The geometry module of the DeCART direct whole core calculation code has been extended in order to analyze BWR cores which might have a mixed loading of different fuel types. First, an assembly based modular ray tracing scheme was implemented for the Method of Characteristic (MOC) calculation, and a CMFD formulation applicable for unaligned mesh conditions was then developed for acceleration the MOC calculation. The new calculation feature has been validated by comparing DeCART BWR assembly calculations with the MCU Monte Carlo calculations. A good agreement identified by the maximum eigenvalue difference of 120 pcm and the maximum pin power error of about 1% has been achieved. The CMFD scheme is shown to reduce the number of MOC iterations by factors of 12-25 without loss of accuracy. (authors)

  15. Travelling wave accelerating structure design for TESLA positron injector linac

    Jin, K; Zhou, F; Flöttmann, K

    2000-01-01

    A modified cup-like TW accelerating structure for TESLA Positron Pre-Accelerator (PPA) is designed by optimizing the structure geometry and by changing the iris thickness cell by cell in a section . This structure has high shunt-impedance and a large iris radius to meet with the requirements of high gradient and large transverse acceptance. The beam dynamics in the structure with the optimum solenoid focus field are studied. A satisfactory positron beam transmission and the beam performance at the PPA output have been obtained. In this paper the accelerating structure design is described in detail and the results are presented.

  16. Manifold damping of the NLC detuned accelerating structure

    In order to investigate the reappearance of the HOM wakefield of a detuned accelerator structure and relax tolerance requirements, we propose to provide low level damping by coupling all cavities to several identical and symmetrically located waveguides (manifolds) which run parallel to each accelerator structure and are terminated at each end by matched loads. The waveguides are designed such that all modes which couple to the acceleration mode are non-propagating at the acceleration mode frequency. Hence the coupling irises can be designed to provide large coupling to higher frequency modes without damping the acceleration mode. Because the higher order modes are detuned, they are localized and have a broad spectrum of phase velocities of both signs. They are therefore capable of coupling effectively to all propagating modes in the waveguides. Methods of analyzing and results obtained for the very complex system of modes in the accelerating structure and manifolds are presented

  17. Compact Couplers for Photonic Crystal Laser-Driven Accelerator Structures

    Photonic crystal waveguides are promising candidates for laser-driven accelerator structures because of their ability to confine a speed-of-light mode in an all-dielectric structure. Because of the difference between the group velocity of the waveguide mode and the particle bunch velocity, fields must be coupled into the accelerating waveguide at frequent intervals. Therefore efficient, compact couplers are critical to overall accelerator efficiency. We present designs and simulations of high-efficiency coupling to the accelerating mode in a three-dimensional photonic crystal waveguide from a waveguide adjoining it at 90o. We discuss details of the computation and the resulting transmission. We include some background on the accelerator structure and photonic crystal-based optical acceleration in general.

  18. Simulation studies of crystal-photodetector assemblies for the Turkish accelerator center particle factory electromagnetic calorimeter

    Kocak, F.

    2015-07-01

    The Turkish Accelerator Center Particle Factory detector will be constructed for the detection of the produced particles from the collision of a 1 GeV electron beam against a 3.6 GeV positron beam. PbWO4 and CsI(Tl) crystals are considered for the construction of the electromagnetic calorimeter part of the detector. The generated optical photons in these crystals are detected by avalanche or PIN photodiodes. Geant4 simulation code has been used to estimate the energy resolution of the calorimeter for these crystal-photodiode assemblies.

  19. Simulation studies of crystal-photodetector assemblies for the Turkish accelerator center particle factory electromagnetic calorimeter

    Kocak, F., E-mail: fkocak@uludag.edu.tr

    2015-07-01

    The Turkish Accelerator Center Particle Factory detector will be constructed for the detection of the produced particles from the collision of a 1 GeV electron beam against a 3.6 GeV positron beam. PbWO{sub 4} and CsI(Tl) crystals are considered for the construction of the electromagnetic calorimeter part of the detector. The generated optical photons in these crystals are detected by avalanche or PIN photodiodes. Geant4 simulation code has been used to estimate the energy resolution of the calorimeter for these crystal–photodiode assemblies.

  20. Simulation studies of crystal-photodetector assemblies for the Turkish accelerator center particle factory electromagnetic calorimeter

    The Turkish Accelerator Center Particle Factory detector will be constructed for the detection of the produced particles from the collision of a 1 GeV electron beam against a 3.6 GeV positron beam. PbWO4 and CsI(Tl) crystals are considered for the construction of the electromagnetic calorimeter part of the detector. The generated optical photons in these crystals are detected by avalanche or PIN photodiodes. Geant4 simulation code has been used to estimate the energy resolution of the calorimeter for these crystal–photodiode assemblies

  1. High frequency single mode traveling wave structure for particle acceleration

    Ivanyan, M. I.; Danielyan, V. A.; Grigoryan, B. A.; Grigoryan, A. H.; Tsakanian, A. V.; Tsakanov, V. M.; Vardanyan, A. S.; Zakaryan, S. V.

    2016-09-01

    The development of the new high frequency slow traveling wave structures is one of the promising directions in accomplishment of charged particles high acceleration gradient. The disc and dielectric loaded structures are the most known structures with slowly propagating modes. In this paper a large aperture high frequency metallic two-layer accelerating structure is studied. The electrodynamical properties of the slowly propagating TM01 mode in a metallic tube with internally coated low conductive thin layer are examined.

  2. Welding device for nuclear fuel assembly structure elements

    The device has two parallel assembling positions next to each other. The welding robot is carried by a carriage with displacement parallel to the guide tubes and has enough degrees of freedom to move from one assembling position to the other and have access to the structural elements

  3. Investigation of IFMIF target assembly structure design

    In the International Fusion Materials Irradiation Facility (IFMIF), the back-wall of target assembly is the part suffered the highest neutron-flux. The back-wall and the assembly are designed to have lips for cutting/welding at the back-wall replacement. To reduce thermal stress and deformation of the back-wall under neutron irradiation, contact pressure between the back-wall and the assembly is one of dominant factors. Therefore, an investigation was performed for feasible clamping pressure of a mechanical clamp set in limited space around the back-wall. It was clarified that the clamp can give a pressure difference up to 0.4 MPa between the contact pressure and atmosphere pressure in the test cell room. Also a research was performed for the dissimilar metal welding in the back-wall. Use of 309 steel was found adequate as the intermediate filler metal through the research of previous welding. Maintaining a temperature of the target assembly so as to avoid a freezing of liquid lithium is needed at the lithium charge into the loop before the beam injection. The assembly is covered with thermal insulation. Therefore, a research and an investigation were performed for compact and light thermal-insulation effective even under helium (i.e. high heat-conduction) condition of the test cell room. The result was as follows; in the case that a thermal conductivity 0.008 W/m·K of one of found insulation materials is available in the temperature range up to 300degC of the IFMIF target assembly, needed thickness and weight of the insulation were respectively only 8.2 mm and 32 kg. Also a research was performed for high-heat-density heaters to maintain temperature of the back-wall which can not be cover with insulation due to limited space. A heater made of silicon-nitride was found to be adequate. Total heat of 8.4 kW on the back-wall was found to be achievable through an investigations of heater arrange. Also an investigation was performed for remote-handling device to

  4. Structural design of neptunium-bearing assembly for transmutation research

    To study the irradiation performance of the long-life nuclide and to lay a foundation for the 'separation-transmutation' advanced fuel cycle technology, an experimental neptunium-bearing assembly is designed on the basis of the standard fuel assembly of CEFR. In this paper, design principles and structure of the experimental neptunium-bearing assembly are explained in detail. The design analysis and validation are briefly introduced. The design of the experimental assembly can meet the demand of irradiation test. Up to now, the out-of-pile hydraulic test is under way and the manufacture of the assembly is nearly completed. It is to be irradiated in the first row of stainless steel reflector assemblies for about 240 effective full power days. (authors)

  5. Fuel assembly support structure for reactor

    Purpose: To restrict a part or whole of injected molten fuel within a predetermined area by constructing interior surfaces of walls and bottom of a molten fuel container with high-melting materials, fixing at an upper opening a fuel assembly support cover, and forming a thru-hole in the bottom. Constitution: A plurality of cover-fitted support elements for fuel assemblies are mounted and fixed on the supports in the reactor container, with leg pipes inserted in insert holes. Fuel assemblies are fitted in insert holes of the support elements to make up the core. If the power increases due to an accident, causing failure of fuel cans installed in bundle in the assemblies, most of the molten fuel falls to the bottom of the container. As the bottom is graded down from center to periphery, the molten fuel settles much in the peripheral area, but the part is lined with high-melting material so that the part will not be melted. (Yoshihara, H.)

  6. Multipactor Physics, Acceleration, and Breakdown in Dielectric-Loaded Accelerating Structures

    Fischer, Richard P. [Naval Research Lab., Washington, DC (United States); Gold, Steven H. [Naval Research Lab., Washington, DC (United States)

    2016-07-01

    The objective of this 3-year program is to study the physics issues associated with rf acceleration in dielectric-loaded accelerating (DLA) structures, with a focus on the key issue of multipactor loading, which has been found to cause very significant rf power loss in DLA structures whenever the rf pulsewidth exceeds the multipactor risetime (~10 ns). The experiments are carried out in the X-band magnicon laboratory at the Naval Research Laboratory (NRL) in collaboration with Argonne National Laboratory (ANL) and Euclid Techlabs LLC, who develop the test structures with support from the DoE SBIR program. There are two main elements in the research program: (1) high-power tests of DLA structures using the magnicon output (20 MW @11.4 GHz), and (2) tests of electron acceleration in DLA structures using relativistic electrons from a compact X-band accelerator. The work during this period has focused on a study of the use of an axial magnetic field to suppress multipactor in DLA structures, with several new high power tests carried out at NRL, and on preparation of the accelerator for the electron acceleration experiments.

  7. A compact accelerating structure for stacked isochronous cyclotrons

    Meitzler, C. R.; Byeon, J.; McIntyre, P. M.; Rogers, Bob; Sattarov, A.

    2003-03-01

    An accelerator-driven thorium cycle power reactor is being developed, based on a flux-coupled stack of isochronous cyclotrons. (IC) The stack consists of seven independent accelerators (total beam power 15 MW at 1 GeV), stacked on a spacing ˜ 20 cm. The close spacing poses unique problems for the design of the accelerating cavities. We have invented a 4-bar RF dipole structure for the purpose. We have built a cold model and are studying its operating characteristics. The structure will be described. We present measurements of the resonant frequency, parasitic capacitances, and electric and magnetic field distributions in the structure.

  8. Atomic structures of peptide self-assembly mimics

    Makabe, Koki; McElheny, Dan; Tereshko, Valentia; Hilyard, Aaron; Gawlak, Grzegorz; Yan, Shude; Koide, Akiko; Koide, Shohei

    2006-01-01

    Although the β-rich self-assemblies are a major structural class for polypeptides and the focus of intense research, little is known about their atomic structures and dynamics due to their insoluble and noncrystalline nature. We developed a protein engineering strategy that captures a self-assembly segment in a water-soluble molecule. A predefined number of self-assembling peptide units are linked, and the β-sheet ends are capped to prevent aggregation, which yields a mono-dispersed soluble p...

  9. Force Feedback for Assembly of Aircraft Structures

    Jonsson, Marie; Murray, Tom; Robertsson, Anders; Stolt, Andreas; Ossbahr, Gilbert; Nilsson, Klas

    2010-01-01

    Variability in composite manufacture and the limitations in positional accuracy of common industrial robots have hampered automation of assembly tasks within aircraft manufacturing. One way to handle geometry variations and robot compliancy is to use force control. Force control technology utilizes a sensor mounted on the robot to feedback force data to the controller system so instead of being position driven, i.e. programmed to achieve a certain position with the tool, the robot can be prog...

  10. Allophycocyanin and phycocyanin crystal structures reveal facets of phycobilisome assembly.

    Marx, Ailie; Adir, Noam

    2013-03-01

    X-ray crystal structures of the isolated phycobiliprotein components of the phycobilisome have provided high resolution details to the description of this light harvesting complex at different levels of complexity and detail. The linker-independent assembly of trimers into hexamers in crystal lattices of previously determined structures has been observed in almost all of the phycocyanin (PC) and allophycocyanin (APC) structures available in the Protein Data Bank. In this paper we describe the X-ray crystal structures of PC and APC from Synechococcus elongatus sp. PCC 7942, PC from Synechocystis sp. PCC 6803 and PC from Thermosynechococcus vulcanus crystallized in the presence of urea. All five structures are highly similar to other PC and APC structures on the levels of subunits, monomers and trimers. The Synechococcus APC forms a unique loose hexamer that may show the structural requirements for core assembly and rod attachment. While the Synechococcus PC assembles into the canonical hexamer, it does not further assemble into rods. Unlike most PC structures, the Synechocystis PC fails to form hexamers. Addition of low concentrations of urea to T. vulcanus PC inhibits this proteins propensity to form hexamers, resulting in a crystal lattice composed of trimers. The molecular source of these differences in assembly and their relevance to the phycobilisome structure is discussed. PMID:23201474

  11. X-band coaxial standing-wave linear accelerator structure

    A new high efficiency X-Band, standing-wave linear accelerator cavity structure has been developed. It utilizes a shaped coaxial cavity as the coupling cavity between accelerating cavities for π/2 mode operation, hence the overall diameter is extremely small while maintaining a very high shunt impedance. The coupling cavity and accelerating cavity are easily machined on opposite sides of a single cell, eliminating any subassembly steps. Cavity geometries were developed using the computer codes LACC and LALA. Prototype 1.5 MeV and 4.0 MeV, 20 cm long accelerators are now under development. The accelerators employ a stepped field focusing technique to keep the beam focused at low field levels. The beam dynamics code PARMELA was used to optimize the longitudinal bunching and transverse beam characteristics. The accelerator design parameters, as well as experimental results, are presented

  12. Two-beam detuned-cavity electron accelerator structure

    Progress has been made in the theory, development, cavity design and optimization, beam dynamics study, beam transport design, and hardware construction for studies of a detuned two-beam electron accelerator structure.

  13. High energy accelerating structures for high gradient proton linac applications

    The high-energy part of a proton linac, following a drift tube section, accelerates protons and H- ions of energies above 150 MeV. High efficiency and high gradients in the accelerating structure considered for this part of a proton linac are studied. Several known and improved structures working at 1350 MHz were optimized for maximum shunt impedance. The study was performed with the extensive use of a computer code--SUPERFISH. The theoretical results of this study are presented

  14. New linear accelerator (Linac) design based on C-band accelerating structures for SXFEL facility

    ZHANG Meng; GU Qiang

    2011-01-01

    A C-band accelerator structure is one promising technique for a compact XFEL facility.It is also attractive in beam dynamics in maintaining a high quality electron beam,which is an important factor in the performance of a free electron laser.In this paper,a comparison between traditional S-band and C-band accelerating structures is made based on the linac configuration of a Shanghai Soft X-ray Free Electron Laser (SXFEL) facility.Throughout the comprehensive simulation,we conclude that the C-band structure is much more competitive.

  15. Spaced Seed Data Structures for De Novo Assembly.

    Birol, Inanç; Chu, Justin; Mohamadi, Hamid; Jackman, Shaun D; Raghavan, Karthika; Vandervalk, Benjamin P; Raymond, Anthony; Warren, René L

    2015-01-01

    De novo assembly of the genome of a species is essential in the absence of a reference genome sequence. Many scalable assembly algorithms use the de Bruijn graph (DBG) paradigm to reconstruct genomes, where a table of subsequences of a certain length is derived from the reads, and their overlaps are analyzed to assemble sequences. Despite longer subsequences unlocking longer genomic features for assembly, associated increase in compute resources limits the practicability of DBG over other assembly archetypes already designed for longer reads. Here, we revisit the DBG paradigm to adapt it to the changing sequencing technology landscape and introduce three data structure designs for spaced seeds in the form of paired subsequences. These data structures address memory and run time constraints imposed by longer reads. We observe that when a fixed distance separates seed pairs, it provides increased sequence specificity with increased gap length. Further, we note that Bloom filters would be suitable to implicitly store spaced seeds and be tolerant to sequencing errors. Building on this concept, we describe a data structure for tracking the frequencies of observed spaced seeds. These data structure designs will have applications in genome, transcriptome and metagenome assemblies, and read error correction. PMID:26539459

  16. Spaced Seed Data Structures for De Novo Assembly

    Inanç Birol

    2015-01-01

    Full Text Available De novo assembly of the genome of a species is essential in the absence of a reference genome sequence. Many scalable assembly algorithms use the de Bruijn graph (DBG paradigm to reconstruct genomes, where a table of subsequences of a certain length is derived from the reads, and their overlaps are analyzed to assemble sequences. Despite longer subsequences unlocking longer genomic features for assembly, associated increase in compute resources limits the practicability of DBG over other assembly archetypes already designed for longer reads. Here, we revisit the DBG paradigm to adapt it to the changing sequencing technology landscape and introduce three data structure designs for spaced seeds in the form of paired subsequences. These data structures address memory and run time constraints imposed by longer reads. We observe that when a fixed distance separates seed pairs, it provides increased sequence specificity with increased gap length. Further, we note that Bloom filters would be suitable to implicitly store spaced seeds and be tolerant to sequencing errors. Building on this concept, we describe a data structure for tracking the frequencies of observed spaced seeds. These data structure designs will have applications in genome, transcriptome and metagenome assemblies, and read error correction.

  17. Structural Assembly for Cold Plate Cooling

    Zaffetti, Mark A. (Inventor); Taddey, Edmund P. (Inventor)

    2014-01-01

    A device including a structural member having a heat spreader and an electronic device mounted directly to a first surface of the heat spreader of the structural member. The device also includes a cold plate mounted directly to the first surface of the heat spreader of the structural member.

  18. Extensive set of macros for structured programing in OS/360 assembly language (STRCMACS)

    Barth, C. W.

    1975-01-01

    Development of consistent assembly language structured programming techniques has been enhanced by use of assembly macros developed for structured programing. Set of macros was written for IBM OS/360 Assembly language.

  19. The tobacco mosaic virus particle: structure and assembly.

    Klug, A

    1999-01-01

    A short account is given of the physical and chemical studies that have led to an understanding of the structure of the tobacco mosaic virus particle and how it is assembled from its constituent coat protein and RNA. The assembly is a much more complex process than might have been expected from the simplicity of the helical design of the particle. The protein forms an obligatory intermediate (a cylindrical disk composed of two layers of protein units), which recognizes a specific RNA hairpin ...

  20. Fabrication and Characterization of Woodpile Structures for Direct Laser Acceleration

    McGuinness, C.; Colby, E.; England, R.J.; Ng, J.; Noble, R.J.; /SLAC; Peralta, E.; Soong, K.; /Stanford U., Ginzton Lab.; Spencer, J.; Walz, D.; /SLAC; Byer, R.L.; /Stanford U., Ginzton Lab.

    2010-08-26

    An eight and nine layer three dimensional photonic crystal with a defect designed specifically for accelerator applications has been fabricated. The structures were fabricated using a combination of nanofabrication techniques, including low pressure chemical vapor deposition, optical lithography, and chemical mechanical polishing. Limits imposed by the optical lithography set the minimum feature size to 400 nm, corresponding to a structure with a bandgap centered at 4.26 {micro}m. Reflection spectroscopy reveal a peak in reflectivity about the predicted region, and good agreement with simulation is shown. The eight and nine layer structures will be aligned and bonded together to form the complete seventeen layer woodpile accelerator structure.

  1. Design and construction of the clean room for proton beam accelerator assembly

    The objective of this report is to design, construction and evaluation of clean room for proton beam accelerator assembly. The design conditions o Class : 1,000(1,000 ea ft3), o Flow Rate : 200 m3/h m2, o Temperature : 22 deg C±2, o Humidity : 55%±5. The main design results are summarized as follows: o Air-handling unit : Cooling Capacity : 13,500 kcal/h, Heating Capacity : 10,300 kcal/h, Humidity Capacity : 4 kg/h, Flow Rate : 150 CMM o Air Shower : Flow Rate : 35 CMM, Size : 1500 x 1000 x 2200, Material : In-steel, Out-SUS304, Filter : PRE + HEPA, AIR Velocity : 25 m/s o Relief Damper : Size : Φ250, Casing : SS41, Blade : AL, Shaft : SUS304, Weight Ring : SS41, Grill : AL o HEPA Filter Box : Filter Box Size : 670 x 670 x 630, Filter Size : 610 x 610 x 150, Frame: Poly Wood, Media : Glass Fiber, Filter Efficiency : 0.3μm, 99.97%, Separator : AL, Flow Rate : 17 CMM, Damper Size : Φ300 Following this report will be used important data for the design, construction, operation and maintenance of the clean room, for high precision apparatus assembly laboratory

  2. An optimized neutron-beam shaping assembly for accelerator-based BNCT

    Different materials and proton beam energies have been studied in order to search for an optimized neutron production target and beam shaping assembly for accelerator-based BNCT. The solution proposed in this work consists of successive stacks of Al, polytetrafluoroethylene, commercially known as Teflon[reg ], and LiF as moderator and neutron absorber, and Pb as reflector. This assembly is easy to build and its cost is relatively low. An exhaustive Monte Carlo simulation study has been performed evaluating the doses delivered to a Snyder model head phantom by a neutron production Li-metal target based on the 7Li(p,n)7Be reaction for proton bombarding energies of 1.92, 2.0, 2.3 and 2.5 MeV. Three moderator thicknesses have been studied and the figures of merit show the advantage of irradiating with near-resonance-energy protons (2.3 MeV) because of the relatively high neutron yield at this energy, which at the same time keeps the fast neutron healthy tissue dose limited and leads to the lowest treatment times. A moderator of 34 cm length has shown the best performance among the studied cases

  3. Structural Diversity of DNA-Coated Particle Assemblies

    Starr, Francis W.

    2012-02-01

    Custom designed nanoparticles (NP) or colloids with specific recognition offer the possibility to control the phase behavior and structure of particle assemblies for a range of applications. One approach to realize these new materials is by attaching DNA to a core particle; the hybridization of double-stranded DNA between particles results in the spontaneous assembly of higher-order structures. Control of the assembled state can be achieved by adjusting several parameters, including sequence selectivity, DNA link orientation, DNA length and flexibility, and the balance between the length of links and non-specific repulsive interactions. I will discuss the results of a coarse-grained molecular model for DNA-linked nanoparticles that helps to rationalize experimental findings and demonstrate new routes to control the assembled structure. We examine how the number and orientation of strands affects the structure, phase behavior, and dynamics. We show that it is possible to realize unusual phase diagrams with many thermodynamically distinct phases, both amorphous and crystal. We further examine the parameters that control the pathways of assembly, which are critical to avoid kinetic bottlenecks. Finally, we discuss strategies to create highly anisoptropic structures using both isotropic and anisotropic core units.

  4. Structural simulation and modeling for assembly in real space

    FIESTA (Finite Element Structural analysis for Assembly) is a large scale simulation, which concerns a simulation space to bring real world in digital space, such as so named either virtual reality or virtual facility. In order to establish a huge and complex object like nuclear facilities of a real world, there are lack of methodology and technology for reproducing facilities in digital space. FIESTA attempts to realize an assembly structural analysis for supplying one of the methodologies to reproduce facilities in digital space. The first attempt of the structural analysis for assembly is accomplished by finite element analysis by integrating parts of facilities. Since the structural analysis for assembly requests massive calculation, parallel and distributed computing was applied for the computational environment. It has been practiced numerical experiments for a test reactor driven by JAEA. The structural analysis for assembly by finite element method is confirmed to be able to analyze a huge and complex facility and show results of numerical experiment by applying to a test reactor driven by JAEA. (author)

  5. Simulation and design of the photonic crystal microwave accelerating structure

    The authors have derived the global band gaps for general two-dimensional (2D) photonic crystal microwave accelerating structures formed by square or triangular arrays of metal posts. A coordinate-space, finite-difference code was used to calculate the complete dispersion curves for the lattices. The fundamental and higher frequency global photonic band gaps were determined numerically. The structure formed by triangular arrays of metal posts with a missing rod at the center has advantages of higher-order-modes (HOM) suppression and main mode restriction under the condition of a/b<0.2. The relationship between the RF properties and the geometrical parameters have been studied for the 9.37 GHz photonic crystal accelerating structure. The Rs, Q, Rs/Q of the new structure may be comparable to the disk-loaded accelerating structure. (authors)

  6. Electrostatic Force Microscopy of Self Assembled Peptide Structures

    Clausen, Casper Hyttel; Dimaki, Maria; Pantagos, Spyros P.;

    2011-01-01

    In this report electrostatic force microscopy (EFM) is used to study different peptide self-assembled structures, such as tubes and particles. It is shown that not only geometrical information can be obtained using EFM, but also information about the composition of different structures. In...

  7. Design and fabrication of a continuous wave electron accelerating structure

    The Physics Institute of Sao Paulo University, SP, Brazil is fabricating a 31 MeV cw racetrack microtron (RTM) designed for nuclear physics research. This is a two-stage microtron that includes a 1.93 MeV injector linac feeding a five-turn microtron booster. After 28 turns, the main microtron delivers a 31 MeV continuous electron beam. The objective of this work is the development and fabrication of an advanced, beta=l, cw accelerating structure for the main microtron. The accelerating structure will be a side-coupled structure (SCS). We have chosen this kind of cavity, because it presents good vacuum properties, allows operation at higher accelerating electric fields and has a shunt impedance better than 81 MQ/m, with a high coupling factor ( 3 - 5%). The engineering design is the Los Alamos one. There will be two tuning plungers placed at both ends of the accelerating structure. They automatically and quickly compensate for the variation in the resonance frequency caused by changes in the structure temperature. Our design represents an advanced accelerating structure with the optimum SCS properties coexisting with the plunger's good tuning properties. (author)

  8. Experimental demonstration of dielectric structure based two beam acceleration.

    Gai, W.; Conde, M. E.; Konecny, R.; Power, J. G.; Schoessow, P.; Sun, X.; Zou, P.

    2000-11-28

    We report on the experimental results of the dielectric based two beam accelerator (step-up transformer). By using a single high charge beam, we have generated and extracted a high power RF pulse from a 7.8 GHz primary dielectric structure and then subsequently transferred to a second accelerating structure with higher dielectric constant and smaller transverse dimensions. We have measured the energy change of a second (witness) beam passing through the acceleration stage. The measured gradient is >4 times the deceleration gradient. The detailed experiment of set-up and results of the measurements are dimmed. Future plans for the development of a 100 MeV demonstration accelerator based on this technique is presented.

  9. Accelerated probabilistic inference of RNA structure evolution

    Holmes Ian

    2005-03-01

    Full Text Available Abstract Background Pairwise stochastic context-free grammars (Pair SCFGs are powerful tools for evolutionary analysis of RNA, including simultaneous RNA sequence alignment and secondary structure prediction, but the associated algorithms are intensive in both CPU and memory usage. The same problem is faced by other RNA alignment-and-folding algorithms based on Sankoff's 1985 algorithm. It is therefore desirable to constrain such algorithms, by pre-processing the sequences and using this first pass to limit the range of structures and/or alignments that can be considered. Results We demonstrate how flexible classes of constraint can be imposed, greatly reducing the computational costs while maintaining a high quality of structural homology prediction. Any score-attributed context-free grammar (e.g. energy-based scoring schemes, or conditionally normalized Pair SCFGs is amenable to this treatment. It is now possible to combine independent structural and alignment constraints of unprecedented general flexibility in Pair SCFG alignment algorithms. We outline several applications to the bioinformatics of RNA sequence and structure, including Waterman-Eggert N-best alignments and progressive multiple alignment. We evaluate the performance of the algorithm on test examples from the RFAM database. Conclusion A program, Stemloc, that implements these algorithms for efficient RNA sequence alignment and structure prediction is available under the GNU General Public License.

  10. Induced activity in accelerator structures, air and water

    Stevenson, Graham Roger

    2001-01-01

    A summary is given of several 'rules of thumb' which can be used to predict the formation and decay of radionuclides in the structure of accelerators together with the dose rates from the induced radioactivity. Models are also given for the activation of gases (air of the accelerator vault) and liquids (in particular cooling water), together with their transport front the activation region to the release point. (18 refs).

  11. Accelerating the design and testing of LEU fuel assemblies for conversion of Russian-designed research reactors outside Russia

    This paper identifies proposed geometries and loading specifications of LEU tube-type and pin-type test assemblies that would be suitable for accelerating the conversion of Russian-designed research reactors outside of Russia if these fuels are manufactured, qualified by irradiation testing, and made commercially available in Russia. (author)

  12. Design and construction of standing wave accelerating structures at TUE

    Two standing wave accelerating structures have been built for the operation of two AVF racetrack microtrons (RTM). For the first RTM a 3 cell 1.3 GHz on axis coupled standing wave structure has been designed to accelerate a 50 A peak current beam in 9 steps from the injection energy of 6 MeV to a final energy of 25 MeV. The beam will be used as drive beam for the free electron laser TEUFEL. The second structure accelerates a 7.5 mA beam in 13 steps from the injection energy of 10 MeV, to a maximum energy of 75 MeV. This 9 cell on-axis coupled structure operates at 3 GHz and was designed with a relatively large aperture radius (8 mm) in order to avoid limitations on the RTM's acceptance. Design, fabrication and testing of the structures have been done in house. For the design of the structures the combination of the codes Superfish and Mafia has been used. Low and high power tests proved that the structures live up to the demands. With the experiences gained a design for the accelerating structure of the H- linac of the ESS project has been made. The design of the cells as well as a novel type of single cell bridge coupler will be presented. (author)

  13. In-Space Structural Assembly: Applications and Technology

    Belvin, W. Keith; Doggett, Bill R.; Watson, Judith J.; Dorsey, John T.; Warren, Jay; Jones, Thomas C.; Komendera, Erik E.; Mann, Troy O.; Bowman, Lynn

    2016-01-01

    As NASA exploration moves beyond earth's orbit, the need exists for long duration space systems that are resilient to events that compromise safety and performance. Fortunately, technology advances in autonomy, robotic manipulators, and modular plug-and-play architectures over the past two decades have made in-space vehicle assembly and servicing possible at acceptable cost and risk. This study evaluates future space systems needed to support scientific observatories and human/robotic Mars exploration to assess key structural design considerations. The impact of in-space assembly is discussed to identify gaps in structural technology and opportunities for new vehicle designs to support NASA's future long duration missions.

  14. Monte Carlo Modeling of Fast Sub-critical Assembly with MOX Fuel for Research of Accelerator-Driven Systems

    Polanski, A.; Barashenkov, V.; Puzynin, I.; Rakhno, I.; Sissakian, A.

    It is considered a sub-critical assembly driven with existing 660 MeV JINR proton accelerator. The assembly consists of a central cylindrical lead target surrounded with a mixed-oxide (MOX) fuel (PuO2 + UO2) and with reflector made of beryllium. Dependence of the energetic gain on the proton energy, the neutron multiplication coefficient, and the neutron energetic spectra have been calculated. It is shown that for subcritical assembly with a mixed-oxide (MOX) BN-600 fuel (28%PuO 2 + 72%UO2) with effective density of fuel material equal to 9 g/cm 3 , the multiplication coefficient keff is equal to 0.945, the energetic gain is equal to 27, and the neutron flux density is 1012 cm˜2 s˜x for the protons with energy of 660 MeV and accelerator beam current of 1 uA.

  15. ELECTRONIC STRUCTURE OF CLUSTER ASSEMBLED Al12C (Si) SOLID

    QUAN HONG-JUN; GONG XIN-GAO

    2000-01-01

    The electronic structures of the cluster-assembled solid Al12C (Si) are studied by the ab initio method. We find that Al12C (Si) can solidify into a van der Waals solid. The electronic band structures show very weak dispersion. The main features in the electronic structure of cluster are retained in the solid, and an energy gap up to about 1.5 eV is observed for Al12C and Al12Si solids.

  16. Design of a beam shaping assembly and preliminary modelling of a treatment room for accelerator-based BNCT at CNEA

    This work reports on the characterisation of a neutron beam shaping assembly (BSA) prototype and on the preliminary modelling of a treatment room for BNCT within the framework of a research programme for the development and construction of an accelerator-based BNCT irradiation facility in Buenos Aires, Argentina. The BSA prototype constructed has been characterised by means of MCNP simulations as well as a set of experimental measurements performed at the Tandar accelerator at the National Atomic Energy Commission of Argentina. - Highlights: ► Characterisation of a neutron beam shaping assembly for accelerator-based BNCT. ► Measurements: total and epi-cadmium neutron fluxes and beam homogeneity. ► Calculations: Monte Carlo simulations with the MCNP code. ► Measured and calculated figure-of-merit parameters in agreement with those of IAEA. ► Initial MCNP dose calculations for a treatment room to define future design actions.

  17. Modified PARMILA code for new accelerating structures

    The PARMILA code was originally developed as a numerical tool to design and simulate the beam performance of the drift-tube linac (DTL). The authors have extended PARMILA to the design of both the coupled-cavity linac (CCL) and the coupled-cavity drift-tube linac (CCDTL). They describe the new design and simulation features associated with these linac structures and improvements to the code that facilitate a seamless linac design process

  18. Design, Fabrication and Measurement of the First Rounded Damped Detuned Accelerator Structure (RDDS1)

    As a joint effort in the JLC/NLC research program, the authors have developed a new type of damped detuned accelerator structure with optimized round-shaped cavities (RDDS). This paper discusses some important R and D aspects of the first structure in this series (RDDS1). The design aspects covered are the cell design with sub-MHz precision, HOM detuning, coupling and damping technique and wakefield simulation. The fabrication issues covered are ultra-precision cell machining with micron accuracy, assembly and diffusion bonding technologies to satisfactorily meet bookshelf, straightness and cell rotational alignment requirements. The measurements described are the RF properties of single cavities and complete accelerator section, as well as wakefields from the ASSET tests at SLAC. Finally, future improvements are also discussed

  19. Highly Compact Accelerator-Driven Subcritical Assembly for Medical and Industrial Applications

    A novel, highly compact, fusion neutron source (CNS) based on a coaxial electrostatic accelerator is under development at the Lawrence Berkeley National Laboratory. This source is designed to generate up to ∼1012 D-D n/s. This source intensity is an order of magnitude too small for Boron Neutron Capture Therapy (BNCT) applications. The objective of this project is to assess the feasibility of using a small, safe and inexpensive subcritical fission assembly to multiply the fusion neutrons by a factor of (ge)30. The overall design objective is to get a treatment time for deep seated rain tumors that does not significantly increase beyond one hour when the effective multiplication factor of the SCM is keff = 0.98. There are two major parts to this study: the optimization of the Sub-Critical Multiplier (SCM) and the optimization of the Beam Shaping Assembly (BSA), including the reflector for both subsystems. The SCM optimization objective is to maximize the current of neutrons that leak out from the SCM in the direction of the patient, without exceeding the maximum permissible keff. Minimizing the required uranium inventory is another objective. SCM design variables considered include the uranium enrichment level in the range not exceeding 20% 235U (for proliferation concerns), SCM geometry and dimensions, fuel thickness and moderator thickness. The objective of the BSA optimization is to maximize the tumor dose rate using the optimal SCM while maintaining a tumor-to-normal tissue dose ratio of at least 20 to 12.5 (corresponding to the tumor control dose and to the healthy tissue dose limit). The BSA design variables include its shape, dimensions and composition. The reflector optimization is, in fact, an integral part of the SCM optimization and of the BSA optimization. The reflector design variables are composition and thickness. The study concludes that it is not quite feasible to achieve the project objective. Nevertheless, it appears feasible to develop a

  20. Laser fields in dynamically ionized plasma structures for coherent acceleration

    Luu-Thanh, Ph.; Pukhov, A.; Kostyukov, I.

    2015-01-01

    With the emergence of the CAN (Coherent Amplification Network) laser technology, a new scheme for direct particle acceleration in periodic plasma structures has been proposed. By using our full electromagnetic relativistic particle-in-cell (PIC) simulation code equipped with ionisation module, we simulate the laser fields dynamics in the periodic structures of different materials. We study how the dynamic ionization influences the field structure.

  1. Assembly and Structural Evolution of Micelleplexes

    Jiang, Yaming; Sprouse, Dustin; Laaser, Jennifer; Reineke, Theresa; Lodge, Timothy

    Cationic micelles complex with DNA to form micelleplexes, which are attractive vehicles for gene delivery. We investigate the formation and structural evolution of micelleplexes in buffered solutions. The micelles are composed of poly((2-dimethylamino)ethyl methacrylate)-block-poly(n-butyl methacrylate). The formation of the micelleplexes is monitored via turbidimetric titration. With DNA oligomers, solutions of the complexes are homogeneous until near the charge neutral point, at which point the complexes precipitate. With plasmid DNA, more than a stoichiometric amount of DNA is needed to reach the inhomogeneous region, which suggests that binding is partially inhibited. This inhibition is not fully relieved when the plasmid DNA is linearized, suggesting that the stiffness of the DNA is the main source of the inhibition. With micelles in excess, the micelleplexes formed at low ionic strength exhibit bimodal size distributions and remain stable in solution. With DNA in excess, soluble micelleplexes aggregate over time and precipitate. We explain the structural evolution of the micelleplexes as an interplay between kinetic trapping and thermodynamic equilibrium, and compare the results for DNA with those for a flexible polyanion.

  2. Structure and Assembly Mechanism for Heteromeric Kainate Receptors

    Kumar, Janesh; Schuck, Peter; Mayer, Mark L. (NIH)

    2012-10-25

    Native glutamate receptor ion channels are tetrameric assemblies containing two or more different subunits. NMDA receptors are obligate heteromers formed by coassembly of two or three divergent gene families. While some AMPA and kainate receptors can form functional homomeric ion channels, the KA1 and KA2 subunits are obligate heteromers which function only in combination with GluR57. The mechanisms controlling glutamate receptor assembly involve an initial step in which the amino terminal domains (ATD) assemble as dimers. Here, we establish by sedimentation velocity that the ATDs of GluR6 and KA2 coassemble as a heterodimer of K{sub d} 11 nM, 32,000-fold lower than the K{sub d} for homodimer formation by KA2; we solve crystal structures for the GluR6/KA2 ATD heterodimer and heterotetramer assemblies. Using these structures as a guide, we perform a mutant cycle analysis to probe the energetics of assembly and show that high-affinity ATD interactions are required for biosynthesis of functional heteromeric receptors.

  3. Verification Test of Automated Robotic Assembly of Space Truss Structures

    Rhodes, Marvin D.; Will, Ralph W.; Quach, Cuong C.

    1995-01-01

    A multidisciplinary program has been conducted at the Langley Research Center to develop operational procedures for supervised autonomous assembly of truss structures suitable for large-aperture antennas. The hardware and operations required to assemble a 102-member tetrahedral truss and attach 12 hexagonal panels were developed and evaluated. A brute-force automation approach was used to develop baseline assembly hardware and software techniques. However, as the system matured and operations were proven, upgrades were incorporated and assessed against the baseline test results. These upgrades included the use of distributed microprocessors to control dedicated end-effector operations, machine vision guidance for strut installation, and the use of an expert system-based executive-control program. This paper summarizes the developmental phases of the program, the results of several assembly tests, and a series of proposed enhancements. No problems that would preclude automated in-space assembly or truss structures have been encountered. The test system was developed at a breadboard level and continued development at an enhanced level is warranted.

  4. 29 CFR 1926.754 - Structural steel assembly.

    2010-07-01

    ... Transportation Officials (AASHTO) and other organizations. (See 23 CFR 625.4). Many of these incorporated..., Div. II, § 3.2.1, 15th edition, 1992, which FHWA incorporates by reference in 23 CFR 625.4). FHWA also... 29 Labor 8 2010-07-01 2010-07-01 false Structural steel assembly. 1926.754 Section 1926.754...

  5. From coordination polymers to hierarchical self-assembled structures

    Yan, Y.; Keizer, de A.; Cohen Stuart, M.A.; Besseling, N.A.M.

    2011-01-01

    In this review, novel hierarchical self-assembled structures based on reversible organo-metallic supramolecular polymers are discussed. Firstly, we discuss recent advances in the field of coordination polymers, considering cases in which transition metal ions and bis- or multiligands are used to bui

  6. High-Throughput Analysis of RNA Structure and Ribonucleoprotein Assembly

    McGinnis, Jennifer L.; Duncan, Caia D. S.; Weeks, Kevin M.

    2016-01-01

    RNA folds to form complex structures vital to many cellular functions. Proteins facilitate RNA folding at both the secondary and tertiary structure levels. An absolute prerequisite for understanding RNA folding and ribonucleoprotein (RNP) assembly reactions is a complete understanding of the RNA structure at each stage of the folding or assembly process. Here we provide a guide for comprehensive and high-throughput analysis of RNA secondary and tertiary structure using SHAPE and hydroxyl radical footprinting. As an example of the strong and sometimes surprising conclusions that can emerge from high-throughput analysis of RNA folding and RNP assembly, we summarize the structure of the bI3 group I intron RNA in four distinct states. Dramatic structural rearrangements occur in both secondary and tertiary structure as the RNA folds from the free state to the active, six-component, RNP complex. As high-throughput and high-resolution approaches are applied broadly to large protein-RNA complexes, other proteins previously viewed as making simple contributions to RNA folding are also likely to be found to exert multifaceted, long-range, cooperative, and non-additive effects on RNA folding. These protein-induced contributions add another level of control, and potential regulatory function, in RNP complexes. PMID:20946765

  7. Fabrication of the CERN/PSI/ST X-Band accelerating structures

    Dehler, Micha; Gudkov, Dmitry; Lebet, Serge; Riddone, Germana; Shi, Jiaru; Citterio, Alessandro; Zennaro, Riccardo; D'Auria, Gerardo; Serpico, Claudio

    2011-01-01

    In a collaboration between CERN, PSI and Sincrotrone Trieste (ST), a multi- purpose X-band accelerating structure has been designed and fabricated, used for high gradients tests in the CLIC structure testing program and in the FEL projects of PSI and ST. The structure has 72 cells with a phase advance of 5 pi/6 and includes upstream and down-stream wakefield monitors to measure the beam alignment. The SLAC mode launcher design is used to feed it with RF power. Following the CERN fabrication procedures for high-gradient structure, diffusion bonding and brazing in hydrogen atmosphere is used to assemble the cells. After tuning, a vacuum bakeout is required before the feedthroughs for the wake field monitors are welded in as a last step. We describe the experiences gained in finishing the first two structures out of a series of four and present the results from the RF tuning and low level RF tests.

  8. RF impedance measurements on the DARHT-II accelerator intercell assembly

    Fawley, William M.; Eylon, Shmuel; Briggs, Richard

    2003-05-05

    We report upon recent experimental measurements made of RF properties of the intercell assembly of the second axis accelerator[1] of Dual Axis Radiographic Hydrodynamic Test (DARHT) facility at LANL. The intercells provide both pumping and diagnostic access to the main DARHT-II beamline. Their design includes a pumping plenum separated from the main beam pipe by return current rods together with RF shielding provided by a copper-coated stainless steel mesh. Measurements using the twin lead technique (see Ref. [2]) at low frequencies (f < 200 MHz) suggest a constant value for the ratio h of the radial and azimuthal magnetic field components to which the transverse impedance is linearly related. We find that these results compare favorably to predictions from a simple analytic, lumped circuit model which includes the effects of the mesh and return current rods. We also present RF loop-to-loop frequency scans above beam pipe cutoff ({approx}600 MHz) showing the existence of many RF modes with relatively high Q's.

  9. Degradation on a PTFE/Nafion membrane electrode assembly with accelerating degradation technique

    Jao, Ting-Chu [Department of Mechanical Engineering, Yuan Ze University, No. 135, Yuandong Rd., Zhongli City, Taoyuan County 320 (China); Ke, Shih-Tsung [Fuel Cell Center, Yuan Ze University, No. 135, Yuandong Rd., Zhongli City, Taoyuan County 320 (China); Chi, Pei-Hung [Department of Mechanical Engineering, Lee-Ming Institute of Technology, No. 2-2, Lee Zhuan Road, Taishan Township, Taipei Country 243 (China); Jung, Guo-Bin; Chan, Shih-Hung [Department of Mechanical Engineering, Yuan Ze University, No. 135, Yuandong Rd., Zhongli City, Taoyuan County 320 (China); Fuel Cell Center, Yuan Ze University, No. 135, Yuandong Rd., Zhongli City, Taoyuan County 320 (China)

    2010-07-15

    Cost and durability are the main issues of Proton exchange membrane fuel cells (PEMFCs) commercializing. This study uses the accelerate degradation technique to analyze the durability of low cost PTFE/Nafion membrane electrode assembly (MEA). Before the MEA degradation experiment, the MEA must be activated at 65 C until the performance is stable. Then increase the operation temperature to 80 C. The experimental process for MEA degradation contains three steps in one cycle. The first step is to open circuit voltage (OCV) for 30 s under R.H. 100%. Then, set 0.6V for 150 s under R.H. 100%. The final step is to set 0.6V for 120 s under R.H. 0%. These three steps take around 5 min to complete. This MEA degradation experiment process includes the OCV, potential cycles, and R.H. cycles. This study uses the polarization curve, AC impedance, cyclic voltammetry (CV), linear sweep voltammetry (LSV), equations and equivalent circuit to analyze state of the MEA. At less than 160 experiment cycles, the result show that catalyst degradation is the main reason for the decay of MEA. After 280 cycles, the MEA begins to exhibit creep deformation due to the R.H. cycle. Electrochemical surface area and high frequency resistance can be used to estimate the degree of MEA degradation approximately. (author)

  10. Cosmic Ray Acceleration during Large Scale Structure Formation

    Blasi, P

    2004-01-01

    Clusters of galaxies are storage rooms of cosmic rays. They confine the hadronic component of cosmic rays over cosmological time scales due to diffusion, and the electron component due to energy losses. Hadronic cosmic rays can be accelerated during the process of structure formation, because of the supersonic motion of gas in the potential wells created by dark matter. At the shock waves that result from this motion, charged particles can be energized through the first order Fermi process. After discussing the most important evidences for non-thermal phenomena in large scale structures, we describe in some detail the main issues related to the acceleration of particles at these shock waves, emphasizing the possible role of the dynamical backreaction of the accelerated particles on the plasmas involved.

  11. Vacuum arc localization in CLIC prototype radio frequency accelerating structures

    AUTHOR|(CDS)2091976; Koivunen, Visa

    2016-04-04

    A future linear collider capable of reaching TeV collision energies should support accelerating gradients beyond 100 MV/m. At such high fields, the occurrence of vacuum arcs have to be mitigated through conditioning, during which an accelerating structure’s resilience against breakdowns is slowly increased through repeated radio frequency pulsing. Conditioning is very time and resource consuming, which is why developing more efficient procedures is desirable. At CERN, conditioning related research is conducted at the CLIC high-power X-band test stands. Breakdown localization is an important diagnostic tool of accelerating structure tests. Abnormal position distributions highlight issues in structure design, manufacturing or operation and may consequently help improve these processes. Additionally, positioning can provide insight into the physics of vacuum arcs. In this work, two established positioning methods based on the time-difference-ofarrival of radio frequency waves are extended. The first method i...

  12. Welding machine and welding process for nuclear fuel assembly structures

    The welding device comprises a mounting jig which receives the guide tubes and the assembly supporting structures in the desired spatial orientation. It also comprises a welding head which can travel on rails along the length of the guide tubes and has at least a welding spring chuck movable in two axes and rotatable relative to the welding machine; the spring chuck can pass between two adjacent tube rows and takes a tubes where a weld is necessary. The welding spring chuck can apply spot-welding pulses. This is used for the assembly of guide tubes and bundles for water-cooled nuclear reactors

  13. Acceleration of stable interface structure searching using a kriging approach

    Kiyohara, Shin; Oda, Hiromi; Tsuda, Koji; Mizoguchi, Teruyasu

    2016-04-01

    Crystalline interfaces have a tremendous impact on the properties of materials. Determination of the atomic structure of the interface is crucial for a comprehensive understanding of the interface properties. Despite this importance, extensive calculation is necessary to determine even one interface structure. In this study, we apply a technique called kriging, borrowed from geostatistics, to accelerate the determination of the interface structure. The atomic structure of simplified coincidence-site lattice interfaces were determined using the kriging approach. Our approach successfully determined the most stable interface structure with an efficiency almost 2 orders of magnitude better than the traditional “brute force” approach.

  14. Dielectric-Lined High-Gradient Accelerator Structure

    Rectangular particle accelerator structures with internal planar dielectric elements have been studied, with a view towards devising structures with lower surface fields for a given accelerating field, as compared with structures without dielectrics. Success with this concept is expected to allow operation at higher accelerating gradients than otherwise on account of reduced breakdown probabilities. The project involves studies of RF breakdown on amorphous dielectrics in test cavities that could enable high-gradient structures to be built for a future multi-TeV collider. The aim is to determine what the limits are for RF fields at the surfaces of selected dielectrics, and the resulting acceleration gradient that could be achieved in a working structure. The dielectric of principal interest in this study is artificial CVD diamond, on account of its advertised high breakdown field (∼2 GV/m for dc), low loss tangent, and high thermal conductivity. Experimental studies at mm-wavelengths on materials and structures for achieving high acceleration gradient were based on the availability of the 34.3 GHz third-harmonic magnicon amplifier developed by Omega-P, and installed at the Yale University Beam Physics Laboratory. Peak power from the magnicon was measured to be about 20 MW in 0.5 (micro)s pulses, with a gain of 54 dB. Experiments for studying RF high-field effects on CVD diamond samples failed to show any evidence after more than 105 RF pulses of RF breakdown up to a tangential surface field strength of 153 MV/m; studies at higher fields were not possible due to a degradation in magnicon performance. A rebuild of the tube is underway at this writing. Computed performance for a dielectric-loaded rectangular accelerator structure (DLA) shows highly competitive properties, as compared with an existing all-metal structure. For example, comparisons were made of a DLA structure having two planar CVD diamond elements with a all-metal CERN structure HDS operating at 30 GHz

  15. Dielectric-Lined High-Gradient Accelerator Structure

    Jay L. Hirshfield

    2012-04-24

    Rectangular particle accelerator structures with internal planar dielectric elements have been studied, with a view towards devising structures with lower surface fields for a given accelerating field, as compared with structures without dielectrics. Success with this concept is expected to allow operation at higher accelerating gradients than otherwise on account of reduced breakdown probabilities. The project involves studies of RF breakdown on amorphous dielectrics in test cavities that could enable high-gradient structures to be built for a future multi-TeV collider. The aim is to determine what the limits are for RF fields at the surfaces of selected dielectrics, and the resulting acceleration gradient that could be achieved in a working structure. The dielectric of principal interest in this study is artificial CVD diamond, on account of its advertised high breakdown field ({approx}2 GV/m for dc), low loss tangent, and high thermal conductivity. Experimental studies at mm-wavelengths on materials and structures for achieving high acceleration gradient were based on the availability of the 34.3 GHz third-harmonic magnicon amplifier developed by Omega-P, and installed at the Yale University Beam Physics Laboratory. Peak power from the magnicon was measured to be about 20 MW in 0.5 {micro}s pulses, with a gain of 54 dB. Experiments for studying RF high-field effects on CVD diamond samples failed to show any evidence after more than 10{sup 5} RF pulses of RF breakdown up to a tangential surface field strength of 153 MV/m; studies at higher fields were not possible due to a degradation in magnicon performance. A rebuild of the tube is underway at this writing. Computed performance for a dielectric-loaded rectangular accelerator structure (DLA) shows highly competitive properties, as compared with an existing all-metal structure. For example, comparisons were made of a DLA structure having two planar CVD diamond elements with a all-metal CERN structure HDS

  16. Amyloid Structure and Assembly: Insights from Scanning Transmission Electron Microscopy

    Goldsbury, C.; Wall, J.; Baxa, U.; Simon, M. N.; Steven, A. C.; Engel, A.; Aebi, U.; Muller, S. A.

    2011-01-01

    Amyloid fibrils are filamentous protein aggregates implicated in several common diseases such as Alzheimer's disease and type II diabetes. Similar structures are also the molecular principle of the infectious spongiform encephalopathies such as Creutzfeldt-Jakob disease in humans, scrapie in sheep, and of the so-called yeast prions, inherited non-chromosomal elements found in yeast and fungi. Scanning transmission electron microscopy (STEM) is often used to delineate the assembly mechanism and structural properties of amyloid aggregates. In this review we consider specifically contributions and limitations of STEM for the investigation of amyloid assembly pathways, fibril polymorphisms and structural models of amyloid fibrils. This type of microscopy provides the only method to directly measure the mass-per-length (MPL) of individual filaments. Made on both in vitro assembled and ex vivo samples, STEM mass measurements have illuminated the hierarchical relationships between amyloid fibrils and revealed that polymorphic fibrils and various globular oligomers can assemble simultaneously from a single polypeptide. The MPLs also impose strong constraints on possible packing schemes, assisting in molecular model building when combined with high-resolution methods like solid-state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR).

  17. Self-assembly protocol design for periodic multicomponent structures.

    Jacobs, William M; Frenkel, Daan

    2015-12-14

    Assembling molecular superstructures with many distinct components will allow unprecedented control over morphology at the nanoscale. Recently, this approach has been used to assemble periodic structures with precisely defined features, such as repeating arrays of pores and channels, using a large number of building blocks. Here we propose a predictive tool that allows us to optimize the nucleation and growth of unbounded, ordered structures. In what follows, we call these structures 'crystals', even though they may only be periodic in one or two dimensions. We find that the nucleation barriers and growth pathways for crystals consisting of many components exhibit generic features that are very different from those of simple crystals. To illustrate the very non-classical nature of the nucleation and growth of such structures, we study the formation of one and two-dimensional crystals with multicomponent unit cells. We find that, whilst the boundaries in the non-periodic dimensions significantly affect the stabilities of these crystals, the nucleation barriers are largely determined by the local connectivity of the associated bulk crystal and are independent of the number of distinct components in the unit cell. We predict that the self-assembly of crystals with complex morphologies can be made to follow specific pathways toward the target structure that successively incorporate key features of the three-dimensional target structure. In contrast with simple crystals, it is possible to tune the kinetics of nucleation and growth separately, thus minimizing defect formation. We show how control over self-assembly pathways can be used to optimize the kinetics of formation of extended structures with arbitrary nanoscale patterns. PMID:26404794

  18. Photonic Band Gap structures: A new approach to accelerator cavities

    Kroll, N. [California Univ., San Diego, La Jolla, CA (United States). Dept. of Physics]|[Stanford Linear Accelerator Center, Menlo Park, CA (United States); Smith, D.R.; Schultz, S. [California Univ., San Diego, La Jolla, CA (United States). Dept. of Physics

    1992-12-31

    We introduce a new accelerator cavity design based on Photonic Band Gap (PGB) structures. The PGB cavity consists of a two-dimensional periodic array of high dielectric, low loss cylinders with a single removal defect, bounded on top and bottom by conducting sheets. We present the results of both numerical simulations and experimental measurements on the PGB cavity.

  19. Photonic Band Gap structures: A new approach to accelerator cavities

    We introduce a new accelerator cavity design based on Photonic Band Gap (PGB) structures. The PGB cavity consists of a two-dimensional periodic array of high dielectric, low loss cylinders with a single removal defect, bounded on top and bottom by conducting sheets. We present the results of both numerical simulations and experimental measurements on the PGB cavity

  20. Status of the Fatigue Studies on the CLIC Accelerating Structures

    Calatroni, S; Neupert, H; Wuensch, Walter; CERN. Geneva

    2006-01-01

    The need for high accelerating gradients for the future multi-TeV e+e- Compact Linear Collider (CLIC) imposes considerable constraints on the materials of the accelerating structures. The surfaces exposed to high pulsed RF (Radio Frequency) currents are subject to cyclic thermal stresses which are expected to induce surface break up by fatigue. Since no fatigue data exists in the literature up to very large numbers of cycles and for the particular stress pattern present in RF cavities, a comprehensive study of copper alloys in this parameter range has been initiated. Fatigue data for selected copper alloys in different states are presented

  1. H-Mode Accelerating Structures with PMQ Beam Focusing

    Kurennoy, Sergey S; O'Hara, James F; Olivas, Eric R; Wangler, Thomas P

    2011-01-01

    We have developed high-efficiency normal-conducting RF accelerating structures by combining H-mode resonator cavities and a transverse beam focusing by permanent-magnet quadrupoles (PMQ), for beam velocities in the range of a few percent of the speed of light. The shunt impedance of inter-digital H-mode (IH-PMQ) structures is 10-20 times higher than that of a conventional drift-tube linac, while the transverse size is 4-5 times smaller. Results of the combined 3-D modeling - electromagnetic computations, multi-particle beam-dynamics simulations with high currents, and thermal-stress analysis - for an IH-PMQ accelerator tank are presented. The accelerating field profile in the tank is tuned to provide the best propagation of a 50-mA deuteron beam using coupled iterations of electromagnetic and beam-dynamics modeling. Measurements of a cold model of the IH-PMQ tank show a good agreement with the calculations. H-PMQ accelerating structures following a short RFQ can be used both in the front end of ion linacs or ...

  2. Passive tailoring of laser-accelerated ion beam cut-off energy by using double foil assembly

    A double foil assembly is shown to be effective in tailoring the maximum energy produced by a laser-accelerated proton beam. The measurements compare favorably with adiabatic expansion simulations, and particle-in-cell simulations. The arrangement proposed here offers for some applications a simple and passive way to utilize simultaneously highest irradiance lasers that have best laser-to-ion conversion efficiency while avoiding the production of undesired high-energy ions

  3. Inhomogeneous structure formation may alleviate need for accelerating universe

    Hansson, Johan

    2009-01-01

    When taking the real, inhomogeneous and anisotropic matter distribution in the semi-local universe into account, there may be no need to postulate an accelerating expansion of the universe despite recent type Ia supernova data. Local curvatures must be integrated (over all space) to obtain the global curvature of the universe, which seems to be very close to zero from cosmic microwave background data. As gravitational structure formation creates bound regions of positive curvature, the regions in between become negatively curved in order to comply with a vanishing global curvature. The actual dynamics of the universe is altered due to the self-induced inhomogeneities, again more prominently so as structure formation progresses. Furthermore, this negative curvature will increase as a function of time as structure formation proceeds, which mimics the effect of "dark energy" with negative pressure. Hence, the "acceleration" may be merely a mirage. We make a qualitative and semi-quantitative analysis, using newto...

  4. Comparison of the conditioning of High Gradient Accelerating Structures

    Degiovanni, Alberto; Giner Navarro, Jorge

    2015-01-01

    Accelerating gradients in excess of 100 MV/m, at very low breakdown rates, have been successfully achieved in numerous CLIC prototype accelerating structures. The conditioning and operational histories of several structures, tested at KEK and CERN, have been compared and there is clear evidence that the conditioning progresses with the number of RF pulses and not the number of breakdowns. This observation opens the possibility that the optimum conditioning strategy, which minimizes the total number of breakdowns the structure is subject to without increasing conditioning time, may be to never exceed the breakdown rate target for operation. The result is also likely to have a strong impact on efforts to understand the physical mechanism underlying conditioning and may lead to preparation procedures which reduce conditioning time.

  5. Simulations of relativistic collisionless shocks: shock structure and particle acceleration

    Spitkovsky, A

    2006-01-01

    We discuss 3D simulations of relativistic collisionless shocks in electron-positron pair plasmas using the particle-in-cell (PIC) method. The shock structure is mainly controlled by the shock's magnetization ("sigma" parameter). We demonstrate how the structure of the shock varies as a function of sigma for perpendicular shocks. At low magnetizations the shock is mediated mainly by the Weibel instability which generates transient magnetic fields that can exceed the initial field. At larger magnetizations the shock is dominated by magnetic reflections. We demonstrate where the transition occurs and argue that it is impossible to have very low magnetization collisionless shocks in nature (in more than one spatial dimension). We further discuss the acceleration properties of these shocks, and show that higher magnetization perpendicular shocks do not efficiently accelerate nonthermal particles in 3D. Among other astrophysical applications, this may pose a restriction on the structure and composition of gamma-ray...

  6. Gravitational energy as dark energy: Cosmic structure and apparent acceleration

    Wiltshire, David L

    2011-01-01

    Below scales of about 100/h Mpc our universe displays a complex inhomogeneous structure dominated by voids, with clusters of galaxies in sheets and filaments. The coincidence that cosmic expansion appears to start accelerating at the epoch when such structures form has prompted a number of researchers to question whether dark energy is a signature of a failure of the standard cosmology to properly account, on average, for the distribution of matter we observe. Here I discuss the timescape scenario, in which cosmic acceleration is understood as an apparent effect, due to gravitational energy gradients that grow when spatial curvature gradients become significant with the nonlinear growth of cosmic structure. I discuss conceptual issues related to the averaging problem, and their impact on the calibration of local geometry to the solutions of the volume-average evolution equations corrected by backreaction, and the question of nonbaryonic dark matter in the timescape framework. I further discuss recent work on ...

  7. Wakefield Monitor Experiments with X-Band Accelerating Structures

    Lillestøl, Reidar; Corsini, Roberto; Döbert, Steffen; Farabolini, Wilfrid; Malina, Lukas; Pfingstner, Juergen; Wuensch, Walter

    2015-01-01

    The accelerating structures for CLIC must be aligned with a precision of a few um with respect to the beam trajectory in order to mitigate emittance growth due to transverse wake fields. We report on first results from wake field monitor tests in an X-band structure, with a probe beam at the CLIC Test Facility. The monitors are currently installed in the CLIC Two-Beam Module. In order to fully demonstrate the feasibility of using wakefield monitors for CLIC, the precision of the monitors must be verified using a probe beam while simultaneously filling the structure with high power rf used to drive the accelerating mode. We outline plans to perform such a demonstration in the CLIC Test Facility.

  8. Performance testing of the LUEhR-40M structure with an accelerated beam

    The results of experimental investigation of the prototype of the accelerating structure of the therapeutic linear accelerator of the LUEhR-40M model with an accelerating beam are presented. The accelerating structure is the standing wave biperiodic structure with inner coupling cells of 1.6 m length. The design energy of accelerated electrons equalling 20 MeV (during single electron beam passage through an accelerating structure) is obtained. 60 % of accelerated particles are accumulated in the energy interval of (20±1) MeV at 20 mA pulse current and at 3.6 MW SHF-power at the structure input

  9. Assembly and phylogenetic structure of Neotropical palm communities

    Eiserhardt, Wolf L.; Svenning, J.-C.; Balslev, Henrik

    Diversity, composition and dynamics of Neotropical palm communities are receiving an increasing amount of attention due to their economic importance, but also because their high species richness and functional diversity render them valuable model systems for overall forest biodiversity. However, to...... better understand these palm communities, it is crucial to gain insight into the mechanisms responsible for their assembly. These can be dispersal limitation, environmental filtering, or biotic interactions. If the degree of niche conservatism is known for a group of organisms, patterns of community...... phylogenetic structure can be directly traced back to mechanisms of community assembly. We aim to examine this for Neotropical palm communities. Phylogenetic structure will be inferred on different spatial scales and for different community definitions (plot-based and environment-based). To overcome an...

  10. Prospects for using self-assembled nucleic acid structures.

    Rudchenko, M N; Zamyatnin, A A

    2015-04-01

    According to the central dogma in molecular biology, nucleic acids are assigned with key functions on storing and executing genetic information in any living cell. However, features of nucleic acids are not limited only with properties providing template-dependent biosynthetic processes. Studies of DNA and RNA unveiled unique features of these polymers able to make various self-assembled three-dimensional structures that, among other things, use the complementarity principle. Here, we review various self-assembled nucleic acid structures as well as application of DNA and RNA to develop nanomaterials, molecular automata, and nanodevices. It can be expected that in the near future results of these developments will allow designing novel next-generation diagnostic systems and medicinal drugs. PMID:25869355

  11. The Effects of Gramicidin on the Structure of Phospholipid Assemblies

    Szule, J. A.; Rand, R. P.

    2003-01-01

    Gramicidin is an antibiotic peptide that can be incorporated into the monolayers of cell membranes. Dimerization through hydrogen bonding between gramicidin monomers in opposing leaflets of the membrane results in the formation of an iontophoretic channel. Surrounding phospholipids influence the gating properties of this channel. Conversely, gramicidin incorporation has been shown to affect the structure of spontaneously formed lipid assemblies. Using small-angle x-ray diffraction and model s...

  12. FIRST STEP blanket structure and fuel assembly design

    FIRST STEP (Fusion, Inertial, Reduced Requirement Systems Test for Special Nuclear Material, Tritium, and Energy Production) is an Inertial Confinement Fusion (ICF) plant designed to produce tritium, SNM, and energy using near-term technology. It is an integrated facility that will serve as a test bed for fusion power plant technology. The design of the blanket structure and blanket fuel assembly for wetted-wall FIRST STEP reactors is presented here

  13. Development of X-band accelerating structures for high gradients

    S. Bini; M. G. Grimaldi; L. Romano; F. Ruffino; R. Parodi; V. Chimenti; A. Marcelli; L. Palumbo; B. Spataro; V. A. Dolgashev; S. Tantawi; A.D. Yeremian; Y. Higashi

    2012-01-01

    Short copper standing wave (SW) structures operating at an X-band frequency have been recently designed and manufactured at the Laboratori Nazionali di Frascati of the Istituto Nazionale di Fisica Nucleare (INFN) using the vacuum brazing technique.High power tests of the structures have been performed at the SLAC National Accelerator Laboratory.In this manuscript we report the results of these tests and the activity in progress to enhance the high gradient performance of the next generation of structures,particularly the technological characterization of high performance coatings obtained via molybdenum sputtering.

  14. Engineering Design of a Multipurpose X-band Accelerating Structure

    Gudkov, Dmitry; Samoshkin, Alexander; Zennaro, Riccardo; Dehler, Micha; Raguin, Jean-Yves

    2010-01-01

    Both FEL projects, SwissFEL and Fermi-Elettra each require an X-band RF accelerating structure for optimal bunch compression at the respective injectors. As the CLIC project is pursuing a program for producing and testing the X-band high-gradient RF structures, a collaboration between PSI, Elettra and CERN has been established to build a multipurpose X-band accelerating structure. This paper focuses on its engineering design, which is based on the disked cells jointed together by diffusion bonding. Vacuum brazing and laser beam welding is used for auxiliary components. The accelerating structure consists of two coupler subassemblies, 73 disks and includes a wakefield monitor and diagnostic waveguides. The engineering study includes the external cooling system, consisting of two parallel cooling circuits and an RF tuning system, which allows phase advance tuning of the cell by deforming the outer wall. The engineering solution for the installation and sealing of the wake field monitor feed-through devices that...

  15. Experimental and Simulated Characterization of a Beam Shaping Assembly for Accelerator- Based Boron Neutron Capture Therapy (AB-BNCT)

    In the frame of the construction of a Tandem Electrostatic Quadrupole Accelerator facility devoted to the Accelerator-Based Boron Neutron Capture Therapy, a Beam Shaping Assembly has been characterized by means of Monte-Carlo simulations and measurements. The neutrons were generated via the 7Li(p, n)7Be reaction by irradiating a thick LiF target with a 2.3 MeV proton beam delivered by the TANDAR accelerator at CNEA. The emerging neutron flux was measured by means of activation foils while the beam quality and directionality was evaluated by means of Monte Carlo simulations. The parameters show compliance with those suggested by IAEA. Finally, an improvement adding a beam collimator has been evaluated.

  16. Material studies in the frame of CLIC Accelerating structures production conducted within the Mechanics program together with Metso Oy

    Nurminen, Janne

    2012-01-01

    MeChanICs (Marie Curie Linking Industry to CERN) is an Industry to Academia Partnership and Pathways (IAPP) platform for precision manufacturing knowledge exchange bringing together five Finnish manufacturing companies with Helsinki Insitute of Physics (HIP) and CERN. The scientific objective of MeChanICs project is to contribute to the manufacturing RTD of CLIC enabling technologies. The focus is on the design, materials, machining, brazing and assembly of A CLIC accelerating structure. This study deals with the materials work package of the program and wants to explore the following items: 1) producing copper accelerating structures for CLIC from raw copper powder by near net shape hot isostatic pressing (HIP). 2) The feasibility to use HIP diffusion bonding of the accelerator structures as a function of surface quality and applied temperature and pressure. 3) Brazing for CLIC AS auxiliary systems, like water cooling or damping manifolds, to the disc stack by coating one of the brazing partners with an enab...

  17. Enhanced Ion Acceleration from Micro-tube Structured Targets

    Snyder, Joseph; Ji, Liangliang; Akli, Kramer

    2015-11-01

    We present an enhanced ion acceleration method that leverages recent advancements in 3D printing for target fabrication. Using the three-dimensional Particle-in-Cell simulation code Virtual Laser-Plasma Lab (VLPL), we model the interaction of a short pulse, high intensity laser with a micro-tube plasma (MTP) structured target. When compared to flat foils, the MTP target enhances the maximum proton energy by a factor of about 4. The ion enhancement is attributed to two main factors: high energy electrons extracted from the tube structure enhancing the accelerating field and light intensification within the MTP target increasing the laser intensity at the location of the foil. We also present results on ion energy scaling with micro-tube diameter and incident laser pulse intensity. This work was supported by the AFOSR under contract No. FA9550-14-1-0085.

  18. Design of input and output couplers for linear accelerator structures

    The input and output couplers for 2m-long S-band linear-accelerator structures for the KEKB linac upgrade have been designed and tested. The dimensions of the coupler cavities were estimated by a simulation of the Kyhl method using the MAFIA code, and determined by low-power tests using the Kyhl method. It has been shown that the coupler dimensions can be predicted with precision to be less than 0.5 mm. The asymmetry of the electromagnetic field (amplitude and phase) in the couplers has been corrected by a crescent-shaped cut on the opposite side of the iris. The total performance of the accelerator structures with these couplers is also described. (author)

  19. Research and Development for Ultra-High Gradient Accelerator Structures

    Tantawi, Sami G.; Dolgashev, Valery; Higashi, Yasuo; Spataro, Bruno

    2010-11-01

    Research on the basic physics of high-gradient, high frequency accelerator structures and the associated RF/microwave technology are essential for the future of discovery science, medicine and biology, energy and environment, and national security. We will review the state-of-the-art for the development of high gradient linear accelerators. We will present the research activities aimed at exploring the basic physics phenomenon of RF breakdown. We present the experimental results of a true systematic study in which the surface processing, geometry, and materials of the structures have been varied, one parameter at a time. The breakdown rate or alternatively, the probability of breakdown/pulse/meter has been recorded for different operating parameters. These statistical data reveal a strong dependence of breakdown probability on surface magnetic field, or alternatively on surface pulsed heating. This is in contrast to the classical view of electric field dependence.

  20. Self-assembled manganese oxide structures through direct oxidation

    Zhao, Chao

    2012-12-01

    The morphology and phase of self-assembled manganese oxides during different stages of thermal oxidation were studied. Very interesting morphological patterns of Mn oxide films were observed. At the initial oxidation stage, the surface was characterized by the formation of ring-shaped patterns. As the oxidation proceeded to the intermediate stage, concentric plates formed to relax the compressive stress. Our experimental results gave a clear picture of the evolution of the structures. We also examined the properties of the structures. © 2012 Elsevier B.V.

  1. Technical infra-structure for accelerators in Brazil

    A minimal technical support infra-structura for, operation, maintenance and development suitable to a multi-user laboratory is presented. The costs of this infra-structure are 1.300 MCr$ in equipment and 700 MCr$ in people. A coordinated utilization of a particle accelerator network existing in the country and its corresponding costs are shown. Considerations in relation to the local of the sinchrotron radiation laboratory implantation are done. (L.C.)

  2. Ordered patterns and structures via interfacial self-assembly: superlattices, honeycomb structures and coffee rings.

    Ma, Hongmin; Hao, Jingcheng

    2011-11-01

    Self-assembly is now being intensively studied in chemistry, physics, biology, and materials engineering and has become an important "bottom-up" approach to create intriguing structures for different applications. Self-assembly is not only a practical approach for creating a variety of nanostructures, but also shows great superiority in building hierarchical structures with orders on different length scales. The early work in self-assembly focused on molecular self-assembly in bulk solution, including the resultant dye aggregates, liposomes, vesicles, liquid crystals, gels and so on. Interfacial self-assembly has been a great concern over the last two decades, largely because of the unique and ingenious roles of this method for constructing materials at interfaces, such as self-assembled monolayers, Langmuir-Blodgett films, and capsules. Nanocrystal superlattices, honeycomb films and coffee rings are intriguing structural materials with more complex features and can be prepared by interfacial self-assembly on different length scales. In this critical review, we outline the recent development in the preparation and application of colloidal nanocrystal superlattices, honeycomb-patterned macroporous structures by the breath figure method, and coffee-ring-like patterns (247 references). PMID:21792458

  3. Accelerating VASP electronic structure calculations using graphic processing units

    Hacene, Mohamed

    2012-08-20

    We present a way to improve the performance of the electronic structure Vienna Ab initio Simulation Package (VASP) program. We show that high-performance computers equipped with graphics processing units (GPUs) as accelerators may reduce drastically the computation time when offloading these sections to the graphic chips. The procedure consists of (i) profiling the performance of the code to isolate the time-consuming parts, (ii) rewriting these so that the algorithms become better-suited for the chosen graphic accelerator, and (iii) optimizing memory traffic between the host computer and the GPU accelerator. We chose to accelerate VASP with NVIDIA GPU using CUDA. We compare the GPU and original versions of VASP by evaluating the Davidson and RMM-DIIS algorithms on chemical systems of up to 1100 atoms. In these tests, the total time is reduced by a factor between 3 and 8 when running on n (CPU core + GPU) compared to n CPU cores only, without any accuracy loss. © 2012 Wiley Periodicals, Inc.

  4. Assembly of nothing: equilibrium fluids with designed structured porosity.

    Lindquist, Beth A; Jadrich, Ryan B; Truskett, Thomas M

    2016-03-14

    Controlled micro- to meso-scale porosity is a common materials design goal with possible applications ranging from molecular gas adsorption to particle size selective permeability or solubility. Here, we use inverse methods of statistical mechanics to design an isotropic pair interaction that, in the absence of an external field, assembles particles into an inhomogeneous fluid matrix surrounding pores of prescribed size ordered in a lattice morphology. The pore size can be tuned via modification of temperature or particle concentration. Moreover, modulating density reveals a rich series of microphase-separated morphologies including pore- or particle-based lattices, pore- or particle-based columns, and bicontinuous or lamellar structures. Sensitivity of pore assembly to the form of the designed interaction potential is explored. PMID:26883309

  5. Electromagnetic simulation study of dielectric wall accelerator structures

    ZHAO Quan-Tang; ZHANG Zi-Min; YUAN Ping; CAO Shu-Chun; SHEN Xiao-Kang; JING Yi; LIU Ming; ZHAO Hong-Wei

    2012-01-01

    Two types of dielectric wall accelerator (DWA) structures,a bi-polar Blumlein line and zero integral pulse line (ZIP) structures were investigated.The high gradient insulator simulated by the particle in cell code confirms that it has little influence on the axial electric field.The results of simulations using CST microwave studio indicate how the axial electric field is formed,and the electric field waveforms agree with the theoretical one very well.The influence of layer-to-layer coupling in a ZIP structure is much smaller and the electric field waveform is much better.The axial of the Blumlein structure's electric field has better axial stability.From both of the above,it found that for a shorter pulse width,the axial electric field is much higher and the pulse stability and fidelity are much better.The CST simulation is very helpful for designing DWA structures.

  6. Simulations and Vacuum Tests of a CLIC Accelerating Structure

    Garion, C

    2011-01-01

    The Compact LInear Collider, under study, is based on room temperature high gradient structures. The vacuum specificities of these cavities are low conductance, large surface areas and a non-baked system. The main issue is to reach UHV conditions (typically 10-7 Pa) in a system where the residual vacuum is driven by water outgassing. A finite element model based on an analogy thermal/vacuum has been built to estimate the vacuum profile in an accelerating structure. Vacuum tests are carried out in a dedicated set-up, the vacuum performances of different configurations are presented and compared with the predictions.

  7. H-Mode Accelerating Structures with PMQ Beam Focusing

    Kurennoy, Sergey S.; Rybarcyk, Lawrence J.; O'Hara, James F.; Olivas, Eric R.; Wangler, Thomas P.

    2011-01-01

    We have developed high-efficiency normal-conducting RF accelerating structures by combining H-mode resonator cavities and a transverse beam focusing by permanent-magnet quadrupoles (PMQ), for beam velocities in the range of a few percent of the speed of light. The shunt impedance of inter-digital H-mode (IH-PMQ) structures is 10-20 times higher than that of a conventional drift-tube linac, while the transverse size is 4-5 times smaller. Results of the combined 3-D modeling - electromagnetic c...

  8. Precise fabrication of X-band accelerating structure

    An accelerating structure with a/λ=0.16 is being fabricated to study a precise fabrication method. A frequency control of each cell better than 10-4 level is required to realize a detuned structure. The present machining level is nearly 1 MHz/11.4 GHz in relative frequency error, which just satisfies the above requirement. To keep this machining precision, the diffusion bonding technique is found preferable to join the cells. Various diffusion conditions were tried. The frequency change can be less than 1 MHz/11.4 GHz and it can be controlled well better than that. (author)

  9. An Asset Test of the CLIC Accelerating Structure

    Transverse wakefield suppression in the CLIC (Compact Linear Collider) multibunch accelerating structure, called the TDS (Tapered Damped Structure), is achieved primarily through heavy damping. In order to verify the performance of the TDS design and the validity of the theoretical tools used to model it, a 15 GHz version of the TDS has been constructed and tested in the ASSET facility at SLAC. The test has directly demonstrated transverse wakefield suppression of over a factor 100, with an excellent agreement between the measured and the calculated wakefield

  10. Accelerator

    The invention claims equipment for stabilizing the position of the front covers of the accelerator chamber in cyclic accelerators which significantly increases accelerator reliability. For stabilizing, it uses hydraulic cushions placed between the electromagnet pole pieces and the front chamber covers. The top and the bottom cushions are hydraulically connected. The cushions are disconnected and removed from the hydraulic line using valves. (J.P.)

  11. Superconducting Accelerating Structure with Gradient as 2 Times Higher as TESLA Structure

    Avrakhov, P V

    2004-01-01

    A proposed new accelerating structure for TESLA is assumed to have an effective gradient 2 times more than existing 9-cell cavity. This structure is an interlaced combination of two side-cavity-coupled standing wave substructures with λ/4 cells length. Intercell coupling provides side-coupled cavities made from a special shape waveguide section. The high accelerating gradient is accomplished by 4 factors: The shortened accelerating cells have transit time factor 0.9 instead of 0.64 for conventional standing wave cells with λ/2 length. The side magnetic coupling has made it possible to reduce the cells beam aperture that reduce relation between the maximum surface field and the acceleration gradient. Stronger intercell coupling allows extending the accelerating cavity and improving a duty factor of linac. Availability of the side coupling elements enables to use them for power input and HOM-couplers. It reduces intercavity distance and enhances duty factor too.

  12. A fast sequence assembly method based on compressed data structures.

    Liang, Peifeng; Zhang, Yancong; Lin, Kui; Hu, Jinglu

    2014-01-01

    Assembling a large genome using next generation sequencing reads requires large computer memory and a long execution time. To reduce these requirements, a memory and time efficient assembler is presented from applying FM-index in JR-Assembler, called FMJ-Assembler, where FM stand for FMR-index derived from the FM-index and BWT and J for jumping extension. The FMJ-Assembler uses expanded FM-index and BWT to compress data of reads to save memory and jumping extension method make it faster in CPU time. An extensive comparison of the FMJ-Assembler with current assemblers shows that the FMJ-Assembler achieves a better or comparable overall assembly quality and requires lower memory use and less CPU time. All these advantages of the FMJ-Assembler indicate that the FMJ-Assembler will be an efficient assembly method in next generation sequencing technology. PMID:25569963

  13. A tuning method for nonuniform traveling-wave accelerating structures

    The tuning method of uniform traveling-wave structures based on non-resonant perturbation field distribution measurement has been widely used in tuning both constant-impedance and constant-gradient structures. In this paper, the method of tuning nonuniform structures is proposed on the basis of the above theory. The internal reflection coefficient of each cell is obtained from analyzing the normalized voltage distribution. A numerical simulation of tuning process according to the coupled cavity chain theory has been done and the result shows each cell is in right phase advance after tuning. The method will be used in the tuning of a disk-loaded traveling-wave structure being developed at the Accelerator Laboratory, Tsinghua University. (authors)

  14. Design of Accelerator Online Simulator Server Using Structured Data

    Model based control plays an important role for a modern accelerator during beam commissioning, beam study, and even daily operation. With a realistic model, beam behaviour can be predicted and therefore effectively controlled. The approach used by most current high level application environments is to use a built-in simulation engine and feed a realistic model into that simulation engine. Instead of this traditional monolithic structure, a new approach using a client-server architecture is under development. An on-line simulator server is accessed via network accessible structured data. With this approach, a user can easily access multiple simulation codes. This paper describes the design, implementation, and current status of PVData, which defines the structured data, and PVAccess, which provides network access to the structured data.

  15. Design of Accelerator Online Simulator Server Using Structured Data

    Shen, Guobao; /Brookhaven; Chu, Chungming; /SLAC; Wu, Juhao; /SLAC; Kraimer, Martin; /Argonne

    2012-07-06

    Model based control plays an important role for a modern accelerator during beam commissioning, beam study, and even daily operation. With a realistic model, beam behaviour can be predicted and therefore effectively controlled. The approach used by most current high level application environments is to use a built-in simulation engine and feed a realistic model into that simulation engine. Instead of this traditional monolithic structure, a new approach using a client-server architecture is under development. An on-line simulator server is accessed via network accessible structured data. With this approach, a user can easily access multiple simulation codes. This paper describes the design, implementation, and current status of PVData, which defines the structured data, and PVAccess, which provides network access to the structured data.

  16. Fabrication Technologies of the High Gradient Accelerator Structures at 100MV/m Range

    Wang, Juwen; Van Pelt, John; Yoneda, Charles; Gudkov, D; Riddone, Germana; Higo, Toshiyasu; Takatomi, Toshikazu

    2010-01-01

    A CERN-SLAC-KEK collaboration on high gradient X-band structure research has been established in order to demonstrate the feasibility of the CLIC baseline design for the main linac stably operating at more than 100 MV/m loaded accelerating gradient. Several prototype CLIC structures were successfully fabricated and high power tested. They operated at 105 MV/m with a breakdown rate that meets the CLIC linear collider specifications of <5×10-7/pulse/m. This paper summarizes the fabrication technologies including the mechanical design, precision machining, chemical cleaning, diffusion bonding as well as vacuum baking and all related assembly technologies. Also, the tolerances control, tuning and RF characterization will be discussed

  17. Problems in understanding the structure and assembly of viruses

    King, J. [MIT, Cambridge, MA (United States)

    1997-12-01

    Though viruses infect the cells of all groups of animals, plants, and microorganisms, their structures follow a limited number of general themes; spherical or cylindrical shells built of hundreds of repeated protein subunits enclosing a nucleic acid - DNA or RNA - genome. Since the 1960s it has been known that the protein shells of spherical viruses in fact conform to icosahedral symmetry or to subtle deviations from icosahedral symmetry. The construction of the shell lattices and the transformations they go through in the different stages of the viral life cycle are not fully understood. The shells contain the nucleic in a highly condensed state, of unknown coiling/organization. Features of the well studied bacterial viruses will be reviewed, with examples from adenoviruses, herpesviruses, poliovirus, and HIV. The emergence of new viral disease has led to increased interest in the development of agents which interfere with virus reproduction at the level of the assembly or function of the organized particle. Recently computational approaches to the problem of virus assembly have made important contributions to clarifying shell assembly processes. 1 ref.

  18. An optimized slab-symmetric dielectric-based laser accelerator structure

    A slab-symmetric, partially dielectric filled, laser excited structure which maybe used to accelerate charged particles is analyzed theoretically and computationally. The fields associated with the accelerating mode are calculated, as are aspects of the resonant filling and impedance matching of the structure to the exciting laser. It is shown through computer simulation that the accelerating mode in this structure can be excited resonantly and with large quality factor Q. Practical aspects of implementing this structure as an accelerator are discussed

  19. Structure of self - assembled two-dimensional spherical crystals

    Bausch, Andreas R.

    2004-03-01

    Dense spherical particles on a flat surface usually pack into a simple triangular lattice, similar to billiard balls at the start of a game. The minimum energy configuration for interacting particles on the curved surface of a sphere, however, presents special difficulties, as recognized already by J.J. Thomson. We describe experimental investigations of the structure of two-dimensional spherical crystals. The crystals, formed by beads self-assembled on water droplets in oil, serve as model systems for exploring very general theories about the minimum energy configurations of particles with arbitrary repulsive interactions on curved surfaces. Above a critical system size we find that crystals develop distinctive high-angle grain boundaries or "scars" not found in planar crystals. The number of excess defects in a scar is shown to grow linearly with the dimensionless system size. First experiments where the melting of the crystal structure was observable will be discussed. Dynamic triangulation methods allow the analysis of the dynamics of the defects. Possible modifications towards mechanically stabilized self assembly structures result in so called Colloidosomes, which are promising for many different encapsulation purposes.

  20. Mesoscopic structure prediction of nanoparticle assembly and coassembly: Theoretical foundation

    Hur, Kahyun

    2010-01-01

    In this work, we present a theoretical framework that unifies polymer field theory and density functional theory in order to efficiently predict ordered nanostructure formation of systems having considerable complexity in terms of molecular structures and interactions. We validate our approach by comparing its predictions with previous simulation results for model systems. We illustrate the flexibility of our approach by applying it to hybrid systems composed of block copolymers and ligand coated nanoparticles. We expect that our approach will enable the treatment of multicomponent self-assembly with a level of molecular complexity that approaches experimental systems. © 2010 American Institute of Physics.

  1. Summary Report of Working Group 3: High Gradient and Laser-Structure Based Acceleration

    The charge for the working group on high gradient and laser-structure based acceleration was to assess the current challenges involved in developing an advanced accelerator based on electromagnetic structures, and survey state-of-the-art methods to address those challenges. The topics of more than 50 presentations in the working group covered a very broad range of issues, from ideas, theoretical models and simulations, to design and manufacturing of accelerating structures and, finally, experimental results on obtaining extremely high accelerating gradients in structures from conventional microwave frequency range up to THz and laser frequencies. Workshop discussion topics included advances in the understanding of the physics of breakdown and other phenomena, limiting high gradient performance of accelerating structures. New results presented in this workshop demonstrated significant progress in the fields of conventional vacuum structure-based acceleration, dielectric wakefield acceleration, and laser-structure acceleration.

  2. Macromolecularly crowded in vitro microenvironments accelerate the production of extracellular matrix-rich supramolecular assemblies

    Kumar, Pramod; Satyam, Abhigyan; Fan, Xingliang; Rodriguez, Brian J.; et al

    2015-01-01

    Therapeutic strategies based on the principles of tissue engineering by self-assembly put forward the notion that functional regeneration can be achieved by utilising the inherent capacity of cells to create highly sophisticated supramolecular assemblies. However, in dilute ex vivo microenvironments, prolonged culture time is required to develop an extracellular matrix-rich implantable device. Herein, we assessed the influence of macromolecular crowding, a biophysical phenomenon that regulate...

  3. Assembling method for large-sized steel structure

    A plurality of batholiths each having substantially the same size as a large-sized steel structure are disposed, and supports which can increase the height corresponding to the height of the large-sized steel structure are disposed at the periphery of the batholiths. An attachable/detachable cover which covers the large-sized steel structure and can be used also as a suspending jig is disposed on the supports such that the cover can disposed on any of the supports. Since the cover which can increase the height as the height of the large-sized steel structure increases and has a function of a suspending jig, this provides a roof, so that operational circumstances upon assembling the large-sized steel structure are improved under the cover. When structural members are carried in, the cover is placed on a support disposed on the other batholiths and the height of the support is increased corresponding to the height of the member, then the cover is disposed again. Additional provision of an area for disposing a suspending jig within a crane reach is not necessary, and a scaffold for operation can be disposed to the support between the large-sized steel structure. (N.H.)

  4. Multipactor discharge in a dielectric-loaded accelerating structure

    Wu, L.; Ang, L. K.

    2007-01-01

    This paper presents a Monte-Carlo model to explain the multipactor discharge and its high-power absorption in a dielectric-loaded accelerating (DLA) structure reported recently [J. G. Power et al., Phys. Rev. Lett. 92, 164801 (2004)]. Susceptibility diagrams are constructed. Dynamic calculations for beam loading and its power absorption by the multipactor discharge are performed. It is found that the fraction of power absorbed by multipactor discharge at saturation is much larger than the case of a simple rf window, and it is sensitive to the incident power, which confirms the prior experimental results. This enhanced power absorption is due to the fact that the length of a DLA structure is much larger than the radius of the structure. A resonant condition of a maximum growth region has also been determined numerically and analytically. The difference between the resonant condition and saturation (due to beam loading) is clarified.

  5. Numerical studies of multipactor in dielectric-loaded accelerator structures

    Sinitsyn, Oleksandr; Nusinovich, Gregory; Antonsen, Thomas

    2009-11-01

    Multipactor (MP) is known as the avalanche growth of the number of secondary electrons emitted from a solid surface exposed to an rf electric field under vacuum conditions. MP may occur in various microwave and rf systems such as microwave tubes, rf windows and launchers, accelerating structures, and rf satellite payloads. In this work we present results of MP analysis in dielectric-loaded accelerator (DLA) structures. The starting point of our work was experimental and theoretical studies of DLA structures jointly done by Argonne National Laboratory and Naval Research Laboratory (J. G. Power et al., Phys. Rev. Lett. 92, 164801 (2004); J. G. Power et al., AIP Conf. Proc. 877, 362 (2006)). In the theoretical model developed during those studies the space-charge field due to the total number of particles is taken into account as a parameter. We perform our studies using a self-consistent approach with the help of time-dependent two-dimensional code developed at the University of Maryland (O. V. Sinitsyn et al., Phys. Plasmas 16, 073102 (2009)). Results include analysis of MP evolution at an early stage, detailed studies of individual electron trajectories, analysis of MP onset time under various conditions and comparison of some results with the experimental data.

  6. Sequence Planning for On-Orbit Assembly of Large Space Truss Structures in a Multirobot Environment

    GUO Jifeng; WANG Ping; CUI Naigang

    2006-01-01

    An approach to sequence planning for on-orbit assembly of large space truss structures in a multirobot environment is presented. A hierarchical representation of large space truss structures at the structural volume element level and strut level is adopted. The representation of connectivity matrix and directed graph is respectively presented at the strut level and SVE level. The multirobot environment that consists of autonomous space robots and struts is supposed. Then the multirobot serial assembly strategy, assembly states, assembly tasks and assembly sequences are described. The assembly sequence planning algorithms at the strut level and SVE level are respectively discussed. The results of the simulations show that this approach is feasible and efficient. Two extensions of this approach include more accurate assessment of the efficiency representation and improvements in planning algorithm. In the future, the assembly sequence planning of more large space truss structures and complex multirobot environments and assembly tasks will be considered.

  7. Accelerating Dynamic Cardiac MR Imaging Using Structured Sparse Representation

    Nian Cai

    2013-01-01

    Full Text Available Compressed sensing (CS has produced promising results on dynamic cardiac MR imaging by exploiting the sparsity in image series. In this paper, we propose a new method to improve the CS reconstruction for dynamic cardiac MRI based on the theory of structured sparse representation. The proposed method user the PCA subdictionaries for adaptive sparse representation and suppresses the sparse coding noise to obtain good reconstructions. An accelerated iterative shrinkage algorithm is used to solve the optimization problem and achieve a fast convergence rate. Experimental results demonstrate that the proposed method improves the reconstruction quality of dynamic cardiac cine MRI over the state-of-the-art CS method.

  8. Structural Insights into KCTD Protein Assembly and Cullin3 Recognition.

    Ji, Alan X; Chu, Anh; Nielsen, Tine Kragh; Benlekbir, Samir; Rubinstein, John L; Privé, Gilbert G

    2016-01-16

    Cullin3 (Cul3)-based ubiquitin E3 ligase complexes catalyze the transfer of ubiquitin from an E2 enzyme to target substrate proteins. In these assemblies, the C-terminal region of Cul3 binds Rbx1/E2-ubiquitin, while the N-terminal region interacts with various BTB (bric-à-brac, tramtrack, broad complex) domain proteins that serve as substrate adaptors. Previous crystal structures of the homodimeric BTB proteins KLHL3, KLHL11 and SPOP in complex with the N-terminal domain of Cul3 revealed the features required for Cul3 recognition in these proteins. A second class of BTB-domain-containing proteins, the KCTD proteins, is also Cul3 substrate adaptors, but these do not share many of the previously identified determinants for Cul3 binding. We report the pentameric crystal structures of the KCTD1 and KCTD9 BTB domains and identify plasticity in the KCTD1 rings. We find that the KCTD proteins 5, 6, 9 and 17 bind to Cul3 with high affinity, while the KCTD proteins 1 and 16 do not have detectable binding. Finally, we confirm the 5:5 assembly of KCTD9/Cul3 complexes by cryo-electron microscopy and provide a molecular rationale for BTB-mediated Cul3 binding specificity in the KCTD family. PMID:26334369

  9. Experimental high gradient testing of a 17.1 GHz photonic band-gap accelerator structure

    Munroe, Brian J.; Zhang, JieXi; Xu, Haoran; Shapiro, Michael A.; Temkin, Richard J.

    2016-03-01

    We report the design, fabrication, and high gradient testing of a 17.1 GHz photonic band-gap (PBG) accelerator structure. Photonic band-gap (PBG) structures are promising candidates for electron accelerators capable of high-gradient operation because they have the inherent damping of high order modes required to avoid beam breakup instabilities. The 17.1 GHz PBG structure tested was a single cell structure composed of a triangular array of round copper rods of radius 1.45 mm spaced by 8.05 mm. The test assembly consisted of the test PBG cell located between conventional (pillbox) input and output cells, with input power of up to 4 MW from a klystron supplied via a TM01 mode launcher. Breakdown at high gradient was observed by diagnostics including reflected power, downstream and upstream current monitors and visible light emission. The testing procedure was first benchmarked with a conventional disc-loaded waveguide structure, which reached a gradient of 87 MV /m at a breakdown probability of 1.19 ×10-1 per pulse per meter. The PBG structure was tested with 100 ns pulses at gradient levels of less than 90 MV /m in order to limit the surface temperature rise to 120 K. The PBG structure reached up to 89 MV /m at a breakdown probability of 1.09 ×10-1 per pulse per meter. These test results show that a PBG structure can simultaneously operate at high gradients and low breakdown probability, while also providing wakefield damping.

  10. A small scale accelerator driven subcritical assembly development and demonstration experiment at LAMPF

    A small scale experiment designed to demonstrate many of the aspects of accelerator-driven transmutation technology is described. The experiment uses the high-power proton beam from the Los Alamos Meson Physics Facility accelerator to produce neutrons with a molten Lead target. The target is surrounded by a molten salt and graphite moderator blanket. Fissionable material can be added to the molten salt to demonstrate Plutonium burning or transmutation of commercial spent fuel or energy production from Thorium

  11. The Structural Basis of Ribozyme-Catalyzed RNA Assembly

    Robertson, M.P.; Scott, W.G.; /UC, Santa Cruz

    2007-07-12

    Life originated, according to the RNA World hypothesis, from self-replicating ribozymes that catalyzed ligation of RNA fragments. We have solved the 2.6 angstrom crystal structure of a ligase ribozyme that catalyzes regiospecific formation of a 5' to 3' phosphodiester bond between the 5'-triphosphate and the 3'-hydroxyl termini of two RNA fragments. Invariant residues form tertiary contacts that stabilize a flexible stem of the ribozyme at the ligation site, where an essential magnesium ion coordinates three phosphates. The structure of the active site permits us to suggest how transition-state stabilization and a general base may catalyze the ligation reaction required for prebiotic RNA assembly.

  12. Further finite element structural analysis of FAST Load Assembly

    The FAST (Fusion Advanced Study Torus) machine is a compact high magnetic field tokamak, that will allow to study in an integrated way the main operational issues relating to plasma-wall interaction, plasma operation and burning plasma physics in conditions relevant for ITER and DEMO. The present work deals with the structural analysis of the machine Load Assembly for a proposed new plasma scenario (10 MA – 8.5 T), aimed to increase the operational limits of the machine. A previous paper has dealt with an integrated set of finite element models (regarding a former reference scenario: 6.5 MA – 7.5 T) of the load assembly, including the Toroidal and Poloidal Field Coils and the supporting structure. This set of models has regarded the evaluation of magnetic field values, the evaluation of the electromagnetic forces and the temperatures in all the current-carrying conductors: these analysis have been a preparatory step for the evaluation of the stresses of the main structural components. The previous models have been analyzed further on and improved in some details, including the computation of the out-of-plane electromagnetic forces coming from the interaction between the poloidal magnetic field and the current flowing in the toroidal magnets. After this updating, the structural analysis has been executed, where all forces and temperatures, coming from the formerly mentioned most demanding scenario (10 MA – 8.5 T) and acting on the tokamak's main components, have been considered. The two sets of analysis regarding the reference scenario and the extreme one have been executed and a useful comparison has been carried on. The analyses were carried out by using the FEM code Ansys rel. 13

  13. The Research of a Novel SW Accelerating Structure with Small Beam Spot

    Yang, X; Chen, Y; Jin, X; Li, Maozhen; Lü, H; Xu, Z

    2004-01-01

    A new kind of on-axis coupled biperiodic standing-wave (SW) accelerating structure has been built for a 9 MeV accelerator. The research progress was introduced in this paper, it includes the choice of the accelerating structure, the analysis of electron beam dynamics, the tuning of the cavity, the measurement of the accelerating tube and the powered test. The small beam spot is the most interesting feature of this accelerating structure, the diameter of the beam spot is 1.4 mm. This accelerator has been used for the x photons generation and the x-ray dose rate is about 3400 rad/min/m.

  14. Studying Radiation Damage in Structural Materials by Using Ion Accelerators

    Hosemann, Peter

    2011-02-01

    Radiation damage in structural materials is of major concern and a limiting factor for a wide range of engineering and scientific applications, including nuclear power production, medical applications, or components for scientific radiation sources. The usefulness of these applications is largely limited by the damage a material can sustain in the extreme environments of radiation, temperature, stress, and fatigue, over long periods of time. Although a wide range of materials has been extensively studied in nuclear reactors and neutron spallation sources since the beginning of the nuclear age, ion beam irradiations using particle accelerators are a more cost-effective alternative to study radiation damage in materials in a rather short period of time, allowing researchers to gain fundamental insights into the damage processes and to estimate the property changes due to irradiation. However, the comparison of results gained from ion beam irradiation, large-scale neutron irradiation, and a variety of experimental setups is not straightforward, and several effects have to be taken into account. It is the intention of this article to introduce the reader to the basic phenomena taking place and to point out the differences between classic reactor irradiations and ion irradiations. It will also provide an assessment of how accelerator-based ion beam irradiation is used today to gain insight into the damage in structural materials for large-scale engineering applications.

  15. Protein GB1 Folding and Assembly from Structural Elements

    Sara Linse

    2009-04-01

    Full Text Available Folding of the Protein G B1 domain (PGB1 shifts with increasing salt concentration from a cooperative assembly of inherently unstructured subdomains to an assembly of partly pre-folded structures. The salt-dependence of pre-folding contributes to the stability minimum observed at physiological salt conditions. Our conclusions are based on a study in which the reconstitution of PGB1 from two fragments was studied as a function of salt concentrations and temperature using circular dichroism spectroscopy. Salt was found to induce an increase in β-hairpin structure for the C-terminal fragment (residues 41 – 56, whereas no major salt effect on structure was observed for the isolated N-terminal fragment (residues 1 – 41. In line with the increasing evidence on the interrelation between fragment complementation and stability of the corresponding intact protein, we also find that salt effects on reconstitution can be predicted from salt dependence of the stability of the intact protein. Our data show that our variant (which has the mutations T2Q, N8D, N37D and reconstitutes in a manner similar to the wild type displays the lowest equilibrium association constant around physiological salt concentration, with higher affinity observed both at lower and higher salt concentration. This corroborates the salt effects on the stability towards denaturation of the intact protein, for which the stability at physiological salt is lower compared to both lower and higher salt concentrations. Hence we conclude that reconstitution reports on molecular factors that govern the native states of proteins.

  16. Assembly History and Structure of Galactic Cold Dark Matter Halos

    Wang, Jie; Frenk, C S; White, S D M; Springel, V; Jenkins, A; Helmi, A; Ludlow, A; Vogelsberger, M

    2010-01-01

    We use the Aquarius simulation series to study the imprint of assembly history on the structure of Galaxy-mass cold dark matter halos. Our results confirm earlier work regarding the influence of mergers on the mass density profile and the inside-out growth of halos. The inner regions that contain the visible galaxies are stable since early times and are significantly affected only by major mergers. Particles accreted diffusely or in minor mergers are found predominantly in the outskirts of halos. Our analysis reveals trends that run counter to current perceptions of hierarchical halo assembly. For example, major mergers (i.e. those with progenitor mass ratios greater than 1:10) contribute little to the total mass growth of a halo, on average less than 20 per cent for our six Aquarius halos. The bulk is contributed roughly equally by minor mergers and by "diffuse" material which is not resolved into individual objects. This is consistent with modeling based on excursion-set theory which suggests that about hal...

  17. Structural Diversity of Self-Assembled Iridescent Arthropod Biophotonic Nanostructures

    Saranathan, Vinod Kumar; Prum, Richard O.

    2015-03-01

    Many organisms, especially arthropods, produce vivid interference colors using diverse mesoscopic (100-350 nm) integumentary biophotonic nanostructures that are increasingly being investigated for technological applications. Despite a century of interest, we lack precise structural knowledge of many biophotonic nanostructures and mechanisms controlling their development, when such knowledge can open novel biomimetic routes to facilely self-assemble tunable, multi-functional materials. Here, we use synchrotron small angle X-ray scattering and electron microscopy to characterize the photonic nanostructure of 140 iridescent integumentary scales and setae from 127 species of terrestrial arthropods in 85 genera from 5 orders. We report a rich nanostructural diversity, including triply-periodic bicontinuous networks, close-packed spheres, inverse columnar, perforated lamellar, and disordered sponge-like morphologies, commonly observed as stable phases of amphiphilic surfactants, block copolymer, and lyotropic lipid-water systems. Diverse arthropod lineages appear to have independently evolved to utilize the self-assembly of infolding bilayer membranes to develop biophotonic nanostructures that span the phase-space of amphiphilic morphologies, but at optical length scales.

  18. Structural Mechanisms in NLR Inflammasome Assembly and Signaling.

    Hu, Zehan; Chai, Jijie

    2016-01-01

    Inflammasomes are multimeric protein complexes that mediate the activation of inflammatory caspases. One central component of inflammasomes is nucleotide-binding domain (NBD)- and leucine-rich repeat (LRR)-containing proteins (NLRs) that can function as pattern recognition receptors (PRRs). In resting cells, NLR proteins exist in an auto-inhibited, monomeric, and ADP-bound state. Perception of microbial or damage-associated signals results in NLR oligomerization, thus recruiting inflammatory caspases directly or through the adaptor molecule apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC). The assembled NLR inflammasomes serve as dedicated machinery to facilitate the activation of the inflammatory caspases. Here, we review current understanding of the structures of NLR inflammasomes with an emphasis on the molecular mechanisms of their assembly and activation. We also discuss implications of the self-propagation model derived from the NAIP-NLRC4 inflammasomes for the activation of other NLR inflammasomes and a potential role of the C-terminal LRR domain in the activation of an NLR protein. PMID:27460803

  19. The assembly and structure of self-assembling peptides: molecular to supramolecular

    Morris, Kyle

    2012-01-01

    Self-assembling molecules are central to a plethora of processes found in nature, biotechnology and even disease. The importance of the non-covalent interaction of monomers to the formation of fibrillar assemblies is evident in the repeated use of this mechanism throughout nature, from essential cellular processes such as the formation of the cytoskeleton to the production of silk. Further, it has been recognised in the last two decades that a self-assembly mechanism, that is t...

  20. DNA/Fusogenic Lipid Nanocarrier Assembly: Millisecond Structural Dynamics.

    Angelov, Borislav; Angelova, Angelina; Filippov, Sergey K; Narayanan, Theyencheri; Drechsler, Markus; Štěpánek, Petr; Couvreur, Patrick; Lesieur, Sylviane

    2013-06-01

    Structural changes occurring on a millisecond time scale during uptake of DNA by cationic lipid nanocarriers are monitored by time-resolved small-angle X-ray scattering (SAXS) coupled to a rapid-mixing stopped-flow technique. Nanoparticles (NPs) of nanochannel organization are formed by PEGylation, hydration, and dispersion of a lipid film of the fusogenic lipid monoolein in a mixture with positively charged (DOMA) and PEGylated (DOPE-PEG2000) amphiphiles and are characterized by the inner cubic structure of very large nanochannels favorable for DNA upload. Ultrafast structural dynamics of complexation and assembly of these cubosome particles with neurotrophic plasmid DNA (pDNA) is revealed thanks to the high brightness of the employed synchrotron X-ray beam. The rate constant of the pDNA/lipid NP complexation is estimated from dynamic roentgenograms recorded at 4 ms time resolution. pDNA upload into the vastly hydrated channels of the cubosome carriers leads to a fast nanoparticle-nanoparticle structural transition and lipoplex formation involving tightly packed pDNA. PMID:26283134

  1. Self-assembled hierarchically structured organic-inorganic composite systems.

    Tritschler, Ulrich; Cölfen, Helmut

    2016-01-01

    Designing bio-inspired, multifunctional organic-inorganic composite materials is one of the most popular current research objectives. Due to the high complexity of biocomposite structures found in nacre and bone, for example, a one-pot scalable and versatile synthesis approach addressing structural key features of biominerals and affording bio-inspired, multifunctional organic-inorganic composites with advanced physical properties is highly challenging. This article reviews recent progress in synthesizing organic-inorganic composite materials via various self-assembly techniques and in this context highlights a recently developed bio-inspired synthesis concept for the fabrication of hierarchically structured, organic-inorganic composite materials. This one-step self-organization concept based on simultaneous liquid crystal formation of anisotropic inorganic nanoparticles and a functional liquid crystalline polymer turned out to be simple, fast, scalable and versatile, leading to various (multi-)functional composite materials, which exhibit hierarchical structuring over several length scales. Consequently, this synthesis approach is relevant for further progress and scientific breakthrough in the research field of bio-inspired and biomimetic materials. PMID:27175790

  2. Synthetic melanin films: Assembling mechanisms, scaling behavior, and structural properties

    Lorite, Gabriela S.; Coluci, Vitor R.; da Silva, Maria Ivonete N.; Dezidério, Shirlei N.; Graeff, Carlos Frederico O.; Galva~O, Douglas S.; Cotta, Mônica A.

    2006-06-01

    In this work we report on the surface characterization of melanin thin films prepared using both water-based and organic solvent-based melanin syntheses. Atomic force microscopy (AFM) analysis of these films suggests that the organic solvent synthesis provides relatively planar basic melanin structures; these basic structures generate surface steps with height in the range of 2-3 nm and small tendency to form larger aggregates. The scaling properties obtained from the AFM data were used to infer the assembling mechanisms of these thin films which depend on the solvent used for melanin synthesis. The behavior observed in organic solvent-based melanin suggests a diffusion-limited aggregation process. Thus films with good adhesion to the substrate and smoother morphologies than water-prepared melanin films are obtained. Electronic structure calculations using a conductorlike screening model were also performed in order to elucidate the microscopic processes of thin film formation. Our results suggest that the agglomerates observed in hydrated samples originate from reaction with water at specific locations on the surface most likely defects on the planar structure.

  3. RF properties of periodic accelerating structures for linear colliders

    With the advent of the SLAC electron-positron linear collider (SLC) in the 100 GeV center-of-mass energy range, research and development work on even higher energy machines of this type has started in several laboratories in the United States, Europe, the Soviet Union and Japan. These linear colliders appear to provide the only promising approach to studying e+e- physics at center-of-mass energies approaching 1 TeV. This thesis concerns itself with the study of radio frequency properties of periodic accelerating structures for linear colliders and their interaction with bunched beams. The topics that have been investigated are: experimental measurements of the energy loss of single bunches to longitudinal modes in two types of structures, using an equivalent signal on a coaxial wire to simulate the beam; a method of canceling the energy spread created within a single bunch by longitudinal wakefields, through appropriate shaping of the longitudinal charge distribution of the bunch; derivation of the complete transient beam-loading equation for a train of bunches passing through a constant-gradient accelerator section, with application to the calculation and minimization of multi-bunch energy spread; detailed study of field emission and radio frequency breakdown in disk-loaded structures at S-, C- and X-band frequencies under extremely high-gradient conditions, with special attention to thermal effects, radiation, sparking, emission of gases, surface damage through explosive emission and its possible control through RF-gas processing. 53 refs., 49 figs., 9 tabs

  4. Assembly and structure of protein phosphatase 2A

    2009-01-01

    Protein phosphatase 2A (PP2A) represents a conserved family of important protein serine/threonine phosphatases in species ranging from yeast to human. The PP2A core enzyme comprises a scaffold subunit and a catalytic subunit. The heterotrimeric PP2A holoenzyme consists of the core enzyme and a variable regulatory subunit. The catalytic subunit of PP2A is subject to reversible methylation, medi-ated by two conserved enzymes. Both the PP2A core and holoenzymes are regulated through interac-tion with a large number of cellular cofactors. Recent biochemical and structural investigation reveals critical insights into the assembly and function of the PP2A core enzyme as well as two families of holoenzyme. This review focuses on the molecular mechanisms revealed by these latest advances.

  5. Assembly and structure of protein phosphatase 2A

    SHI YiGong

    2009-01-01

    Protein phosphatase 2A (PP2A) represents a conserved family of important protein serinetthreonine phosphatases in species ranging from yeast to human. The PP2A core enzyme comprises a scaffold subunit and a catalytic subunit. The heterotrimeric PP2A holoenzyme consists of the core enzyme and a variable regulatory subunit. The catalytic subunit of PP2A is subject to reversible methylation, mediated by two conserved enzymes. Both the PP2A core and holoenzymes are regulated through interaction with a large number of cellular cofactors. Recent biochemical and structural investigation reveals critical insights into the assembly and function of the PP2A core enzyme as well as two families of holoenzyme. This review focuses on the molecular mechanisms revealed by these latest advances.

  6. Printable semiconductor structures and related methods of making and assembling

    Nuzzo, Ralph G.; Rogers, John A.; Menard, Etienne; Lee, Keon Jae; Khang; , Dahl-Young; Sun, Yugang; Meitl, Matthew; Zhu, Zhengtao; Ko, Heung Cho; Mack, Shawn

    2013-03-12

    The present invention provides a high yield pathway for the fabrication, transfer and assembly of high quality printable semiconductor elements having selected physical dimensions, shapes, compositions and spatial orientations. The compositions and methods of the present invention provide high precision registered transfer and integration of arrays of microsized and/or nanosized semiconductor structures onto substrates, including large area substrates and/or flexible substrates. In addition, the present invention provides methods of making printable semiconductor elements from low cost bulk materials, such as bulk silicon wafers, and smart-materials processing strategies that enable a versatile and commercially attractive printing-based fabrication platform for making a broad range of functional semiconductor devices.

  7. RF-thermal-structural-RF coupled analysis on a travelling wave disk-loaded accelerating structure

    The travelling wave (TW) disk-loaded accelerating structure is one of the key components in normal conducting (NC) linear accelerators, and has been studied for many years. In the design process, usually after the dimensions of each cell and the two couplers are finalized, the structure is fabricated and tuned, and then the whole structure RF characteristics are measured by using a vector network analyzer. Before fabrication, the whole structure characteristics (including RF, thermal and structural ones) are less simulated due to the limited capability of currently available computers. In this paper, we described a method for performing RF-thermal-structural-RF coupled analysis on a TW disk-loaded structure using only one PC. In order to validate our method, we first analyzed and compared our RF simulation results on the 3 m long BEPC Ⅱ structure with the corresponding experimental results, which shows very good consistency. Finally, the RF-thermal-structure-RF coupled analysis results on the 1.35 m long NSC KIPT linac accelerating structure are presented. (authors)

  8. Towards a molecular description of intermediate filament structure and assembly

    Intermediate filaments (IFs) represent one of the prominent cytoskeletal elements of metazoan cells. Their constituent proteins are coded by a multigene family, whose members are expressed in complex patterns that are controlled by developmental programs of differentiation. Hence, IF proteins found in epidermis differ significantly from those in muscle or neuronal tissues. Due to their fibrous nature, which stems from a fairly conserved central α-helical coiled-coil rod domain, IF proteins have long resisted crystallization and thus determination of their atomic structure. Since they represent the primary structural elements that determine the shape of the nucleus and the cell more generally, a major challenge is to arrive at a more rational understanding of how their nanomechanical properties effect the stability and plasticity of cells and tissues. Here, we review recent structural results of the coiled-coil dimer, assembly intermediates and growing filaments that have been obtained by a hybrid methods approach involving a rigorous combination of X-ray crystallography, small angle X-ray scattering, cryo-electron tomography, computational analysis and molecular modeling

  9. Lipid self-assembled structures for reactivity control in food.

    Sagalowicz, L; Moccand, C; Davidek, T; Ghanbari, R; Martiel, I; Negrini, R; Mezzenga, R; Leser, M E; Blank, I; Michel, M

    2016-07-28

    Lipid self-assembled structures (SASs) have recently gained considerable interest for their potential applications, especially for sustained nutrient release and protein crystallization. An additional property, which is underexploited, is their ability to control chemical reactions in food products. Here, we concentrate on SASs formed by phospholipids (PLs) and monoglycerides (MGs), those compounds being the most natural surfactants and therefore, the best compatible with food products, in view of providing new functionalities through the formation of SASs. In this work, the phase behaviour of these amphiphiles when mixed with oil and water is described and compared. Subsequently, we address the influence of these structures to the oxidation and Maillard-type reactions. Finally, we show that SASs formed by MGs can strongly increase the yield of key aroma impact compounds generated by Maillard-type reactions when compared with the reaction performed in aqueous precursor solutions. Various SASs are compared. In particular, addition of oil to a reversed bicontinuous structure formed by MG leads to a reversed microemulsion, which, considering its low viscosity, is particularly suitable for food products and act as a very efficient reactor system. The influence of oil and precursors on phase behaviour is discussed and related to the efficiency of the Maillard reactions.This article is part of the themed issue 'Soft interfacial materials: from fundamentals to formulation'. PMID:27298441

  10. Structure and Order of Phosphonic Acid-Based Self-Assembled Based Self-Assembled

    Dubey, M.; Weidner, T; Gamble, L; Castner, D

    2010-01-01

    Organophosphonic acid self-assembled monolayers (SAMs) on oxide surfaces have recently seen increased use in electrical and biological sensor applications. The reliability and reproducibility of these sensors require good molecular organization in these SAMs. In this regard, packing, order, and alignment in the SAMs is important, as it influences the electron transport measurements. In this study, we examine the order of hydroxyl- and methyl-terminated phosphonate films deposited onto silicon oxide surfaces by the tethering by aggregation and growth method using complementary, state-of-art surface characterization tools. Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and in situ sum frequency generation (SFG) spectroscopy are used to study the order of the phosphonate SAMs in vacuum and under aqueous conditions, respectively. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry results show that these samples form chemically intact monolayer phosphonate films. NEXAFS and SFG spectroscopy showed that molecular order exists in the octadecylphosphonic acid and 11-hydroxyundecylphosphonic acid SAMs. The chain tilt angles in these SAMs were approximately 37{sup o} and 45{sup o}, respectively.

  11. A Lot of Work or a Work of Art: How the Structure of a Customized Assembly Task Determines the Utility Derived from Assembly Effort

    Eva C. Buechel; Chris Janiszewski

    2014-01-01

    Customized assembly occurs when a consumer makes customization decisions and participates in the construction or modification of a product. While customization increases satisfaction with the end-product, less is known about the utility derived from the assembly effort. Three studies show that the structure of the customized assembly task determines whether consumers derive negative or positive utility from the assembly effort. When customization decisions and assembly processes are segregate...

  12. A small scale accelerator driven subcritical assembly development and demonstration experiment at LAMPF

    A small scale experiment is described that will demonstrate many of the aspects of accelerator-driven transmutation technology. This experiment uses the high-power proton beam from the Los Alamos Meson Physics Facility accelerator and will be located in the Area-A experimental hall. Beam currents of up to 1 mA will be used to produce neutrons with a molten lead target. The target is surrounded by a molten salt and graphite moderator blanket. Fissionable material can be added to the molten salt to demonstrate plutonium burning or transmutation of commercial spent fuel or energy production from thorium. The experiment will be operated at power levels up to 5 MWt

  13. Design and RF measurements of an X-band accelerating structure for linearizing the longitudinal emittance at SPARC

    Alesini, D.; Falone, A.; Migliorati, M.; Mostacci, A.; Palpini, F.; Palumbo, L.; Spataro, B.

    2005-12-01

    The paper presents the design of an X-band accelerating section for linearizing the longitudinal phase space in the Frascati Linac Coherent Light Source (SPARC). The nine cells structure, operating on the π standing wave mode, is fed by a central coupler and has been designed to obtain a 42 MV/m accelerating gradient. The two-dimensional (2D) profile has been obtained using the electromagnetic codes Superfish and Oscar-2D while the coupler has been designed using HFSS. Bead-pull measurements made on a copper prototype have been performed and the results are illustrated and compared with the numerical predictions. Mechanical details of the realized prototype and RF properties of the structure as a function of the assembly characteristics are also discussed.

  14. TRIM5alpha disrupts the structure of assembled HIV-1 capsid complexes in vitro.

    Black, Lesa R; Aiken, Christopher

    2010-07-01

    The host restriction factor TRIM5alpha provides intrinsic defense against retroviral infections in mammalian cells. TRIM5alpha blocks infection by targeting the viral capsid after entry but prior to completion of reverse transcription, but whether this interaction directly alters the structure of the viral capsid is unknown. A previous study reported that rhesus macaque TRIM5alpha protein stably associates with cylindrical complexes formed by assembly of recombinant HIV-1 CA-NC protein in vitro and that restriction leads to accelerated HIV-1 uncoating in target cells. To gain further insight into the mechanism of TRIM5alpha-dependent restriction, we examined the structural effects of TRIM5 proteins on preassembled CA-NC complexes by electron microscopy. Incubation of assembled complexes with lysate of cells expressing the restrictive rhesus TRIM5alpha protein resulted in marked disruption of the normal cylindrical structure of the complexes. In contrast, incubation with lysate of control cells or cells expressing comparable levels of the nonrestrictive human TRIM5alpha protein had little effect on the complexes. Incubation with lysate of cells expressing the TRIMCyp restriction factor also disrupted the cylinders. The effect of TRIMCyp was prevented by the addition of cyclosporine, which inhibits binding of TRIMCyp to the HIV-1 capsid. Thus, disruption of CA-NC cylinders by TRIM5alpha and TRIMCyp was correlated with the specificity of restriction. Collectively, these results suggest that TRIM5alpha-dependent restriction of HIV-1 infection results from structural perturbation of the viral capsid leading to aberrant HIV-1 uncoating in target cells. PMID:20410272

  15. PARTICLE ACCELERATION IN PLASMOID EJECTIONS DERIVED FROM RADIO DRIFTING PULSATING STRUCTURES

    Nishizuka, N. [National Institute of Information and Communications Technology, 4-2-1, Nukui-Kitamachi, Koganei, Tokyo 184-8795 (Japan); Karlický, M.; Bárta, M. [Astronomical Institute of the Academy of Sciences of the Czech Republic, 25165 Ondřejov (Czech Republic); Janvier, M., E-mail: nishizuka.naoto@nict.go.jp [Department of Mathematics, University of Dundee, Dundee DD1 4HN (United Kingdom)

    2015-02-01

    We report observations of slowly drifting pulsating structures (DPSs) in the 0.8-4.5 GHz frequency range of the RT4 and RT5 radio spectrographs at Ondřejov Observatory, between 2002 and 2012. We found 106 events of DPSs, which we classified into four cases: (I) single events with a constant frequency drift (12 events), (II) multiple events occurring in the same flare with constant frequency drifts (11 events), (III) single or multiple events with increasing or decreasing frequency drift rates (52 events), and (IV) complex events containing multiple events occurring at the same time in a different frequency range (31 events). Many DPSs are associated with hard X-ray (HXR) bursts (15-25 keV) and soft X-ray (SXR) gradient peaks, as they typically occurred at the beginning of HXR peaks. This indicates that DPS events are related to the processes of fast energy release and particle acceleration. Furthermore, interpreting DPSs as signatures of plasmoids, we measured their ejection velocity, their width, and their height from the DPS spectra, from which we also estimated the reconnection rate and the plasma beta. In this interpretation, constant frequency drift indicates a constant velocity of a plasmoid, and an increasing/decreasing frequency drift indicates a deceleration/acceleration of a plasmoid ejection. The reconnection rate shows a good positive correlation with the plasmoid velocity. Finally we confirmed that some DPS events show plasmoid counterparts in Solar Dynamics Observatory/Atmospheric Imaging Assembly images.

  16. Characteristics of a standing wave accelerating structure for common-series medical electron linacs

    Calculated and experimental RF-parameters of the accelerating structure of the LUEhR-40 linear electron accelerator designed for radiotherapy application are presented. A standing wave accelerating structure with a two-fold beam aceleration in opposite directions is used in the accelerator. The accelerating structure length makes up 1.6 m. At 2.5 MW SHF-power at the structure inlet and 20 keV electron injection energy the accelerated electron energy obtained made up 16.2 MeV at 20 μA current which agrees with the calculated values within the limits of measurement accuracy. Electron beam diameter after a one-turn acceleration did not exceed 2 mm

  17. Protein structure prediction: assembly of secondary structure elements by basin-hopping.

    Hoffmann, Falk; Vancea, Ioan; Kamat, Sanjay G; Strodel, Birgit

    2014-10-20

    The prediction of protein tertiary structure from primary structure remains a challenging task. One possible approach to this problem is the application of basin-hopping global optimization combined with an all-atom force field. In this work, the efficiency of basin-hopping is improved by introducing an approach that derives tertiary structures from the secondary structure assignments of individual residues. This approach is termed secondary-to-tertiary basin-hopping and benchmarked for three miniproteins: trpzip, trp-cage and ER-10. For each of the three miniproteins, the secondary-to-tertiary basin-hopping approach successfully and reliably predicts their three-dimensional structure. When it is applied to larger proteins, correctly folded structures are obtained. It can be concluded that the assembly of secondary structure elements using basin-hopping is a promising tool for de novo protein structure prediction. PMID:25056272

  18. Cell wall assembly and intracellular trafficking in plant cells are directly affected by changes in the magnitude of gravitational acceleration.

    Youssef Chebli

    Full Text Available Plants are able to sense the magnitude and direction of gravity. This capacity is thought to reside in selected cell types within the plant body that are equipped with specialized organelles called statoliths. However, most plant cells do not possess statoliths, yet they respond to changes in gravitational acceleration. To understand the effect of gravity on the metabolism and cellular functioning of non-specialized plant cells, we investigated a rapidly growing plant cell devoid of known statoliths and without gravitropic behavior, the pollen tube. The effects of hyper-gravity and omnidirectional exposure to gravity on intracellular trafficking and on cell wall assembly were assessed in Camellia pollen tubes, a model system with highly reproducible growth behavior in vitro. Using an epi-fluorescence microscope mounted on the Large Diameter Centrifuge at the European Space Agency, we were able to demonstrate that vesicular trafficking is reduced under hyper-gravity conditions. Immuno-cytochemistry confirmed that both in hyper and omnidirectional gravity conditions, the characteristic spatial profiles of cellulose and callose distribution in the pollen tube wall were altered, in accordance with a dose-dependent effect on pollen tube diameter. Our findings suggest that in response to gravity induced stress, the pollen tube responds by modifying cell wall assembly to compensate for the altered mechanical load. The effect was reversible within few minutes demonstrating that the pollen tube is able to quickly adapt to changing stress conditions.

  19. Hierarchical assembly may be a way to make large information-rich structures

    Whitelam, Stephen

    2015-01-01

    Self-assembly in the laboratory can now yield `information-rich' nanostructures in which each component is of a distinct type and has a defined spatial position. Ensuring the thermodynamic stability of such structures requires inter-component interaction energies to increase logarithmically with structure size, in order to counter the entropy gained upon mixing component types in solution. However, self-assembly in the presence of strong interactions results in general in kinetic trapping, so suggesting a limit to the size of an (equilibrium) structure that can be self-assembled from distinguishable components. Here we study numerically a two-dimensional hierarchical assembly scheme already considered in experiment. We show that this scheme is immune to the kinetic traps associated with strong `native' interactions (interactions designed to stabilize the intended structure), and so, in principle, offers a way to make large information-rich structures. In this scheme the size of an assembled structure scales e...

  20. Autonomous Assembly of Modular Structures in Space and on Extraterrestrial Locations

    Alhorn, Dean C.

    2005-02-01

    The new U.S. National Vision for Space Exploration requires many new enabling technologies to accomplish the goals of space commercialization and returning humans to the moon and extraterrestrial environments. Traditionally, flight elements are complete sub-systems requiring humans to complete the integration and assembly. These bulky structures also require the use of heavy launch vehicles to send the units to a desired location. This philosophy necessitates a high degree of safety, numerous space walks at a significant cost. Future space mission costs must be reduced and safety increased to reasonably achieve exploration goals. One proposed concept is the autonomous assembly of space structures. This concept is an affordable, reliable solution to in-space and extraterrestrial assembly. Assembly is autonomously performed when two components join after determining that specifications are correct. Local sensors continue monitor joint integrity post assembly, which is critical for safety and structural reliability. Achieving this concept requires a change in space structure design philosophy and the development of innovative technologies to perform autonomous assembly. Assembly of large space structures will require significant numbers of integrity sensors. Thus simple, low-cost sensors are integral to the success of this concept. This paper addresses these issues and proposes a novel concept for assembling space structures autonomously. Core technologies required to achieve in space assembly are presented. These core technologies are critical to the goal of utilizing space in a cost efficient and safe manner. Additionally, these novel technologies can be applied to other systems both on earth and extraterrestrial environments.

  1. Experimental Studies Of W-band Accelerator Structures At High Field

    Hill, M E

    2001-01-01

    A high-gradient electron accelerator is desired for high- energy physics research, where frequency scalings of breakdown and trapping of itinerant beamline particles dictates operation of the accelerator at short wavelengths. The first results of design and test of a high-gradient mm-wave linac with an operating frequency at 91.392 GHz (W-band) are presented. A novel approach to particle acceleration is presented employing a planar, dielectric lined waveguide used for particle acceleration. The traveling wave fields in the planar dielectric accelerator (PDA) are analyzed for an idealized structure, along with a circuit equivalent model used for understanding the structure as a microwave circuit. Along with the W-band accelerator structures, other components designed and tested are high power rf windows, high power attenuators, and a high power squeeze-type phase shifter. The design of the accelerator and its components where eased with the aide of numerical simulations using a finite-difference electromagneti...

  2. Integrated quality assurance for assembly and testing of complex structures

    von Kopylow, Christoph; Bothe, Thorsten; Elandaloussi, Frank; Kalms, Michael; Jüptner, Werner

    2005-11-01

    Modern production processes are directed by properties of the components to be manufactured. These components have different sizes, functionalities, high assembly complexity and high security requirements. The increasing requirements during the manufacturing of complex products like cars and aircrafts demand new solutions for the quality assurance - especially for the production at different places. The main focus is to find a measurement strategy that is cost effective, flexible and adaptive. That means a clear definition of the measurement problem, the measurement with adapted resolution, the data preparation and evaluation and support during measurement and utilisation of the results directly in the production. In this paper we describe flexible measurement devices on example of three different techniques: fringe projection, fringe reflection and shearography. These techniques allow the detection of surface and subsurface defects like bumps, dents and delaminations with high resolution. The defects can be optically mapped onto the object's surface. Results are demonstrated with big components taken from automotive and aircraft production. We will point out the most important adaptations of the systems to realize miniaturized, robust and mobile devices for the quality assurance in an industrial environment. Additionally the implementation into a Mobile Maintenance and Control structure is demonstrated.

  3. Design study of double-layer beam trajectory accelerator based on the Rhodotron structure

    Jabbari, Iraj; Poursaleh, Ali Mohammad; Khalafi, Hossein

    2016-08-01

    In this paper, the conceptual design of a new structure of industrial electron accelerator based on the Rhodotron accelerator is presented and its properties are compared with those of Rhodotron-TT200 accelerator. The main goal of this study was to reduce the power of RF system of accelerator at the same output electron beam energy. The main difference between the new accelerator structure with the Rhodotron accelerator is the length of the coaxial cavity that is equal to the wavelength at the resonant frequency. Also two sets of bending magnets were used around the acceleration cavity in two layers. In the new structure, the beam crosses several times in the coaxial cavity by the bending magnets around the cavity at the first layer and then is transferred to the second layer using the central bending magnet. The acceleration process in the second layer is similar to the first layer. Hence, the energy of the electron beam will be doubled. The electrical power consumption of the RF system and magnet system were calculated and simulated for the new accelerator structure and TT200. Comparing the calculated and simulated results of the TT200 with those of experimental results revealed good agreement. The results showed that the overall electrical power consumption of the new accelerator structure was less than that of the TT200 at the same energy and power of the electron beam. As such, the electrical efficiency of the new structure was improved.

  4. Effect of supporting structure stiffness on the drive train assembly of an induced draft cooling tower under seismic effects

    In a nuclear power project an induced draft cooling tower, as a safety-related structure and part of the main cooling system, has to perform satisfactorily under designated seismic effects. While the structural elements can be designed by conventional methods to ensure adequate safety, the seismic qualification of the mechanical components poses a challenge. The paper describes a methodology adopted for the seismic qualification of a typical Drive Train Assembly for the axial flow fan of an induced draft cooling tower, to ensure the structural integrity and functional operability of the assembly during Operating Base Earthquake and Safe Shutdown Earthquake conditions. This is achieved by performing a detailed finite element analysis of the rotating equipment assembly consisting of the electric motor, gear box and fan along with the drive shaft between the motor and the gear box. The various components are modeled using beam elements, plate elements and spring elements to idealize the flexible connections and supports. The floor response spectra derived from a dynamic analysis of the overall structure under stipulated seismic acceleration spectra are the main excitation inputs into the system. The results validate the adequacy of gaps for movement and the strengths of the couplings and bolts to withstand the applied loads. The assumed modeling and analysis methodology are seen to be acceptable procedures for seismic qualification of important components of the cooling tower. (authors)

  5. Assembly, Structure and Properties of DNA Programmable Nanoclusters

    Chi, Cheng

    Finite size nanoclusters can be viewed as a nanoscale analogue of molecules. Just as molecules, synthesized from atoms, give access to new properties, clusters composed of nanoparticles modulate of their functional properties of nanoparticles. In contrast to synthetic chemistry which is a mature field, the creation of nanoscale clusters with well-defined architectures is a new and challenging area of research. My work explores how to assemble model systems of nanoclusters using DNA-programmable interparticle linkages. The simplest clusters of two particles, dimers, allow one to investigate fundamental effects in these systems. Such clusters serve as a versatile platform to understand DNA-mediated interactions, especially in the non-trivial regime where the nanoparticle and DNA chains are comparable in size. I systematically studied a few fundamental questions as follows: Firstly, we examined the structure of nanoparticle dimers in detail by a combination of X-ray scattering experiments and molecular simulations. We found that, for a given DNA length, the interparticle separation within the dimer is controlled primarily by the number of linking DNA. We summarized our findings in a simple model that captures the interplay of the number of DNA bridges, their length, the particle's curvature and the excluded volume effects. We demonstrated the applicability of the model to our results, without any free parameters. As a consequence, the increase of dimer separation with increasing temperature can be understood as a result of changing the number of connecting DNA. Later, we investigated the self-assembly process of DNA-functionalized particles in the presence of various lengths of the DNA linkage strands using 3 different pathways. We observed a high yield of dimer formation when significantly long linkers were applied. Small Angle X-ray Scattering revealed two configurations of the small clusters by different pathways. In one case, the interparticle distance increases

  6. Horizon structure of rotating Bardeen black hole and particle acceleration

    We investigate the horizon structure and ergosphere in a rotating Bardeen regular black hole, which has an additional parameter (g) due to the magnetic charge, apart from the mass (M) and the rotation parameter (a). Interestingly, for each value of the parameter g, there exists a critical rotation parameter (a = aE), which corresponds to an extremal black hole with degenerate horizons, while for a < aE it describes a non-extremal black hole with two horizons, and no black hole for a > aE. We find that the extremal value aE is also influenced by the parameter g, and so is the ergosphere. While the value of aE remarkably decreases when compared with the Kerr black hole, the ergosphere becomes thicker with the increase in g.We also study the collision of two equal mass particles near the horizon of this black hole, and explicitly show the effect of the parameter g. The center-of-mass energy (ECM) not only depend on the rotation parameter a, but also on the parameter g. It is demonstrated that the ECM could be arbitrarily high in the extremal cases when one of the colliding particles has a critical angular momentum, thereby suggesting that the rotating Bardeen regular black hole can act as a particle accelerator. (orig.)

  7. Horizon structure of rotating Bardeen black hole and particle acceleration

    Ghosh, Sushant G. [Jamia Millia Islamia, Centre for Theoretical Physics, New Delhi (India); University of KwaZulu-Natal, Astrophysics and Cosmology Research Unit, School of Mathematics, Statistics and Computer Science, Durban (South Africa); Amir, Muhammed [Jamia Millia Islamia, Centre for Theoretical Physics, New Delhi (India)

    2015-11-15

    We investigate the horizon structure and ergosphere in a rotating Bardeen regular black hole, which has an additional parameter (g) due to the magnetic charge, apart from the mass (M) and the rotation parameter (a). Interestingly, for each value of the parameter g, there exists a critical rotation parameter (a = a{sub E}), which corresponds to an extremal black hole with degenerate horizons, while for a < a{sub E} it describes a non-extremal black hole with two horizons, and no black hole for a > a{sub E}. We find that the extremal value a{sub E} is also influenced by the parameter g, and so is the ergosphere. While the value of a{sub E} remarkably decreases when compared with the Kerr black hole, the ergosphere becomes thicker with the increase in g.We also study the collision of two equal mass particles near the horizon of this black hole, and explicitly show the effect of the parameter g. The center-of-mass energy (E{sub CM}) not only depend on the rotation parameter a, but also on the parameter g. It is demonstrated that the E{sub CM} could be arbitrarily high in the extremal cases when one of the colliding particles has a critical angular momentum, thereby suggesting that the rotating Bardeen regular black hole can act as a particle accelerator. (orig.)

  8. Structural Aspects of Bacterial Outer Membrane Protein Assembly.

    Calmettes, Charles; Judd, Andrew; Moraes, Trevor F

    2015-01-01

    The outer membrane of Gram-negative bacteria is predominantly populated by β-Barrel proteins and lipid anchored proteins that serve a variety of biological functions. The proper folding and assembly of these proteins is essential for bacterial viability and often plays a critical role in virulence and pathogenesis. The β-barrel assembly machinery (Bam) complex is responsible for the proper assembly of β-barrels into the outer membrane of Gram-negative bacteria, whereas the localization of lipoproteins (Lol) system is required for proper targeting of lipoproteins to the outer membrane. PMID:26621472

  9. Development of High-Gradient Dielectric Laser-Driven Particle Accelerator Structures

    Byer, Robert L.

    2013-11-07

    The thrust of Stanford's program is to conduct research on high-gradient dielectric accelerator structures driven with high repetition-rate, tabletop infrared lasers. The close collaboration between Stanford and SLAC (Stanford Linear Accelerator Center) is critical to the success of this project, because it provides a unique environment where prototype dielectric accelerator structures can be rapidly fabricated and tested with a relativistic electron beam.

  10. Software design for automated assembly of truss structures

    Herstrom, Catherine L.; Grantham, Carolyn; Allen, Cheryl L.; Doggett, William R.; Will, Ralph W.

    1992-01-01

    Concern over the limited intravehicular activity time has increased the interest in performing in-space assembly and construction operations with automated robotic systems. A technique being considered at LaRC is a supervised-autonomy approach, which can be monitored by an Earth-based supervisor that intervenes only when the automated system encounters a problem. A test-bed to support evaluation of the hardware and software requirements for supervised-autonomy assembly methods was developed. This report describes the design of the software system necessary to support the assembly process. The software is hierarchical and supports both automated assembly operations and supervisor error-recovery procedures, including the capability to pause and reverse any operation. The software design serves as a model for the development of software for more sophisticated automated systems and as a test-bed for evaluation of new concepts and hardware components.

  11. X-band Dielectric Loaded Rf Driven Accelerator Structures Theoretical And Experimental Investigations

    Zou, P

    2001-01-01

    An important area of application of high-power radio frequency (RF) and microwave sources is particle acceleration. A major challenge for the current worldwide research and development effort in linear accelerator is the search for a compact and affordable very-high-energy accelerator technology for the next generation supercolliders. It has been recognized for sometime that dielectric loaded accelerator structures are attractive candidates for the next generation very-high-energy linear accelerators, because they possess several distinct advantages over conventional metallic iris- loaded accelerator structures. However, some fundamental issues, such as RF breakdown in the dielectric, Joule heating, and vacuum properties of dielectric materials, are still the subjects of intense investigation, requiring the validation by experiments conducted at high power levels. An X-band traveling-wave accelerator based on dielectric-lined waveguide has been designed and constructed. Numerical calculation, bench measuremen...

  12. Self-assembly of PEGylated gold nanoparticles with satellite structures as seeds.

    Bachelet, Marie; Chen, Rongjun

    2016-07-21

    We report a very simple method for the self-assembly of spherical gold nanoparticles (AuNPs), coated with poly(ethylene glycol) (PEG), through a slow evaporation process at room temperature. Clusters of particles forming satellite structures may act as seeds for the self-assembly in a crystallization-like process. Based on the transmission electron microscopy (TEM) images obtained a mechanism for the self-assembly was suggested. PMID:27384086

  13. Electrophoretic dynamics of self-assembling branched DNA structures

    Heuer, Daniel Milton

    This study advances our understanding of the electrophoretic dynamics of branched biopolymers and explores technologies designed to exploit their unique properties. New self-assembly techniques were developed to create branched DNA for visualization via fluorescence microscopy. Experiments in fixed gel networks reveal a distinct trapping behavior, in contrast with linear topologies. The finding that detection can be achieved by introducing a branch point contributes significantly to the field of separation science and can be exploited to develop new applications. Results obtained in polymer solutions point to identical mobilities for branched and linear topologies, despite large differences in their dynamics. This finding led to a new description of electrophoresis based on non-Newtonian viscoelastic effects in the electric double layer surrounding a charged object. This new theoretical framework presents a new outlook important not only to the electrophoretic physics of nucleic acids, but all charged objects including proteins, colloids, and nanoparticles. To study the behavior of smaller biopolymers, such as restriction fragments and recombination intermediates, a library of symmetrically branched DNA was synthesized followed by characterization in gels. The experimental results contribute a large body of information relating molecular architecture and the dynamics of rigid structures in an electric field. The findings allow us to create new separation technologies based on topology. These contributions can also be utilized in a number of different applications including the study of recombination intermediates and the separation of proteins according to structure. To demonstrate the importance of these findings, a sequence and mutation detection technique was envisioned and applied for genetic analysis. Restriction fragments from mutation "hotspots" in the p53 tumor suppressor gene, known to play a role in cancer development, were analyzed with this technique

  14. Autonomous Assembly of Modular Structures in Space and on Extraterrestrial Locations

    Alhorn, Dean C.

    2005-01-01

    The fulfillment of the new US. National Vision for Space Exploration requires many new enabling technologies to accomplish the goal of utilizing space for commercial activities and for returning humans to the moon and extraterrestrial environments. Traditionally, flight structures are manufactured as complete systems and require humans to complete the integration and assembly in orbit. These structures are bulky and require the use of heavy launch vehicles to send the units to the desired location, e.g. International Space Station (ISS). This method requires a high degree of safety, numerous space walks and significant cost for the humans to perform the assembly in orbit. For example, for assembly and maintenance of the ISS, 52 Extravehicular Activities (EVA's) have been performed so far with a total EVA time of approximately 322 hours. Sixteen (16) shuttle flights haw been to the ISS to perform these activities with an approximate cost of $450M per mission. For future space missions, costs have to be reduced to reasonably achieve the exploration goals. One concept that has been proposed is the autonomous assembly of space structures. This concept is an affordable, reliable solution to in-space and extraterrestrial assembly operations. Assembly is autonomously performed when two components containing onboard electronics join after recognizing that the joint is appropriate and in the precise position and orientation required for assembly. The mechanism only activates when the specifications are correct and m a nominal range. After assembly, local sensors and electronics monitor the integrity of the joint for feedback to a master controller. To achieve this concept will require a shift in the methods for designing space structures. In addition, innovative techniques will be required to perform the assembly autonomously. Monitoring of the assembled joint will be necessary for safety and structural integrity. If a very large structure is to be assembled in orbit, then

  15. Structural Consequences of Anionic Host-Cationic Guest Interactions in a Supramolecular Assembly

    Pluth, Michael D.; Johnson, Darren W.; Szigethy, Geza; Davis, Anna V.; Teat, Simon J.; Oliver, Allen G.; Bergman, Robert G.; Raymond, Kenneth N.

    2008-07-09

    The molecular structure of the self-assembled supramolecular assembly [M{sub 4}L{sub 6}]{sup 12-} has been explored with different metals (M = Ga{sup III}, Fe{sup III}, Ti{sup IV}) and different encapsulated guests (NEt{sub 4}{sup +}, BnNMe{sub 3}{sup +}, Cp{sub 2}Co{sup +}, Cp*{sub 2}Co{sup +}) by X-ray crystallography. While the identity of the metal ions at the vertices of the M{sub 4}L{sub 6} structure is found to have little effect on the assembly structure, encapsulated guests significantly distort the size and shape of the interior cavity of the assembly. Cations on the exterior of the assembly are found to interact with the assembly through either {pi}-{pi}, cation-{pi}, or CH-{pi} interactions. In some cases, the exterior guests interact with only one assembly, but cations with the ability to form multiple {pi}-{pi} interactions are able to interact with adjacent assemblies in the crystal lattice. The solvent accessible cavity of the assembly is modeled using the rolling probe method and found to range from 253-434 {angstrom}{sup 3}, depending on the encapsulated guest. Based on the volume of the guest and the volume of the cavity, the packing coefficient for each host-guest complex is found to range from 0.47-0.67.

  16. The structure of heart rate asymmetry: deceleration and acceleration runs

    A family of new heart rate asymmetry measures is introduced, namely deceleration and acceleration runs, as well as entropic measures summarizing their distribution. We introduce the theoretical run distribution for shuffled data and use it as a reference for interpreting the results. The measures defined in the paper are applied to actual 24 h Holter ECG recordings from 87 healthy people, and it is demonstrated that the patterns of accelerations are different from those of decelerations. Acceleration runs are longer and more numerous: all runs of accelerations, with the exception of lengths 3 and 4, are more numerous than those of decelerations. These findings are reflected in the difference between the entropic measures for acceleration and deceleration runs: for 74 subjects the acceleration-related entropic parameter is greater than that of decelerations (p < 0.001). For shuffled data there is no difference in the above parameters, and there are more short runs and fewer long runs than in physiological data. The influence of the measuring equipment resolution is also discussed

  17. Dielectric laser acceleration of non-relativistic electrons at a photonic structure

    This thesis reports on the observation of dielectric laser acceleration of non-relativistic electrons via the inverse Smith-Purcell effect in the optical regime. Evanescent modes in the vicinity of a periodic grating structure can travel at the same velocity as the electrons along the grating surface. A longitudinal electric field component is used to continuously impart momentum onto the electrons. This is only possible in the near-field of a suitable photonic structure, which means that the electron beam has to pass the structure within about one wavelength. In our experiment we exploit the third spatial harmonic of a single fused silica grating excited by laser pulses derived from a Titanium:sapphire oscillator and accelerate non-relativistic 28 keV electrons. We measure a maximum energy gain of 280 eV, corresponding to an acceleration gradient of 25 MeV/m, already comparable with state-of-the-art radio-frequency linear accelerators. To experience this acceleration gradient the electrons approach the grating closer than 100 nm. We present the theory behind grating-based particle acceleration and discuss simulation results of dielectric laser acceleration in the near-field of photonic grating structures, which is excited by near-infrared laser light. Our measurements show excellent agreement with our simulation results and therefore confirm the direct acceleration with the light field. We further discuss the acceleration inside double grating structures, dephasing effects of non-relativistic electrons as well as the space charge effect, which can limit the attainable peak currents of these novel accelerator structures. The photonic structures described in this work can be readily concatenated and therefore represent a scalable realization of dielectric laser acceleration. Furthermore, our structures are directly compatible with the microstructures used for the acceleration of relativistic electrons demonstrated in parallel to this work by our collaborators in

  18. Dielectric laser acceleration of non-relativistic electrons at a photonic structure

    Breuer, John

    2013-08-29

    This thesis reports on the observation of dielectric laser acceleration of non-relativistic electrons via the inverse Smith-Purcell effect in the optical regime. Evanescent modes in the vicinity of a periodic grating structure can travel at the same velocity as the electrons along the grating surface. A longitudinal electric field component is used to continuously impart momentum onto the electrons. This is only possible in the near-field of a suitable photonic structure, which means that the electron beam has to pass the structure within about one wavelength. In our experiment we exploit the third spatial harmonic of a single fused silica grating excited by laser pulses derived from a Titanium:sapphire oscillator and accelerate non-relativistic 28 keV electrons. We measure a maximum energy gain of 280 eV, corresponding to an acceleration gradient of 25 MeV/m, already comparable with state-of-the-art radio-frequency linear accelerators. To experience this acceleration gradient the electrons approach the grating closer than 100 nm. We present the theory behind grating-based particle acceleration and discuss simulation results of dielectric laser acceleration in the near-field of photonic grating structures, which is excited by near-infrared laser light. Our measurements show excellent agreement with our simulation results and therefore confirm the direct acceleration with the light field. We further discuss the acceleration inside double grating structures, dephasing effects of non-relativistic electrons as well as the space charge effect, which can limit the attainable peak currents of these novel accelerator structures. The photonic structures described in this work can be readily concatenated and therefore represent a scalable realization of dielectric laser acceleration. Furthermore, our structures are directly compatible with the microstructures used for the acceleration of relativistic electrons demonstrated in parallel to this work by our collaborators in

  19. The assembly of large structures in space. [radio astronomy telescope and microwave antenna

    Smith, G. W.; Brodie, S. B.

    1975-01-01

    Techniques developed for orbital assembly of the support structure for a 1000 meter diameter microwave power transmission system antenna are described. The operation is performed in two phases using the shuttle remote manipulator system in low earth orbit, and a mobile assembler in geosynchronous orbit.

  20. Structural integrity assessment and stress measurement of CHASNUPP-1 fuel assembly

    Waseem; Murtaza Ghulam; Siddiqui Ashfaq Ahmad; Akhtar Syed Waseem

    2016-01-01

    Fuel assembly of the PWR nuclear power plant is a long and flexible structure. This study has been made in an attempt to find the structural integrity of the fuel assembly (FA) of Chashma Nuclear Power Plant-1 (CHASNUPP-1) at room temperature in air. The non-linear contact and structural tensile analysis have been performed using ANSYS 13.0, in order to determine the fuel assembly (FA) elongation behaviour as well as the location and values of the stress intensity and stresses developed in ax...

  1. Structural simulations of nanomaterials self-assembled from ionic macrocycles.

    van Swol, Frank B.; Medforth, Craig John (University of New Mexico, Albuquerque, NM)

    2010-10-01

    Recent research at Sandia has discovered a new class of organic binary ionic solids with tunable optical, electronic, and photochemical properties. These nanomaterials, consisting of a novel class of organic binary ionic solids, are currently being developed at Sandia for applications in batteries, supercapacitors, and solar energy technologies. They are composed of self-assembled oligomeric arrays of very large anions and large cations, but their crucial internal arrangement is thus far unknown. This report describes (a) the development of a relevant model of nonconvex particles decorated with ions interacting through short-ranged Yukawa potentials, and (b) the results of initial Monte Carlo simulations of the self-assembly binary ionic solids.

  2. Development of laboratory acceleration test method for service life prediction of concrete structures

    Service life prediction of nuclear power plants depends on the application of history of structures, field inspection and test, the development of laboratory acceleration tests, their analysis method and predictive model. In this study, laboratory acceleration test method for service life prediction of concrete structures and application of experimental test results are introduced. This study is concerned with environmental condition of concrete structures and is to develop the acceleration test method for durability factors of concrete structures e.g. carbonation, sulfate attack, freeze-thaw cycles and shrinkage-expansion etc

  3. Fabrication and tuning techniques for side-coupled electron accelerator structures

    Beginning in 1979, Los Alamos entered into a collaboration with the National Bureau of Standards (NBS) to develop an advanced cw microtron accelerator. The accelerating structures (one 0.9-m-long, one 2.7-m-long, and two 4.0-m-long) containing a total of 184 accelerating cavities have been fabricated and tuned to the 2380-MHz operating frequency. New methods simplified the fabrication of these structures and eliminated several furnace-brazing steps. These fabrication methods, lathe-mounted tuning fixtures, and streamlined tuning techniques were developed to allow efficient production of side-coupled structures. These techniques are now being applied to the 2450-MHz racetrack microtron accelerator structures being fabricated at Los Alamos for the Nuclear Physics Department of the University of Illinois. Refinements of the described techniques will allow future accelerators of this type to be fabricated by private industry

  4. ON FABRICATION AND BRAZING OF 15A, 120 keV CONTINUOUS DUTY ACCELERATOR GRID ASSEMBLIES

    Biagi, L.A.; Koehler, G.W.; Paterson, J.A.

    1980-05-01

    The development of high intensity neutral beam injectors at the Lawrence Berkeley Laboratory has progressed from relatively low duty cycle, low energy devices to the next generation of continuous duty high energy units. The earlier pulsed versions were designed with edge cooled grid structures described ·in a previous publication. The prerequisites set by the higher duty cycle devices no longer allow the edge cooling methods to be employed. Hollow molybdenum grid rails with deionized cooling water flowing at pressures of approximately 1.73 x 10{sup 6}Pa (250 PSI) at from 1.135 to 1.89 liters per minute (.3 to .5 GPM) are brazed to Type 304L stainless steel rail holders.

  5. Confinement and internal structure of radiatively accelerated quasar clouds

    Weymann, R.

    1976-09-01

    The equation of transfer for Lyman ..cap alpha.. and the Lyman continuum is solved for plane-parallel slabs of hydrogen with optical depths up to 25,000 in the line center to find the radiative acceleration as a function of position in the slab. The distribution of gas pressure and density which yields a constant acceleration and which matches the prescribed external pressure on the boundaries is then found. For optical depths less than about 36, solutions are obtained for arbitrarily low ratios of external pressure to incident radiation pressure. For optical depths larger than this, solutions are possible only if this ratio exceeds a critical value, and the acceleration of the cloud goes to zero and the column density to infinity as this critical value is approached. (AIP)

  6. Confinement and internal structure of radiatively accelerated quasar clouds

    The equation of transfer for Lyman α and the Lyman continuum is solved for plane-parallel slabs of hydrogen with optical depths up to 25,000 in the line center to find the radiative acceleration as a function of position in the slab. The distribution of gas pressure and density which yields a constant acceleration and which matches the prescribed external pressure on the boundaries is then found. For optical depths less than about 36, solutions are obtained for arbitrarily low ratios of external pressure to incident radiation pressure. For optical depths larger than this, solutions are possible only if this ratio exceeds a critical value, and the acceleration of the cloud goes to zero and the column density to infinity as this critical value is approached

  7. Molybdenum sputtering film characterization for high gradient accelerating structures

    S.Bini; B.Spataro; A.Marcelli; S.Sarti; V.A.Dolgashev; S.Tantawi; A.D.Yeremian

    2013-01-01

    Technological advancements are strongly required to fulfill the demands of new accelerator devices with the highest accelerating gradients and operation reliability for the future colliders.To this purpose an extensive R&D regarding molybdenum coatings on copper is in progress.In this contribution we describe chemical composition,deposition quality and resistivity properties of different molybdenum coatings obtained via sputtering.The deposited films are thick metallic disorder layers with different resistivity values above and below the molibdenum dioxide reference value.Chemical and electrical properties of these sputtered coatings have been characterized by Rutherford backscattering,XANES and photoemission spectroscopy.We will also consider multiple cells standing wave section coated by a molybdenum layer designed to improve the performance of X-Band accelerating systems.

  8. Accelerate!

    Kotter, John P

    2012-11-01

    The old ways of setting and implementing strategy are failing us, writes the author of Leading Change, in part because we can no longer keep up with the pace of change. Organizational leaders are torn between trying to stay ahead of increasingly fierce competition and needing to deliver this year's results. Although traditional hierarchies and managerial processes--the components of a company's "operating system"--can meet the daily demands of running an enterprise, they are rarely equipped to identify important hazards quickly, formulate creative strategic initiatives nimbly, and implement them speedily. The solution Kotter offers is a second system--an agile, networklike structure--that operates in concert with the first to create a dual operating system. In such a system the hierarchy can hand off the pursuit of big strategic initiatives to the strategy network, freeing itself to focus on incremental changes to improve efficiency. The network is populated by employees from all levels of the organization, giving it organizational knowledge, relationships, credibility, and influence. It can Liberate information from silos with ease. It has a dynamic structure free of bureaucratic layers, permitting a level of individualism, creativity, and innovation beyond the reach of any hierarchy. The network's core is a guiding coalition that represents each level and department in the hierarchy, with a broad range of skills. Its drivers are members of a "volunteer army" who are energized by and committed to the coalition's vividly formulated, high-stakes vision and strategy. Kotter has helped eight organizations, public and private, build dual operating systems over the past three years. He predicts that such systems will lead to long-term success in the 21st century--for shareholders, customers, employees, and companies themselves. PMID:23155997

  9. Summary report: Working Group 3 on 'Novel Structure-Based Acceleration Concepts'

    The Working Group 3 papers were divided into two general categories, those related to laser-based schemes and those based on microwave technology. In the laser-based area highlights include ongoing theoretical and experimental efforts to demonstrate electron acceleration in vacuum based either on ponderomotive or nonponderomotive mechanisms. Papers on advanced issues such as staging the laser acceleration process, compensating for space charge effects, improving inverse bremsstrahlung acceleration, and possible laser linear collider designs were also presented. In the microwave area, noteworthy contributions were reviewed on slow-wave accelerating structures employing dielectric loading; smooth-wall, fast-wave structures with a helical wiggler for inverse FEL acceleration; multistaging of smooth-wall, fast-wave structures with an axial magnetic field for increased energy cyclotron autoresonance acceleration; and technological approaches for fabrication and diamond coating of W-band structures to achieve high acceleration gradients. Dielectric-loaded structures to support multimode, multibunch wakefield excitations for trailing bunch acceleration were also discussed

  10. Tandem accelerators

    After the installation of Ti-acceleration tubes and substantial modifications and additions to the EN tandem accelerator the performance of the machine has stabilized. The voltage behaviour of the tubes obviously improves as conditioning times necessary to run up to 6 MV decrease. A gridded lens has been added at the entrance of the first acceleration tube, and a second foil stripper is now installed in the short dead section between the high-energy tubes. The MP tandem also has been running stably during most of the year. However, beam instabilities originating from the last tube section and wear problems at the low-energy set of pelletron-chains caused some loss of beam time. During the fall, one set of pelletron charging chains has to be replaced after 49,000 hours of operation. In the course of the year, the MP and the EN tandem accelerators finished their 100,000th and 150,000th hours of operations, respectively. Preparations for the installation of the 3 MV negative heavy ion injector for the MP are progressing steadily. External beam transport, terminal ion optics, and data acquisition and control systems are to a major extent completed; the integration of the terminal power supplies has started. After the final assembly of the accelerator column structure, first voltage runs can be performed. (orig.)

  11. Effect of Structural Modifications on the Self-Assembly of Oligoprolines Conjugated with Sterically Demanding Chromophores.

    Lewandowska, Urszula; Zajaczkowski, Wojciech; Pisula, Wojciech; Ma, Yingjie; Li, Chen; Müllen, Klaus; Wennemers, Helma

    2016-03-01

    Conjugates between oligoprolines and sterically demanding perylene monoimides (PMIs) form hierarchical supramolecular self-assemblies. The influence of the length and stereochemistry at the attachment site between the peptide backbone and the chromophore on the self-assembly properties of the conjugates was explored. Comparison between oligoprolines bearing 4R- or 4S-configured azidoprolines (Azp) for the conjugation with the PMIs revealed that diastereoisomers with 4R configuration guide the self-assembly consistently better than conjugates with 4S configuration. Elongating the peptide chain beyond nine proline residues or introducing structural "errors", by altering the absolute configuration of one stereogenic center at the outside of the functionalizable oligoproline helix, lowered the efficacy of self-assembly significantly, both in solution phase and in the solid state. The results showed how subtle structural modifications allow for tuning the self-assembly of chromophores and provided further design principles for the development of peptide-chromophore conjugates into nanostructured materials. PMID:26891419

  12. Development and verification testing of automation and robotics for assembly of space structures

    Rhodes, Marvin D.; Will, Ralph W.; Quach, Cuong C.

    1993-01-01

    A program was initiated within the past several years to develop operational procedures for automated assembly of truss structures suitable for large-aperture antennas. The assembly operations require the use of a robotic manipulator and are based on the principle of supervised autonomy to minimize crew resources. A hardware testbed was established to support development and evaluation testing. A brute-force automation approach was used to develop the baseline assembly hardware and software techniques. As the system matured and an operation was proven, upgrades were incorprated and assessed against the baseline test results. This paper summarizes the developmental phases of the program, the results of several assembly tests, the current status, and a series of proposed developments for additional hardware and software control capability. No problems that would preclude automated in-space assembly of truss structures have been encountered. The current system was developed at a breadboard level and continued development at an enhanced level is warranted.

  13. Moments applied in the manual assembly of space structures - Ease biomechanics results from STS-61B. [Experimental Assembly of Structures in EVA

    Cousins, D.; Akin, D. L.

    1989-01-01

    Measurements of the level and pattern of moments applied in the manual assembly of a space structure were made in extravehicular activity (EVA) and neutral buoyancy simulation (NBS). The Experimental Assembly of Structures in EVA program included the repeated assembly of a 3.6 m tetrahedral truss structure in EVA on STS-61B after extensive neutral buoyancy crew training. The flight and training structures were of equivalent mass and geometry to allow a direct correlation between EVA and NBS performance. A stereo photographic motion camera system was used to reconstruct in three dimensions rotational movements of structural beams during assembly. Moments applied in these manual handling tasks were calculated on the basis of the reconstructed movements taking into account effects of inertia, drag and virtual mass. Applied moments of 2.0 Nm were typical for beam rotations in EVA. Corresponding applied moments in NBS were typically up to five times greater. Moments were applied as impulses separated by several seconds of coasting in both EVA and NBS. Decelerating impulses were only infrequently observed in NBS.

  14. Real space simulation with reality modeling for vibration table by an assembly structural analysis

    It has been disciplined to realize a simulation space, which can emulate real world in digital space, such as so named either virtual reality or virtual facility. In order to create a huge and complex space like nuclear facilities of a real world, there are lack of methodology and technology for reproducing facilities in digital space. In this paper, it is realized an assembly structural analysis for supplying one of the methodology to reproduce facilities in digital space. The first attempt of the assembly structural analysis is accomplished by finite element analysis by integrating parts of facilities. Since the assembly structural analysis requests massive calculation, grid computing was applied for the computational resource. It has been practiced numerical experiments for a test reactor, HTTR: High Temperature engineering Test Reactor driven by Japan Atomic Energy Agency. The assembly structural analysis by finite element method is confirmed to be able to analyze a huge and complex facility. (author)

  15. Superconducting accelerating structures for very low velocity ion beams

    Xu, J.; Shepard, K.W.; Ostroumov, P.N.; Fuerst, J.D.; Waldschmidt, G.; /Argonne; Gonin, I.V.; /Fermilab

    2008-01-01

    This paper presents designs for four types of very-low-velocity superconducting accelerating cavity capable of providing several MV of accelerating potential per cavity, and suitable for particle velocities in the range 0.006 < v/c < 0.06. Superconducting TEM-class cavities have been widely applied to CW acceleration of ion beams. SC linacs can be formed as an array of independently-phased cavities, enabling a variable velocity profile to maximize the output energy for each of a number of different ion species. Several laboratories in the US and Europe are planning exotic beam facilities based on SC linacs. The cavity designs presented here are intended for the front-end of such linacs, particularly for the post-acceleration of rare isotopes of low charge state. Several types of SC cavities have been developed recently to cover particle velocities above 0.06c. Superconducting four-gap quarter-wave resonators for velocities 0.008 < {beta} = v/c < 0.05 were developed about two decades ago and have been successfully operated at the ATLAS SC linac at Argonne National Laboratory. Since that time, progress in simulation tools, cavity fabrication and processing have increased SC cavity gradients by a factor of 3-4. This paper applies these tools to optimize the design of a four-gap quarter-wave resonator for exotic beam facilities and other low-velocity applications.

  16. Numerically optimized structures for dielectric asymmetric dual-grating laser accelerators

    Optical scale dielectric structures are promising candidates to realize future compact, low cost particle accelerators, since they can sustain high acceleration gradients in the range of GeV/m. Here, we present numerical simulation results for a dielectric asymmetric dual-grating accelerator. It was found that the asymmetric dual-grating structures can efficiently modify the laser field to synchronize it with relativistic electrons, therefore increasing the average acceleration gradient by ∼10% in comparison to symmetric structures. The optimum pillar height which was determined by simulation agrees well with that estimated analytically. The effect of the initial kinetic energy of injected electrons on the acceleration gradient is also discussed. Finally, the required laser parameters were calculated analytically and a suitable laser is proposed as energy source

  17. Experimental demonstration of wakefield effects in a THz planar diamond accelerating structure

    Antipov, S; Kanareykin, A; Butler, J E; Yakimenko, V; Fedurin, M; Kusche, K; Gai, W

    2012-01-01

    We have directly measured THz wakefields induced by a subpicosecond, intense relativistic electron bunch in a diamond loaded accelerating structure via the wakefield acceleration method. We present here the beam test results from the first diamond based structure. Diamond has been chosen for its high breakdown threshold and unique thermoconductive properties. Fields produced by a leading (drive) beam were used to accelerate a trailing (witness) electron bunch which followed the drive bunch at a variable distance. The energy gain of a witness bunch as a function of its separation from the drive bunch describes the time structure of the generated wakefield.

  18. Analytical formulae for the loss factors and wakefields of a rectangular accelerating structure

    Wakefields is a rectangular accelerating structure can be calculated in time domain by directly solving Maxwell's equations by a 3D numerical code. In this paper we will give analytical formulae to calculate the synchronous modes' loss factors. From these analytical formulae one can get the delta function wakefields. The relations between the loss factors (wakefields) and the structure's geometrical dimensions are well established. These analytical expressions of loss factors can be used also in a single rectangular resonant cavity. It is shown that the potential application of a rectangular accelerating structure is to accelerate a flat beam in a linear collider. (author)

  19. Design and validation of wireless acceleration sensor network for structural health monitoring

    Yu Yan; Ou Jinping

    2006-01-01

    A wireless sensor network is proposed to monitor the acceleration of structures for the purpose of structural health monitoring of civil engineering structures. Using commercially available parts, several modules are constructed and integrated into complete wireless sensors and base stations. The communication protocol is designed and the fusion arithmetic of the temperature and acceleration is embedded in the wireless sensor node so that the measured acceleration values are more accurate. Measures are adopted to finish energy optimization, which is an important issue for a wireless sensor network. The test is performed on an offshore platform model, and the experimental results are given to show the feasibility of the designed wireless sensor network.

  20. Contribution to the study of accelerating structure for electrons and respective radiofrequency couplers

    In this work, the experimental results pertaining to the construction and evaluation of a constant gradient accelerating structure and of the radiofrequency couplers are presented. The theoretical methods to determine the initial dimensions of the iris-loaded accelerating structure are presented. The final dimensions have been experimentally determined utilizing four three-cavity sections representing the 4 sup(th), 12 sup(th), 20 sup(th) and 27 sup(th) cavities of the final structure. The diameters of the cavities were corrected for variations of temperature, pressure and humidity. A v sub(p) = c, constant gradient, twelve-cavity prototype of the accelerating structure have been constructed and its principal parameters were experimentally determined according to methods also described in this work. Two prototypes of door-knob type radiofrequency couplers have been constructed and experimental procedures to match and tune the couplers and the accelerating structure were implemented. (author)

  1. Linear Accelerators

    Vretenar, M

    2014-01-01

    The main features of radio-frequency linear accelerators are introduced, reviewing the different types of accelerating structures and presenting the main characteristics aspects of linac beam dynamics.

  2. Inflatable Hangar for Assembly of Large Structures in Space

    Wilcox, Brian H.

    2012-01-01

    The NASA Human Space Flight program is interested in projects where humans, beyond low-Earth orbit (LEO), can make an important and unique contribution that cannot be reasonably accomplished purely by robotic means, and is commensurate with the effort and cost associated with human spaceflight. Robotic space telescope missions have been conceived and launched as completed assemblies (e.g., Hubble) or as jack-in-the-box one-time deployments (e.g., James Webb). If it were possible to assemble components of a very large telescope from one or two launches into a telescope that was vastly greater in light-gathering power and resolution, that would constitute a breakthrough. Large telescopes on Earth, like all one-off precision assembly tasks, are done by humans. Humans in shirtsleeves (or cleanroom bunny suits) can perform tasks of remarkable dexterity and precision. Unfortunately, astronauts in pressure suits cannot perform such dexterous and precise tasks because of the limitations of the pressurized gloves. If a large, inflatable hangar were placed in high orbit, along with all the components needed for a large assembly such as a large telescope, then humans in bunny suits could perform the same sorts of extremely precise and dexterous assembly that they could be expected to perform on Earth. Calculations show that such an inflatable hangar, and the necessary gas to make it safe to occupy by shirtsleeves humans wearing oxygen masks, fits within the mass and volume limitations of the proposed "Space Launch System" heavy-lift rocket. A second launch could bring up all the components of an approximately 100-meter-diameter or larger telescope. A large [200 ft (approximately 61 m) in diameter] inflated fabric sphere (or hangar) would contain four humans in bunny suits. The sphere would contain sufficient atmospheric pressure so that spacesuits would not be necessary [about 3.2 psi (approximately 22 kPa)]. The humans would require only oxygen masks and small backpacks

  3. M4D: a powerful tool for structured programming at assembly level for MODCOMP computers

    Structured programming techniques offer numerous benefits for software designers and form the basis of the current high level languages. However, these techniques are generally not available to assembly programmers. The M4D package was therefore developed for a large project to enable the use of structured programming constructs such as DO.WHILE-ENDDO and IF-ORIF-ORIF...-ELSE-ENDIF in the assembly code for MODCOMP computers. Programs can thus be produced that have clear semantics and are considerably easier to read than normal assembly code, resulting in reduced program development and testing effort, and in improved long-term maintainability of the code. This paper describes the M4D structured programming tool as implemented for MODCOMP'S MAX III and MAX IV assemblers, and illustrates the use of the facility with a number of examples

  4. Direct assembly of nanoparticles for large-scale fabrication of nanodevices and structures

    Non-uniform electric fields are utilized to direct the large scale assembly of colloidal nanoparticles in nanoscale structures over large areas. Using micro- and nanoscale templates, various nanoparticles can be directly assembled into parallel wires, cross-wires, and many other complex structures. The assembly process is controlled by electric field, time, and geometric design of templates. The results show that single nanoparticle wires as small as 10 nm wide and 100,000 nm long as well as other nanoparticle structures can be fabricated using electrophoresis over a large area. In addition, the directed assembly of polymeric and conductive nanoparticle nanowires and networks has been demonstrated using dielectrophoresis. The nanoparticle wires can be further oriented along the direction of an externally introduced hydrodynamic flow. The presented technique is a promising approach for large scale manufacturing of nanoscale devices for many applications including biosensors and nanoelectronics.

  5. Robotic Assembly of Truss Structures for Space Systems and Future Research Plans

    Doggett, William

    2002-01-01

    Many initiatives under study by both the space science and earth science communities require large space systems, i.e. with apertures greater than 15 m or dimensions greater than 20 m. This paper reviews the effort in NASA Langley Research Center's Automated Structural Assembly Laboratory which laid the foundations for robotic construction of these systems. In the Automated Structural Assembly Laboratory reliable autonomous assembly and disassembly of an 8 meter planar structure composed of 102 truss elements covered by 12 panels was demonstrated. The paper reviews the hardware and software design philosophy which led to reliable operation during weeks of near continuous testing. Special attention is given to highlight the features enhancing assembly reliability.

  6. Photo-induced reversible structural transition of cationic diphenylalanine peptide self-assembly.

    Ma, Hongchao; Fei, Jinbo; Li, Qi; Li, Junbai

    2015-04-17

    The photo-induced self-assembly of a cationic diphenylalanine peptide (CDP) is investigated using a photoswitchable sulfonic azobenzene as the manipulating unit. A reversible structural transition between a branched structure and a vesicle-like structure is observed by alternating between UV and visible light irradiation. PMID:25405602

  7. Self-assembly of nanocomponents into composite structures: derivation and simulation of Langevin equations.

    Pankavich, S; Shreif, Z; Miao, Y; Ortoleva, P

    2009-05-21

    The kinetics of the self-assembly of nanocomponents into a virus, nanocapsule, or other composite structure is analyzed via a multiscale approach. The objective is to achieve predictability and to preserve key atomic-scale features that underlie the formation and stability of the composite structures. We start with an all-atom description, the Liouville equation, and the order parameters characterizing nanoscale features of the system. An equation of Smoluchowski type for the stochastic dynamics of the order parameters is derived from the Liouville equation via a multiscale perturbation technique. The self-assembly of composite structures from nanocomponents with internal atomic structure is analyzed and growth rates are derived. Applications include the assembly of a viral capsid from capsomers, a ribosome from its major subunits, and composite materials from fibers and nanoparticles. Our approach overcomes errors in other coarse-graining methods, which neglect the influence of the nanoscale configuration on the atomistic fluctuations. We account for the effect of order parameters on the statistics of the atomistic fluctuations, which contribute to the entropic and average forces driving order parameter evolution. This approach enables an efficient algorithm for computer simulation of self-assembly, whereas other methods severely limit the timestep due to the separation of diffusional and complexing characteristic times. Given that our approach does not require recalibration with each new application, it provides a way to estimate assembly rates and thereby facilitate the discovery of self-assembly pathways and kinetic dead-end structures. PMID:19466829

  8. Accelerator driven assembly

    Balderas, J.; Cappiello, M.; Cummings, C.E.; Davidson, R. [and others

    1997-01-01

    This report addresses a Los Alamos National Laboratory (LANL) proposal to build a pulsed neutron source for simulating nuclear-weapons effects. A point design for the pulsed neutron facility was initiated early in FY94 after hosting a Defense Nuclear Agency (DNA) panel review and after subsequently visiting several potential clients and users. The technical and facility designs contained herein fulfill the Statement of Work (SOW) agreed upon by LANL and DNA. However, our point designs and parametric studies identify a unique, cost-effective, above-ground capability for neutron nuclear-weapons-effects studies at threat levels. This capability builds on existing capital installations and infrastructure at LANL. We believe that it is appropriate for us, together with the DNA, to return to the user community and ask for their comments and critiques. We also realize that the requirements of last year have changed significantly. Therefore, the present report is a `working document` that may be revised where feasible as we learn more about the most recent Department of Defense (DoD) and Department of Energy (DOE) needs.

  9. Spectrographic Approach to Study of RF Conditioning Process in Accelerating RF Structures

    Tomizawa, H; Taniuchi, T

    2004-01-01

    The acceleration gradient of a linac is limited by rf breakdown in its accelerating structure. We applied an imaging spectrograph system to study the mechanism of rf breakdown phenomena in accelerating rf structures. Excited outgases emit light during rf breakdown, and the type of outgases depend on surface treatments and rinsing methods for their materials. To study rf breakdown, we used 2-m-long accelerating structures and investigated the effects when high-pressure ultrapure water rinsing (HPR) treatment was applied to these rf structures. We performed experiments to study the outgases under rf conditioning with quadruple mass spectroscopy and imaging spectrography. As a result, we could observe instantly increasing signals at mass numbers of 2 (H2

  10. New structure for accelerating heavy ions; Une nouvelle structure acceleratrice d'ions lourds

    Pottier, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1969-06-01

    A new type of accelerating structure is described which is particular suited to heavy ions (high wavelength, high shunt impedance, small size). Its properties are analyzed and compared to those of other structures (more particularly the lines). It is shown that a mode of operation exists of which the shunt impedance in the station mode has 80 per cent of its value for the progressive mode. Finally results are given obtained with a small experimental apparatus which uses this structure. (author) [French] On decrit un nouveau type de structure acceleratrice, particulierement appropriee aux ions lourds (grande longueur d'onde, forte impedance-shunt, faibles dimensions). Ses proprietes sont analysees et comparees a celles d'autres structures (plus particulierement les lignes). On met en evidence un mode de fonctionnement pour lequel l'impedance shunt en regime stationnaire vaut 80 pour cent de l'impedance shunt en regime progressif. Enfin on decrit les resultats obtenus a l'aide d'une petite machine experimentale mettant en oeuvre cette structure. (auteur)

  11. CPU-GPU hybrid accelerating the Zuker algorithm for RNA secondary structure prediction applications

    2012-01-01

    Background Prediction of ribonucleic acid (RNA) secondary structure remains one of the most important research areas in bioinformatics. The Zuker algorithm is one of the most popular methods of free energy minimization for RNA secondary structure prediction. Thus far, few studies have been reported on the acceleration of the Zuker algorithm on general-purpose processors or on extra accelerators such as Field Programmable Gate-Array (FPGA) and Graphics Processing Units (GPU). To the best of ou...

  12. Modification of the beam transfer model of travelling wave accelerator structures at SACLA

    In order to perform efficient beam tuning at SACLA, we had developed a beam transfer model to calculate the beam transverse envelope in a linear accelerator using linear symplectic matrices. However the measured beam orbit responses were not consistent with the calculated orbit. In order to investigate the error source, we modify the transfer matrix of an accelerator structure so that the matrix model reproduces the measured orbit response. In this paper, we report detail of the error source and how the beam transfer model of a travelling wave accelerator structure is modified. (author)

  13. Cold test results of a side-coupled standing-wave electron-accelerating structure

    Song, Ki Baek; Li, Yonggui; Lee, Sanghyun; Lee, Byeong-No; Park, Hyung Dal; Cha, Sung-Su; Lee, Byung Cheol

    2013-07-01

    The radio-frequency (RF) cavity for the dual-energy S-band electron linear accelerator (LINAC) is designed for a cargo inspection system (CIS) at the Korea Atomic Energy Research Institute (KAERI). The cold test results of the electron accelerator structure, which has a side-coupled standing-wave interlaced-pulse dual-energy mode, are described. The design concept, basic structure, microwave-tuning method, and cold-test procedure are described as well. The measured dispersion curve, spectrum characteristics, ρ-f relation of the power coupler, and axial field distribution of the accelerating gradient are provided.

  14. Theory of factors limiting high gradient operation of warm accelerating structures

    Nusinovich, Gregory S. [Univ. of Maryland, College Park, MD (United States)

    2014-07-22

    This report consists of two parts. In the first part we describe a study of the heating of microprotrusions on surfaces of accelerating structures. This ;process is believed to lead to breakdown in these structures. Our study revealed that for current accelerator parameters melting should not occur due to space charge limitations of the current emitted by a protrusion. The second part describes a novel concept to develop THz range sources based on harmonic cyclotron masers for driving future colliders. This work was stimulated by a recent request of SLAC to develop high power, high-efficiency sources of sub-THz radiation for future high-gradient accelerators.

  15. Accelerating convergence of molecular dynamics-based structural relaxation

    Christensen, Asbjørn

    2005-01-01

    We describe strategies to accelerate the terminal stage of molecular dynamics (MD)based relaxation algorithms, where a large fraction of the computational resources are used. First, we analyze the qualitative and quantitative behavior of the QuickMin family of MD relaxation algorithms and explore...... the influence of spectral properties and dimensionality of the molecular system on the algorithm efficiency. We test two algorithms, the MinMax and Lanczos, for spectral estimation from an MD trajectory, and use this to derive a practical scheme of time step adaptation in MD relaxation algorithms to...

  16. Structure and energetics of diphenylalanine self-assembling on Cu(110).

    Tomba, Giulia; Lingenfelder, Magalí; Costantini, Giovanni; Kern, Klaus; Klappenberger, Florian; Barth, Johannes V; Ciacchi, Lucio Colombi; De Vita, Alessandro

    2007-12-13

    We investigate the dynamical features of the adsorption of diphenylalanine molecules on the Cu(110) surface and of their assembling into supramolecular structures by a combination of quantum and classical atomistic modeling with dynamic scanning tunneling microscopy and spectroscopic experiments. Our results reveal a self-assembling mechanism in which isolated adsorbed molecules change their conformation and adsorption mode as a consequence of their mutual interactions. In particular, the formation of zwitterions after proton transfer between initially neutral molecules is found to be the key event of the assembling process, which stabilizes the supramolecular structures. Because of the constraints on the intermolecular bonds exerted by the surface-molecule interactions, the assembly process is strictly stereoselective, and may suggest a general model for patterning and functionalization of bare metal surfaces with short chiral peptides. PMID:17999478

  17. Automated assembly of large space structures using an expert system executive

    Allen, Cheryl L.

    1993-01-01

    NASA LaRC has developed a unique testbed for investigating the practical problems associated with the assembly of large space structures using robotic manipulators. The testbed is an interdisciplinary effort which considers the full spectrum of assembly problems from the design of mechanisms to the development of software. This paper will describe the automated structures assembly testbed and its operation, detail the expert system executive and its development, and discuss the planned system evolution. Emphasis will be placed on the expert system development of the program executive. The executive program must be capable of directing and reliably performing complex assembly tasks with the flexibility to recover from realistic system errors. By employing an expert system, information pertaining to the operation of the system was encapsulated concisely within a knowledge base. This lead to a substantial reduction in code, increased flexibility, eased software upgrades, and realized a savings in software maintenance costs.

  18. An expert system executive for automated assembly of large space truss structures

    Allen, Cheryl L.

    1993-01-01

    Langley Research Center developed a unique test bed for investigating the practical problems associated with the assembly of large space truss structures using robotic manipulators. The test bed is the result of an interdisciplinary effort that encompasses the full spectrum of assembly problems - from the design of mechanisms to the development of software. The automated structures assembly test bed and its operation are described, the expert system executive and its development are detailed, and the planned system evolution is discussed. Emphasis is on the expert system implementation of the program executive. The executive program must direct and reliably perform complex assembly tasks with the flexibility to recover from realistic system errors. The employment of an expert system permits information that pertains to the operation of the system to be encapsulated concisely within a knowledge base. This consolidation substantially reduced code, increased flexibility, eased software upgrades, and realized a savings in software maintenance costs.

  19. Thermal and structural stability of medium energy target carrier assembly for NOvA at Fermilab

    McGee, M.W.; Ader, C.; Anderson, K.; Hylen, J.; Martens, M.; /Fermilab

    2010-05-01

    The NOvA project will upgrade the existing Neutrino at Main Injector (NuMI) project beamline at Fermilab to accommodate beam power of 700 kW. The Medium Energy (ME) graphite target assembly is provided through an accord with the State Research Center of Russia Institute for High Energy Physics (IHEP) at Protvino, Russia. The effects of proton beam energy deposition within beamline components are considered as thermal stability of the target carrier assembly and alignment budget are critical operational issues. Results of finite element thermal and structural analysis involving the target carrier assembly is provided with detail regarding the target's beryllium windows.

  20. A spacer grid hysteretic model for the structural analysis of spent fuel assemblies under impact

    This paper presents a methodology for determining the response of spent fuel assembly spacer grids subjected to transport cask impact loading. The spacer grids and their interaction with rod-to-rod loading are the most critical components governing the structural response of spent fuel assemblies. The purpose of calculating the assembly response is to determine the resistance to failure of spent fuel during regulatory transport. The failure frequency computed from these analyses is used in calculating category B spent fuel cask containment source term leakage rates for licensing calculations. Without defensible fuel rod failure frequency prediction calculations, assumptions of 100% fuel failure must be made, leading to leak tight cask design requirements

  1. Experimental measurement of acceleration correlations and pressure structure functions in high Reynolds number turbulence

    Xu, Haitao; Vincenzi, Dario; Bodenschatz, Eberhard

    2007-01-01

    We present measurements of fluid particle accelerations in turbulent water flows between counter-rotating disks using three-dimensional Lagrangian particle tracking. By simultaneously following multiple particles with sub-Kolmogorov-time-scale temporal resolution, we measured the spatial correlation of fluid particle acceleration at Taylor microscale Reynolds numbers between 200 and 690. We also obtained indirect, non-intrusive measurements of the Eulerian pressure structure functions by integrating the acceleration correlations. Our experimental data provide strong support to the theoretical predictions of the acceleration correlations and the pressure structure function in isotropic high Reynolds number turbulence by Obukhov and Yaglom in 1951. The measured pressure structure functions display K41 scaling in the inertial range.

  2. Purely peptidic amphiphiles : understanding and controlling their self-assembled structures

    Schuster, Thomas Bernhard

    2011-01-01

    Amphiphilic molecules spontaneously self-assemble into a variety of structures in solution. The term amphiphilic indicates that one part of the molecule is attracted to the solvent, while the other is not. Interactions such as between solute-solvent and solute-solute thus determine the organization. Understanding the self-assembly means understanding those interactions and their driving forces. In the first chapter an overview of the self-organization of amphiphilic molecules into supermolecu...

  3. Structure formation in binary mixtures of lipids and detergents: Self-assembly and vesicle division

    Noguchi, Hiroshi

    2012-01-01

    Self-assembly dynamics in binary surfactant mixtures and structure changes of lipid vesicles induced by detergent solution are studied using coarse-grained molecular simulations. Disk-shaped micelles, the bicelles, are stabilized by detergents surrounding the rim of a bilayer disk of lipids. The self-assembled bicelles are considerably smaller than bicelles formed from vesicle rupture, and their size is determined by the concentrations of lipids and detergents and the interactions between the...

  4. Biomimetic Branched Hollow Fibers Templated by Self-assembled Fibrous Polyvinylpyrrolidone (PVP) Structures in Aqueous Solution

    Qiu, Penghe; Mao, Chuanbin

    2010-01-01

    Branched hollow fibers are common in nature, but to form artificial fibers with a similar branched hollow structure is still a challenge. We discovered that polyvinylpyrrolidone (PVP) could self-assemble into branched hollow fibers in an aqueous solution after aging the PVP solution for about two weeks. Based on this finding, we demonstrated two approaches by which the self-assembly of PVP into branched hollow fibers could be exploited to template the formation of branched hollow inorganic fi...

  5. STRUCTURE DEPENDENT IRRADIATON-INDUCED DESORPTION OF BIPHENYL ALKANETHIOL SELF-ASSEMBLED MONOLAYERS

    Wyczawska, Sabina; Lievens, Peter; Silverans, Roger

    2006-01-01

    1. INTRODUCTION Many nanotechnological applications rely on the patterned functionalization of surfaces with complex organic molecules. In this context, self-assembled monolayers (SAMs) play an important role [ ]. SAMs are spontaneously formed highly ordered and oriented molecular assemblies on a solid substrate. Although most of the insight has been compiled for relatively simple alkanethiol model systems, SAMs containing aromatic structures are gaining much attention lately. They are...

  6. Cumulative Laws,Team Assembling Mechanisms Determining Network Structure

    WU Bin; LIU Qi; YE Qi

    2008-01-01

    A number of researching works have shed light on the field of complex networks recently.We investigate a wide range of real-world networks and find several interesting phenomena.Firstly,almost all of these networks evolve by overlapping new small graphs on former networks.Secondly,not only the degree sequence of the mature network follows a power-law distribution,but also the distribution of the cumulative occurrence times during the growing process are revealed to have a heavy tail.Existing network evolving models do not provide interpretation to these phenomena.We suggest a model based on the team assembling mechanism,which is extracted from the growing processes of real-world networks and requires simple parameters,and produces networks exhibiting these properties observed in the present study and in previous works.

  7. Self-assembly of hierarchically ordered structures in DNA nanotube systems

    Glaser, Martin; Schnauß, Jörg; Tschirner, Teresa; Schmidt, B. U. Sebastian; Moebius-Winkler, Maximilian; Käs, Josef A.; Smith, David M.

    2016-05-01

    The self-assembly of molecular and macromolecular building blocks into organized patterns is a complex process found in diverse systems over a wide range of size and time scales. The formation of star- or aster-like configurations, for example, is a common characteristic in solutions of polymers or other molecules containing multi-scaled, hierarchical assembly processes. This is a recurring phenomenon in numerous pattern-forming systems ranging from cellular constructs to solutions of ferromagnetic colloids or synthetic plastics. To date, however, it has not been possible to systematically parameterize structural properties of the constituent components in order to study their influence on assembled states. Here, we circumvent this limitation by using DNA nanotubes with programmable mechanical properties as our basic building blocks. A small set of DNA oligonucleotides can be chosen to hybridize into micron-length DNA nanotubes with a well-defined circumference and stiffness. The self-assembly of these nanotubes to hierarchically ordered structures is driven by depletion forces caused by the presence of polyethylene glycol. This trait allowed us to investigate self-assembly effects while maintaining a complete decoupling of density, self-association or bundling strength, and stiffness of the nanotubes. Our findings show diverse ranges of emerging structures including heterogeneous networks, aster-like structures, and densely bundled needle-like structures, which compare to configurations found in many other systems. These show a strong dependence not only on concentration and bundling strength, but also on the underlying mechanical properties of the nanotubes. Similar network architectures to those caused by depletion forces in the low-density regime are obtained when an alternative hybridization-based bundling mechanism is employed to induce self-assembly in an isotropic network of pre-formed DNA nanotubes. This emphasizes the universal effect inevitable

  8. A new compact structure for a high intensity low-energy heavy-ion accelerator

    A new compact accelerating structure named Hybrid RFQ is proposed to accelerate a high-intensity low-energy heavy ion beam in HISCL (High Intensive heavy ion SuperConducting Linear accelerator), which is an injector of HIAF (Heavy Ion Advanced Research Facility). It is combined by an alternative series of acceleration gaps and RFQ sections. The proposed structure has a high accelerating ability compared with a conventional RFQ and is more compact than traditional DTLs. A Hybrid RFQ is designed to accelerate 238U34+ from 0.38 MeV/u to 1.33 MeV/u. The operation frequency is described to be 81.25 MHz at CW (continuous wave) mode. The design beam current is 1.0 mA. The results of beam dynamics and RF simulation of the Hybrid RFQ show that the structure has a good performance at the energy range for ion acceleration. The emittance growth is less than 5% in both directions and the RF power is less than 150 kW. In this paper, the results of beam dynamics and RF simulation of the Hybrid RFQ are presented. (authors)

  9. Self-Assembly of Nanocomponents into Composite Structures: Derivation and Simulation of Langevin Equations

    Pankavich, Stephen; Miao, Yinglong; Ortoleva, Peter

    2010-01-01

    The kinetics of the self-assembly of nanocomponents into a virus, nanocapsule, or other composite structure is analyzed via a multiscale approach. The objective is to achieve predictability and to preserve key atomic-scale features that underlie the formation and stability of the composite structures. We start with an all-atom description, the Liouville equation, and the order parameters characterizing nanoscale features of the system. An equation of Smoluchowski type for the stochastic dynamics of the order parameters is derived from the Liouville equation via a multiscale perturbation technique. The self-assembly of composite structures from nanocomponents with internal atomic structure is analyzed and growth rates are derived. Applications include the assembly of a viral capsid from capsomers, a ribosome from its major subunits, and composite materials from fibers and nanoparticles. Our approach overcomes errors in other coarse-graining methods which neglect the influence of the nanoscale configuration on ...

  10. 1.15 Å resolution structure of the proteasome-assembly chaperone Nas2 PDZ domain

    Singh, Chingakham R. [Kansas State University, 338 Ackert Hall, Manhattan, KS 66506 (United States); Lovell, Scott; Mehzabeen, Nurjahan [University of Kansas, Del Shankel Structural Biology Center, Lawrence, KS 66047 (United States); Chowdhury, Wasimul Q.; Geanes, Eric S. [Kansas State University, 338 Ackert Hall, Manhattan, KS 66506 (United States); Battaile, Kevin P. [IMCA-CAT Hauptman–Woodward Medical Research Institute, 9700 South Cass Avenue, Building 435A, Argonne, IL 60439 (United States); Roelofs, Jeroen, E-mail: jroelofs@ksu.edu [Kansas State University, 338 Ackert Hall, Manhattan, KS 66506 (United States)

    2014-03-25

    The proteasome-assembly chaperone Nas2 binds to the proteasome subunit Rpt5 using its PDZ domain. The structure of the Nas2 PDZ domain has been determined. The 26S proteasome is a 2.5 MDa protease dedicated to the degradation of ubiquitinated proteins in eukaryotes. The assembly of this complex containing 66 polypeptides is assisted by at least nine proteasome-specific chaperones. One of these, Nas2, binds to the proteasomal AAA-ATPase subunit Rpt5. The PDZ domain of Nas2 binds to the C-terminal tail of Rpt5; however, it does not require the C-terminus of Rpt5 for binding. Here, the 1.15 Å resolution structure of the PDZ domain of Nas2 is reported. This structure will provide a basis for further insights regarding the structure and function of Nas2 in proteasome assembly.

  11. Application of virtual material in joint surface of complex assembled structures

    崔志琴; 景银萍

    2008-01-01

    In order to acquire the dynamic characteristics of joint surfaces of complex assembled structures, a novel parameter identification technique was adopted. Virtual materials were introduced to simulate the stiffness and damping features of the joint surfaces between two different structures. Properties of the virtual materials, including elasticity modulus, density, and Poisson ratio, were gradually modified. At last, FEM modal results of the assembled structures are consistent with the experimental ones. This proves the feasibility of the simulating method and paves a solid foundation of the further research of the dynamic simulation.

  12. Formation of the self-assembled structures by the ultrasonic cavitation erosion-corrosion effect on carbon steel

    Dayun Yan; Jiadao Wang; Fengbin Liu; Kenan Rajjoub

    2015-01-01

    The cavitation erosion-corrosion effect on the metal surface always forms irregular oxide structures. In this study, we reported the formation of regular self-assembled structures of amorphous nanoparticles around the cavitation erosion pits on carbon steel upon the ultrasonic cavitation in methylene blue solution. Each self-assembled structure was composed of linearly aligned nanoparticles of about 100 nm. The formation of self-assembled structures might be due to the combined effect of corr...

  13. Creating Prebiotic Sanctuary: Self-Assembling Supramolecular Peptide Structures Bind and Stabilize RNA

    Carny, Ohad; Gazit, Ehud

    2011-04-01

    Any attempt to uncover the origins of life must tackle the known `blind watchmaker problem'. That is to demonstrate the likelihood of the emergence of a prebiotic system simple enough to be formed spontaneously and yet complex enough to allow natural selection that will lead to Darwinistic evolution. Studies of short aromatic peptides revealed their ability to self-assemble into ordered and stable structures. The unique physical and chemical characteristics of these peptide assemblies point out to their possible role in the origins of life. We have explored mechanisms by which self-assembling short peptides and RNA fragments could interact together and go through a molecular co-evolution, using diphenylalanine supramolecular assemblies as a model system. The spontaneous formation of these self-assembling peptides under prebiotic conditions, through the salt-induced peptide formation (SIPF) pathway was demonstrated. These peptide assemblies possess the ability to bind and stabilize ribonucleotides in a sequence-depended manner, thus increase their relative fitness. The formation of these peptide assemblies is dependent on the homochirality of the peptide monomers: while homochiral peptides (L-Phe-L-Phe and D-Phe-D-Phe) self-assemble rapidly in aqueous environment, heterochiral diastereoisomers (L-Phe-D-Phe and D-Phe-L-Phe) do not tend to self-assemble. This characteristic consists with the homochirality of all living matter. Finally, based on these findings, we propose a model for the role of short self-assembling peptides in the prebiotic molecular evolution and the origin of life.

  14. Fuel nozzle assembly for use as structural support for a duct structure in a combustor of a gas turbine engine

    Wiebe, David J; Fox, Timothy A

    2015-03-31

    A fuel nozzle assembly for use in a combustor apparatus of a gas turbine engine. An outer housing of the fuel nozzle assembly includes an inner volume and provides a direct structural connection between a duct structure and a fuel manifold. The duct structure defines a flow passage for combustion gases flowing within the combustor apparatus. The fuel manifold defines a fuel supply channel therein in fluid communication with a source of fuel. A fuel injector of the fuel nozzle assembly is provided in the inner volume of the outer housing and defines a fuel passage therein. The fuel passage is in fluid communication with the fuel supply channel of the fuel manifold for distributing the fuel from the fuel supply channel into the flow passage of the duct structure.

  15. Nanoscale superstructures assembled by polymerase chain reaction (PCR): programmable construction, structural diversity, and emerging applications.

    Kuang, Hua; Ma, Wei; Xu, Liguang; Wang, Libing; Xu, Chuanlai

    2013-11-19

    Polymerase chain reaction (PCR) is an essential tool in biotechnology laboratories and is becoming increasingly important in other areas of research. Extensive data obtained over the last 12 years has shown that the combination of PCR with nanoscale dispersions can resolve issues in the preparation DNA-based materials that include both inorganic and organic nanoscale components. Unlike conventional DNA hybridization and antibody-antigen complexes, PCR provides a new, effective assembly platform that both increases the yield of DNA-based nanomaterials and allows researchers to program and control assembly with predesigned parameters including those assisted and automated by computers. As a result, this method allows researchers to optimize to the combinatorial selection of the DNA strands for their nanoparticle conjugates. We have developed a PCR approach for producing various nanoscale assemblies including organic motifs such as small molecules, macromolecules, and inorganic building blocks, such as nanorods (NRs), metal, semiconductor, and magnetic nanoparticles (NPs). We start with a nanoscale primer and then modify that building block using the automated steps of PCR-based assembly including initialization, denaturation, annealing, extension, final elongation, and final hold. The intermediate steps of denaturation, annealing, and extension are cyclic, and we use computer control so that the assembled superstructures reach their predetermined complexity. The structures assembled using a small number of PCR cycles show a lower polydispersity than similar discrete structures obtained by direct hybridization between the nanoscale building blocks. Using different building blocks, we assembled the following structural motifs by PCR: (1) discrete nanostructures (NP dimers, NP multimers including trimers, pyramids, tetramers or hexamers, etc.), (2) branched NP superstructures and heterochains, (3) NP satellite-like superstructures, (4) Y-shaped nanostructures and DNA

  16. Thermal joining studies of CLIC accelerating structures and Establishment of a test bench and studies of thermomechanical behaviour of a CLIC two beam module

    Rossi, Fabrizio

    2013-01-01

    The assembly procedure of the CLIC accelerating structures is constituted of several steps, involving ultra-precision machining, heating cycles at very high temperatures and many quality controls necessary to fulfil the very tight technical requirements. Diverse issues are related to the diffusion bonding process of CLIC accelerating structures; due to diffusion creep mechanisms occurring at high temperature and low stress, residual deformations might be present at the end of the joining process. A theoretical and experimental approach is presented here in order to understand this issue further and feedback on the design process. As a second issue tackled here, the final alignment of CLIC is also affected by the power dissipation occurring in the module during the normal operation modes and resulting in time-varying non-uniform thermal fields. The thermo-mechanical models of CLIC two-beam modules developed in the past are then useful to predict the structural deformations affecting the final alignment of the ...

  17. Structural transformation of peptide amphiphile self-assembly induced by headgroup charge and size regulation

    Gao, Changrui; Bedzyk, Michael; Olvera, Monica; Kewalramani, Sumit; Palmer, Liam

    The ability to control the nano and the meso-scale architecture of molecular assemblies is one of the major challenges in nanoscience. Significantly, structural transformations of amphiphilic aggregates induced by variations in environmental conditions have attracted attention due to their biotechnological relevance. Here, we study the assembly in aqueous solution for a modular series of peptide amphiphiles with 3, 2 or 1 lysine groups conjugated to a C16 carbon tail (C16K3, C16K2 and C16K1) . This system design allow us to probe how the equilibrium structure of the self-assembly can be tuned by controlling the coupling between steric (via choice of headgroup: K3, K2, or K1) and electrostatic (via solution pH) interactions. Solution small- and wide-angle X-ray scattering (SAXS/WAXS) and transmission electron microscopy (TEM) studies reveal that depending on pH and number of lysines in the lipid headgroup, amphiphiles can assemble into a range of structures: spherical micelles, bilayer ribbons and vesicles. We also perform detailed phase space mapping of pH-and headgroup size dependency of the structures of assembly over 0.1-100 nm length scales via SAXS/WAXS. The experimental results in conjunction with molecular dynamics (MD) simulations deduce quantitative relations between pH-dependent molecular charges, steric constraints and self-assembly morphologies, which is significant for developing experimental routes to obtain assembly structures with specific nano- and meso-scale features through controlled external stimuli.

  18. Probing structural changes of self assembled i-motif DNA

    Lee, Iljoon

    2015-01-01

    We report an i-motif structural probing system based on Thioflavin T (ThT) as a fluorescent sensor. This probe can discriminate the structural changes of RET and Rb i-motif sequences according to pH change. This journal is

  19. Structure and Interaction in 2D Assemblies of Tobacco Mosaic Viruses

    Fukuto, M.; Yang, L.; Wang, S.; Fukuto, M.; Checco, A.; Niu, Z.; Wang, Q.

    2009-12-07

    We created two-dimensional (2D) assemblies of tobacco mosaic viruses (TMVs) and characterized their structures using Atomic Force Microscopy (AFM) and X-ray scattering. The TMVs were adsorbed on an oppositely charged, fluid lipid monolayer supported by a solid substrate and submerged in a buffer solution. The lipid monolayer confined the viral particles within a plane, while providing them with lateral mobility so that overall the TMV assembly behaved like a 2D liquid. We controlled the inter-particle interaction by adjusting the chemical condition in the buffer to induce ordered TMV assemblies. We found that the presence of the lipid layer was essential for forming ordered TMV assemblies. Packed TMV assemblies formed on the lipid layer, with an average inter-particle spacing of 42 nm. By introducing Ca{sup 2+} ions into the buffer solution, we were able to improve the in-plane order within the TMV assemblies and reduce the average inter-particle spacing to 20 nm, compared to the TMV diameter of 18 nm. Quantitative analysis of the X-ray scattering data shows that the structural order within the TMV assemblies prepared under a Ca{sup 2+}-free buffer solution is consistent with purely repulsive, electrostatic inter-particle interaction. In contrast, the structural order within Ca{sup 2+}-induced TMV assemblies is consistent with the behavior of a fluid of sticky rods, implying the presence of a strong attraction between TMVs. In addition to the screening of Coulomb repulsion, this behavior is likely the result of counterion-induced as well as membrane-mediated attractions.

  20. Structure and interaction in 2D assemblies of tobacco mosaic viruses

    Yang, L.; Wang. S.; Masafumi, F.; Checco, A.; Zhongwei, N.; Wang, Q.

    2009-08-27

    We created two-dimensional (2D) assemblies of tobacco mosaic viruses (TMVs) and characterized their structures using Atomic Force Microscopy (AFM) and X-ray scattering. The TMVs were adsorbed on an oppositely charged, fluid lipid monolayer supported by a solid substrate and submerged in a buffer solution. The lipid monolayer confined the viral particles within a plane, while providing them with lateral mobility so that overall the TMV assembly behaved like a 2D liquid. We controlled the inter-particle interaction by adjusting the chemical condition in the buffer to induce ordered TMV assemblies. We found that the presence of the lipid layer was essential for forming ordered TMV assemblies. Packed TMV assemblies formed on the lipid layer, with an average inter-particle spacing of 42 nm. By introducing Ca2+ ions into the buffer solution, we were able to improve the in-plane order within the TMV assemblies and reduce the average inter-particle spacing to 20 nm, compared to the TMV diameter of 18 nm. Quantitative analysis of the X-ray scattering data shows that the structural order within the TMV assemblies prepared under a Ca{sup 2+}-free buffer solution is consistent with purely repulsive, electrostatic inter-particle interaction. In contrast, the structural order within Ca{sup 2+}-induced TMV assemblies is consistent with the behavior of a fluid of sticky rods, implying the presence of a strong attraction between TMVs. In addition to the screening of Coulomb repulsion, this behavior is likely the result of counterion-induced as well as membrane-mediated attractions.

  1. The Limits of Bound Structures in the Accelerating Universe

    D"unner, R; Meza, A; Reisenegger, A; D\\"unner, Rolando; Araya, Pablo A.; Meza, Andr\\'es; Reisenegger, Andreas

    2006-01-01

    According to the latest evidence, the Universe is entering an era of exponential expansion, where gravitationally bound structures will get disconnected from each other, forming isolated `island universes'. In this scenario, we present a theoretical criterion to determine the boundaries of gravitationally bound structures and a physically motivated definition of superclusters as the largest bound structures in the Universe. We use the spherical collapse model self-consistently to obtain an analytical condition for the mean density enclosed by the last bound shell of the structure (2.36 times the critical density in the present Universe, assumed to be flat, with 30 per cent matter and 70 per cent cosmological constant, in agreement with the previous, numerical result of Chiueh and He). $N$-body simulations extended to the future show that this criterion, applied at the present cosmological epoch, defines a sphere that encloses $\\approx 99.7$ per cent of the particles that will remain bound to the structure at ...

  2. Structural integrity assessment and stress measurement of CHASNUPP-1 fuel assembly

    Waseem

    2016-01-01

    Full Text Available Fuel assembly of the PWR nuclear power plant is a long and flexible structure. This study has been made in an attempt to find the structural integrity of the fuel assembly (FA of Chashma Nuclear Power Plant-1 (CHASNUPP-1 at room temperature in air. The non-linear contact and structural tensile analysis have been performed using ANSYS 13.0, in order to determine the fuel assembly (FA elongation behaviour as well as the location and values of the stress intensity and stresses developed in axial direction under applied tensile load of 9800 N or 2 g being the fuel assembly handling or lifting load [Y. Zhang et al., Fuel assembly design report, SNERDI, China, 1994]. The finite element (FE model comprises spacer grids, fuel rods, flexible contacts between the fuel rods and grid's supports system and guide thimbles with dash-pots and flow holes, in addition to the spot welds between spacer grids and guide thimbles, has been developed using Shell181, Conta174 and Targe170 elements. FA is a non-straight structure. The actual behavior of the geometry is non-linear due to its curvature or design tolerance. It has been observed that fuel assembly elongation values obtained through FE analysis and experiment [SNERDI Tech. Doc., Mechanical strength and calculation for fuel assembly, Technical Report, F3.2.1, China, 1994] under applied tensile load are comparable and show approximately linear behaviors. Therefore, it seems that the permanent elongation of fuel assembly may not occur at the specified load. Moreover, the values of stresses obtained at different locations of the fuel assembly are also comparable with the stress values of the experiment determined at the same locations through strain gauges. Since the results of both studies (analytical and experimental are comparable, therefore, validation of the FE methodology is confirmed. The stress intensity of the FE model and maximum stresses developed along the guide thimbles in axial direction are

  3. Structural Materials for Liquid Metal Cooled Fast Reactor Fuel Assemblies. Operational Behaviour

    One of the IAEA's statutory objectives is to 'seek to accelerate and enlarge the contribution of atomic energy to peace, health and prosperity throughout the world'. One way this objective is achieved is through the publication of a range of technical series. Two of these are the IAEA Nuclear Energy Series and the IAEA Safety Standards Series. According to Article III.A.6 of the IAEA Statute, the safety standards establish 'standards of safety for protection of health and minimization of danger to life and property.' The safety standards include the Safety Fundamentals, Safety Requirements and Safety Guides. These standards are written primarily in a regulatory style, and are binding on the IAEA for its own programmes. The principal users are the regulatory bodies in Member States and other national authorities. The IAEA Nuclear Energy Series comprises reports designed to encourage and assist R and D on, and application of, nuclear energy for peaceful uses. This includes practical examples to be used by owners and operators of utilities in Member States, implementing organizations, academia, and government officials, among others. This information is presented in guides, reports on technology status and advances, and best practices for peaceful uses of nuclear energy based on inputs from international experts. The IAEA Nuclear Energy Series complements the IAEA Safety Standards Series. This report summarizes the results of two IAEA sponsored technical meetings, conducted in 2008 and 2011, and associated consultancies directed toward a common set of goals. These technical meetings and their venues were as follows: - IAEA Technical Meeting on Status and Trends of Stainless Steel Cladding and Fuel Assembly Materials and Components for LMR, held in Hyderabad, India, 2-4 July 2008; - IAEA Technical Meeting on Design, Manufacturing and Irradiation Behaviour of Fast Reactor Fuels, held in Obninsk, Russian Federation, 30 May-3 June 2011. One of the main objectives of these

  4. Beam Momentum Changes due to Discharges in High-gradient Accelerator Structures

    Palaia, Andrea

    2013-01-01

    The key questions left unanswered by the Standard Model, and the recent discovery of a Standard Model-like Higgs boson, demand an extension of the research on particle physics to the TeV energy scale. The Compact Linear Collider, CLIC, is a candidate project to achieve such goal. It is a linear lepton collider based on a novel two-beam acceleration scheme capable of high-gradient acceleration in X-band accelerator structures. The high electric fields required, however, entail the occurrence o...

  5. Analysis of Higher Order Modes in Large Superconducting Radio Frequency Accelerating Structures

    Galek, Tomasz; Brackebusch, Korinna; Van Rienen, Ursula

    2015-01-01

    Superconducting radio frequency cavities used for accelerating charged particle beams are commonly used in accelerator facilities around the world. The design and optimization of modern superconducting RF cavities requires intensive numerical simulations. Vast number of operational parameters must be calculated to ensure appropriate functioning of the accelerating structures. In this study, we primarily focus on estimation and behavior of higher order modes in superconducting RF cavities connected in chains. To calculate large RF models the state-space concatenation scheme, an efficient hybrid method, is employed.

  6. Enzyme-mediated self-assembly of highly ordered structures from disordered proteins

    Wheat gluten is an amorphous storage protein. Trypsin hydrolysis of wheat gluten produced glutamine-rich peptides. Some peptides were able to self-assemble into fibrous structures extrinsic to native wheat gluten. The final material was an in situ formed peptide composite of highly ordered nanometer-sized fibrils and micron-sized fibers embedded in an unassembled peptide matrix. Fourier transform infrared spectroscopic and x-ray diffraction data suggested that the new structures resembled that of cross- β fibrils found in some insect silk and implicated in prion diseases. The largest self-assembled fibers were about 10 µm in diameter with right-handed helicity and appeared to be bundles of smaller nanometer-sized fibrils. Results demonstrated the potential for utilizing natural mechanisms of protein self-assembly to design advanced materials that can provide a wide range of structural and chemical functionality

  7. Structural basis for proteasome formation controlled by an assembly chaperone nas2.

    Satoh, Tadashi; Saeki, Yasushi; Hiromoto, Takeshi; Wang, Ying-Hui; Uekusa, Yoshinori; Yagi, Hirokazu; Yoshihara, Hidehito; Yagi-Utsumi, Maho; Mizushima, Tsunehiro; Tanaka, Keiji; Kato, Koichi

    2014-05-01

    Proteasome formation does not occur due to spontaneous self-organization but results from a highly ordered process assisted by several assembly chaperones. The assembly of the proteasome ATPase subunits is assisted by four client-specific chaperones, of which three have been structurally resolved. Here, we provide the structural basis for the working mechanisms of the last, hereto structurally uncharacterized assembly chaperone, Nas2. We revealed that Nas2 binds to the Rpt5 subunit in a bivalent mode: the N-terminal helical domain of Nas2 masks the Rpt1-interacting surface of Rpt5, whereas its C-terminal PDZ domain caps the C-terminal proteasome-activating motif. Thus, Nas2 operates as a proteasome activation blocker, offering a checkpoint during the formation of the 19S ATPase prior to its docking onto the proteolytic 20S core particle. PMID:24685148

  8. Prediction of welding distortion during assembly process of thin plate structures

    Luo Yu; Deng De'an; Jiang Xiaoling

    2005-01-01

    Ships and automobiles are fabricated from thin plates. To assemble parts, welding is commonly employed.However, welding distortion in large thin-plate panel structure is usually cased by buckling due to the residual stress. In this study, an elastic finite element method for predicting the welding distortion of three-dimensional thin-plate structures with considering welding sequence was proposed. In this method, the inherent strain was employed to model the local shrinkage due to welding itself, and the interface element was introduced to simulate the assembly process. The proposed method was applied to study the influence of welding sequence on the buckling distortion of the large thin-plate panel structure during assembly.

  9. Hexagonal ZnO nanorods assembled flowers for photocatalytic dye degradation: Growth, structural and optical properties

    Rahman, Qazi Inamur; Ahmad, Musheer; Misra, Sunil Kumar; Lohani, Minaxi B.

    2013-12-01

    A facile hydrothermal method was used to synthesize highly crystalline hexagonal ZnO nanorods assembled flowers by the reaction of zinc acetate and hexamethylenetetraamine (HMTA) at 105 °C. The morphological characterizations revealed that well defined ZnO nanorods were assembled into flowers morphology. X-rays diffraction patterns showed the highly crystalline nature of ZnO with hexagonal wurtzite structure. The structural and optical properties of hexagonal ZnO nanorods assembled flowers were measured by Fourier transform infra-red (FT-IR) and ultraviolet-visible (UV-Vis) measurements. The as-synthesized hexagonal ZnO nanorods assembled flowers were applied as an efficient photocatalyst for the photodegradation of organic dyes under UV-light irradiation. The methylene blue (MB) and rhodamine B (RhB) over the surface of hexagonal ZnO nanorods assembled flowers considerably degraded by ∼91% and ∼80% within 140 min respectively. The degradation rate constants were found to be kapp (0.01313 mint-1) and kapp(0.0104 mint-1) for MB and RhB dye respectively. The enhanced dye degradation might be attributed to the efficient charge separation and the large number of oxyradicals generation on the surface of the hexagonal ZnO nanorods assembled flowers.

  10. AC loss measurements in HTS coil assemblies with hybrid coil structures

    Jiang, Zhenan; Long, Nicholas J.; Staines, Mike; Badcock, Rodney A.; Bumby, Chris W.; Buckley, Robert G.; Amemiya, Naoyuki

    2016-09-01

    Both AC loss and wire cost in coil windings are critical factors for high temperature superconductor (HTS) AC machinery applications. We present AC loss measurement results in three HTS coil assemblies at 77 K and 65 K which have a hybrid coil structure comprising one central winding (CW) and two end windings (EWs) wound with ReBCO and BSCCO wires with different self-field I c values at 77 K. All AC loss results in the coil assemblies are hysteretic and the normalized AC losses in the coil assemblies at different temperatures can be scaled with the I c value of the coil assemblies. The normalised results show that AC loss in a coil assembly with BSCCO CW can be reduced by using EWs wound with high I c ReBCO wires, whilst further AC loss reduction can be achieved by replacing the BSCCO CW with ReBCO CW. The results imply that a flexible hybrid coil structure is possible which considers both AC loss and wire cost in coil assemblies.

  11. Tuners, microphonics, and control systems in superconducting accelerating structures

    Manufacturing tolerances, thermal stresses, acoustic noise, and cooling fluid pressure fluctuations all conspire to make the field in the cavity not precisely what the accelerator physicist has in mind. Tuners and control systems are the tools used to fight back: they regulate the field in the cavity to the desired magnitude and phase. Amplitude and phase stabilities are usually of greater concern in superconducting cavities than in copper cavities. The key to achieving a stable gradient and phase is feedback. A probe must be placed in the cavity itself to sense the present cavity status. Electronic control is then given the responsibility to correct for any measured disturbance. The electronic modulation of forward power has been implemented in a number of ways. Perhaps the easiest implementation to understand has two separate control loops, one for amplitude and one for phase (phase-amplitude loops). Other major electronic control devices include complex phasor modulator (CPM-amplitude loops), vector loop, and variable reactance. 'Slow' tuners are used when the tuning range of the 'fast' tuner plus electronic tuning is not enough to compensate for unpredictability or drift in the static frequency setting. (N.K.)

  12. Research on cw electron accelerators using room-temperature rf structures: Annual report

    This joint NBS-Los Alamos project of ''Research on CW Electron Accelerators Using Room-Temperature RF Structures'' began seven years ago with the goal of developing a technology base for cw electron accelerators. In this report we describe our progress during FY 1986 and present our plans for completion of the project. First, however, it is appropriate to review the past contributions of the project, describe its status, and indicate its future benefits

  13. Experimental measurement of acceleration correlations and pressure structure functions in high Reynolds number turbulence

    Xu, Haitao; Ouellette, Nicholas T.; Vincenzi, Dario; Bodenschatz, Eberhard

    2007-01-01

    We present measurements of fluid particle accelerations in turbulent water flows between counter-rotating disks using three-dimensional Lagrangian particle tracking. By simultaneously following multiple particles with sub-Kolmogorov-time-scale temporal resolution, we measured the spatial correlation of fluid particle acceleration at Taylor microscale Reynolds numbers between 200 and 690. We also obtained indirect, non-intrusive measurements of the Eulerian pressure structure functions by inte...

  14. An Update on the DOE Early Career Project on Photonic Band Gap Accelerator Structures

    Simakov, Evgenya I. [Los Alamos National Laboratory; Edwards, Randall L. [Los Alamos National Laboratory; Haynes, William B. [Los Alamos National Laboratory; Madrid, Michael A. [Los Alamos National Laboratory; Romero, Frank P. [Los Alamos National Laboratory; Tajima, Tsuyoshi [Los Alamos National Laboratory; Tuzel, Walter M. [Los Alamos National Laboratory; Boulware , Chase H. [Niowave, Inc; Grimm, Terry [Niowave, Inc.

    2012-06-07

    We performed fabrication of two SRF PBG resonators at 2.1 GHz and demonstrated their proof-of-principle operation at high gradients. Measured characteristics of the resonators were in good agreement with theoretical predictions. We demonstrated that SRF PBG cavities can be operated at 15 MV/m accelerating gradients. We completed the design and started fabrication of the 16-cell PBG accelerating structure at 11.7 GHz for wakefield testing at AWA.

  15. Demonstration of a 17-GHz, High-Gradient Accelerator with a Photonic-Band-Gap Structure

    We report the testing of a high gradient electron accelerator with a photonic-band-gap (PBG) structure. The photonic-band-gap structure confines a fundamental TM01-like accelerating mode, but does not support higher-order modes (HOM). The absence of HOM is a major advantage of the PBG accelerator, since it suppresses dangerous beam instabilities caused by wakefields. The PBG structure was designed as a triangular lattice of metal rods with a missing central rod forming a defect confining the TM01-like mode and allowing the electron beam to propagate along the axis. The design frequency of the six-cell structure was 17.14 GHz. The PBG structure was excited by 2 MW, 100 ns pulses. A 16.5 MeV electron beam was transmitted through the PBG accelerator. The observed electron beam energy gain of 1.4 MeV corresponds to an accelerating gradient of 35 MV/m, in excellent agreement with theory

  16. Assembly, Loading, and Cool‐down of the FRESCA2 Support Structure

    Muñoz Garcia, J E; Ziemianski, D T; Rondeaux, F; de Rijk, G; Bajas, H; Rifflet, J M; Perez, J C; Durante, M; Charrondiere, M; Bajko, M; Devaux, M; Guinchard, M; Ferracin, P; Fessia, P; Manil, P

    2014-01-01

    This paper reports on the assembly process and cool-down to cryogenic temperature of the support structure of FRESCA2, which is a dipole magnet for upgrading the actual CERN cable test facility FRESCA. The structure of the FRESCA2 magnet is designed to provide the adequate pre-stress, through the use of keys, bladders, and an Al alloy shrinking cylinder. In order to qualify the assembly and loading procedures, the structure was assembled with Al blocks (dummy coils) that replaced the brittle Nb3Sn coils, and then cooled-down to 77 K with liquid nitrogen. The evolution of the mechanical behaviour was monitored via strain gauges located on different components of the structure (shell, rods, yokes and dummy coils). We focus on the expected stresses within the structure after assembly, loading and cool-down. The expected stresses were determined from the 3D finite element model of the structure. A comparison of the 3D model stress predictions with the strain gauge data measurements is made. The coherence between ...

  17. Multi-stacks of epitaxial GeSn self-assembled dots in Si: Structural analysis

    Oliveira, F.; Fischer, I. A.; De Benedetti, A.; Cerqueira, M.F.; Vasilevskiy, Mikhail; Stefanov, S; Chiussi, S.; Schulze, J

    2015-01-01

    We report on the growth and structural and morphologic characterization of stacked layers of self-assembled GeSn dots grown on Si (100) substrates by molecular beam epitaxy at low substrate temperature T = 350 °C. Samples consist of layers (from 1 up to 10) of Ge0.96Sn0.04 self-assembled dots separated by Si spacer layers, 10 nm thick. Their structural analysis was performed based on transmission electron microscopy, atomic force microscopy and Raman scattering. We found that up to 4 stacks ...

  18. Inflatable shape changing colonies assembling versatile smart space structures

    Sinn, Thomas; Hilbich, Daniel; Vasile, Massimiliano

    2014-11-01

    Various plants have the ability to follow the sun with their flowers or leaves during the course of a day via a mechanism known as heliotropism. This mechanism is characterised by the introduction of pressure gradients between neighbouring motor cells in the plant's stem, enabling the stem to bend. By adapting this bio-inspired mechanism to mechanical systems, a new class of smart structures can be created. The developed overall structure is made up of a number of cellular colonies, each consisting of a central pressure source surrounded by multiple cells. After launch, the cellular arrays are deployed in space and are either preassembled or alternatively are attached together during their release or afterwards. A central pressure source is provided by a high-pressure storage unit with an integrated valve, which provides ingress gas flow to the system; the gas is then routed through the system via a sequence of valve operations and cellular actuations, allowing for any desired shape to be achieved within the constraints of the deployed array geometry. This smart structure consists of a three dimensional adaptable cellular array with fluid controlling Micro Electromechanical Systems (MEMS) components enabling the structure to change its global shape. The proposed MEMS components include microvalves, pressure sensors, mechanical interconnect structures, and electrical routing. This paper will also give an overview of the system architecture and shows the feasibility and shape changing capabilities of the proposed design with multibody dynamic simulations. Example applications of this lightweight shape changing structure include concentrators, mirrors, and communications antennas that are able to dynamically change their focal point, as well as substructures for solar sails that are capable of steering through solar winds by altering the sails' subjected area.

  19. Active vibration suppression through positive acceleration feedback on a building-like structure: An experimental study

    Enríquez-Zárate, J.; Silva-Navarro, G.; Abundis-Fong, H. F.

    2016-05-01

    This work deals with the structural and dynamic analysis of a building-like structure consisting of a three-story building with one active vibration absorber. The base of the structure is perturbed using an electromagnetic shaker, which provides forces with a wide range of excitation frequencies, including some resonance frequencies of the structure. One beam-column of the structure is coupled with a PZT stack actuator to reduce the vibrations. The overall mechanical structure is modeled using Euler-Lagrange methodology and validated using experimental modal analysis and Fine Element Method (FEM) techniques. The active control laws are synthesized to actively attenuate the vibration system response via the PZT stack actuator, caused by excitation forces acting on the base of the structure. The control scheme is obtained using Positive Acceleration Feedback (PAF) and Multiple Positive Acceleration Feedback (MPAF) to improve the closed-loop system response. Some experimental results are included to illustrate the overall system performance.

  20. Automated Eukaryotic Gene Structure Annotation Using EVidenceModeler and the Program to Assemble Spliced Alignments

    Haas, B J; Salzberg, S L; Zhu, W; Pertea, M; Allen, J E; Orvis, J; White, O; Buell, C R; Wortman, J R

    2007-12-10

    EVidenceModeler (EVM) is presented as an automated eukaryotic gene structure annotation tool that reports eukaryotic gene structures as a weighted consensus of all available evidence. EVM, when combined with the Program to Assemble Spliced Alignments (PASA), yields a comprehensive, configurable annotation system that predicts protein-coding genes and alternatively spliced isoforms. Our experiments on both rice and human genome sequences demonstrate that EVM produces automated gene structure annotation approaching the quality of manual curation.

  1. A novel method to precisely assemble loose nanofiber structures for regenerative medicine applications.

    Beachley, Vince; Katsanevakis, Eleni; Zhang, Ning; Wen, Xuejun

    2013-02-01

    Polymer nanofibers are favorable for tissue engineering scaffolds because of their high surface-to-volume ratio and biomimicry of the extracellular matrix. Random and uniaxially oriented polymer nanofibers are easily fabricated by conventional electrospinning techniques; however, control over fiber organization within nanofiber structures is limited when they are collected directly from an electrospinning jet. The regenerative medicine applications of electrospun scaffolds could be expanded by developing assembly methods that allow better control of fiber organization. Here, a novel technique is presented that utilizes parallel automated tracks to orient and collect nanofibers from an electrospinning jet. The stabilized fibers are then subsequently assembled into desirable structures. It is difficult to assemble complex structures directly from an electrospinning jet because of high electrical charge and velocities, so this technology adds an intermediate step where nanofibers are immobilized on automated tracks. The result is a continuous steady-state delivery of static stabilized nanofibers that provides a unique and promising platform for automated post processing into useful nanofiber structures. This technique also allows for an indefinite amount of time, as determined by design parameters, for fibers to dry or cool before they contact other nanofibers in the collection site, thus eliminating potential for fiber-to-fiber adhesions even with slow evaporating solvents or high-temperature melts. To demonstrate potential in regenerative medicine applications, several nanofiber structures were fabricated, including: 2D structures with well-controlled fiber density; 3D loosely assembled aligned nanofiber structures with good cell penetration properties; and, complex layer-by-layer 3D aligned fiber structures assembled by integration with post-processing techniques. PMID:23184622

  2. Supramolecular Assembly of Calcium Metal - Organic Frameworks with Structural Transformation

    Liang, P.-Ch.; Liu, H.-K.; Yeh, Ch.-T.; Lin, Ch.-H.; Zima, Vítězslav

    2011-01-01

    Roč. 11, č. 3 (2011), 699-708. ISSN 1528-7483 R&D Projects: GA ČR GA203/08/0208 Institutional research plan: CEZ:AV0Z40500505 Keywords : metal - organic frameworks * calcium * structure Subject RIV: CA - Inorganic Chemistry Impact factor: 4.720, year: 2011

  3. Structure of a Venezuelan equine encephalitis virus assembly intermediate isolated from infected cells

    Venezuelan equine encephalitis virus (VEEV) is a prototypical enveloped ssRNA virus of the family Togaviridae. To better understand alphavirus assembly, we analyzed newly formed nucleocapsid particles (termed pre-viral nucleocapsids) isolated from infected cells. These particles were intermediates along the virus assembly pathway, and ultimately bind membrane-associated viral glycoproteins to bud as mature infectious virus. Purified pre-viral nucleocapsids were spherical with a unimodal diameter distribution. The structure of one class of pre-viral nucleocapsids was determined with single particle reconstruction of cryo-electron microscopy images. These studies showed that pre-viral nucleocapsids assembled into an icosahedral structure with a capsid stoichiometry similar to the mature nucleocapsid. However, the individual capsomers were organized significantly differently within the pre-viral and mature nucleocapsids. The pre-viral nucleocapsid structure implies that nucleocapsids are highly plastic and undergo glycoprotein and/or lipid-driven rearrangements during virus self-assembly. This mechanism of self-assembly may be general for other enveloped viruses.

  4. An Ag(i) energetic metal-organic framework assembled with the energetic combination of furazan and tetrazole: synthesis, structure and energetic performance.

    Qu, Xiao-Ni; Zhang, Sheng; Wang, Bo-Zhou; Yang, Qi; Han, Jing; Wei, Qing; Xie, Gang; Chen, San-Ping

    2016-04-19

    A novel Ag(i) energetic MOF [Ag16(BTFOF)9]n·[2(NH4)]n () assembled with Ag(i) ions and a furazan derivative, 4,4'-oxybis[3,3'-(1H-5-tetrazol)]furazan (H2BTFOF) was successfully synthesized and structurally characterized, featuring a three-dimensional porous structure incorporating ammonium cations. The thermal stability and energetic properties were determined, revealing that the 3D energetic MOF had an outstanding insensitivity (IS > 40 J), an ultrahigh detonation pressure (P) of 65.29 GPa and a detonation velocity (D) of 11.81 km cm(-3). In addition, the self-accelerating decomposition temperature (TSADT) and the critical temperature of thermal explosion (Tb) are also discussed in detail. The finding exemplifies that the assembly strategy plays a decisive role in the density and energetic properties of MOF-based energetic materials. PMID:26987079

  5. Spectrographic approach for the diagnosis of rf breakdown in accelerating rf structures

    Tomizawa, H.; Taniuchi, T.; Hanaki, H.; Igarashi, Y.; Yamaguchi, S.; Enomoto, A

    2004-07-31

    The acceleration gradient of an electron linac is limited by rf breakdown in its accelerating structure. We applied an imaging spectrograph system to study the mechanism of rf breakdown phenomena in accelerating rf structures. Excited gases released from the surface emit light during rf breakdown with the type of gases dependent upon surface treatments and rinsing methods. To study rf breakdown, we used 2-m-long accelerating structures and investigated the effects of a high-pressure ultrapure water rinsing (HPR) treatment applied to these rf structures. We performed experiments to study the gases released from the surface of rf structures with quadrupole mass spectroscopy and imaging spectrography of atomic lines. As a result, just after rf breakdown, we could observe instantly increasing signals at mass numbers 2 (H{sub 2}), 28 (CO), and 44 (CO{sub 2}), but not 18 (H{sub 2}O). We also conducted spectral imaging of the light emissions from the atoms and ions in a vacuum excited through rf breakdown. Using an accelerating structure without HPR treatment, we observed atomic lines at 511 nm (Cu I), 622 nm (Cu II), and 711 nm (C I). With HPR treatment, the atomic lines were observed at 395 nm (O I), 459 nm (O II), 511 nm (Cu I), 538 nm (C I), 570 nm (Cu I), 578 nm (Cu I), 656 nm (H: Balmer alpha), and 740 nm (Cu II). In an additional surface analysis, we found carbon as the most dominant element, with the exception of copper, on the blackened surface of the rf-conditioned accelerating structure without HPR treatment. Based on these experiments, we concluded that some components of the plasma can affect a copper surface. We also have provided a phenomenological review of our experimental results and a simple explanation of rf conditioning with rf breakdown.

  6. Spectrographic approach for the diagnosis of rf breakdown in accelerating rf structures

    The acceleration gradient of an electron linac is limited by rf breakdown in its accelerating structure. We applied an imaging spectrograph system to study the mechanism of rf breakdown phenomena in accelerating rf structures. Excited gases released from the surface emit light during rf breakdown with the type of gases dependent upon surface treatments and rinsing methods. To study rf breakdown, we used 2-m-long accelerating structures and investigated the effects of a high-pressure ultrapure water rinsing (HPR) treatment applied to these rf structures. We performed experiments to study the gases released from the surface of rf structures with quadrupole mass spectroscopy and imaging spectrography of atomic lines. As a result, just after rf breakdown, we could observe instantly increasing signals at mass numbers 2 (H2), 28 (CO), and 44 (CO2), but not 18 (H2O). We also conducted spectral imaging of the light emissions from the atoms and ions in a vacuum excited through rf breakdown. Using an accelerating structure without HPR treatment, we observed atomic lines at 511 nm (Cu I), 622 nm (Cu II), and 711 nm (C I). With HPR treatment, the atomic lines were observed at 395 nm (O I), 459 nm (O II), 511 nm (Cu I), 538 nm (C I), 570 nm (Cu I), 578 nm (Cu I), 656 nm (H: Balmer alpha), and 740 nm (Cu II). In an additional surface analysis, we found carbon as the most dominant element, with the exception of copper, on the blackened surface of the rf-conditioned accelerating structure without HPR treatment. Based on these experiments, we concluded that some components of the plasma can affect a copper surface. We also have provided a phenomenological review of our experimental results and a simple explanation of rf conditioning with rf breakdown

  7. Astronaut Ross Approaches Assembly Concept for Construction of Erectable Space Structure (ACCESS)

    1999-01-01

    The crew assigned to the STS-61B mission included Bryan D. O'Conner, pilot; Brewster H. Shaw, commander; Charles D. Walker, payload specialist; mission specialists Jerry L. Ross, Mary L. Cleave, and Sherwood C. Spring; and Rodolpho Neri Vela, payload specialist. Launched aboard the Space Shuttle Atlantis November 28, 1985 at 7:29:00 pm (EST), the STS-61B mission's primary payload included three communications satellites: MORELOS-B (Mexico); AUSSAT-2 (Australia); and SATCOM KU-2 (RCA Americom). Two experiments were conducted to test assembling erectable structures in space: EASE (Experimental Assembly of Structures in Extravehicular Activity), and ACCESS (Assembly Concept for Construction of Erectable Space Structure). In a joint venture between NASA/Langley Research Center in Hampton, Virginia, and the Marshall Space Flight Center (MSFC), EASE and ACCESS were developed and demonstrated at MSFC's Neutral Buoyancy Simulator (NBS). In this STS-61B onboard photo, astronaut Ross, perched on the Manipulator Foot Restraint (MFR) approaches the erected ACCESS. The primary objective of these experiments was to test the structural assembly concepts for suitability as the framework for larger space structures and to identify ways to improve the productivity of space construction.

  8. Moments applied in the manual assembly of space structures: Ease biomechanics results from STS-61B

    Cousins, D.; Akin, D. L.

    Measurements of the level and pattern of moments applied in the manual assembly of a space structure were made in extravehicular activity (EVA) and neutral buoyancy simulation (NBS). The Experimental Assembly of Structures in EVA program included the repeated assembly of a 3.6 m tetrahedral truss structure in EVA on STS-61B after extensive neutral buoyancy crew training. The flight and training structures were of equivalent mass and geometry to allow a direct correlation between EVA and NBS performance. A stereo photographic motion camera system was used to reconstruct in three dimensions rotational movements of structural beams during assembly. Moments applied in these manual handling tasks were calculated on the basis of the reconstructed movements taking into account effects of inertia, drag and virtual mass. Applied moments of 2.0 Nm were typical for beam rotations in EVA. Corresponding applied moments in NBS were typically up to five times greater. Moments were applied as impulses separated by several seconds of coasting in both EVA and NBS. Decelerating impulses were only infrequently observed in NBS.

  9. From structure to function : Protein assemblies dissected by mass spectrometry

    Lorenzen, K.

    2008-01-01

    This thesis demonstrates some of the possibilities mass spectrometry can provide to gain new insight into structure and function of protein complexes. While technologies in native mass spectrometry are still under development, it already allows research on complete proteins and protein complexes up to a seemingly unlimited size. This would not have been possible without the technical developments in all related fields, for example ionization, instrumentation and sample preparation and handlin...

  10. Small-scale structure of the auroral electron and ion acceleration mechanisms

    High time resolution data obtained from sounding rocket flights reaching altitudes of 1,000 km now permit spatial measurements on the order of the particle gyrodiameters. The electron precipitation responsible for the auroral light emission has two distinct populations; the isotropic in pitch angle electrons that apparently have a magnetospheric source and have been further accelerated within one or two Re of the ionosphere, and, a very field-aligned component which is cold and apparently has an ionospheric source. The field-aligned component provides much of the fine structure and dynamic motion of the visual aurora. Time dispersion of these electrons also places their acceleration region one to two Re from the ionosphere. Much of the heavy ion population of the trapped radiation comes from the ionosphere. These ions apparently receive their initial acceleration transverse to B at altitudes on the order of 1,000 km during auroral events and then are further accelerated as they pass through the higher altitude auroral acceleration region. Recent measurements show that the volume of transverse ion acceleration can be as small as several tens of meters transverse to B and arc also volumes of ionospheric density depletion and intense waves near the lower hybrid frequency having electric field amplitudes of hundreds of mv/m. These regions of microscale transverse ion acceleration are generally co-located with the auroral field-aligned electron bursts

  11. A high-gradient test of a 30 GHz copper accelerating structure

    Corsini, Roberto; Fandos, Raquel; Grudiev, Alexei; Jensen, Erk; Mete, Oznur; Ramsvik, Trond; Rodríguez, José Alberto; Sladen, Jonathan P H; Syratchev, Igor V; Taborelli, Mauro; Tecker, Frank A; Urschütz, Peter; Wilson, Ian H; Wuensch, Walter

    2006-01-01

    The CLIC study is investigating a number of different materials at different frequencies in order to find ways to increase achievable accelerating gradient and to understand what are the important parameters for high-gradient operation. So far a series of rf tests have been made with a set of identical-geometry 30 GHz and X-band structures in copper, tungsten and molybdenum. A new test of a 30 GHz copper accelerating structure has been completed in CTF3 with pulse lengths up to 70 ns. The new results are presented and compared to the previous structures to determine dependencies of quantities such accelerating gradient, material, frequency, pulse length, conditioning rate, breakdown rate and surface damage.

  12. Structural investigation of fuel rods basing on dynamic model of heat flow phenomena in fuel assemblies

    The structural investigation of reactor materials are usually by calculations determining the working conditions of particulars elements of fuel assemblies or the hole reactor core. For this analysis the mathematical model of heat flow phenomena was proposed which enable the calculations of temperature field within the assembly. The differential equations for mass, energy and momentum of cooling medium conservation in coaxial and transversal flow direction enable the steady state and transient analysis for the cases of change in heat flow in cooling medium velocity and the pressure in the assembly. The introduced empire correlation which are completing the set of equations make possible the analysis for violent changes of cladding temperature of fuel elements for cooling medium in two-phase flow. The computer program basing on the presented model was prepared for the calculations of initial parameters necessary for beginning the cladding and fuel material structural investigations. (author)

  13. An anisotropic snowflake-like structural assembly of polymer-capped gold nanoparticles

    Parab, Harshala; Jung, Cheulhee; Woo, Min-Ah; Park, Hyun Gyu, E-mail: hgpark@kaist.ac.kr [Korea Advanced Institute of Science and Technology, Department of Chemical and Biomolecular Engineering (Korea, Republic of)

    2011-05-15

    Snowflake-like structural assembly of isotropic gold nanoparticles (GNPs) is reported. A modified polyamine method has been employed to synthesize positively charged GNPs in presence of a polymeric metaphosphate. This process yields fascinating dendritic self-assembled morphologies. Structural characterization revealed that there was aggregation of crystalline GNPs. The aggregates of GNPs formed in the initial stage of synthesis are assumed to act as the bulging seeds for final growth of complex morphologies at nanometer to micrometer length scale. Self-assembly of GNPs was found to be greatly influenced by the concentration of gold precursor. Diffusion limited aggregation of GNPs is suggested as the plausible mechanism for this nanoparticle self-organization process.

  14. Computation of Eigenmodes in Long and Complex Accelerating Structures by Means of Concatenation Strategies

    Fligsen, T; Van Rienen, U

    2014-01-01

    The computation of eigenmodes for complex accelerating structures is a challenging and important task for the design and operation of particle accelerators. Discretizing long and complex structures to determine its eigenmodes leads to demanding computations typically performed on super computers. This contribution presents an application example of a method to compute eigenmodes and other parameters derived from these eigenmodes for long and complex structures using standard workstation computers. This is accomplished by the decomposition of the complex structure into several single segments. In a next step, the electromagnetic properties of the segments are described in terms of a compact state-space model. Subsequently, the state-space models of the single structures are concatenated to the full structure. The results of direct calculations are compared with results obtained by the concatenation scheme in terms of computational time and accuracy.

  15. Structure and process design of separated function radio frequency quadruple accelerator

    The construction features of separated function radio frequency quadrupole(SFRFQ) accelerator are presented, which include the structure of diaphragms electrodes, integral split ring supporting system, cooling system, tuning system and their manufacturing engineering. The analysis with 8753ES network analyzer proves that the tuning system works successfully to tune the SFRFQ frequency at 26.07 MHz as required by the whole acceleration system without significant quality factor declining. The Roentgen spectrum test at high power proves that the inter-vane Jantage can reach higher than the design value of 70 kV. Beam commissioning was carried out to accelerate the O+ ions from 1.03 MeV to 1.65 MeV, which demonstrates that the mechanical design of SFRFQ accelerator can satisfy the experimental demands and the SFRFQ prototype cavity runs stably as designed. (authors)

  16. Enhancement of maximum attainable ion energy in the radiation pressure acceleration regime using a guiding structure

    Bulanov, S. S.; Esarey, E.; Schroeder, C. B.; Bulanov, S. V.; Esirkepov, T. Zh.; Kando, M.; Pegoraro, F.; Leemans, W. P.

    2015-03-13

    Radiation Pressure Acceleration is a highly efficient mechanism of laser driven ion acceleration, with the laser energy almost totally transferrable to the ions in the relativistic regime. There is a fundamental limit on the maximum attainable ion energy, which is determined by the group velocity of the laser. In the case of a tightly focused laser pulses, which are utilized to get the highest intensity, another factor limiting the maximum ion energy comes into play, the transverse expansion of the target. Transverse expansion makes the target transparent for radiation, thus reducing the effectiveness of acceleration. Utilization of an external guiding structure for the accelerating laser pulse may provide a way of compensating for the group velocity and transverse expansion effects.

  17. Theory for a cylindrical pillbox accelerator cavity using layered structures for reducing skin-effect losses

    It is shown that for a cylindrical pillbox accelerator cavity operating in a TM0n0 mode, the use of laminated conductors for the flat walls in conjunction with a multilayered dielectric structure for the round walls can decrease skin-effect losses by an order of magnitude over that of a copper cavity having the same accelerating field. The layered dielectric structure for the round walls works in a fashion similar to a quarter-wave interferometer. The laminated conductor on the flat walls reduces the ohmic losses by effectively increasing the skin depth

  18. Three-dimensional dielectric photonic crystal structures for laser-driven acceleration

    Cowan, Benjamin M

    2007-01-01

    We present the design and simulation of a three-dimensional photonic crystal waveguide for linear laser-driven acceleration in vacuum. The structure confines a synchronous speed-of-light accelerating mode in both transverse dimensions. We report the properties of this mode, including sustainable gradient and optical-to-beam efficiency. We present a novel method for confining a particle beam using optical fields as focusing elements. This technique, combined with careful structure design, is shown to have a large dynamic aperture and minimal emittance growth, even over millions of optical wavelengths.

  19. Probing structure and dynamics of protein assemblies by magic angle spinning NMR spectroscopy.

    Yan, Si; Suiter, Christopher L; Hou, Guangjin; Zhang, Huilan; Polenova, Tatyana

    2013-09-17

    In living organisms, biological molecules often organize into multicomponent complexes. Such assemblies consist of various proteins and carry out essential functions, ranging from cell division, transport, and energy transduction to catalysis, signaling, and viral infectivity. To understand the biological functions of these assemblies, in both healthy and disease states, researchers need to study their three-dimensional architecture and molecular dynamics. To date, the large size, the lack of inherent long-range order, and insolubility have made atomic resolution studies of many protein assemblies challenging or impractical using traditional structural biology methods such as X-ray diffraction and solution NMR spectroscopy. In the past 10 years, we have focused our work on the development and application of magic angle spinning solid-state NMR (MAS NMR) methods to characterize large protein assemblies at atomic-level resolution. In this Account, we discuss the rapid progress in the field of MAS NMR spectroscopy, citing work from our laboratory and others on methodological developments that have facilitated the in-depth analysis of biologically important protein assemblies. We emphasize techniques that yield enhanced sensitivity and resolution, such as fast MAS (spinning frequencies of 40 kHz and above) and nonuniform sampling protocols for data acquisition and processing. We also discuss the experiments for gaining distance restraints and for recoupling anisotropic tensorial interactions under fast MAS conditions. We give an overview of sample preparation approaches when working with protein assemblies. Following the overview of contemporary MAS NMR methods, we present case studies into the structure and dynamics of two classes of biological systems under investigation in our laboratory. We will first turn our attention to cytoskeletal microtubule motor proteins including mammalian dynactin and dynein light chain 8. We will then discuss protein assemblies from the

  20. General Framework of Pressure Effects on Structures Formed by Entropically Driven Self-Assembly

    Takashi Yoshidome

    2010-06-01

    Full Text Available We review a general framework of pressure effects on the structures formed by entropically driven self-assembly (for example, denaturation of proteins from their native structure and dissociation of ordered structure of the amyloid fibril occur at high pressures. In the framework, the translational entropy of water is an essential factor. Our findings are as follows: at low pressures, the structures almost minimizing the excluded volume (EV generated for water molecules are stable. On the other hand, at high pressures, the structures possessing the largest possible water-accessible surface area together with sufficiently small EV become more stable. These characteristics are consistent with experimental observations.

  1. Expanding the structural diversity of self-assembling dendrons and supramolecular dendrimers via complex building blocks.

    Percec, Virgil; Won, Betty C; Peterca, Mihai; Heiney, Paul A

    2007-09-12

    The design and synthesis of the first examples of AB4 and AB5 dendritic building blocks with complex architecture are reported. Structural and retrostructural analysis of supramolecular dendrimers self-assembled from hybrid dendrons based on different combinations of AB4 and AB5 building blocks with AB2 and AB3 benzyl ether dendrons demonstrated that none of these new hybrid dendrons exhibit the previously encountered conformations of libraries of benzyl ether dendrons. These hybrid dendrons enabled the discovery of some highly unusual tapered and conical dendrons generated by the intramolecular back-folding of their repeat units and of their apex. The new back-folded tapered dendrons have double thickness and self-assemble into pine-tree-like columns exhibiting a long-range 7/2 helical order. The back-folded conical dendrons self-assemble into spherical dendrimers. Non-back-folded truncated conical dendrons were also discovered. They self-assemble into spherical dendrimers with a less densely packed center. The discovery of dendrons displaying a novel crown-like conformation is also reported. Crown-like dendrons self-assemble into long-range 5/1 helical pyramidal columns. The long-range 7/2 and 5/1 helical structures were established by applying, for the first time, the helical diffraction theory to the analysis of X-ray patterns obtained from oriented fibers of supramolecular dendrimers. PMID:17705390

  2. Baseline tests of an autonomous telerobotic system for assembly of space truss structures

    Rhodes, Marvin D.; Will, Ralph W.; Quach, Coung

    1994-01-01

    Several proposed space missions include precision reflectors that are larger in diameter than any current or proposed launch vehicle. Most of these reflectors will require a truss structure to accurately position the reflector panels and these reflectors will likely require assembly in orbit. A research program has been conducted at the NASA Langley Research Center to develop the technology required for the robotic assembly of truss structures. The focus of this research has been on hardware concepts, computer software control systems, and operator interfaces necessary to perform supervised autonomous assembly. A special facility was developed and four assembly and disassembly tests of a 102-strut tetrahedral truss have been conducted. The test procedures were developed around traditional 'pick-and-place' robotic techniques that rely on positioning repeatability for successful operation. The data from two of the four tests were evaluated and are presented in this report. All operations in the tests were controlled by predefined sequences stored in a command file, and the operator intervened only when the system paused because of the failure of an actuator command. The tests were successful in identifying potential pitfalls in a telerobotic system, many of which would not have been readily anticipated or incurred through simulation studies. Addressing the total integrated task, instead of bench testing the component parts, forced all aspects of the task to be evaluated. Although the test results indicate that additional developments should be pursued, no problems were encountered that would preclude automated assembly in space as a viable construction method.

  3. Synthesis of GoldMag particles with assembled structure and their applications in immunoassay

    CUI; Yali; ZHANG; Lianying; SU; Jing; ZHANG; Caifeng; LI; Qi; CUI; Ting; JIN; Boquan; CHEN; Chao

    2006-01-01

    Micrometer-sized Fe3O4 particles and nano-sized gold particles were first synthesized by methods of self-aggregation of surface-chemically modified Fe3O4 nanoparticles and citrate reduction of the Au3+ to Au0, respectively. Interaction between these two types of particles resulted in the assembly of nano-sized gold particles on the surface of the micrometer-sized Fe3O4 particles, forming an assembled structure with the Fe3O4 core particles around which are attached nano-sized gold particles. The Fe3O4/Au structure is named GoldMag particles with assembled structure. The synthetic process, structure, and magnetic property of the GoldMag particles were analyzed. GoldMag particles with assembled structure have an irregular shape, rough surface with a diameter of 2-3 (m. These particles exhibit the superparamagnetic property with saturated magnetization of 41 A·m2/kg. In a single step, antibodies could be readily immobilized onto the surface of the particles with a high binding capacity. The GoldMag particles can be used as a novel carrier in immunoassays. The maximum quantity of human IgG immobilized onto GoldMag particles was 330 (g/mg. In order to validate the quality of the GoldMag particles as immunoassay carriers, an immunoassay system was used. The relative amount of immobilized human IgG was measured by HRP-labeled anti human IgG. The coefficient of variation within parallel samples of each group was below 6% and the coefficient of variation of means between five groups carried out separately was below 7%. Based on the sandwich method, the Hepatitis B surface antigen (HBsAg) and interleukin-8 (IL-8) were also analyzed by qualitative and quantitative detection, respectively. The result indicated that the GoldMag particles with assembled structure were an ideal carrier in immunoassay.

  4. A Structural analysis of M protein in coronavirus assembly and morphology

    W. Neuman, Benjamin; Kiss, Gabriella; H. Kunding, Andreas;

    2011-01-01

    The M protein of coronavirus plays a central role in virus assembly, turning cellular membranes into workshops where virus and host factors come together to make new virus particles. We investigated how M structure and organization is related to virus shape and size using cryo-electron microscopy...

  5. Assembly and structural analysis of a covalently closed nano-scale DNA cage

    Andersen, Felicie F; Knudsen, Bjarne; Oliveira, Cristiano Luis Pinto De; Frøhlich, Rikke F; Krüger, Dinna; Bungert, Jörg; Agbandje-McKenna, Mavis; McKenna, Robert; Jensen, Sissel Juul; Veigaard, Christopher; Koch, Jørn; Rubinstein, John L; Guldbrandtsen, Bernt; Hede, Marianne S; Karlsson, Göran; Andersen, Anni H; Pedersen, Jan Skov; Knudsen, Birgitta R

    2008-01-01

     The inherent properties of DNA as a stable polymer with unique affinity for partner molecules determined by the specific Watson-Crick base pairing makes it an ideal component in self-assembling structures. This has been exploited for decades in the design of a variety of artificial substrates fo...

  6. Monte Carlo study on the self-assembly of nanoparticles into a nanorod structure.

    Matin, Mohammad A; Kim, Hyojeong; Saha, Joyanta K; Zhang, Zhengqing; Kim, Jinkwon; Jang, Joonkyung

    2013-09-01

    It is well known that semiconductor nanoparticles (NPs) can assemble into a range of low dimensional structures, such as nanowires, nanorods and nanosheets. In this study, we investigate the self-assembly of CdTe NPs by using Monte Carlo simulation. Using a simple model for the anisotropic interaction of NPs, the present Monte Carlo simulation demonstrated that NPs with large dipole moments assemble spontaneously into a nanorod even if the short range interactions among NPs is isotropic. Interestingly, we found that the present nanorod grew by forming a transient structure which looks similar to a double ring. For NPs similar to CdTe, the dipole-dipole interaction had a dominant effect over van der Waals attractions and steric repulsion on the final structure of the NP aggregates. The simulated rods are similar to those observed in the experimental self-assembly of CdTe NPs. The NPs with relatively small electric dipole moments aggregated into more or less isotropic structures. PMID:24205640

  7. Self-assembled structures of Gaussian nematic particles

    Nikoubashman, Arash; Likos, Christos N [Institute of Theoretical Physics, Heinrich Heine University of Duesseldorf, Universitaetsstrasse 1, D-40225 Duesseldorf (Germany)

    2010-03-17

    We investigate the stable crystalline configurations of a nematic liquid crystal made of soft parallel ellipsoidal particles interacting via a repulsive, anisotropic Gaussian potential. For this purpose, we use genetic algorithms (GA) in order to predict all relevant and possible solid phase candidates into which this fluid can freeze. Subsequently we present and discuss the emerging novel structures and the resulting zero-temperature phase diagram of this system. The latter features a variety of crystalline arrangements, in which the elongated Gaussian particles in general do not align with any one of the high-symmetry crystallographic directions, a compromise arising from the interplay and competition between anisotropic repulsions and crystal ordering. Only at very strong degrees of elongation does a tendency of the Gaussian nematics to align with the longest axis of the elementary unit cell emerge.

  8. Small angle scattering examination of structures self-assembled during human breast milk digestion

    Human breast milk is the critical part of an infant’s diet and the complete diet for a baby’s first months of life. As such, breast milk contains both water soluble and water insoluble components all of which are made bioavailable during digestion to provide everything needed for growth and development. Following the recent discovery of self-assembled structures as bovine milk is digested, a similar progression through a range of different self-assembled structures has been studied during the in-situ digestion of human breast milk. These highly organized structures were studied using small angle scattering to follow the formation and progression of the structures in real time during digestion. Cryo-TEM was also used to study the phases formed. The duration of the digestion, pH and bile salt concentration were found to act together to gradually shift the lipophilic environment inside breast milk fat globules to more hydrophilic surfaces in highly ordered structure with high internal surface area. The formation and transitions in self-assembled structures are likely to be key to making water insoluble species bioavailable in the gastrointestinal tract of the infant. Further small angle scattering studies will allow a greater understanding of how individual components impact the digestion and whether additional species, e.g. adding sparingly soluble vitamins, changes the digestion stages. Understanding the different stages and structures of digestion offers scope to develop improved nutritional supplements or controlled release drug delivery systems for infants.

  9. Rapid excavation with a newly developed retaining system:Spiral assembly steel structure

    关成立; 杨宇友; 王成彪

    2015-01-01

    The spiral assembly steel structure, a newly developed retaining wall for the rapid excavation of small-sized foundation pits in unsaturated soil, is presented. This new type of retaining structure is prefabricated in the factory and is assembled on site in the excavation of a pit. This retaining structure is composed of several prefabricated steel structural units, in which the adjacent steel structural units are joined with connectors. Each steel structural unit has one steel pipe in the radial direction and is welded to a single piece of steel plate. After full installation in situ, the retaining structure becomes a cylindrical steel structure. With the protection afforded by this new type of retaining structure, excavation work can be completed within 24 h to a depth up to 5 m. In order to verify the reliability and effectiveness of this new retaining structure, field construction tests were conducted in Beijing, China. The test construction was monitored. The monitoring program included measuring stress in the structure, lateral earth pressure, and lateral deformation of the surrounding soil. The monitoring data from the field test were compared with the theoretical results. The results show that the proposed new structure is reliable and effective.

  10. Self-Assembled Structures of Colloidal Silver Nanoparticles on Solid Substrates

    LIU Yulan; HE Shengtai; HUANG Keyang

    2011-01-01

    With a two-phase method,well-dispersed 5.2 nm Ag nanoparticles with narrow size distribution (±0.5 nm) are synthesized.The assembled structures of colloidal Ag nanoparticles on highly oriented pyrolytic graphite (HOPG),silicon chip and microscopic glass have been investigated by atomic force microscopy (AFM).With different spin-coating speeds and concentrations of colloidal silver nanoparticles,various assembly structures could form on those substrates.On HOPG,Ag nanoparticles were absorbed and aligned along single-atom-height step edges to form a linear one-layer structure.And on silicon chip and microscopic glass,one-layer closed packing fractal structure and two-layer closed packing ring were observed respectively.

  11. Manipulating the dimensional assembly pattern and crystalline structures of iron oxide nanostructures with a functional polyolefin

    He, Qingliang; Yuan, Tingting; Wang, Yiran; Guleria, Abhishant; Wei, Suying; Zhang, Guoqi; Sun, Luyi; Liu, Jingjing; Yu, Jingfang; Young, David P.; Lin, Hongfei; Khasanov, Airat; Guo, Zhanhu

    2016-01-01

    Controlled crystalline structures (α- and γ-phase) and assembly patterns (1-D, 2-D and 3-D) were achieved in the synthesized iron oxide (Fe2O3) nanoparticles (NPs) using polymeric surfactant-polypropylene grafted maleic anhydride (PP-g-MA) with different concentrations. In addition, the change of the crystalline structure from the α- and γ-phase also led to the significantly increased saturation magnetization and coercivity.Controlled crystalline structures (α- and γ-phase) and assembly patterns (1-D, 2-D and 3-D) were achieved in the synthesized iron oxide (Fe2O3) nanoparticles (NPs) using polymeric surfactant-polypropylene grafted maleic anhydride (PP-g-MA) with different concentrations. In addition, the change of the crystalline structure from the α- and γ-phase also led to the significantly increased saturation magnetization and coercivity. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07213a

  12. Contribution to the study of standing wave bi-periodical accelerating structures for electrons

    Experimental results on bi-periodic standing wave accelerating structures are presented. These structures which are characterized by a high effective shunt impedance, are designed for standing wave, high duty cycle electron accelerators. Two types of structures are studied: the on-axis coupled structure and the coaxial coupled structure. The expressions for the dispersion relation, coupling coefficients, phase and group velocity are derived from a coupled resonator model. An experimental method to eliminate the stop-band is put forward. The influence of the coupling slots on the dispersion curves is studied experimentally. The effective shunt impedance and the transit time factor are measured by the field perturbation techniques. Measured parameters are compared with SUPERFISH theoretical calculations. The field perturbation technique is also applied to measure the transverse shunt impedance of the dipole modes which are responsible for the beam breakup phenomenon. (author)

  13. Self-Assembly of Nanocomponents into Composite Structures: Derivation and Simulation of Langevin Equations

    Pankavich, Stephen; Shreif, Zeina; Miao, Yinglong; Ortoleva, Peter

    2010-01-01

    The kinetics of the self-assembly of nanocomponents into a virus, nanocapsule, or other composite structure is analyzed via a multiscale approach. The objective is to achieve predictability and to preserve key atomic-scale features that underlie the formation and stability of the composite structures. We start with an all-atom description, the Liouville equation, and the order parameters characterizing nanoscale features of the system. An equation of Smoluchowski type for the stochastic dynam...

  14. Molecular Dynamics Study on Mechanical Properties in the Structure of Self-Assembled Quantum Dot

    Tatsuya Yamaguchi; Ken-ichi Saitoh

    2012-01-01

    Stress and strain in the structure of self-assembled quantum dots constructed in the Ge/Si(001) system is calculated by using molecular dynamics simulation. Pyramidal hut cluster composed of Ge crystal with {105} facets surfaces observed in the early growth stage are computationally modeled. We calculate atomic stress and strain in relaxed pyramidal structure. Atomic stress for triplet of atoms is approximately defined as an average value of pairwise (virial) quantity inside triplet, which is...

  15. Linear hydrogen adsorbate structures on graphite induced by self-assembled molecular monolayers

    Nilsson, Louis; Sljivancanin, Zeljko; Balog, Richard; Xu, Wei; Linderoth, Trolle René; Lægsgaard, Erik; Stensgaard, Ivan; Hammer, Bjørk; Besenbacher, Flemming; Hornekær, Liv

    2012-01-01

    Combined scanning tunnelling microscopy measurements and density functional theory calculations reveal a method to induce linear structures of hydrogen adsorbates on graphite by covering the surface with a self-assembled molecular monolayer of cyanuric acid and exposing it to atomic hydrogen. The...... method can in principle be applied to obtain nanopatterned hydrogen structures on free standing graphene and graphene laid down on insulating substrates, hereby opening up for the possibility of substrate independent bandgap engineering of graphene....

  16. Free-electron laser as a power source for a high-gradient accelerating structure

    A two beam colliding linac accelerator is proposed in which one beam is intense (approx. = 1KA), of low energy (approx. = MeV), and long (approx. = 100 ns) and provides power at 1 cm wavelength through a free-electron-laser-mechanism to the second beam of a few electrons (approx. = 1011), which gain energy at the rate of 250 MeV/m in a high-gradient accelerating structure and hence reach 375 GeV in 1.5 km. The intense beam is given energy by induction units and gains, and losses by radiation, 250 keV/m thus supplying 25 J/m to the accelerating structure. The luminosity, L, of two such linacs would be, at a repetition rate of 1 kHz, L = 4. x 1032 cm-2 s-1

  17. X-Band Photonic Band-Gap Accelerator Structure Breakdown Experiment

    Marsh, Roark A.; /MIT /MIT /NIFS, Gifu /JAERI, Kyoto /LLNL, Livermore; Shapiro, Michael A.; Temkin, Richard J.; /MIT; Dolgashev, Valery A.; Laurent, Lisa L.; Lewandowski, James R.; Yeremian, A.Dian; Tantawi, Sami G.; /SLAC

    2012-06-11

    In order to understand the performance of photonic band-gap (PBG) structures under realistic high gradient, high power, high repetition rate operation, a PBG accelerator structure was designed and tested at X band (11.424 GHz). The structure consisted of a single test cell with matching cells before and after the structure. The design followed principles previously established in testing a series of conventional pillbox structures. The PBG structure was tested at an accelerating gradient of 65 MV/m yielding a breakdown rate of two breakdowns per hour at 60 Hz. An accelerating gradient above 110 MV/m was demonstrated at a higher breakdown rate. Significant pulsed heating occurred on the surface of the inner rods of the PBG structure, with a temperature rise of 85 K estimated when operating in 100 ns pulses at a gradient of 100 MV/m and a surface magnetic field of 890 kA/m. A temperature rise of up to 250 K was estimated for some shots. The iris surfaces, the location of peak electric field, surprisingly had no damage, but the inner rods, the location of the peak magnetic fields and a large temperature rise, had significant damage. Breakdown in accelerator structures is generally understood in terms of electric field effects. These PBG structure results highlight the unexpected role of magnetic fields in breakdown. The hypothesis is presented that the moderate level electric field on the inner rods, about 14 MV/m, is enhanced at small tips and projections caused by pulsed heating, leading to breakdown. Future PBG structures should be built to minimize pulsed surface heating and temperature rise.

  18. Observation of multipactor suppression in a dielectric-loaded accelerating structure using an applied axial magnetic field

    Jing, C.; Chang, C.; Gold, S. H.; Konecny, R.; Antipov, S.; Schoessow, P.; Kanareykin, A.; Gai, W.

    2013-11-01

    Efforts by a number of institutions to develop a Dielectric-Loaded Accelerating (DLA) structure capable of supporting high gradient acceleration when driven by an external radio frequency source have been ongoing over the past decade. Single surface resonant multipactor has been previously identified as one of the major limitations on the practical application of DLA structures in electron accelerators. In this paper, we report the results of an experiment that demonstrated suppression of multipactor growth in an X-band DLA structure through the use of an applied axial magnetic field. This represents an advance toward the practical use of DLA structures in many accelerator applications.

  19. Observation of multipactor suppression in a dielectric-loaded accelerating structure using an applied axial magnetic field

    Jing, C.; Konecny, R.; Antipov, S. [Euclid Techlabs, LLC, 5900 Harper Rd., Solon, Ohio 44139 (United States); High Energy Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Chang, C. [Science and Technology on High Power Microwave Laboratory, Xi' an City 710024 (China); Institute of Energy, Tsinghua University, Beijing 100084 (China); Gold, S. H. [Naval Research Laboratory, Plasma Physics Division, Washington, DC 20375 (United States); Schoessow, P.; Kanareykin, A. [Euclid Techlabs, LLC, 5900 Harper Rd., Solon, Ohio 44139 (United States); Gai, W. [High Energy Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

    2013-11-18

    Efforts by a number of institutions to develop a Dielectric-Loaded Accelerating (DLA) structure capable of supporting high gradient acceleration when driven by an external radio frequency source have been ongoing over the past decade. Single surface resonant multipactor has been previously identified as one of the major limitations on the practical application of DLA structures in electron accelerators. In this paper, we report the results of an experiment that demonstrated suppression of multipactor growth in an X-band DLA structure through the use of an applied axial magnetic field. This represents an advance toward the practical use of DLA structures in many accelerator applications.

  20. Management of research reactor; dynamic characteristics analysis for reactor structures related with vibration of HANARO fuel assembly

    Ahn, Chang Kee; Shim, Joo Sup [Shinwa Technology Information, Seoul (Korea)

    2001-04-01

    The objective of this study is to deduce the dynamic correlation between the fuel assembly and the reactor structure. Dynamic characteristics analyses for reactor structure related with vibration of HANARO fuel assembly have been performed For the dynamic characteristic analysis, the in-air models of the round and hexagonal flow tubes, 18-element and 36-element fuel assemblies, and reactor structure were developed. By calculating the hydrodynamic mass and distributing it on the in-air models, the in-water models of the flow tubes, the fuel assemblies, and the reactor structure were developed. Then, modal analyses for developed in-air and in-water models have been performed. Especially, two 18-element fuel assemblies and three 36-element fuel assemblies were included in the in-water reactor models. For the verification of the modal analysis results, the natural frequencies and the mode shapes of the fuel assembly were compared with those obtained from the experiment. Finally the analysis results of the reactor structure were compared with them performed by AECL Based on the reactor model without PCS piping, the in-water reactor model including the fuel assemblies was developed, and its modal analysis was performed. The analysis results demonstrate that there are no resonance between the fuel assembly and the reactor structures. 26 refs., 419 figs., 85 tabs. (Author)

  1. Hierarchical Structures from Inorganic Nanocrystal Self-Assembly for Photoenergy Utilization

    Yun-Pei Zhu

    2014-01-01

    Full Text Available Self-assembly has emerged as a powerful strategy for controlling the structure and physicochemical properties of ensembles of inorganic nanocrystals. Hierarchical structures from nanocrystal assembly show collective properties that differ from individual nanocrystals and bulk samples. Incorporation of structural hierarchy into nanostructures is of great importance as a result of enhancing mass transportation, reducing resistance to diffusion, and high surface areas for adsorption and reaction, and thus much effort has been devoted to the exploration of various novel organizing schemes through which inorganic porous structure with architectural design can be created. In this paper, the recent research progress in this field is reviewed. The general strategies for the synthesis of hierarchical structures assembled from nanobuilding blocks are elaborated. The well-defined hierarchical structures provide new opportunities for optimizing, tuning, and/or enhancing the properties and performance of these materials and have found applications in photoenergy utilization including photodegradation, photocatalytic H2 production, photocatalytic CO2 conversion, and sensitized solar cells, and these are discussed illustratively.

  2. Accelerated safety analyses - structural analyses Phase I - structural sensitivity evaluation of single- and double-shell waste storage tanks

    Accelerated Safety Analyses - Phase I (ASA-Phase I) have been conducted to assess the appropriateness of existing tank farm operational controls and/or limits as now stipulated in the Operational Safety Requirements (OSRs) and Operating Specification Documents, and to establish a technical basis for the waste tank operating safety envelope. Structural sensitivity analyses were performed to assess the response of the different waste tank configurations to variations in loading conditions, uncertainties in loading parameters, and uncertainties in material characteristics. Extensive documentation of the sensitivity analyses conducted and results obtained are provided in the detailed ASA-Phase I report, Structural Sensitivity Evaluation of Single- and Double-Shell Waste Tanks for Accelerated Safety Analysis - Phase I. This document provides a summary of the accelerated safety analyses sensitivity evaluations and the resulting findings

  3. Structural rigidity in the capsid assembly of cowpea chlorotic mottle virus

    The cowpea chlorotic mottle virus (CCMV) has a protein cage, or capsid, which encloses its genetic material. The structure of the capsid consists of 180 copies of a single protein that self-assemble inside a cell to form a complete capsid with icosahedral symmetry. The icosahedral surface can be naturally divided into pentagonal and hexagonal faces, and the formation of either of these faces has been proposed to be the first step in the capsid assembly process. We have used the software FIRST to analyse the rigidity of pentameric and hexameric substructures of the complete capsid to explore the viability of certain capsid assembly pathways. FIRST uses the 3D pebble game to determine structural rigidity, and a brief description of this algorithm, as applied to body-bar networks, is given here. We find that the pentameric substructure, which corresponds to a pentagonal face on the icosahedral surface, provides the best structural properties for nucleating the capsid assembly process, consistent with experimental observations

  4. Cooperative, reversible self-assembly of covalently pre-linked proteins into giant fibrous structures.

    Averick, Saadyah; Karácsony, Orsolya; Mohin, Jacob; Yong, Xin; Moellers, Nicholas M; Woodman, Bradley F; Zhu, Weipu; Mehl, Ryan A; Balazs, Anna C; Kowalewski, Tomasz; Matyjaszewski, Krzysztof

    2014-07-28

    We demonstrate a simple bioconjugate polymer system that undergoes reversible self-assembling into extended fibrous structures, reminiscent of those observed in living systems. It is comprised of green fluorescent protein (GFP) molecules linked into linear oligomeric strands through click step growth polymerization with dialkyne poly(ethylene oxide) (PEO). Confocal microscopy, atomic force microscopy, and dynamic light scattering revealed that such strands form high persistence length fibers, with lengths reaching tens of micrometers, and uniform, sub-100 nm widths. We ascribe this remarkable and robust form of self-assembly to the cooperativity arising from the known tendency of GFP molecules to dimerize through localized hydrophobic patches and from their covalent pre-linking with flexible PEO. Dissipative particle dynamics simulations of a coarse-grained model of the system revealed its tendency to form elongated fibrous aggregates, suggesting the general nature of this mode of self-assembly. PMID:25044628

  5. Structure of Hepatitis E Virion-Sized Particle Reveals an RNA-Dependent Viral Assembly Pathway

    Xing, L.; Wall, J.; Li, T.-C.; Mayazaki, N.; Simon, M. N.; Moore, M.; Wang, C.-Y.; Takeda, N.; Wakita, T.; Miyamura, T.; Cheng, R. H.

    2010-10-22

    Hepatitis E virus (HEV) induces acute hepatitis in humans with a high fatality rate in pregnant women. There is a need for anti-HEV research to understand the assembly process of HEV native capsid. Here, we produced a large virion-sized and a small T=1 capsid by expressing the HEV capsid protein in insect cells with and without the N-terminal 111 residues, respectively, for comparative structural analysis. The virion-sized capsid demonstrates a T=3 icosahedral lattice and contains RNA fragment in contrast to the RNA-free T=1 capsid. However, both capsids shared common decameric organization. The in vitro assembly further demonstrated that HEV capsid protein had the intrinsic ability to form decameric intermediate. Our data suggest that RNA binding is the extrinsic factor essential for the assembly of HEV native capsids.

  6. Experimental Study Of X-band Dielectric-loaded Accelerating Structures

    Jing, C

    2005-01-01

    A joint Argonne National Laboratory (ANL)/Naval Research Laboratory (NRL) program is under way to investigate X- band dielectric-loaded accelerating (DLA) structures, using high-power 11.424GHz radiation from the NRL Magnicon facility. As an advanced accelerator concepts, the dielectric-loaded accelerator offers the potential for a simple, inexpensive alternative to high-gradient RF linear accelerators. In this thesis, a comprehensive account of X-band DLA structure design, including theoretical calculation, numerical simulation, fabrication and testing, is presented in detail. Two types of loading dielectrics, alumina and MgxCa1−xTiO 3 (MCT), are investigated. For alumina (with dielectric constant 9.4), no RF breakdown has been observed up to 5 MW of drive power (equivalent to 8MV/m accelerating gradient) in the high power RF testing at NRL, but multipactor was observed to absorb a large fraction of the incident microwave power. Experimental results on suppression of multipactor using TiN coating o...

  7. Beam Momentum Changes due to Discharges in High-gradient Accelerator Structures

    Palaia, Andrea; Ruber, Roger; Ekelöf, Tord

    2013-11-21

    The key questions left unanswered by the Standard Model, and the recent discovery of a Standard Model-like Higgs boson, demand an extension of the research on particle physics to the TeV energy scale. The Compact Linear Collider, CLIC, is a candidate project to achieve such goal. It is a linear lepton collider based on a novel two-beam acceleration scheme capable of high-gradient acceleration in X-band accelerator structures. The high electric fields required, however, entail the occurrence of vacuum discharges, or rf breakdowns, a phenomenon whose microscopic dynamics is not yet completely understood, and whose impact on the beam can lead to a severe degradation of the collider luminosity. The understanding of the physics of rf breakdowns has therefore become a significant issue in the design of a reliable accelerator based on CLIC technology. That is addressed experimentally through the study of accelerator structures performance during high-power operations. We report on such a study carried out on a CLIC...

  8. Formation of the self-assembled structures by the ultrasonic cavitation erosion-corrosion effect on carbon steel

    Dayun Yan

    2015-11-01

    Full Text Available The cavitation erosion-corrosion effect on the metal surface always forms irregular oxide structures. In this study, we reported the formation of regular self-assembled structures of amorphous nanoparticles around the cavitation erosion pits on carbon steel upon the ultrasonic cavitation in methylene blue solution. Each self-assembled structure was composed of linearly aligned nanoparticles of about 100 nm. The formation of self-assembled structures might be due to the combined effect of corrosion, specific sonochemical reaction in methylene blue solution, and the magnetic domain structures on the carbon steel.

  9. Engineering Mathematical Analysis Method for Productivity Rate in Linear Arrangement Serial Structure Automated Flow Assembly Line

    Tan Chan Sin

    2015-01-01

    Full Text Available Productivity rate (Q or production rate is one of the important indicator criteria for industrial engineer to improve the system and finish good output in production or assembly line. Mathematical and statistical analysis method is required to be applied for productivity rate in industry visual overviews of the failure factors and further improvement within the production line especially for automated flow line since it is complicated. Mathematical model of productivity rate in linear arrangement serial structure automated flow line with different failure rate and bottleneck machining time parameters becomes the basic model for this productivity analysis. This paper presents the engineering mathematical analysis method which is applied in an automotive company which possesses automated flow assembly line in final assembly line to produce motorcycle in Malaysia. DCAS engineering and mathematical analysis method that consists of four stages known as data collection, calculation and comparison, analysis, and sustainable improvement is used to analyze productivity in automated flow assembly line based on particular mathematical model. Variety of failure rate that causes loss of productivity and bottleneck machining time is shown specifically in mathematic figure and presents the sustainable solution for productivity improvement for this final assembly automated flow line.

  10. Progress on High Power Tests of Dielectric-Loaded Accelerating Structures

    Jing, Chunguang; Gold, Steven H; Kinkead, Allen; Konecny, Richard; Power, John G

    2005-01-01

    This paper presents a progress report on a series of high-power rf experiments that were carried out to evaluate the potential of the Dielectric-Loaded Accelerating (DLA) structure for high-gradient accelerator operation. Since the last PAC meeting in 2003, we have tested DLA structures loaded with two different ceramic materials: Alumina (Al2O3) and MCT (MgxCa1-xTiO3). The alumina-based DLA experiments have concentrated on the effects of multipactor in the structures under high-power operation, and its suppression using TiN coatings, while the MCT experiments have investigated the dielectric joint breakdown observed in the structures due to local field enhancement. In both cases, physical models have been set up, and the potential engineering solutions are being investigated.

  11. Structure, Dynamics, and Assembly of Filamentous Bacteriophages by Nuclear Magnetic Resonance Spectroscopy

    Opella, Stanley J.; Zeri, Ana Carolina; Park, Sang Ho

    2008-05-01

    Filamentous bacteriophages serve as model systems for the development and implementation of spectroscopic methods suitable for biological supramolecular assemblies. Not only are their coat proteins small and readily prepared in the laboratory, but they also have two primary roles as membrane proteins and as the principal structural element of the virus particles. As a bacterial system, they are readily labeled with stable isotopes, and this has opened possibilities for the many nuclear magnetic resonance (NMR) studies described in this review. In particular, solid-state NMR of aligned samples has been used to determine the three-dimensional structures of both the membrane-bound forms of coat proteins in phospholipid bilayers and structural forms in virus particles, which has led to an analysis of the assembly mechanism for virus particles as they are extruded through the cell membrane.

  12. Structure and dynamics of optically directed self-assembly of nanoparticles

    Roy, Debjit; Mondal, Dipankar; Goswami, Debabrata

    2016-03-01

    Self-assembly of nanoparticles leading to the formation of colloidal clusters often serves as the representative analogue for understanding molecular assembly. Unravelling the in situ structure and dynamics of such clusters in liquid suspensions is highly challenging. Presently colloidal clusters are first isolated from their generating environment and then their structures are probed by light scattering methods. In order to measure the in situ structure and dynamics of colloidal clusters, we have generated them using the high-repetition-rate femtosecond laser pulse optical tweezer. Since the constituent of our dimer, trimer or tetramer clusters are 250 nm radius two-photon resonant fluorophore coated nanospheres under the optical trap, they inherently produce Two-Photon Fluorescence, which undergo intra-nanosphere Fluorescence Energy Transfer. This unique energy transfer signature, in turn, enables us to visualize structures and orientations of these colloidal clusters during the process of their formation and subsequent dynamics in a liquid suspension. We also show that due to shape-birefringence, orientation and structural control of these colloidal clusters are possible as the polarization of the trapping laser is changed from linear to circular. We thus report important progress in sampling the smallest possible aggregates of nanoparticles, dimers, trimers or tetramers, formed early in the self-assembly process.

  13. Preferential Acceleration of Coherent Magnetic Structures and Bursty Bulk Flows in Earth's Magnetotail

    Chang, T; Angelopoulos, V; Chang, Tom; Wu, Cheng-chin; Angelopoulos, Vassilis

    2001-01-01

    Observations indicate that the magnetotail convection is turbulent and bi-modal, consisting of fast bursty bulk flows (BBF) and a nearly stagnant background. We demonstrate that this observed phenomenon may be understood in terms of the intermittent interactions, dynamic mergings and preferential accelerations of coherent magnetic structures under the influence of a background magnetic field geometry that is consistent with the development of an X-point mean-field structure.

  14. Control of local structures and photophysical properties of zinc porphyrin-based supramolecular assemblies structurally organized by regioselective ligand coordination.

    Sakuma, Takao; Sakai, Hayato; Araki, Yasuyuki; Wada, Takehiko; Hasobe, Taku

    2016-02-10

    Nano- and micro-sized molecular assemblies of zinc porphyrins [5,10,15,20-tetrakis(4-carboxyphenyl)porphyrinato-zinc(ii) (ZnTCPP)] utilizing bridging nitrogen ligands such as diazabicycro[2.2.2]octane (DABCO) were prepared to demonstrate the regioselective coordination by two different synthetic strategies such as (i) the solvothermal method and (ii) the colloidal metal organic framework (MOF) method. The initial organization process is a planar checkerboard patterned formation (2D platform) of zinc porphyrins organized by paddlewheel secondary building units (PSBUs) between carboxylate and zinc ions. Then, DABCO moieties are decorated on zinc atoms in the metal centres of the porphyrin rings (m-cPDC) in the solvothermal method, whereas the metal centres in the porphyrin rings (n-uPDC) remain uncoordinated in the colloidal MOF method. These internal structural changes between m-cPDC and n-uPDC are in sharp contrast with the corresponding reference systems using ZnTCPP and a 4,4'-bipyridine (BPY) ligand (i.e., m-cPBC and n-cPBC). Concretely, the metal centres of zinc porphyrins in n-uPDC were unsaturated and uncoordinated with the DABCO ligands, which was confirmed by XRD and steady-state spectroscopic measurements. These different coordination features have great effect on the spectroscopic and photophysical properties. For example, the average fluorescence lifetime of m-cPDC is much smaller than that of n-uPDC because of the acceleration of nonradiative processes, which are highly related with the coordination of DABCO to the Zn(ii) centre of the ZnTCPP unit. Finally, fluorescence quenching experiments via photoinduced electron transfer (PET) utilizing an electron acceptor: benzoquinone (BQ) were performed. The apparent association constant (Kapp) of n-uPDC is larger than that of m-cPDC. This suggested that the unsaturated ZnTCPP units embedded in n-uPDC easily accommodate guest molecules as compared to the other systems. PMID:26821786

  15. The conceptual design for fuel assembly and reactor structures of a new research reactor

    A new Research Reactor(ARR) is being designed by KAERI since 2002. The final goal of the project is to develop a new and unique research reactor model which is superior in safety and economical aspect. In this work, as a first step for the design of the fuel assembly and reactor structures of the ARR, the conceptual design has been carried out. The vibration characteristics of the tubular fuel model and the locking performance of the preliminary designed locking devices were investigated. The basic design of the reactor core, reactor structure, and CRDM of the ARR has been carried out. In order to investigate the effects of the stiffener on the vibration characteristics of the tubular fuel, modal analysis was performed for the finite element models of the tubular fuel with stiffener and without stiffener. The analysis results show that the vibration characteristics of the tubular fuel with stiffener is better than those of the tubular fuel without stiffener. To investigate the locking performance of the preliminary designed locking devices for the fuel assembly of the ARR, the elements of the locking devices were fabricated. Then the rotating resistance, fixing status and vibration characteristics of the locking devices were tested. The test results show that using the locking device with fins on the bottom guide can prevent the rotating motion of the fuel assembly, and additional spring or guide on the top of the fuel assembly is needed to suppress the lateral motion of the fuel assembly. Based on the modal analysis and experimental results, the fuel assembly and locking device of the ARR were newly designed. The locking performance of the newly designed locking device, pressure drop characteristics and vibration characteristics of the newly designed fuel assembly will be tested in the near future. In addition, based on the technical experiences on the design and operation of the HANARO, the reactor core, reactor structures, and CRDM of the ARR were conceptually

  16. SpRoUTS (Space Robot Universal Truss System): Reversible Robotic Assembly of Deployable Truss Structures of Reconfigurable Length

    Jenett, Benjamin; Cellucci, Daniel; Cheung, Kenneth

    2015-01-01

    Automatic deployment of structures has been a focus of much academic and industrial work on infrastructure applications and robotics in general. This paper presents a robotic truss assembler designed for space applications - the Space Robot Universal Truss System (SpRoUTS) - that reversibly assembles a truss from a feedstock of hinged andflat-packed components, by folding the sides of each component up and locking onto the assembled structure. We describe the design and implementation of the robot and show that the assembled truss compares favorably with prior truss deployment systems.

  17. Some problems on rf breakdown in room temperature accelerator structure, a possible criterion

    The discussion is confined to high gradient, room-temperature accelerators which have clean well-finished cavity surfaces and good vacuum conditions. Breakdown-initiating mechanisms due to ''cold'' field electron emission occurring at isolated sites on broad-area cavity surfaces, where the field is enhanced, are described. The influences of an alternating field and transition time tunneling are taken into account. The thermal instability resulting in vacuum voltage breakdown is hypothesized to derive a new criterion for room-temperature accelerator structure. 18 refs., 5 figs

  18. Structure of period-2 step-1 accelerator island in area preserving maps

    Since the multi-periodic accelerator modes manifest their contribution even in the region of small stochastic parameters, analysis of such regular motion appears to be critical to explore the stochastic properties of the Hamiltonian system. Here, structure of period-2 step-1 accelerator mode is analyzed for the systems described by the Harper map and by the standard map. The stability criterions have been analyzed in detail in comparison with numerical analyses. The period-3 squeezing around the period-2 step-1 islands is identified in the standard map. (author)

  19. Design and RF Measurements of AN X-Band Accelerating Structure for the Sparc Project

    Alesini, D.; Bacci, A.; Falone, A.; Migliorati, M.; Mostacci, A.; Palpini, F.; Palumbo, L.; Spataro, B.

    2007-09-01

    The paper presents the design of an X-band accelerating section for linearizing the longitudinal phase space in the Frascati Linac Coherent Light Source (SPARC). The nine cells structure, operating on the π standing wave mode, is fed by a central coupler and has been designed to obtain a 42 MV/m accelerating gradient. The 2D profile has been obtained using the electromagnetic codes Superfish and Oscar2D while the coupler has been designed using HFSS. Bead-pull measurements made on a copper prototype have been performed and the results are illustrated and compared with the numerical predictions.

  20. Effects of rf breakdown on the beam in the Compact Linear Collider prototype accelerator structure

    Palaia, Andrea; Jacewicz, Marek; Ruber, Roger; Ziemann, Volker; Farabolini, Wilfrid

    2013-01-01

    Understanding the effects of rf breakdown in high-gradient accelerator structures on the acceleratedbeam is an extremely relevant aspect in the development of the Compact Linear Collider (CLIC) andis one of the main issues addressed at the Two-beam Test Stand at the CLIC Test Facility 3 at CERN.During a rf breakdown high currents are generated causing parasitic magnetic fields that interact withthe accelerated beam affecting its orbit. The beam energy is also affected because the power is part...

  1. Solving Large Sparse Linear Systems in End-to-end Accelerator Structure Simulations

    This paper presents a case study of solving very large sparse linear systems in end-to-end accelerator structure simulations. Both direct solvers and iterative solvers are investigated. A parallel multilevel preconditioner based on hierarchical finite element basis functions is considered and has been implemented to accelerate the convergence of iterative solvers. A linear system with matrix size 93,147,736 and with 3,964,961,944 non-zeros from 3D electromagnetic finite element discretization has been solved in less than 8 minutes with 1024 CPUs on the NERSC IBM SP. The resource utilization as well as the application performance for these solvers is discussed

  2. Solvent-induced structural transition of self-assembled dipeptide: from organogels to microcrystals.

    Zhu, Pengli; Yan, Xuehai; Su, Ying; Yang, Yang; Li, Junbai

    2010-03-01

    Organogels that are self-assembled from simple peptide molecules are an interesting class of nano- and mesoscale soft matter with simplicity and functionality. Investigating the precise roles of the organic solvents and their effects on stabilization of the formed organogel is an important topic for the development of low-molecular-weight gelators. We report the structural transition of an organogel self-assembled from a single dipeptide building block, diphenylalanine (L-Phe-L-Phe, FF), in toluene into a flower-like microcrystal merely by introducing ethanol as a co-solvent; this provides deeper insights into the phase transition between mesostable gels and thermodynamically stable microcrystals. Multiple characterization techniques were used to reveal the transitions. The results indicate that there are different molecular-packing modes formed in the gels and in the microcrystals. Further studies show that the co-solvent, ethanol, which has a higher polarity than toluene, might be involved in the formation of hydrogen bonds during molecular self-assembly of the dipeptide in mixed solvents, thus leading to the transition of organogels into microcrystals. The structural transformation modulated by the co-solvent might have a potential implication in controllable molecular self-assembly. PMID:20119986

  3. Future accelerators (?)

    I describe the future accelerator facilities that are currently foreseen for electroweak scale physics, neutrino physics, and nuclear structure. I will explore the physics justification for these machines, and suggest how the case for future accelerators can be made

  4. Future accelerators (?)

    John Womersley

    2003-08-21

    I describe the future accelerator facilities that are currently foreseen for electroweak scale physics, neutrino physics, and nuclear structure. I will explore the physics justification for these machines, and suggest how the case for future accelerators can be made.

  5. Structural changes in mature rat thymus under the systematic exposure to +Gx acceleration and Glutarginum

    Maxim A. Kriventsov

    2013-04-01

    Full Text Available Objective: Experimental work was designed primary to study morphological and functional changes in the mature rat's thymus under systematic exposure to +Gx acceleration. Secondary task is to determine a possible corrective potential of Glutarginum (L-arginine and L-glutamic acid. Methods: Mature male Wistar rats were exposed to systematic +Gx acceleration (9G, 10 min daily, 10 times. Morphology of the thymus was investigated by light and transmission electron microscopy. Results: Analysis of changes in the thymus of the mature rats under systematic exposure to +Gx acceleration showed marked structural transformation, which is characterized by a process of accidental involution and microcirculatory disturbances caused by the systematic action of gravitational forces. Such changes were potentiated by the age-related involution. Proliferation and expanding of the connective tissue structures, replacement of the parenchyma by the adipose tissue, degeneration of the epithelial component are characteristics of mature rat's thymus. At the same time, histoarchitecture of the thymus was characterized by typical stress-induced changes. Concomitant usage of Glutarginum promotes less pronounced circulatory injuries and involutive changes than in the experiments without Glutarginum treatment. Conclusion: Systematic action of +Gx acceleration causes significant alteration of normal structural organisation of the thymus of the matured rats. Using L-arginine + L-glutamate increases the adaptive capacity of the thymus. [J Exp Integr Med 2013; 3(2.000: 87-92

  6. Statistical model for field emitter activation on metallic surfaces used in high-gradient accelerating structures

    Lagotzky, S.; Müller, G.

    2016-01-01

    Both super- and normal-conducting high-gradient linear accelerators are limited by enhanced field emission (EFE) in the accelerating structures, e.g. due to power loss or ignition of discharges. We discuss the dependence of the number density of typical emitters, i.e. particulates and surface defects, on the electric field level at which they are activated for naturally oxidized metallic surfaces. This activation is explained by the transition of a metal-insulator interface into geometric features that enhance the EFE process. A statistical model is successfully compared to systematic studies of niobium and copper relevant for recent and future linear accelerators. Our results show that the achievable surface quality of Nb might be sufficient for the suppression of EFE in the superconducting accelerating structures for the actual European XFEL but not for the planned International Linear Collider. Moreover, some effort will be required to reduce EFE and thus the breakdown rate of the normal conducting Cu structures for the Compact Linear Collider.

  7. A model for earthquake acceleration monitoring with wireless sensor networks in a structure

    Fujiwara, Takahiro; Nakamura, Yugo; Jinno, Kousei; Matsubara, Taku; Uehara, Hideyuki

    2014-03-01

    Wireless sensor networks (WSNs) technologies have attracted much attention to collect damage information in a natural disaster. WSNs to monitor temperature or humidity usually collect data once in some seconds or some minutes. Since structural health monitoring (SHM), meanwhile, aims to make a diagnosis for the state of a structure based on detected acceleration, WSNs are a promising technology to collect acceleration data. One concern to employ WSNs in SHM is to detect phenomena at a high sampling rate under energy-aware condition. In this paper, we describe a model for seismic acceleration monitoring, configured with multi-layer networks: WSNs, a wireless distribution system (WDS) and a database server, where the WDS is mainly operating in a wireless local area network (WLAN). Examining the performance in the test bed for the monitoring system, the results showed the system was capable of collecting acceleration at a rate of 100 sampling per second (sps) even in the fashion of intermittent operation, and capable of storing data into a database. We also suggest that the method using intermittent operation with appropriate sampling rate is effective in providing a long time operation for the system by considering in the response motion of a structure.

  8. Two-Dimensional Layered Oxide Structures Tailored by Self-Assembled Layer Stacking via Interfacial Strain.

    Zhang, Wenrui; Li, Mingtao; Chen, Aiping; Li, Leigang; Zhu, Yuanyuan; Xia, Zhenhai; Lu, Ping; Boullay, Philippe; Wu, Lijun; Zhu, Yimei; MacManus-Driscoll, Judith L; Jia, Quanxi; Zhou, Honghui; Narayan, Jagdish; Zhang, Xinghang; Wang, Haiyan

    2016-07-01

    Study of layered complex oxides emerge as one of leading topics in fundamental materials science because of the strong interplay among intrinsic charge, spin, orbital, and lattice. As a fundamental basis of heteroepitaxial thin film growth, interfacial strain can be used to design materials that exhibit new phenomena beyond their conventional forms. Here, we report a strain-driven self-assembly of bismuth-based supercell (SC) with a two-dimensional (2D) layered structure. With combined experimental analysis and first-principles calculations, we investigated the full SC structure and elucidated the fundamental growth mechanism achieved by the strain-enabled self-assembled atomic layer stacking. The unique SC structure exhibits room-temperature ferroelectricity, enhanced magnetic responses, and a distinct optical bandgap from the conventional double perovskite structure. This study reveals the important role of interfacial strain modulation and atomic rearrangement in self-assembling a layered singe-phase multiferroic thin film, which opens up a promising avenue in the search for and design of novel 2D layered complex oxides with enormous promise. PMID:27295399

  9. Electronic structure and self-assembly of cross-linked semiconductor nanocrystal arrays

    We studied the electronic level structure of assemblies of InAs quantum dots and CdSe nanorods cross-linked by 1,4-phenylenediamine molecules using scanning tunneling spectroscopy. We found that the bandgap in these arrays is reduced with respect to the corresponding ligand-capped nanocrystal arrays. In addition, a pronounced sub-gap spectral structure commonly appeared which can be attributed to unpassivated nanocrystal surface states or associated with linker-molecule-related levels. The exchange of the ligands by the linker molecules also affected the structural array properties. Most significantly, clusters of close-packed standing CdSe nanorods were formed

  10. RF characteristic study on whole accelerating structure for BEPC Ⅱ linac

    In order to understand and obtain the whole structure RF characteristics of the disk-loaded accelerating tube, the redesigned axis-symmetric coupler was adopted to replace the real 3-D one during the calculation process by ANSYS. Much less computer sources and time were required to simulate the whole structure with only one single PC by taking full advantage of the structure's axis-symmetric characteristic. The accelerating tube for the BEPC Ⅱ linac was used as an example to validate this method. The ANSYS simulated filling time, attenuation factor and bandwidth are 856 ns, 0.56 Np and 3.55 MHz respectively, while the experimental measured ones are 830 ns, 0.57 Np and 4.7 MHz respectively. It can be seen that the ANSYS simulation and experimental measurement are consistent as a whole, and the simulation can provide very valuable reference for the real design and fabrication. (authors)

  11. Multi-stacks of epitaxial GeSn self-assembled dots in Si: Structural analysis

    Oliveira, F. [Institute for Semiconductor Engineering, University of Stuttgart, 70569 Stuttgart (Germany); Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Fischer, I. A.; Schulze, J. [Institute for Semiconductor Engineering, University of Stuttgart, 70569 Stuttgart (Germany); Benedetti, A. [CACTI, Univ. de Vigo, Campus Universitario Lagoas Marcosende 15, Vigo (Spain); Cerqueira, M. F.; Vasilevskiy, M. I. [Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Stefanov, S.; Chiussi, S. [Dpto. Fisica Aplicada, Univ. de Vigo, Rua Maxwell s/n, Campus Universitario Lagoas Marcosende, Vigo (Spain)

    2015-03-28

    We report on the growth and structural and morphologic characterization of stacked layers of self-assembled GeSn dots grown on Si (100) substrates by molecular beam epitaxy at low substrate temperature T = 350 °C. Samples consist of layers (from 1 up to 10) of Ge{sub 0.96}Sn{sub 0.04} self-assembled dots separated by Si spacer layers, 10 nm thick. Their structural analysis was performed based on transmission electron microscopy, atomic force microscopy, and Raman scattering. We found that up to 4 stacks of dots could be grown with good dot layer homogeneity, making the GeSn dots interesting candidates for optoelectronic device applications.

  12. Polymorphism in Self-Assembled Structures of 9-Anthracene Carboxylic Acid on Ag(111

    Bo Xu

    2012-06-01

    Full Text Available Surface self-assembly process of 9-anthracene carboxylic acid (AnCA on Ag(111 was investigated using STM. Depending on the molecular surface density, four spontaneously formed and one annealed AnCA ordered phases were observed, namely a straight belt phase, a zigzag double-belt phase, two simpler dimer phases, and a kagome phase. The two high-density belt phases possess large unit cells on the scale length of 10 nm, which are seldom observed in molecular self-assembled structures. This structural diversity stems from a complicated competition of different interactions of AnCA molecules on metal surface, including intermolecular and molecular-substrate interactions, as well as the steric demand from high molecular surface density.

  13. Multi-stacks of epitaxial GeSn self-assembled dots in Si: Structural analysis

    We report on the growth and structural and morphologic characterization of stacked layers of self-assembled GeSn dots grown on Si (100) substrates by molecular beam epitaxy at low substrate temperature T = 350 °C. Samples consist of layers (from 1 up to 10) of Ge0.96Sn0.04 self-assembled dots separated by Si spacer layers, 10 nm thick. Their structural analysis was performed based on transmission electron microscopy, atomic force microscopy, and Raman scattering. We found that up to 4 stacks of dots could be grown with good dot layer homogeneity, making the GeSn dots interesting candidates for optoelectronic device applications

  14. Clonal structure affects the assembling behavior in the Japanese queenless ant Pristomyrmex punctatus

    Nishide, Yudai; Satoh, Toshiyuki; Hiraoka, Tuyosi; Obara, Yoshiaki; Iwabuchi, Kikuo

    2007-10-01

    The queenless ant Pristomyrmex punctatus (Hymenoptera: Myrmicinae) has a unique society that differs from those of other typical ants. This species does not have a queen, and the workers lay eggs and produce their clones parthenogenetically. However, a colony of these ants does not always comprise members derived from a single clonal line. In this study, we examined whether P. punctatus changes its “assembling behavior” based on colony genetic structure. We prepared two subcolonies—a larger one comprising 200 individuals and a smaller one comprising 100 individuals; these subcolonies were established from a single stock colony. We investigated whether these subcolonies assemble into a single nest. The genetically monomorphic subcolonies (single clonal line) always fused into a single nest; however, the genetically polymorphic subcolonies (multiple clonal lines) did not tend to form a single colony. The present study is the first to demonstrate that the colony genetic structure significantly affects social viscosity in social insects.

  15. Laser Wakefield Acceleration: Structural and Dynamic Studies. Final Technical Report ER40954

    Downer, Michael

    2014-12-19

    Particle accelerators enable scientists to study the fundamental structure of the universe, but have become the largest and most expensive of scientific instruments. In this project, we advanced the science and technology of laser-plasma accelerators, which are thousands of times smaller and less expensive than their conventional counterparts. In a laser-plasma accelerator, a powerful laser pulse exerts light pressure on an ionized gas, or plasma, thereby driving an electron density wave, which resembles the wake behind a boat. Electrostatic fields within this plasma wake reach tens of billions of volts per meter, fields far stronger than ordinary non-plasma matter (such as the matter that a conventional accelerator is made of) can withstand. Under the right conditions, stray electrons from the surrounding plasma become trapped within these “wake-fields”, surf them, and acquire energy much faster than is possible in a conventional accelerator. Laser-plasma accelerators thus might herald a new generation of compact, low-cost accelerators for future particle physics, x-ray and medical research. In this project, we made two major advances in the science of laser-plasma accelerators. The first of these was to accelerate electrons beyond 1 gigaelectronvolt (1 GeV) for the first time. In experimental results reported in Nature Communications in 2013, about 1 billion electrons were captured from a tenuous plasma (about 1/100 of atmosphere density) and accelerated to 2 GeV within about one inch, while maintaining less than 5% energy spread, and spreading out less than ½ milliradian (i.e. ½ millimeter per meter of travel). Low energy spread and high beam collimation are important for applications of accelerators as coherent x-ray sources or particle colliders. This advance was made possible by exploiting unique properties of the Texas Petawatt Laser, a powerful laser at the University of Texas at Austin that produces pulses of 150 femtoseconds (1 femtosecond is 10

  16. Antireflective sub-wavelength structures on fused silica via self-assembly of silica

    Antireflective sub-wavelength structures with high laser-induced damage threshold on fused silica are fabricated using a self-assembly technique, in which a porous yttrium oxide film is deposited as a mask followed by alkaline etching. By controlling the etching time, several sub-wavelength structures with different height, density and diameter have been made. The best reflectance is less than 2.87% for wavelengths from 300 to 1000 nm after 1.5 h etching. The laser-induced damage threshold of the etched glass measured by a 10 ns Nd:YAG laser at a wavelength of 532 nm was as high as 30 J/cm2 compared to 16 J/cm2 of blank glass. The specular reflectance of structures matches the theoretical simulation using a thin-film multilayer model, and the results reveal that the shape of the structures is similar to the calculated parabolic shape. Achieving antireflective sub-wavelength structures on fused silica paves the way for applications in laser systems. - Highlights: • Antireflective structures on fused silica are grown using a self-assembly technique. • The properties of structures with different etching time were studied. • The laser-induced damage threshold of glass was enhanced after etching. • The reflection matches the theoretical simulation using a thin-film multilayer model

  17. Template-assembled melittin: structural and functional characterization of a designed, synthetic channel-forming protein.

    PAWLAK, M.; Meseth, U; Dhanapal, B.; Mutter, M.; Vogel, H.

    1994-01-01

    Template-assembled proteins (TASPs) comprising 4 peptide blocks, each of either the natural melittin sequence (melittin-TASP) or of a truncated melittin sequence (amino acids 6-26, melittin6-26-TASP), C-terminally linked to a (linear or cyclic) 10-amino acid template were synthesized and characterized, structurally by CD, by fluorescence spectroscopy, and by monolayer experiments, and functionally, by electrical conductance measurements on planar bilayers and release experiments on dye-loaded...

  18. Hierarchical structural control of visual properties in self-assembled photonic-plasmonic pigments

    Koay, Natalie; Burgess, Ian B.; Kay, Theresa M.; Nerger, Bryan A.; Miles-Rossouw, Malaika; Shirman, Tanya; Vu, Thy L.; England, Grant; Phillips, Katherine R.; Utech, Stefanie; Vogel, Nicolas; Kolle, Mathias; Aizenberg, Joanna

    2014-01-01

    We present a simple one-pot co-assembly method for the synthesis of hierarchically structured pigment particles consisting of silica inverse-opal bricks that are doped with plasmonic absorbers. We study the interplay between the plasmonic and photonic resonances and their effect on the visual appearance of macroscopic collections of photonic bricks that are distributed in randomized orientations. Manipulating the pore geometry tunes the wavelength- and angle-dependence of the scattering profi...

  19. TRIM5α Disrupts the Structure of Assembled HIV-1 Capsid Complexes In Vitro▿

    Black, Lesa R.; Aiken, Christopher

    2010-01-01

    The host restriction factor TRIM5α provides intrinsic defense against retroviral infections in mammalian cells. TRIM5α blocks infection by targeting the viral capsid after entry but prior to completion of reverse transcription, but whether this interaction directly alters the structure of the viral capsid is unknown. A previous study reported that rhesus macaque TRIM5α protein stably associates with cylindrical complexes formed by assembly of recombinant HIV-1 CA-NC protein in vitro and that ...

  20. Topology optimization and digital assembly of advanced space-frame structures

    Søndergaard, Asbjørn; Amir, Oded; Michael, Knauss

    2014-01-01

    this paper presents a novel method for integrated design, optimization and fabrication of optimized space-frame structures in an autonomous, digital process. Comparative numerical studies are presented, demonstrating achievable mass reduction by application of the method by comparison to equivalent...... to normative space truss designs and dimensions. As such, a principal digital fabrication and assembly scheme is developed, where an architectural design methodology relative to the described process is established, and the proposed process demonstrated through scaled digital fabrication experiments....

  1. Development status and research directions on the structural components of the fuel assembly

    Survey on the structural components of the state-of-the art of the PWR fuel assembly developed by various nuclear fuel vendors has been performed. As a result, some developmental directions and mechanical/structural basic technology to be established for these structural components have been drawn out. The developmental directions are as follows; The top end piece shall be designed in shape to reduce its height to accommodate the fuel rod growth for high burnup and to have a function for easy reconstitution of the fuel assembly. The bottom end piece shall be designed in shape to reduce its height to accommodate the fuel rod growth for high burnup and to have a function for easy reconstitution of the fuel assembly. The bottom end piece shall be designed in shape to reduce its height to accommodate the fuel rod growth for high burnup and to have a function of debris protection. The spacer grid shall be designed in shape to have a function of enhancing the thermal margin and maintaining the fuel rod integrity without fuel failure due to fuel rod fretting and vibration. The mechanical/structural basic technology which must be established is as follows; The stress analysis results shall comply with the stress criteria specified in the ASME code stress limits and the shape optimization technology shall be developed for the top/bottom end pieces. For the spacer grid cell, the nonlinear analysis model of the fuel rod and the analysis model on the flow-induced fuel rod vibration, and a study of the mechanism and a quantified model on the fuel rod fretting wear shall be developed. In addition, numerical analysis model to estimate the buckling strength of the spacer grid assembly shall be developed. Besides above technology, technology related the verification test should be developed. (author). 30 figs., 54 refs

  2. Structural, nanomechanical, and computational characterization of D,L-cyclic peptide assemblies.

    Rubin, Daniel J; Amini, Shahrouz; Zhou, Feng; Su, Haibin; Miserez, Ali; Joshi, Neel S

    2015-03-24

    The rigid geometry and tunable chemistry of D,L-cyclic peptides makes them an intriguing building-block for the rational design of nano- and microscale hierarchically structured materials. Herein, we utilize a combination of electron microscopy, nanomechanical characterization including depth sensing-based bending experiments, and molecular modeling methods to obtain the structural and mechanical characteristics of cyclo-[(Gln-D-Leu)4] (QL4) assemblies. QL4 monomers assemble to form large, rod-like structures with diameters up to 2 μm and lengths of tens to hundreds of micrometers. Image analysis suggests that large assemblies are hierarchically organized from individual tubes that undergo bundling to form larger structures. With an elastic modulus of 11.3 ± 3.3 GPa, hardness of 387 ± 136 MPa and strength (bending) of 98 ± 19 MPa the peptide crystals are among the most robust known proteinaceous micro- and nanofibers. The measured bending modulus of micron-scale fibrils (10.5 ± 0.9 GPa) is in the same range as the Young's modulus measured by nanoindentation indicating that the robust nanoscale network from which the assembly derives its properties is preserved at larger length-scales. Materials selection charts are used to demonstrate the particularly robust properties of QL4 including its specific flexural modulus in which it outperforms a number of biological proteinaceous and nonproteinaceous materials including collagen and enamel. The facile synthesis, high modulus, and low density of QL4 fibers indicate that they may find utility as a filler material in a variety of high efficiency, biocompatible composite materials. PMID:25757883

  3. Complex crystal structures formed by the self assembly of di-tethered nanospheres

    Iacovella, Christopher R.; Glotzer, Sharon C.

    2009-01-01

    We report the results from a computational study of the self-assembly of amphiphilic di-tethered nanospheres using molecular simulation. As a function of the interaction strength and directionality of the tether-tether interactions, we predict the formation of four highly ordered phases not previously reported for nanoparticle systems. We find a double diamond structure comprised of a zincblende (binary diamond) arrangement of spherical micelles with a complementary diamond network of nanopar...

  4. Development of the heat sink structure of a beam dump for the proton accelerator

    The beam dump is the essential component for the good beam quality and the reliable performance of the proton accelerator. The beam dump for a 20 MeV and 20 mA proton accelerator was designed and manufactured in this study. The high heats deposited, and the large amount of radioactivity produced in beam dump should be reduced by the proper heat sink structure. The heat source by the proton beam of 20 MeV and 20 mA was calculated. The radioactivity assessments of the beam dump were carried out for the economic shielding design with safety. The radioactivity by the protons and secondary neutrons in designed beam dump were calculated in this sturdy. The effective engineering design for the beam dump cooling was performed, considering the mitigation methods of the deposited heats with small angle, the power densities with the stopping ranges in the materials and the heat distributions in the beam dump. The heat sink structure of the beam dump was designed to meet the accelerator characteristics by placing two plates of 30 cm by 60 cm at an angle of 12 degree. The highest temperatures of the graphite, copper, and copper faced by cooling water were designed to be 223 degree, 146 degree, and 85 degree, respectively when the velocity of cooling water was 3 m/s. The heat sink structure was manufactured by the brazing graphite tiles to a copper plate with the filler alloy of Ti-Cu-Ag. The brazing procedure was developed. The tensile stress of the graphite was less than 75% of a maximum tensile stress during the accelerator operation based on the analysis. The safety analyses for the commissioning of the accelerator operation were also performed. The specimens from the brazed parts of beam dump structure were made to identify manufacturing problems. The soundness of the heat sink structure of the beam dump was confirmed by the fatigue tests of the brazed specimens of the graphite-copper tile components with the repetitive heating and cooling. The heat sink structure developed

  5. Hemolysin coregulated protein 1 as a molecular gluing unit for the assembly of nanoparticle hybrid structures.

    Pham, Tuan Anh; Schreiber, Andreas; Sturm Née Rosseeva, Elena V; Schiller, Stefan; Cölfen, Helmut

    2016-01-01

    Hybrid nanoparticle (NP) structures containing organic building units such as polymers, peptides, DNA and proteins have great potential in biosensor and electronic applications. The nearly free modification of the polymer chain, the variation of the protein and DNA sequence and the implementation of functional moieties provide a great platform to create inorganic structures of different morphology, resulting in different optical and magnetic properties. Nevertheless, the design and modification of a protein structure with functional groups or sequences for the assembly of biohybrid materials is not trivial. This is mainly due to the sensitivity of its secondary, tertiary and quaternary structure to the changes in the interaction (e.g., hydrophobic, hydrophilic, electrostatic, chemical groups) between the protein subunits and the inorganic material. Here, we use hemolysin coregulated protein 1 (Hcp1) from Pseudomonas aeruginosa as a building and gluing unit for the formation of biohybrid structures by implementing cysteine anchoring points at defined positions on the protein rim (Hcp1_cys3). We successfully apply the Hcp1_cys3 gluing unit for the assembly of often linear, hybrid structures of plasmonic gold (Au NP), magnetite (Fe3O4 NP), and cobalt ferrite nanoparticles (CoFe2O4 NP). Furthermore, the assembly of Au NPs into linear structures using Hcp1_cys3 is investigated by UV-vis spectroscopy, TEM and cryo-TEM. One key parameter for the formation of Au NP assembly is the specific ionic strength in the mixture. The resulting network-like structure of Au NPs is characterized by Raman spectroscopy, showing surface-enhanced Raman scattering (SERS) by a factor of 8·10(4) and a stable secondary structure of the Hcp1_cys3 unit. In order to prove the catalytic performance of the gold hybrid structures, they are used as a catalyst in the reduction reaction of 4-nitrophenol showing similar catalytic activity as the pure Au NPs. To further extend the functionality of the

  6. Comparative self-assembly studies and self-sorting of two structurally isomeric naphthalene-diimide (NDI)-gelators

    Anindita Das; Mijanur Rahaman Molla; Suhrit Ghosh

    2011-11-01

    We have reported here a comparative self-assembly and gelation studies of two isomeric bis-amide functionalized NDI-derivatives. In one case (NDI-1) the two amide groups were placed symmetrically on either side of the chromophore while for the other system (NDI-2) they were located on same side. In non-polar solvent both isomers formed self-assembled structures by synergistic effect of -stacking and hydrogen-bonding. The propensity for self-assembly of NDI-1 was greater due to symmetrical placement of two amide groups on either arms of this chromophore which allowed -stacking in tandem with hydrogen-bonding, while NDI-2 formed thermally more stable self-assembled fibres possibly due to location of two amide groups in close proximity along single arm of this chromophore. The structural difference in these two isomers lead to distinctly different morphology of their respective self-assembled structures which was further reflected on their gelation properties. Morphology of the self-assembled array of NDI-1 showed organized and regular entangled bundles of nanorods which imparted better gelation ability to this chromophore while the self-assembled fibres of NDI-2 showed less ordered and irregular fibres. We also probed self- assembly of these two chromophores in their mixture which revealed orthogonal assembly of the individual chromophores and no molecular mixing was noticed.

  7. Bio-inspired Structural Colors from Deposition of Synthetic Melanin Nanoparticles by Evaporative Self-assembly

    Xiao, Ming; Li, Yiwen; Deheyn, Dimitri; Yue, Xiujun; Gianneschi, Nathan; Shawkey, Matthew; Dhinojwala, Ali

    2015-03-01

    Melanin, a ubiquitous black or brown pigment in the animal kingdom, is a unique but poorly understood biomaterial. Many bird feathers contain melanosomes (melanin-containing organelles), which pack into ordered nanostructures, like multilayer or two-dimensional photonic crystal structures, to produce structural colors. To understand the optical properties of melanin and how melanosomes assemble into certain structures to produce colors, we prepared synthetic melanin (polydopamine) particles with variable sizes and aspect ratios. We have characterized the absorption and refractive index of the synthetic melanin particles. We have also shown that we can use an evaporative process to self-assemble melanin films with a wide range of colors. The colors obtained using this technique is modeled using a thin-film interference model and the optical properties of the synthetic melanin nanoparticles. Our results on self-assembly of synthetic melanin nanoparticles provide an explanation as why the use of melanosomes to produce colors is prevalent in the animal kingdom. National science foundation, air force office of scientific research, human frontier science program.

  8. Structural Integrity Evaluation of In-Pool Assembly in Cold Neutron Source

    Kim, Seok Hoon; Lee, K. H.; Kim, H. R.; Choi, J. W.; Kim, Y. K

    2007-03-15

    The condition for the transient operation was defined to provide the design data of the load combination, which is needed for the fatigue analysis and the component design for the In-Pool Assembly. Although the moderator vessel is classified by the Safety Class 3, the evaluation of the structural integrity was performed by the design procedure of ASME Sec. III, NB based on the concept of the design by analysis. The material for the moderator vessel and vacuum vessel is AL6061 T6. The material properties is prepared by ASME Sec. II, Part D,but those over the temperature were made using the extrapolation and the conservative value. Code Case N-519 was applied to provide the design stress intensity in condition of low temperature. The structural analysis of the vacuum tube was carried out for the vacuum pressure vessel, upper flange and bolt and the material of the upper flange and the bolt is SA182 F304 and SA193 B8, respectively. The detail analysis considering the load combination according to the service level was performed to evaluate the structural integrity. Also, the fracture mechanics evaluation for the In-Pool Assembly was carried out to guarantee the integrity of the In-Pool Assembly from the rapid fracture damage.

  9. Effect of temperature and loading on the structure of β-casein/ibuprofen assemblies.

    Turovsky, Tanya; Portnaya, Irina; Kesselman, Ellina; Ionita-Abutbul, Inbal; Dan, Nily; Danino, Dganit

    2015-07-01

    β-Casein is a 24 kDa amphiphilic and unstructured protein that self-assembles into small core-shell micelles at a wide range of concentrations, pH values and temperatures. We recently developed the micelles as nanocarriers for oral delivery of hydrophobic drugs. In this paper we examined the effect of the hydrophobic non-steroidal anti-inflammatory drug (NSAID) ibuprofen on the micellar structure, as a function of temperature and loading. Using cryo-transmission electron microscopy (cryo-TEM) we find two routes of organization – mixed micellization and co-assembly (aggregation). The time-dependent events that characterize the second routes has been examined in detail. At 25 °C we find coexistence of small assemblies and larger aggregates of irregular (but defined) structures that contain the drug. Increasing the drug loading increases the relative number of the larger aggregates and their dimensions, leading eventually to the formation of long then branched structures, like in amphiphilic block copolymer solutions. Similar trends were identified for changes in the temperature. Combined, our results suggest that ibuprofen acts as a co-surfactant that possibly is localizes to the interface rather than being encapsulated in the micellar core as other NSAID hydrophobic drugs. PMID:25754442

  10. Simulations of super-structure domain walls in two dimensional assemblies of magnetic nanoparticles

    We simulate the formation of domain walls in two-dimensional assemblies of magnetic nanoparticles. Particle parameters are chosen to match recent electron holography and Lorentz microscopy studies of almost monodisperse cobalt nanoparticles assembled into regular, elongated lattices. As the particles are small enough to consist of a single magnetic domain each, their magnetic interactions can be described by a spin model in which each particle is assigned a macroscopic “superspin.” Thus, the magnetic behaviour of these lattices may be compared to magnetic crystals with nanoparticle superspins taking the role of the atomic spins. The coupling is, however, different. The superspins interact only by dipolar interactions as exchange coupling between individual nanoparticles may be neglected due to interparticle spacing. We observe that it is energetically favorable to introduce domain walls oriented along the long dimension of nanoparticle assemblies rather than along the short dimension. This is unlike what is typically observed in continuous magnetic materials, where the exchange interaction introduces an energetic cost proportional to the area of the domain walls. Structural disorder, which will always be present in realistic assemblies, pins longitudinal domain walls when the external field is reversed, and makes a gradual reversal of the magnetization by migration of longitudinal domain walls possible, in agreement with previous experimental results

  11. Development of an S-band accelerating structure with quasi-symmetric single-feed racetrack couplers

    Heo, Hoon; Joo, Young-Do; Park, Yong-Jung; Kang, Heung-Sik; Lee, Heung-Soo; Oh, Kyoung-Min; Seo, Hyung-Seok; Noh, Sung-Ju

    2015-03-01

    We developed an S-band traveling-wave accelerating structure for the Pohang Accelerator Laboratory's X-ray free-electron laser (PAL-XFEL), and we fabricated and tested a full-scale prototype. In order to reduce the field asymmetry inside the coupler cavity, we used the SUPERFISH code and the CST MWS electromagnetic field solvers to design the constant-gradient traveling-wave accelerator to use quasi-symmetric single-feed racetrack couplers. The RF measurement results indicate that the accelerating gradient of the prototype structure is as high as 27 MV/m for an input RF power of 65 MW.

  12. Role of Species-Specific Primary Structure Differences in Aβ42 Assembly and Neurotoxicity.

    Roychaudhuri, Robin; Zheng, Xueyun; Lomakin, Aleksey; Maiti, Panchanan; Condron, Margaret M; Benedek, George B; Bitan, Gal; Bowers, Michael T; Teplow, David B

    2015-12-16

    A variety of species express the amyloid β-protein (Aβ (the term "Aβ" refers both to Aβ40 and Aβ42, whereas "Aβ40" and "Aβ42" refer to each isoform specifically). Those species expressing Aβ with primary structure identical to that expressed in humans have been found to develop amyloid deposits and Alzheimer's disease-like neuropathology. In contrast, the Aβ sequence in mice and rats contains three amino acid substitutions, Arg5Gly, His13Arg, and Tyr10Phe, which apparently prevent the development of AD-like neuropathology. Interestingly, the brush-tailed rat, Octodon degus, expresses Aβ containing only one of these substitutions, His13Arg, and does develop AD-like pathology. We investigate here the biophysical and biological properties of Aβ peptides from humans, mice (Mus musculus), and rats (Octodon degus). We find that each peptide displays statistical coil → β-sheet secondary structure transitions, transitory formation of hydrophobic surfaces, oligomerization, formation of annuli, protofibrils, and fibrils, and an inverse correlation between rate of aggregation and aggregate size (faster aggregation produced smaller aggregates). The rank order of assembly rate was mouse > rat > Aβ42. The rank order of neurotoxicity of assemblies formed by each peptide immediately after preparation was Aβ42 > mouse ≈ rat. These data do not support long-standing hypotheses that the primary factor controlling development of AD-like neuropathology in rodents is Aβ sequence. Instead, the data support a hypothesis that assembly quaternary structure and organismal responses to toxic peptide assemblies mediate neuropathogenetic effects. The implication of this hypothesis is that a valid understanding of disease causation within a given system (organism, tissue, etc.) requires the coevaluation of both biophysical and cell biological properties of that system. PMID:26421877

  13. Acceleration response spectrum for prediction of structural vibration due to individual bouncing

    Chen, Jun; Wang, Lei; Racic, Vitomir; Lou, Jiayue

    2016-08-01

    This study is designed to develop an acceleration response spectrum that can be used in vibration serviceability assessment of civil engineering structures, such as floors and grandstands those are dynamically excited by individual bouncing. The spectrum is derived from numerical simulations and statistical analysis of acceleration responses of a single degree of freedom system with variable natural frequency and damping under a large number of experimentally measured individual bouncing loads. Its mathematical representation is fit for fast yet reliable application in design practice and is comprised of three equations that describe three distinct frequency regions observed in the actual data: the first resonant plateau (2-3.5 Hz), the second resonant plateau (4-7 Hz) and a descension region (7-15 Hz). Finally, this paper verifies the proposed response spectrum approach to predict structural vibration by direct comparison against numerical simulations and experimental results.

  14. Heavy ion acceleration using drift-tube structures with optimized focusing

    For the proposed lead ion accelerating facility at CERN various options for accelerating ions with q/A < 1/8 (relative to protons) from 0.25 MeV/u to 4.2 MeV/u, have been studied. At the preferred frequency of 202.56 MHz, the βλ drift-tube linac requires excessive quadrupole field gradients. However, starting with a 2βλ structure as reference, it is shown that a hybrid 2βλ/βλ structure with quadrupole lenses separated by 4βλ or more has acceptable focusing characteristics. In addition, this approach leads to a significant reduction in the number of quadrupoles and in the RF power, and yet retains well-behaved longitudinal and transverse acceptances. 4 refs., 2 figs

  15. Wakefield and surface electromagnetic field optimisation of manifold damped accelerating structures for CLIC

    The main travelling wave linacs of the compact linear collider (CLIC) operate at a frequency of 11.9942 GHz with a phase advance per cell of 2π/3. In order to minimise the overall footprint of the accelerator, large accelerating gradients are sought. The present baseline design for the main linacs of CLIC demands an average electric field of 100 MV/m. To achieve this in practical cavities entails the dual challenges of minimising the potential for electrical breakdown and ensuring the beam excited wakefield is sufficiently suppressed. We present a design to meet both of these conditions, together with a description of the structure, CLICDDSA, expressively designed to experimentally test the ability of the structure to cope with high powers.

  16. Focusing characteristics of an accelerating structure with non-circular beam holes

    High energy linacs of the next generation are required to keep stably high bunch populations and very small beam spots at colliding points, in order to realize high luminosity at TeV energy region. CERN proposed to apply the rf focusing technology which makes a strong focusing force according to the rf phase within a bunch, and rf focusing power is proportional to both the accelerating gradient and the operating frequency. Some computed results of the focusing property of 3 GHz accelerating structures are presented which has non-circular beam holes. The construction of this 3 GHz structure, because an rf technology for 3 GHz is well-established, will be useful in order to know, at an early stage of the development, whether the idea will be successful or not. The 3D code MAFIA was used to investigate the deflecting force caused by the asymmetry of the beam aperture. (R.P.) 5 refs., 14 figs., 3 tabs

  17. STRCMACS: An extensive set of Macros for structured programming in OS/360 assembly language

    Barth, C. W.

    1974-01-01

    Two techniques are discussed that have been most often referred to as structured programming. One is that of programming with high level control structures (such as the if and while) replacing the branch instruction (goto-less programming); the other is the process of developing a program by progressively refining descriptions of components in terms of more primitive components (called stepwise refinement or top-down programming). In addition to discussing what these techniques are, it is shown why their use is advised and how both can be implemented in OS assembly language by the use of a special macro instruction package.

  18. Structure of Self-Assembled Mn Atom Chains on Si(001).

    Villarreal, R; Longobardi, M; Köster, S A; Kirkham, Ch J; Bowler, D; Renner, Ch

    2015-12-18

    Mn has been found to self-assemble into atomic chains running perpendicular to the surface dimer reconstruction on Si(001). They differ from other atomic chains by a striking asymmetric appearance in filled state scanning tunneling microscopy (STM) images. This has prompted complicated structural models involving up to three Mn atoms per chain unit. Combining STM, atomic force microscopy, and density functional theory we find that a simple necklacelike chain of single Mn atoms reproduces all their prominent features, including their asymmetry not captured by current models. The upshot is a remarkably simpler structure for modeling the electronic and magnetic properties of Mn atom chains on Si(001). PMID:26722930

  19. On the computation of electromagnetic fields excited by relativistic bunches of charged particles in accelerating structures

    A numerical method is described for the calculaion of electromagnetic fields excited by arbitrarily shaped bunches of charged particles travelling through accelerating structures with cylindrical symmetry. The fields are computed by numerical integration of Maxwell's equations in the time domain. The computer program based on this method enables the user to calculate transient electromagnetic fields as well as the energy gain of particles inside the bunch. Some results are given for the LEP cavity and a pillbox. (orig.)

  20. Studies of Coupled Cavity Linac (CCL) Accelerating Structures with 3-D Codes

    Spalek, G; Smith, P D; Greninger, P T; Charman, C M

    2000-01-01

    The cw CCL being designed for the Accelerator Production of Tritium (APT) project accelerates protons from 96MeV to 211MeV. It consists of 99 segments each containing up to seven accelerating cavities. Segments are coupled by intersegment coupling cavities and grouped into supermodules. The design method needs to address not only basic cavity sizing for a given coupling and pi/2 mode frequency, but also the effects of high power densities on the cavity frequency, mechanical stresses, and the structure's stop band during operation. On the APT project, 3-D RF (Ansoft Corp.'s HFSS) and coupled RF/structural (Ansys Inc.'s ANSYS) codes are being used to develop tools to address the above issues and guide cooling channel design. The code's predictions are being checked against available low power Aluminum models. Stop band behavior under power will be checked once the tools are extended to CCDTL structures that have been tested at high power. A summary of calculations made to date and agreement with measured result...

  1. Studies of coupled cavity LINAC (CCL) accelerating structures with 3-D codes

    The cw CCL being designed for the Accelerator Production of Tritium (APT) project accelerates protons from 96 MeV to 211 MeV. It consists of 99 segments each containing up to seven accelerating cavities. Segments are coupled by intersegment coupling cavities and grouped into supermodules. The design method needs to address not only basic cavity sizing for a given coupling and pi/2 mode frequency, but also the effects of high power densities on the cavity frequency, mechanical stresses, and the structure's stop band during operation. On the APT project, 3-D RF (Ansoft Corp.'s HFSS) and coupled RF/structural (Ansys Inc.'s ANSYS) codes are being used. to develop tools to address the above issues and guide cooling channel design. The code's predictions are being checked against available low power Aluminum models. Stop band behavior under power will be checked once the tools are extended to CCDTL structures that have been tested at high power. A summary of calculations made to date and agreement with measured results will be presented

  2. Analytical researches on the accelerating structures, wakefields, and beam dynamics for future linear colliders

    The research works presented in this memoir are oriented not only to the R and D programs towards future linear colliders, but also to the pedagogic purposes. The first part of this memoir (from Chapter 2 to Chapter 9) establishes an analytical framework of the disk-loaded slow wave accelerating structures with can be served as the advanced courses for the students who have got some basic trainings in the linear accelerator theories. The analytical formulae derived in this part describe clearly the properties of the disk-loaded accelerating structures, such as group velocity, shunt impedance, coupling coefficients κ and β, loss factors, and wake fields. The second part (from Chapter 11 to Chapter 13) gives the beam dynamics simulations and the final proposal of an S-Band Superconducting Linear Collider (SSLC) which is aimed to avoid the dark current problem in TESLA project. This memoir has not included all the works conducted since April 1992, such as beam dynamics simulations for CLIC Test Facility (CFT-2) and the design of High Charge Structures (HCS) (11π/12 mode) for CFT-2, in order to make this memoir more harmonious, coherent and continuous. (author)

  3. Nanoscale self-assembly of starch: Phase relations, formation, and structure

    Creek, John A.

    This project has been undertaken to develop a fundamental understanding of the spherulitic self-assembly of starch polymers from aqueous solution, both as a model for starch granule initiation in vivo and as a biologically-inspired material with applications in the food and pharmaceutical industries. Botanical starches were observed to form semi-crystalline spherulites from aqueous solution when cooled after a high temperature treatment, and the processes resulting in spherulite formation were investigated. Based on the influence of cooling rate on spherulite formation from a botanical starch, liquid-liquid demixing in competition with crystallization was proposed as the mechanism leading to spherulite formation (summarized in a hypothetical phase diagram). Study of amylose and amylopectin self-assembly demonstrated that the linear polymer plays the primary role in forming spherulites. As a result, the roles of degree of polymerization, concentration, and thermal processing conditions on amylose self-assembly were explored. Thermal properties, final system morphology, and crystalline allomorph were characterized. In all cases the experimental findings supported the proposed phase diagram. Finally, the crystalline nanostructure of the spherulites was probed using atomic force microscopy (AFM), revealing a seemingly universal level of structure in crystalline starch materials. This was compared to an existing model of crystallization for synthetic polymers involving a transitional liquid crystalline-like ordering---a comparison that makes sense in light of the known helical structure of starch.

  4. Structure of promoter-bound TFIID and model of human pre-initiation complex assembly.

    Louder, Robert K; He, Yuan; López-Blanco, José Ramón; Fang, Jie; Chacón, Pablo; Nogales, Eva

    2016-03-31

    The general transcription factor IID (TFIID) plays a central role in the initiation of RNA polymerase II (Pol II)-dependent transcription by nucleating pre-initiation complex (PIC) assembly at the core promoter. TFIID comprises the TATA-binding protein (TBP) and 13 TBP-associated factors (TAF1-13), which specifically interact with a variety of core promoter DNA sequences. Here we present the structure of human TFIID in complex with TFIIA and core promoter DNA, determined by single-particle cryo-electron microscopy at sub-nanometre resolution. All core promoter elements are contacted by subunits of TFIID, with TAF1 and TAF2 mediating major interactions with the downstream promoter. TFIIA bridges the TBP-TATA complex with lobe B of TFIID. We also present the cryo-electron microscopy reconstruction of a fully assembled human TAF-less PIC. Superposition of common elements between the two structures provides novel insights into the general role of TFIID in promoter recognition, PIC assembly, and transcription initiation. PMID:27007846

  5. Development of mechanical test techniques for structural components of irradiated PWR fuel assembly

    An increase of fuel burnup and duration of fuel life remains one of the main methods for a nuclear power engineering enhancement. Properties of structural materials providing corrosion resistance, mechanical strength, and dimensional instability of the components of a fuel assembly (FA) are of great importance for fuel operational reliability in such fuel life cycles. Generally, PWR fuel assemblies consist of a top nozzle, spacer grid, bottom nozzle, and guide/instrumentation tubes. The top and bottom nozzle are fixed to the guide tubes using a screw or bulge method. The spacer grid fixed to the guide/instrumentation tubes using a spot weld or bulge method. To understand the in-reactor performance of PWR FA, several devices and test techniques have been developed for mechanical property tests. Among the structural components of PWR FA, a spacer grid, a hold down spring of a top nozzle and a connecting part of FA were considered. Experimental works were carried out for the unirradiated and irradiated components of advanced nuclear fuel assemblies for KSNPs and Westinghouse type PWRs at IMEF (Irradiated Materials Examination Facility) at KAERI. The developed techniques were verified through a hot cell tests. (author)

  6. Subcritical Multiplication Parameters of the Accelerator-Driven System with 100 MeV Protons at the Kyoto University Critical Assembly

    Jae-Yong Lim

    2012-01-01

    Full Text Available Basic experiments on the accelerator-driven system (ADS at the Kyoto University Critical Assembly are carried out by combining a solid-moderated and -reflected core with the fixed-field alternating gradient accelerator. The reaction rates are measured by the foil activation method to obtain the subcritical multiplication parameters. The numerical calculations are conducted with the use of MCNPX and JENDL/HE-2007 to evaluate the reaction rates of activation foils set in the core region and at the location of the target. Here, a comparison between the measured and calculated eigenvalues reveals a relative difference of around 10% in C/E values. A special mention is made of the fact that the reaction rate analyses in the subcritical systems demonstrate apparently the actual effect of moving the tungsten target into the core on neutron multiplication. A series of further ADS experiments with 100 MeV protons needs to be carried out to evaluate the accuracy of subcritical multiplication parameters.

  7. Structural activation calculations due to proton beam loss in the APT accelerator design

    For the new, high-power accelerators currently being designed, the amount of activation of the accelerator structure has become an important issue. To quantify this activation, a methodology was utilized that coupled transport and depletion codes to obtain dose rate estimates at several locations near the accelerator. This research focused on the 20 and 100 MeV sections of the Bridge-Coupled Drift Tube Linear Accelerator. The peak dose rate was found to be approximately 6 mR/hr in the 100 MeV section near the quadrupoles at a 25-cm radius for an assumed beam loss of 1 nA/m. It was determined that the activation was dominated by the proton interactions and subsequent spallation product generation, as opposed to the presence of the generated neutrons. The worst contributors were the spallation products created by proton bombardment of iron, and the worst component was the beam pipe, which consists mostly of iron. No definitive conclusions about the feasibility of hands-on maintenance can be determined, as the design is still not finalized

  8. The transcriptional regulator GalR self-assembles to form highly regular tubular structures

    Agerschou, Emil D; Christiansen, Gunna; Schafer, Nicholas P;

    2016-01-01

    The Gal repressor regulates transport and metabolism of D-galactose in Escherichia coli and can mediate DNA loop formation by forming a bridge between adjacent or distant sites. GalR forms insoluble aggregates at lower salt concentrations in vitro, which can be solubilized at higher salt...... concentrations. Here, we investigate the assembly and disassembly of GalR aggregates. We find that a sharp transition from aggregates to soluble species occurs between 200 and 400 mM NaCl, incompatible with a simple salting-in effect. The aggregates are highly ordered rod-like structures, highlighting a......-tolerant polymers for chromosome compaction in stationary phase cells, in effect linking self-assembly with regulatory function....

  9. Structure formation in binary mixtures of lipids and detergents: Self-assembly and vesicle division

    Noguchi, Hiroshi

    2013-01-01

    Self-assembly dynamics in binary surfactant mixtures and structure changes of lipid vesicles induced by detergent solution are studied using coarse-grained molecular simulations. Disk-shaped micelles, the bicelles, are stabilized by detergents surrounding the rim of a bilayer disk of lipids. The self-assembled bicelles are considerably smaller than bicelles formed from vesicle rupture, and their size is determined by the concentrations of lipids and detergents and the interactions between the two species. The detergent-adsorption induces spontaneous curvature of the vesicle bilayer and results in vesicle division into two vesicles or vesicle rupture into worm-like micelles. The division occurs mainly via the inverse pathway of the modified stalk model. For large spontaneous curvature of the monolayers of the detergents, a pore is often opened, thereby leading to vesicle division or worm-like micelle formation.

  10. Service properties of structural materials of BN-600 reactor fuel assemblies at high damaging doses

    Based on postradiation investigation of fuel assembly materials of BN-600 reactor a consideration is given to main ways of designing materials which can provide for high burn-up of nuclear fuels in fast reactors. Austenitic steels 08KhN11M3T, 10Kh17N13M2T and ferrite-martensitic steels 1Kh13M213FR, 05Kh12N2M were tested as fuel assembly cans in BN-600 reactor. Austenitic steels EhJ-847, EhP-172, ChS-68 were used for fuel cans. It'is shown that radiation resistance of the steels can be improved by optimization of chemical composition and by enhanced homogeneity of composition, structure and initial mechanical properties. 20 refs.; 4 figs

  11. Structure and function of Enterotoxigenic Escherichia coli fimbriae from differing assembly pathways

    Mortezaei, Narges; Shao, Paul P; Shirdel, Mariam; Singh, Bhupender; McVeigh, Annette; Uhlin, Bernt Eric; Savarino, Stephen J; Andersson, Magnus; Bullitt, Esther

    2014-01-01

    Pathogenic enterotoxigenic Escherichia coli (ETEC) are the major bacterial cause of diarrhea in young children in developing countries and in travelers, causing significant mortality in children. Adhesive fimbriae are a prime virulence factor for ETEC, initiating colonization of the small intestinal epithelium. Similar to other Gram-negative bacteria, ETEC express one or more diverse fimbriae, some assembled by the chaperone-usher pathway and others by the alternate chaperone pathway. Here we elucidate structural and biophysical aspects and adaptations of each fimbrial type to its respective host niche. CS20 fimbriae are compared to CFA/I fimbriae, which are two ETEC fimbriae assembled via different pathways, and to Pfimbriae from uropathogenic E. coli. Many fimbriae unwind from their native helical filament to an extended linear conformation under force, thereby sustaining adhesion by reducing load at the point of contact between the bacterium and the target cell. CFA/I fimbriae require the least force to un...

  12. Studies on high-precision machining of accelerator disks of X-band structure for a linear collider

    One of the critical requirements for the accelerating structures of the main linacs for a linear collider is the precise control of the distributions of the accelerating and higher order mode frequencies. This paper describes major challenges in the fabrication of disks for such accelerating structures. We have studied the issues associated with high-precision machining of copper disks that are used for the Detuned Structure(DS), Damped Detuned Structure(DDS) and Rounded Damped Detuned Structure(RDDS). We have proven that the 3D curved surface of such disks can be machined with a precision of better than ± 1 μm. We have established that the resonant frequencies of the accelerating mode for these copper disks can be controlled within 1 MHz. (author)

  13. Self-assembly and structural-functional flexibility of oxygenic photosynthetic machineries: personal perspectives.

    Garab, Győző

    2016-01-01

    This short review, with a bit of historical aspect and a strong personal bias and emphases on open questions, is focusing on the (macro-)organization and structural-functional flexibilities of the photosynthetic apparatus of oxygenic photosynthetic organisms at different levels of the structural complexity-selected problems that have attracted most my attention in the past years and decades. These include (i) the anisotropic organization of the pigment-protein complexes and photosynthetic membranes-a basic organizing principle of living matter, which can, and probably should be adopted to intelligent materials; (ii) the organization of protein complexes into chiral macrodomains, large self-assembling highly organized but structurally flexible entities with unique spectroscopic fingerprints-structures, where, important, high-level regulatory functions appear to 'reside'; (iii) a novel, dissipation-assisted mechanism of structural changes, based on a thermo-optic effect: ultrafast thermal transients in the close vicinity of dissipation of unused excitation energy, which is capable of inducing elementary structural changes; it makes plants capable of responding to excess excitation with reaction rates proportional to the overexcitation above the light-saturation of photosynthesis; (iv) the 3D ultrastructure of the granum-stroma thylakoid membrane assembly and other multilamellar membrane systems, and their remodelings-associated with regulatory mechanisms; (v) the molecular organization and structural-functional plasticity of the main light-harvesting complex of plants, in relation to their crystal structure and different in vivo and in vitro states; and (vi) the enigmatic role of non-bilayer lipids and lipid phases in the bilayer thylakoid membrane-warranting its high protein content and contributing to its structural flexibility. PMID:26494196

  14. Complete multipactor suppression in an X-band dielectric-loaded accelerating structure

    Jing, C.; Gold, S. H.; Fischer, Richard; Gai, W.

    2016-05-01

    Multipactor is a major issue limiting the gradient of rf-driven Dielectric-Loaded Accelerating (DLA) structures. Theoretical models have predicted that an axial magnetic field applied to DLA structures may completely block the multipactor discharge. However, previous attempts to demonstrate this magnetic field effect in an X-band traveling-wave DLA structure were inconclusive, due to the axial variation of the applied magnetic field, and showed only partial suppression of the multipactor loading [Jing et al., Appl. Phys. Lett. 103, 213503 (2013)]. The present experiment has been performed under improved conditions with a uniform axial magnetic field extending along the length of an X-band standing-wave DLA structure. Multipactor loading began to be continuously reduced starting from 3.5 kG applied magnetic field and was completely suppressed at ˜8 kG. Dependence of multipactor suppression on the rf gradient inside the DLA structure was also measured.

  15. Numerical studies of the jungle gym slow-wave accelerating structure

    Many structures of interest to accelerator physicists have been inaccessible to analysis because there was no three-dimensional electromagnetic field-solving code. This report discusses the analysis of one such structure, the Jungle Gym, using the recently developed MAFIA codes. The Cornell version of the Jungle Gym has been modeled and the dispersion curves for the TM010 and TM020 modes calculated and plotted. The shunt impedance (r) and r/Q for the π-mode were also calculated and compared with experimental data. The calculations and experimental results were in good agreement. (author) 2 refs., 4 figs., 3 tabs

  16. Surface-structured bacterial cellulose with guided assembly-based biolithography (GAB).

    Bottan, Simone; Robotti, Francesco; Jayathissa, Prageeth; Hegglin, Alicia; Bahamonde, Nicolas; Heredia-Guerrero, José A; Bayer, Ilker S; Scarpellini, Alice; Merker, Hannes; Lindenblatt, Nicole; Poulikakos, Dimos; Ferrari, Aldo

    2015-01-27

    A powerful replica molding methodology to transfer on-demand functional topographies to the surface of bacterial cellulose nanofiber textures is presented. With this method, termed guided assembly-based biolithography (GAB), a surface-structured polydimethylsiloxane (PDMS) mold is introduced at the gas-liquid interface of an Acetobacter xylinum culture. Upon bacterial fermentation, the generated bacterial cellulose nanofibers are assembled in a three-dimensional network reproducing the geometric shape imposed by the mold. Additionally, GAB yields directional alignment of individual nanofibers and memory of the transferred geometrical features upon dehydration and rehydration of the substrates. Scanning electron and atomic force microscopy are used to establish the good fidelity of this facile and affordable method. Interaction of surface-structured bacterial cellulose substrates with human fibroblasts and keratinocytes illustrates the efficient control of cellular activities which are fundamental in skin wound healing and tissue regeneration. The deployment of surface-structured bacterial cellulose substrates in model animals as skin wound dressing or body implant further proves the high durability and low inflammatory response to the material over a period of 21 days, demonstrating beneficial effects of surface structure on skin regeneration. PMID:25525956

  17. Artificial intelligence approach to planning the robotic assembly of large tetrahedral truss structures

    Homemdemello, Luiz S.

    1992-01-01

    An assembly planner for tetrahedral truss structures is presented. To overcome the difficulties due to the large number of parts, the planner exploits the simplicity and uniformity of the shapes of the parts and the regularity of their interconnection. The planning automation is based on the computational formalism known as production system. The global data base consists of a hexagonal grid representation of the truss structure. This representation captures the regularity of tetrahedral truss structures and their multiple hierarchies. It maps into quadratic grids and can be implemented in a computer by using a two-dimensional array data structure. By maintaining the multiple hierarchies explicitly in the model, the choice of a particular hierarchy is only made when needed, thus allowing a more informed decision. Furthermore, testing the preconditions of the production rules is simple because the patterned way in which the struts are interconnected is incorporated into the topology of the hexagonal grid. A directed graph representation of assembly sequences allows the use of both graph search and backtracking control strategies.

  18. Structural Investigations of Surfaces and Orientation-SpecificPhenomena in Nanocrystals and Their Assemblies

    Aruguete, Deborah Michiko

    2006-06-17

    Studies of colloidal nanocrystals and their assemblies are presented. Two of these studies concern the atomic-level structural characterization of the surfaces, interfaces, and interiors present in II-VI semiconductor nanorods. The third study investigates the crystallographic arrangement of cobalt nanocrystals in self-assembled aggregates. Crystallographically-aligned assemblies of colloidal CdSe nanorods are examined with linearly-polarized Se-EXAFS spectroscopy, which probes bonding along different directions in the nanorod. This orientation-specific probe is used, because it is expected that the presence of specific surfaces in a nanorod might cause bond relaxations specific to different crystallographic directions. Se-Se distances are found to be contracted along the long axis of the nanorod, while Cd-Se distances display no angular dependence, which is different from the bulk. Ab-initio density functional theory calculations upon CdSe nanowires indicate that relaxations on the rod surfaces cause these changes. ZnS/CdS-CdSe core-shell nanorods are studied with Se, Zn, Cd, and S X-ray absorption spectroscopy (XAS). It is hypothesized that there are two major factors influencing the core and shell structures of the nanorods: the large surface area-to-volume ratio, and epitaxial strain. The presence of the surface may induce bond rearrangements or relaxations to minimize surface energy; epitaxial strain might cause the core and shell lattices to contract or expand to minimize strain energy. A marked contraction of Zn-S bonds is observed in the core-shell nanorods, indicating that surface relaxations may dominate the structure of the nanorod (strain might otherwise drive the Zn-S lattice to accommodate the larger CdS or CdSe lattices via bond expansion). EXAFS and X-ray diffraction (XRD) indicate that Cd-Se bond relaxations might be anisotropic, an expected phenomenon for a rod-shaped nanocrystal. Ordered self-assembled aggregates of cobalt nanocrystals are

  19. Theory of factors limiting high gradient operation of warm accelerating structures

    Nusinovich, Gregory S. [University of Maryland; Antonsen, Thomas M. [University of Maryland; Kishek, Rami [University of Maryland

    2014-07-25

    This final report summarizes the research performed during the time period from 8/1/2010 to 7/31/2013. It consists of two parts describing our studies in two directions: (a) analysis of factors limiting operation of dielectric-loaded accelerating (DLA) structures where the main problem is the occurrence of multipactor on dielectric surfaces, and (b) studies of effects associated with either RF magnetic or RF electric fields which may cause the RF breakdown in high-gradient metallic accelerating structures. In the studies of DLA structures, at least, two accomplishments should be mentioned: the development of a 3D non-stationary, self-consistent code describing the multipactor phenomena and yielding very good agreement with some experimental data obtained in joint ANL/NRL experiments. In the metallic structures, such phenomena as the heating and melting of micro-particles (metallic dust) by RF electric and magnetic fields in single-shot and rep-rate regimes is analyzed. Also, such processes in micro-protrusions on the structure surfaces as heating and melting due to the field emitted current and the Nottingham effect are thoroughly investigated with the account for space charge of emitted current on the field emission from the tip.

  20. Conceptual Design of Dielectric Accelerating Structures for Intense Neutron and Monochromatic X-ray Sources

    Bright compact photon sources, which utilize electron beam interaction with periodic structures, may benefit a broad range of medical, industrial and scientific applications. A class of dielectric-loaded periodic structures for hard and soft X-ray production has been proposed that would provide a high accelerating gradient when excited by an external RF and/or primary electron beam. Target-distributed accelerators (TDA), in which an additional electric field compensates for lost beam energy in internal targets, have been shown to provide the necessary means to drive a high flux subcritical reactor (HFSR) for nuclear waste transmutation. The TDA may also be suitable for positron and nuclear isomer production, X-ray lithography and monochromatic computer tomography. One of the early assumptions of the theory of dielectric wake-field acceleration was that, in electrodynamics, the vector potential was proportional to the scalar potential. The analysis takes into consideration a wide range of TDA design aspects including the wave model of observed phenomena, a layered compound separated by a Van der Waals gap and a compact energy source based on fission electric cells (FEC) with a multistage collector. The FEC is a high-voltage power source that directly converts the kinetic energy of the fission fragments into electrical potential of about 2MV

  1. Structural Basis for Accelerated Cleavage of Bovine Pancreatic Trypsin Inhibitor (BPTI) by Human Mesotrypsin

    Salameh,M.; Soares, A.; Hockla, A.; Radisky, E.

    2008-01-01

    Human mesotrypsin is an isoform of trypsin that displays unusual resistance to polypeptide trypsin inhibitors and has been observed to cleave several such inhibitors as substrates. Whereas substitution of arginine for the highly conserved glycine 193 in the trypsin active site has been implicated as a critical factor in the inhibitor resistance of mesotrypsin, how this substitution leads to accelerated inhibitor cleavage is not clear. Bovine pancreatic trypsin inhibitor (BPTI) forms an extremely stable and cleavage-resistant complex with trypsin, and thus provides a rigorous challenge of mesotrypsin catalytic activity toward polypeptide inhibitors. Here, we report kinetic constants for mesotrypsin and the highly homologous (but inhibitor sensitive) human cationic trypsin, describing inhibition by, and cleavage of BPTI, as well as crystal structures of the mesotrypsin-BPTI and human cationic trypsin-BPTI complexes. We find that mesotrypsin cleaves BPTI with a rate constant accelerated 350-fold over that of human cationic trypsin and 150,000-fold over that of bovine trypsin. From the crystal structures, we see that small conformational adjustments limited to several side chains enable mesotrypsin-BPTI complex formation, surmounting the predicted steric clash introduced by Arg-193. Our results show that the mesotrypsin-BPTI interface favors catalysis through (a) electrostatic repulsion between the closely spaced mesotrypsin Arg-193 and BPTI Arg-17, and (b) elimination of two hydrogen bonds between the enzyme and the amine leaving group portion of BPTI. Our model predicts that these deleterious interactions accelerate leaving group dissociation and deacylation.

  2. Accelerated corrosion test and corrosion failure distribution model of aircraft structural aluminum alloy

    LIU Wen-lin; MU Zhi-tao; JIN Ping

    2006-01-01

    Based on corrosion damage data of 10 years for a type of aircraft aluminum alloy, the statistical analysis was conducted by Gumbel, Normal and two parameters Weibull distribution function. The results show that aluminum alloy structural member has the corrosion history of pitting corrosion-intergranular corrosion-exfoliation corrosion, and the maximum corrosion depth is in conformity to normal distribution. The accelerated corrosion test was carried out with the complied equivalent airport accelerated environment spectrum. The corrosion damage failure modes of aluminum alloy structural member indicate that the period of validity of the former protective coating is about 2.5 to 3 years, and that of the novel protective coating is about 4.0 to 4.5 years. The corrosion kinetics law of aluminum spar flange was established by fitting corrosion damage test data. The law indicates two apparent corrosion stages of high strength aluminum alloy section material: pitting corrosion and intergranular corrosion/exfoliation corrosion.The test results agree with the statistical fit result of corrosion data collected from corrosion member in service. The fractional error is 5.8% at the same calendar year. The accelerated corrosion test validates the corrosion kinetics law of aircraft aluminum alloy in service.

  3. Survivability of integrated PVDF film sensors to accelerated ageing conditions in aeronautical/aerospace structures

    This work validates the use of integrated polyvinylidene fluoride (PVDF) film sensors for dynamic testing, even after being subjected to UV-thermo-hygro-mechanical accelerated ageing conditions. The verification of PVDF sensors’ survivability in these environmental conditions, typically confronted by civil and military aircraft, is the main concern of the study. The evaluation of survivability is made by a comparison of dynamic testing results provided by the PVDF patch sensors subjected to an accelerated ageing protocol, and those provided by neutral non-aged sensors (accelerometers). The available measurements are the time-domain response signals issued from a modal analysis procedure, and the corresponding frequency response functions (FRF). These are in turn used to identify the constitutive properties of the samples by extraction of the modal parameters, in particular the natural frequencies. The composite specimens in this study undergo different accelerated ageing processes. After several weeks of experimentation, the samples exhibit a loss of stiffness, represented by a decrease in the elastic moduli down to 10%. Despite the ageing, the integrated PVDF sensors, subjected to the same ageing conditions, are still capable of providing reliable data to carry out a close followup of these changes. This survivability is a determinant asset in order to use integrated PVDF sensors to perform structural health monitoring (SHM) in the future of full-scale composite aeronautical structures. (paper)

  4. Structural integrity assessment and stress measurement of CHASNUPP-1 fuel assembly

    Highlights: • Finite element model of CHASNUPP-1 fuel assembly produced, using Shell181 elements. • Non-linear contact and buckling analysis have been performed. • Structural integrity and stress measurement of fuel assembly is calculated. • Calculated stresses and deformations, are compared with test results. • Results of both studies are comparable, which validate finite element methodology. - Abstract: Fuel assembly of the PWR nuclear power plant is a long and flexible structure. This study has been made in an attempt to find the structural integrity of the fuel assembly (FA) of Chashma Nuclear Power Plant-1 (CHASNUPP-1) at room temperature in air. Non-linear contact and buckling analyses have been performed using ANSYS 13.0, in-order to determine the FA's deformation behaviour as well as the location/values of the maximum stress intensity and stresses developed in axial direction under applied compression load of 7350 N or 1.6 g being the FA's handling load (Zhang et al., 1994). The finite element (FE) model comprises spacer grids, fuel rods, flexible contact between the fuel rods and grids’ supports system (springs and dimples) and guide thimbles with dash-pots and flow holes, in addition to the spot welds between spacer grids and guide thimbles, has been developed using Shell181, Conta174 and Targe170 elements. FA is a non-straight structure. The actual behaviour of the geometry is non-linear. The value of the perturbation force is related to the geometry of the model and/or the tolerance defined for the geometry. Therefore, a sensitivity study has been made to determine the appropriate value of an arbitrary perturbation load. It has been observed that FA deformation values obtained through FE analysis and experiment (SNERDI Tech Doc, 1994) under applied compression load are comparable and show linear behaviours. Therefore, it is confirmed that buckling of FA will not occur at the specified load. Moreover, the values of stresses obtained

  5. A synthetic pulse method for excitation of RF-accelerator structures

    Caspers, Fritz

    1986-01-01

    It is proposed to excite RF-cavity accelerator structures in a phaselocked multifrequency mode of operation. The purpose is to obtain high accelerating gradients with smaller average losses than in the conventional single-frequency operation scheme. In general the resonant frequencies are not harmonically related to each other. Assuming finite Q-values one can always find a frequency fo such that within a 3 dB bandwidth all resonances considered are at integer multiples of f0. For the gap voltage one obtains in this case a periodic pulse in the time domain with T = 1/f0. Increasing the peak gap voltage by adding (exciting) further higher modes with equal CW power on each mode (equal shout impedances assumed) results in power losses proportional to $V_{peak}$ instead of $P_{loss} ~ V_{peak}^2$ for single-frequency operation.

  6. An FFT-accelerated fdtd scheme with exact absorbing conditions for characterizing axially symmetric resonant structures

    Sirenko, Kostyantyn

    2011-01-01

    An accurate and efficient finite-difference time-domain (FDTD) method for characterizing transient waves interactions on axially symmetric structures is presented. The method achieves its accuracy and efficiency by employing localized and/or fast Fourier transform (FFT) accelerated exact absorbing conditions (EACs). The paper details the derivation of the EACs, discusses their implementation and discretization in an FDTD method, and proposes utilization of a blocked-FFT based algorithm for accelerating the computation of temporal convolutions present in nonlocal EACs. The proposed method allows transient analyses to be carried for long time intervals without any loss of accuracy and provides reliable numerical data pertinent to physical processes under resonant conditions. This renders the method highly useful in characterization of high-Q microwave radiators and energy compressors. Numerical results that demonstrate the accuracy and efficiency of the method are presented.

  7. Self-Assembled, Iridescent, Crustacean-Mimetic Nanocomposites with Tailored Periodicity and Layered Cuticular Structure.

    Wang, Baochun; Walther, Andreas

    2015-11-24

    Natural high-performance materials inspire the pursuit of ordered hard/soft nanocomposite structures at high fractions of reinforcements and with balanced molecular interactions. Herein, we develop a facile, waterborne self-assembly pathway to mimic the multiscale cuticle structure of the crustacean armor by combining hard reinforcing cellulose nanocrystals (CNCs) with soft poly(vinyl alcohol) (PVA). We show iridescent CNC nanocomposites with cholesteric liquid-crystal structure, in which different helical pitches and photonic band gaps can be realized by varying the CNC/PVA ratio. We further show that multilayered crustacean-mimetic materials with tailored periodicity and layered cuticular structure can be obtained by sequential preparation pathways. The transition from a cholesteric to a disordered structure occurs for a critical polymer concentration. Correspondingly, we find a transition from stiff and strong mechanical behavior to materials with increasing ductility. Crack propagation studies using scanning electron microscopy visualize the different crack growth and toughening mechanisms inside cholesteric nanocomposites as a function of the interstitial polymer content for the first time. Different extents of crack deflection, layered delamination, ligament bridging, and constrained microcracking can be observed. Drawing of highly plasticized films sheds light on the mechanistic details of the transition from a cholesteric/chiral nematic to a nematic structure. The study demonstrates how self-assembly of biobased CNCs in combination with suitable polymers can be used to replicate a hierarchical biological structure and how future design of these ordered multifunctional nanocomposites can be optimized by understanding mechanistic details of deformation and fracture. PMID:26372330

  8. HOM-Free Linear Accelerating Structure for e+ e- Linear Collider at C-Band

    Kubo, K

    2003-01-01

    HOM-free linear acceleration structure using the choke mode cavity (damped cavity) is now under design for e sup + e sup - linear collider project at C-band frequency (5712 MHz). Since this structure shows powerful damping effect on most of all HOMs, there is no multibunch problem due to long range wakefields. The structure will be equipped with the microwave absorbers in each cells and also the in-line dummy load in the last few cells. The straightness tolerance for 1.8 m long structure is closer than 30 (micro)m for 25% emittance dilution limit, which can be achieved by standard machining and braising techniques. Since it has good vacuum pumping conductance through annular gaps in each cell, instabilities due to the interaction of beam with the residual-gas and ions can be minimized.

  9. The buncher optimization for the biperiodic accelerating structure with the high-frequency focusing

    Fadin, A. I.

    2006-03-01

    The bunching part optimization results of an on-axis-coupled biperiodic accelerating structure for electron linac with high-frequency focusing are presented. System is intended for operation in the continuous regime at operating frequency of 2856 MHz and input power 5.5 MW. The basic development challenge for such installations on average input currents is the effective beam transfer through the structure. Some variants of the bunching sections distinguished by number of bunching cells were considered. The optimum capture ratio and an acceptable spectrum are provided by structure with five bunching cells. Optimization was carried out by means of dynamics simulation code PARMELA and a package of applied programs for the axial symmetric structures calculation SUPERFISH. Taking into account, space-charge limitation, the maximum capture ratio is 55%.

  10. Structure of a strong supernova shock wave and rapid electron acceleration confined in its transition region

    Shimada, Nobue; Amano, Takanobu; 10.1063/1.3322828

    2010-01-01

    A new rapid energization process within a supernova shock transition region (STR) is reported by utilizing numerical simulation. Although the scale of a STR as a main dissipation region is only several hundreds of thousands km, several interesting structures are found relating to generation of a root of the energetic particles. The nonlinear evolution of plasma instabilities lead to a dynamical change in the ion phase space distribution which associates with change of the field properties. As a result, different types of large-amplitude field structures appear. One is the leading wave packet and another is a series of magnetic solitary humps. Each field structure has a microscopic scale (~ the ion inertia length). Through the multiple nonlinear scattering between these large-amplitude field structures, electrons are accelerated directly. Within a STR, quick thermalization realizes energy equipartition between the ion and electron, hot electrons play an important role in keeping these large-amplitude field str...

  11. The stimulated dielectric wake-field accelerator: A structure with novel properties

    We describe a multi-bunch wake-field accelerator in an annular, cylindrical dielectric structure in which many modes can participate in the wake-field formation, and where the wake-field period equals the period of a train of drive bunches of electrons. The structure can be designed so that the TM0n modes, all with phase velocities equal to the bunch velocity, have nearly equally-spaced eigenfrequencies, and thus interfere constructively. The composite wake-field is shown to cause highly peaked axial electric fields localized on each driving bunch in a periodic sequence of bunches. This permits stimulated emission of wake-field energy to occur at a rate that is larger than the coherent spontaneous emission from a single driving bunch having the same total charge. We present calculations for an annular alumina structure which will use 2 nC bunches of electrons obtained from a 100 MeV rf linac operating at 11.4 Ghz. Numerical examples are given, including acceleration of a test bunch to >200 MeV in a structure 75 cm long, using three drive bunches

  12. The stimulated dielectric wake-field accelerator: A structure with novel properties

    We describe a multi-bunch wake-field accelerator in an annular, cylindrical dielectric structure in which many modes can participate in the wake-field formation, and where the wake-field period equals the period of a train of drive bunches of electrons. The structure can be designed so that the TM0n modes, all with phase velocities equal to the bunch velocity, have nearly equally-spaced eigenfrequencies, and thus interfere constructively. The composite wake-field is shown to cause highly peaked axial electric fields localized on each driving bunch in a periodic sequence of bunches. This permits stimulated emission of wake-field energy to occur at a rate that is larger than the coherent spontaneous emission from a single driving bunch having the same total charge. We present calculations for an annular alumina structure which will use 2 nC bunches of electrons obtained from a 100 MeV rf linac operating at 11.4 Ghz. Numerical examples are given, including acceleration of a test bunch to >200 MeV in a structure 75 cm long, using three drive bunches. copyright 1999 American Institute of Physics

  13. Dynamic structural analysis of a head assembly for a large loop-type LMFBR

    An investigation is presented on the dynamic structural response of the primary vessel's head closure to slug impact loadings generated from a 1000 MJ source term. The reference reactor considered was designed in a loop configuration. The head structure consisted of a deck and a triple rotatable plug assembly. Two designs were considered for the deck structure: a reference design and an alternate design. The reference deck was designed as a single flat annular plate. For the alternate design, the deck plate was reinforced by adding an extender cylinder with a flange and flanged webs between the deck-plate and cylinder. The investigation showed that the reference design cannot maintain containment integrity when subjected to slug loading generated by a 1000 MJ source term. It was determined that the head deformed excessively

  14. Cryogenic Electron Microscopy Studies: Structure and Formation of Self-assembled Nanostructures in Solution

    Lee, Han Seung

    Cryogenic electron microscopy (Cryo-EM) techniques are among the most powerful to characterize self-assembling soft materials (colloids, polymers, and microemulsions, etc.) at the nanometer scale, without any need for implicit models or assumptions about the structure. We can even visualize structure under dynamic conditions, capturing each stage of development. In this thesis, cryo-EM has been used to investigate the formation and structure of a variety of self-assembling soft materials. Visualization is complemented by small angle X-ray scattering (SAXS), dynamic light scattering, and conductivity measurements. In each case, cryo-EM provides new insights, not otherwise available, into the nanostructure development. Self-assembly phenomena at the molecular level are critical to the performance of tremendous number of applied systems ranging from personal care products to industrial products. To evaluate these self-assembled materials, multiple characterization techniques are required. We investigated aggregation behavior of cesium dodecyl sulfate (CsDS) ionic surfactant in aqueous solution. Coupled with the real space data from cryogenic transmission electron microscopy (Cryo-TEM) and the inverse space data from SAXS, the experimental result of CsDS in aqueous solution gave a new insight in CsDS micellar structures and their development as a function of concentration. Cryo-TEM showed the presence of the liquid-like hydrocarbon core in the CsDS micelles and relatively thick shell structures at a low CsDS concentration. The core-shell sphere structure micelle shifted to core-shell cylindrical micelle structure at high concentration. The morphology and structure of paclitaxel silicate (PTX) prodrug, encapsulated with amphiphilic poly(ethylene glycol)-b-poly(lactic-co-glycolic acid) diblock copolymers were studied. The six different silicate PTX prodrug candidates were characterized with cryo-TEM. Direct imaging with cryo-TEM illustrated structure of prodrug

  15. Japanese contributions to containment structure, assembly and maintenance and reactor building for ITER

    Joint design work on Conceptual Design Activity of International Thermonuclear Experimental Reactor (ITER) with four parties, Japan, the United States, the Soviet Union and the European Community began in April 1988 and was successfully completed in December 1990. In Japan, the home team was established in wide range of collaboration between JAERI and national institute, universities and heavy industries. The Fusion Experimental Reactor (FER) Team at JAERI is assigned as a core of the Japanese home team to support the joint Team activity and mainly conducted the design and R and D in the area of containment structure, remote handling and plant system. This report mainly describes the Japanese contribution on the ITER containment structure, remote handling and reactor building design. Main areas of contributions are vacuum vessel, attaching locks, electromagnetic analysis, cryostat, port and service line layout for containment structure, in-vessel handling equipment design and analysis, blanket handling equipment design and related short term R and D for assembly and maintenance, and finally reactor building design and analysis based on the equipment and service line layout and components flow during assembly and maintenance. (author)

  16. Dynamic structural analysis of a head assembly for a large loop-type LMFBR

    An investigation is presented here on the dynamic structural response of the primary vessel's head closure to slug impact loadings generated from a 1000 MJ source term. The reference reactor considered was designed in a loop configuration. The head structure consisted of a deck and a triple rotatable plug assembly. Two designs were considered for the deck structure: a reference design and an alternate design. The reference deck was designed as a single flat annular plate. For the alternate design, the deck plate was reinforced by adding an extender cylinder with a flange and flanged webs between the deck-plate and cylinder. This investigation showed that the reference design cannot maintain containment integrity when subjected to slug loading generated by a 1000 MJ source term. It was determined that the head deformed excessively. The excessive deformation would, at least, permanently disengage the HCDA seals. More importantly, however, it appears that the entire TRP assembly would be disengaged from the deck creating a large opening for sodium expulsion. With regard to the alternate design, the computations indicated that the deck deformations were acceptable and that no sodium expulsion would occur at the deck-plug juncture

  17. Affect on the structures self-assembly as modification factor for the cultured cell radiosensitivity

    An assumption is confirmed that the directed effect on the processes of subcellular organelle assembly can be one of the approaches to the modification of radiation damage. It is shown that total cell death rate is conditioned by the effect of toxic compounds (preparations of colchicine, phalloidine and taxol), and by radiobiological effects. It seems that the status of microtubules and microfilaments as integral structures, their organization in 3D cell space, level of different posttranslational modifications of cytoscheleton proteins may be of s-quipicant importance for the realization of the programme of interphase and reproductive death of irradiated cells

  18. Assembl y of Poly-3-Hexylthiophene Nano-Crystallites into Low Dimensional Structures Using Indandione Derivatives

    Amir Fahmi

    2013-02-01

    Full Text Available Conductive polymer poly-3-hexylthiophene (P3HT needles were self-assembled using a second component (indandione derivatives as a linking agent to enhance their long range alignment. The morphologies of the hybrid organic/organic materials were characterized by transmission electron microscopy (TEM. Both linear and branched structures could be produced, with the degree of branching depending upon the linker used. Incorporation of indandione derivatives broadened the UV absorbance band of P3HT without significant change to its photoluminescence. This hybrid material could open a promising avenue in photovoltaic applications due to its interesting morphologies and optical properties.

  19. Structural Characterization and Assembly of the Distal Tail Structure of the Temperate Lactococcal Bacteriophage TP901-1

    Vegge, Christina S.; Brøndsted, Lone; Neve, Horst; Mc Grath, Stephen; van Sinderen, Douwe; Vogensen, Finn K.

    2005-01-01

    The tail structures of bacteriophages infecting gram-positive bacteria are largely unexplored, although the phage tail mediates the initial interaction with the host cell. The temperate Lactococcus lactis phage TP901-1 of the Siphoviridae family has a long noncontractile tail with a distal baseplate. In the present study, we investigated the distal tail structures and tail assembly of phage TP901-1 by introducing nonsense mutations into the late transcribed genes dit (orf46), talTP901-1 (orf47), bppU (orf48), bppL (orf49), and orf50. Transmission electron microscopy examination of mutant and wild-type TP901-1 phages showed that the baseplate consisted of two different disks and that a central tail fiber is protruding below the baseplate. Evaluation of the mutant tail morphologies with protein profiles and Western blots revealed that the upper and lower baseplate disks consist of the proteins BppU and BppL, respectively. Likewise, Dit and TalTP901-1 were shown to be structural tail proteins essential for tail formation, and TalTP901-1 was furthermore identified as the tail fiber protein by immunogold labeling experiments. Determination of infection efficiencies of the mutant phages showed that the baseplate is fundamental for host infection and the lower disk protein, BppL, is suggested to interact with the host receptor. In contrast, ORF50 was found to be nonessential for tail assembly and host infection. A model for TP901-1 tail assembly, in which the function of eight specific proteins is considered, is presented. PMID:15937180

  20. Investigating the Structure-Property Relationships of Aqueous Self-Assembled Materials

    Krogstad, Daniel Vincent

    The components of all living organisms are formed through aqueous self-assembly of organic and inorganic materials through physical interactions including hydrophobic, electrostatic, and hydrogen bonding. In this dissertation, these physical interactions were exploited to develop nanostructured materials for a range of applications. Peptide amphiphiles (PAs) self-assemble into varying structures depending on the physical interactions of the peptides and tails. PA aggregation was investigated by cryo-TEM to provide insight on the effects of varying parameters, including the number and length of the lipid tails as well as the number, length, charge, hydrophobicity, and the hydrogen bonding ability of the peptides. It was determined that cylindrical micelles are most commonly formed, and that specific criteria must be met in order to form spherical micelles, nanoribbons, vesicles or less ordered aggregates. Controlling the aggregated structure is necessary for many applications---particularly in therapeutics. Additionally, two-headed PAs were designed to act as a catalyst and template for biomimetic mineralization to control the formation of inorganic nanomaterials. Finally, injectable hydrogels made from ABA triblock copolymers were synthesized with the A blocks being functionalized with either guanidinium or sulfonate groups. These oppositely charged polyelectrolyte endblocks formed complex coacervate domains, which served as physical crosslinks in the hydrogel network. The mechanical properties, the network structure, the nature of the coacervate domain and the kinetics of hydrogel formation were investigated as a function of polymer concentration, salt concentration, pH and stoichiometry with rheometry, SAXS and SANS. It was shown that the mechanical properties of the hydrogels was highly dependent on the structural organization of the coacervate domains and that the properties could be tuned with polymer and salt concentration. Polymer and salt concentration were

  1. Thermally Induced Ultra High Cycle Fatigue of Copper Alloys of the High Gradient Accelerating Structures

    Heikkinen, Samuli; Wuensch, Walter

    2010-01-01

    In order to keep the overall length of the compact linear collider (CLIC), currently being studied at the European Organization for Nuclear Research (CERN), within reasonable limits, i.e. less than 50 km, an accelerating gradient above 100 MV/m is required. This imposes considerable demands on the materials of the accelerating structures. The internal surfaces of these core components of a linear accelerator are exposed to pulsed radio frequency (RF) currents resulting in cyclic thermal stresses expected to cause surface damage by fatigue. The designed lifetime of CLIC is 20 years, which results in a number of thermal stress cycles of the order of 2.33•1010. Since no fatigue data existed in the literature for CLIC parameter space, a set of three complementary experiments were initiated: ultra high cycle mechanical fatigue by ultrasound, low cycle fatigue by pulsed laser irradiation and low cycle thermal fatigue by high power microwaves, each test representing a subset of the original problem. High conductiv...

  2. Structural behaviour of fuel assemblies for water cooled reactors. Proceedings of a technical meeting

    At the invitation of the Government of France and in response to a proposal of the IAEA Technical Working Group on Water Reactor Fuel Performance and Technology (TWGFPT), the IAEA convened a Technical Meeting on Fuel Assembly Structural Behaviour in Cadarache, France, from 22 to 26 November 2004. The meeting was hosted by the CEA Cadarache Centre, AREVA Framatome-ANP and Electricite de France. The meeting aimed to provide in depth technical exchanges on PWR and WWER operational experience in the field of fuel assembly mechanical behaviour and the potential impact of future high burnup fuel management on fuel reliability. It addressed in-service experience and remedial solutions, loop testing experience, qualification and damage assessment methods (analytic or experimental ones), mechanical behaviour of the fuel assembly including dynamic and fluid structure interaction aspects, modelling and numerical analysis methods, and impact of the in-service evolution of the structural materials. Sixty-seven participants from 17 countries presented 30 papers in the course of four sessions. The topics covered included the impact of hydraulic loadings on fuel assembly (FA)performance, FA bow and control rod (CR) drop kinetics, vibrations and rod-to-grid wear and fretting, and, finally, evaluation and modelling of accident conditions, mainly from seismic causes. FA bow, CR drop kinetics and hydraulics are of great importance under conditions of higher fuel duties including burnup increase, thermal uprates and longer fuel cycles. Vibrations and rod-to-grid wear and fretting have been identified as a key cause of fuel failure at PWRs during the past several years. The meeting demonstrated that full-scale hydraulic tests and modelling provide sufficient information to develop remedies to increase FA skeleton resistance to hydraulic loads, including seismic ones, vibrations and wear. These proceedings are presented as a book with an attached CD-ROM. The first part of the CD

  3. On the estimation of the wake potential for an ultrarelativistic charge in an accelerating structure

    The method to derive the analytic estimations for wake fields of an ultrarelativistic charge in an accelerating structure, that are valid in the range of distances smalller or compared to the effective structure dimensions. The method is based on the approximate space-time domain integrating of the maxwell equations in the Kirchhoff formulation. the method is demonstrated on the examples of obtaining the wake potentials for energy loss of a bunch traversing a scraper, a cavity or periodic iris-loaded structure. Likewise formulae are derived for Green functions that describe transverse force action of wake fields. Simple formulae for the total energy loss evaluation of a bunch with the Gaussian charge density distribution are derived as well. The derived estimations are compared with the computer results and predictions of other models

  4. High-Gradient test results from a CLIC prototype accelerating structure : TD26CC

    Degiovanni, A; Farabolini, W; Grudiev, A; Kovermann, J; Montessinos, E; Riddone, G; Syratchev, I; Wegner, R; Wuensch, W; Solodko, A; Woolley, B

    2014-01-01

    The CLIC study has progressively tested prototype accelerating structures which incorporate an ever increasing number of features which are needed for a final version ready to be installed in a linear collider. The most recent high power test made in the CERN X-band test stand, Xbox-1, is of a CERN-built prototype which includes damping features but also compact input and output power couplers, which maximize the overall length to active gradient ratio of the structure. The structure’s high-gradient performance, 105 MV/m at 250 ns pulse length and low breakdown rate, matches previously tested structures validating both CERN fabrication and the compact coupler design.

  5. LIGA fabrication of mm-wave accelerating cavity structures at the Advanced Photon Source (APS)

    Recent microfabrication technologies based on the LIGA (German acronym for Lithographe, Galvanoformung, und Abformung) process have been applied to build high-aspect-ratio, metallic or dielectric planar structures suitable for high-frequency rf cavity structures. The cavity structures would be used as parts of linear accelerators, microwave undulators, and mm-wave amplifiers. The microfabrication process includes manufacture of precision x-ray masks, exposure of positive resist x-rays through the mask, resist development, and electroforming of the final microstructure. Prototypes of a 32-cell, 108-GHz constant-impedance cavity and a 66-cell, 94-GHz constant-gradient cavity were fabricated with the synchrotron radiation sources at APS and NSLS. This paper will present an overview of the new technology and details of the mm-wave cavity fabrication

  6. Dielectric Wakefield Accelerating Structure as a Source of Terahertz Coherent Cerenkov Radiation

    We discuss future experimental work proposed to study the performance of a cylindrical dielectric wakefield accelerating structure as a coherent Cerenkov radiation source at the Neptune laboratory at UCLA. The Cerenkov wakefield acceleration experiment carried out recently by UCLA/SLAC/USC, using the ultrashort and high charge beam (Q = 3 nC, σz = 20 micron) at the SLAC FFTB, demonstrated electromagnetic wakes at the few GV/m level. The motivation of our prospective experiment is to investigate the operation of a similar scenario using the comparatively long pulse, low charge beam (Q = 0.5 nC, σz = 200 micron) at UCLA Neptune. The field amplitude produced in this setup would be one to two orders of magnitude lower, at the few tens to few 100 MV/m level. Such a decelerating field would extract a significant amount of energy from a low-energy beam in a distance on the order of a few centimeters, allowing the use of short dielectric structures. We discuss details of the geometry and composition of the structures to be used in the experiment. We also examine the possibility of a future dedicated facility at UCLA Neptune based on a hybrid photoinjector currently in development. The intrinsic bunch compression capabilities and improved beam parameters (σz = 100 micron, Q = 1 nC) of the photoinjector would allow the creation of a high power radiation source in the terahertz regime

  7. A STUDY ON APPLICABILITY OF GROUND RESPONSE ACCELERATION METHOD TO DEEP VERTICAL UNDERGROUND STRUCTURES

    Matsumoto, Mai; Shiba, Yukio; Watanabe, Kazuaki

    This paper discusses the applicability of ground response acceleration method to seismic analysis for deep vertical underground structures. To examine the applicability, an analysis of relationships between response of ground and the shaft was conducted. It was found from the analysis that vertical axial stress of the shaft was not correspond with shear stress of ground. Accordingly, it was concluded that the axial stress was not evaluated correctly by the existing method. Therefore, to extend the applicability of the method, ground responses correlated with the axial stress were analyzed and a new method using these ground responses was proposed.

  8. Temporal evolution and electric potential structure of the auroral acceleration region from multispacecraft measurements

    Forsyth, C.; Fazakerley, A. N.; Walsh, A. P.; Watt, C. E.; Garza, K.; Owen, C. J.; Constantinescu, D. O.; Dandouras, I. S.; Fornacon, K.; Lucek, E. A.; Marklund, G. T.; Sadeghi, S. S.; Khotyaintsev, Y. V.; Masson, A.; Doss, N.

    2013-12-01

    Bright aurorae can be excited by the acceleration of electrons into the atmosphere in violation of ideal magnetohydrodynamics. Modelling studies predict that the accelerating electric potential consists of electric double layers at the boundaries of an acceleration region but observations suggest that particle acceleration occurs throughout this region. Using multispacecraft observations from Cluster, we have examined two upward current regions on 14 December 2009. Our observations show that the potential difference below C4 and C3 changed by up to 1.7 kV between their respective crossings, which were separated by 150 s. The field-aligned current density observed by C3 was also larger than that observed by C4. The potential drop above C3 and C4 was approximately the same in both crossings. Using a novel technique of quantitively comparing the electron spectra measured by Cluster 1 and 3, which were separated in altitude, we determine when these spacecraft made effectively magnetically conjugate observations, and we use these conjugate observations to determine the instantaneous distribution of the potential drop in the AAR. Our observations show that an average of 15% of the potential drop in the AAR was located between C1 at 6235 km and C3 at 4685 km altitude, with a maximum potential drop between the spacecraft of 500 V, and that the majority of the potential drop was below C3. Assuming a spatial invariance along the length of the upward current region, we discuss these observations in terms of temporal changes and the vertical structure of the electrostatic potential drop and in the context of existing models and previous single- and multispacecraft observations.

  9. Morphometric structural diversity of a natural armor assembly investigated by 2D continuum strain analysis.

    Varshney, Swati; Song, Juha; Li, Yaning; Boyce, Mary C; Ortiz, Christine

    2015-12-01

    Many armored fish scale assemblies use geometric heterogeneity of subunits as a design parameter to provide tailored biomechanical flexibility while maintaining protection from external penetrative threats. This study analyzes the spatially varying shape of individual ganoid scales as a structural element in a biological system, the exoskeleton of the armored fish Polypterus senegalus (bichir). X-ray microcomputed tomography is used to generate digital 3D reconstructions of the mineralized scales. Landmark-based geometric morphometrics is used to measure the geometric variation among scales and to define a set of geometric parameters to describe shape variation. A formalism using continuum mechanical strain analysis is developed to quantify the spatial geometry change of the scales and illustrate the mechanisms of shape morphing between scales. Five scale geometry variants are defined (average, anterior, tail, ventral, and pectoral fin) and their functional implications are discussed in terms of the interscale mobility mechanisms that enable flexibility within the exoskeleton. The results suggest that shape variation in materials design, inspired by structural biological materials, can allow for tunable behavior in flexible composites made of segmented scale assemblies to achieve enhanced user mobility, custom fit, and flexibility around joints for a variety of protective applications. PMID:26481418

  10. Understanding the structure and performance of self-assembled triblock terpolymer membranes

    Pendergast, MaryTheresa M.

    2013-10-01

    Nanoporous membranes represent a possible route towards more precise particle and macromolecular separations, which are of interest across many industries. Here, we explored membranes with vertically-aligned nanopores formed from a poly(isoprene-. b-styrene-. b-4 vinyl pyridine) (ISV) triblock terpolymer via a hybrid self-assembly/nonsolvent induced phase separation process (S-NIPS). ISV concentration, solvent composition, and evaporation time in the S-NIPS process were varied to tailor ordering of the selective layer and produce enhanced water permeability. Here, water permeability was doubled over previous versions of ISV membranes. This was achieved by increasing volatile solvent concentration, thereby decreasing the evaporation period required for self-assembly. Fine-tuning was required, however, since overly-rapid evaporation did not yield the desired pore structure. Transport models, used to relate the in-. situ structure to the performance of these materials, revealed narrowing of pores and blocking by the dense region below. It was shown that these vertically aligned nanoporous membranes compare favorably with commercial ultrafiltration membranes formed by NIPS and track-etching processes, which suggests that there is practical value in further developing and optimizing these materials for specific industrial separations. © 2013 Elsevier B.V.

  11. Structural domains of vault proteins: a role for the coiled coil domain in vault assembly.

    van Zon, Arend; Mossink, Marieke H; Schoester, Martijn; Scheffer, George L; Scheper, Rik J; Sonneveld, Pieter; Wiemer, Erik A C

    2002-03-01

    Vaults consist of multiple copies of three proteins (MVP, VPARP, and TEP1) and several untranslated RNAs. The function of vaults is unknown but the typical and evolutionary conserved structure indicates a role in intracellular transport. Although all vault components have been identified and characterized, not much is known about vault protein assembly. In this study we identified and analyzed structural domains involved in vault assembly with emphasis on protein-protein interactions. Using a yeast two-hybrid system, we demonstrate within MVP an intramolecular binding site and show that MVP molecules interact with each other via their coiled coil domain. We show that purified MVP is able to bind calcium, most likely at calcium-binding EF-hands. No interactions could be detected between TEP1 and other vault proteins. However, the N-terminal half of MVP binds to a specific domain in the C-terminus of VPARP. Furthermore, VPARP contains amino acid stretches mediating intramolecular binding. PMID:11855821

  12. Integrated Self-Assembly of the Mms6 Magnetosome Protein to Form an Iron-Responsive Structure

    Marit Nilsen-Hamilton

    2013-07-01

    Full Text Available A common feature of biomineralization proteins is their self-assembly to produce a surface consistent in size with the inorganic crystals that they produce. Mms6, a small protein of 60 amino acids from Magnetospirillum magneticum strain AMB-1 that promotes the in vitro growth of superparamagnetic magnetite nanocrystals, assembles in aqueous solution to form spherical micelles that could be visualized by TEM and AFM. The results reported here are consistent with the view that the N and C-terminal domains interact with each other within one polypeptide chain and across protein units in the assembly. From studies to determine the amino acid residues important for self-assembly, we identified the unique GL repeat in the N-terminal domain with additional contributions from amino acids in other positions, throughout the molecule. Analysis by CD spectroscopy identified a structural change in the iron-binding C-terminal domain in the presence of Fe3+. A change in the intrinsic fluorescence of tryptophan in the N-terminal domain showed that this structural change is transmitted through the protein. Thus, self-assembly of Mms6 involves an interlaced structure of intra- and inter-molecular interactions that results in a coordinated structural change in the protein assembly with iron binding.

  13. Self-assembly of three-dimensional prestressed tensegrity structures from DNA

    Liedl, Tim; Högberg, Björn; Tytell, Jessica; Ingber, Donald E.; Shih, William M.

    2010-07-01

    Tensegrity, or tensional integrity, is a property of a structure indicating a reliance on a balance between components that are either in pure compression or pure tension for stability. Tensegrity structures exhibit extremely high strength-to-weight ratios and great resilience, and are therefore widely used in engineering, robotics and architecture. Here, we report nanoscale, prestressed, three-dimensional tensegrity structures in which rigid bundles of DNA double helices resist compressive forces exerted by segments of single-stranded DNA that act as tension-bearing cables. Our DNA tensegrity structures can self-assemble against forces up to 14 pN, which is twice the stall force of powerful molecular motors such as kinesin or myosin. The forces generated by this molecular prestressing mechanism can be used to bend the DNA bundles or to actuate the entire structure through enzymatic cleavage at specific sites. In addition to being building blocks for nanostructures, tensile structural elements made of single-stranded DNA could be used to study molecular forces, cellular mechanotransduction and other fundamental biological processes.

  14. Complete Structure of an Epithelial Keratin Dimer: Implications for Intermediate Filament Assembly.

    David J Bray

    Full Text Available Keratins are cytoskeletal proteins that hierarchically arrange into filaments, starting with the dimer sub-unit. They are integral to the structural support of cells, in skin, hair and nails. In skin, keratin is thought to play a critical role in conferring the barrier properties and elasticity of skin. In general, the keratin dimer is broadly described by a tri-domain structure: a head, a central rod and a tail. As yet, no atomistic-scale picture of the entire dimer structure exists; this information is pivotal for establishing molecular-level connections between structure and function in intermediate filament proteins. The roles of the head and tail domains in facilitating keratin filament assembly and function remain as open questions. To address these, we report results of molecular dynamics simulations of the entire epithelial human K1/K10 keratin dimer. Our findings comprise: (1 the first three-dimensional structural models of the complete dimer unit, comprising of the head, rod and tail domains; (2 new insights into the chirality of the rod-domain twist gained from analysis of the full domain structure; (3 evidence for tri-subdomain partitioning in the head and tail domains; and, (4 identification of the residue characteristics that mediate non-covalent contact between the chains in the dimer. Our findings are immediately applicable to other epithelial keratins, such as K8/K18 and K5/K14, and to intermediate filament proteins in general.

  15. Structural features of anodic oxide films formed on aluminum substrate coated with self-assembled microspheres

    Asoh, Hidetaka [Department of Applied Chemistry, Faculty of Engineering, Kogakuin University, 2665-1 Nakano, Hachioji, Tokyo 192-0015 (Japan)], E-mail: asoh@cc.kogakuin.ac.jp; Uchibori, Kota; Ono, Sachiko [Department of Applied Chemistry, Faculty of Engineering, Kogakuin University, 2665-1 Nakano, Hachioji, Tokyo 192-0015 (Japan)

    2009-07-15

    The structural features of anodic oxide films formed on an aluminum substrate coated with self-assembled microspheres were investigated by scanning electron microscopy and atomic force microscopy. In the first anodization in neutral solution, the growth of a barrier-type film was partially suppressed in the contact area between the spheres and the underlying aluminum substrate, resulting in the formation of ordered dimple arrays in an anodic oxide film. After the subsequent second anodization in acid solution at a voltage lower than that of the first anodization, nanopores were generated only within each dimple. The nanoporous region could be removed selectively by post-chemical etching using the difference in structural dimensions between the porous region and the surrounding barrier region. The mechanism of anodic oxide growth on the aluminum substrate coated with microspheres through multistep anodization is discussed.

  16. Sampling the structure and chemical order in assemblies of ferromagnetic nanoparticles by nuclear magnetic resonance

    Liu, Yuefeng; Luo, Jingjie; Shin, Yooleemi; Moldovan, Simona; Ersen, Ovidiu; Hébraud, Anne; Schlatter, Guy; Pham-Huu, Cuong; Meny, Christian

    2016-05-01

    Assemblies of nanoparticles are studied in many research fields from physics to medicine. However, as it is often difficult to produce mono-dispersed particles, investigating the key parameters enhancing their efficiency is blurred by wide size distributions. Indeed, near-field methods analyse a part of the sample that might not be representative of the full size distribution and macroscopic methods give average information including all particle sizes. Here, we introduce temperature differential ferromagnetic nuclear resonance spectra that allow sampling the crystallographic structure, the chemical composition and the chemical order of non-interacting ferromagnetic nanoparticles for specific size ranges within their size distribution. The method is applied to cobalt nanoparticles for catalysis and allows extracting the size effect from the crystallographic structure effect on their catalytic activity. It also allows sampling of the chemical composition and chemical order within the size distribution of alloyed nanoparticles and can thus be useful in many research fields.

  17. Final Report on "Development and Testing of Advanced Accelerator Structures and Technologies at 11.424 GHz"

    Gold, Steven H. [Naval Research Laboratory

    2013-10-13

    This is the final report on the research program ?Development and Testing of Advanced Accelerator Structures and Technologies at 11.424 GHz,? which was carried out by the Naval Research Laboratory (NRL) under Interagency Agreement DE?AI02?01ER41170 with the Department of Energy. The period covered by this report is 15 July 2010 ? 14 July 2013. The program included two principal tasks. Task 1 involved a study of the key physics issues related to the use of high gradient dielectric-loaded accelerating (DLA) structures in rf linear accelerators and was carried out in collaboration with Argonne National Laboratory (ANL) and Euclid Techlabs LLC. Task 2 involved a study of high power active microwave pulse compressors and was carried out in collaboration with Omega-P, Inc. and the Institute of Applied Physics of the Russian Academy of Sciences in Nizhny Novgorod. The studies under Task 1 were focused on rf-induced multipactor and breakdown in externally driven DLA structures at the 200-ns timescale. Suppression of multipactor and breakdown are essential to the practical application of dielectric structures in rf linear accelerators. The structures that were studied were developed by ANL and Euclid Techlabs and their performance was evaluated at high power in the X-band Magnicon Laboratory at NRL. Three structures were designed, fabricated, and tested, and the results analyzed in the first two years of the program: a clamped quartz traveling-wave (TW) structure, a externally copper-coated TW structure, and an externally copper-coated dielectric standing-wave (SW) structure. These structures showed that rf breakdown could be largely eliminated by eliminating dielectric joints in the structures, but that the multipactor loading was omnipresent. In the third year of the program, the focus of the program was on multipactor suppression using a strong applied axial magnetic field, as proposed by Chang et al. [C. Chang et al., J. Appl. Phys. 110, 063304 (2011).], and a

  18. 介质壁加速腔加速结构优化%Optimization of accelerating structure in dielectric wall accelerator

    叶茂; 张篁; 刘毅; 王卫; 谌怡; 杨超; 夏连胜; 石金水; 章林文

    2016-01-01

    In the dielectric wall accelerator (DWA),the intensity and the distribution of the axial and radial electric fields generated by the electrode structure are obviously different.In order to enhance the axial accelerating field,improve the accelera-ting gradient and suppress the beam profile expansion caused by the radial electric field,metal grids are embedded in between each accelerating unit.Electromagnetic simulation software based on particle-in-cell method is used to numerically simulate structures with and without metal grids,and to analyze the distribution of electric field as well as the change of the beam profile under differ-ent structures.The experimental results agree well with the simulation outcome,which demonstrate that the DWA with the met-al grid structure has stronger and more uniform axial accelerating field than the DWA without metal grids.Furthermore,for the metal grid structure,the radial electric field is suppressed efficiently and the radial divergence of the accelerated particle beam in free drift space is improved.%为了在介质壁加速器中增大轴向加速电场,提高加速梯度的同时抑制径向电场对束包络的扩张,提出了在每个加速电极上添加金属栅网结构.采用基于粒子云网格方法的电磁粒子模拟软件对不加栅网与添加栅网的电极结构进行了数值仿真,分析了不同结构下加速管道中的电场分布和束包络变化.通过实验对比了两种不同结构下经过相同的加速长度获得的粒子能量.结果表明:添加金属栅网结构相对于不加栅网的金属小孔式结构,轴向加速电场强度提高 20%,同时径向电场得到有效抑制;栅网结构下,被加速的粒子束在自由漂移空间中的径向发散基本得到抑制;在相同的加速长度下加速 H+3 粒子,栅网结构得到的能量增益提高了一倍.

  19. GeauxDock: Accelerating Structure-Based Virtual Screening with Heterogeneous Computing.

    Ye Fang

    Full Text Available Computational modeling of drug binding to proteins is an integral component of direct drug design. Particularly, structure-based virtual screening is often used to perform large-scale modeling of putative associations between small organic molecules and their pharmacologically relevant protein targets. Because of a large number of drug candidates to be evaluated, an accurate and fast docking engine is a critical element of virtual screening. Consequently, highly optimized docking codes are of paramount importance for the effectiveness of virtual screening methods. In this communication, we describe the implementation, tuning and performance characteristics of GeauxDock, a recently developed molecular docking program. GeauxDock is built upon the Monte Carlo algorithm and features a novel scoring function combining physics-based energy terms with statistical and knowledge-based potentials. Developed specifically for heterogeneous computing platforms, the current version of GeauxDock can be deployed on modern, multi-core Central Processing Units (CPUs as well as massively parallel accelerators, Intel Xeon Phi and NVIDIA Graphics Processing Unit (GPU. First, we carried out a thorough performance tuning of the high-level framework and the docking kernel to produce a fast serial code, which was then ported to shared-memory multi-core CPUs yielding a near-ideal scaling. Further, using Xeon Phi gives 1.9× performance improvement over a dual 10-core Xeon CPU, whereas the best GPU accelerator, GeForce GTX 980, achieves a speedup as high as 3.5×. On that account, GeauxDock can take advantage of modern heterogeneous architectures to considerably accelerate structure-based virtual screening applications. GeauxDock is open-sourced and publicly available at www.brylinski.org/geauxdock and https://figshare.com/articles/geauxdock_tar_gz/3205249.

  20. GeauxDock: Accelerating Structure-Based Virtual Screening with Heterogeneous Computing.

    Fang, Ye; Ding, Yun; Feinstein, Wei P; Koppelman, David M; Moreno, Juana; Jarrell, Mark; Ramanujam, J; Brylinski, Michal

    2016-01-01

    Computational modeling of drug binding to proteins is an integral component of direct drug design. Particularly, structure-based virtual screening is often used to perform large-scale modeling of putative associations between small organic molecules and their pharmacologically relevant protein targets. Because of a large number of drug candidates to be evaluated, an accurate and fast docking engine is a critical element of virtual screening. Consequently, highly optimized docking codes are of paramount importance for the effectiveness of virtual screening methods. In this communication, we describe the implementation, tuning and performance characteristics of GeauxDock, a recently developed molecular docking program. GeauxDock is built upon the Monte Carlo algorithm and features a novel scoring function combining physics-based energy terms with statistical and knowledge-based potentials. Developed specifically for heterogeneous computing platforms, the current version of GeauxDock can be deployed on modern, multi-core Central Processing Units (CPUs) as well as massively parallel accelerators, Intel Xeon Phi and NVIDIA Graphics Processing Unit (GPU). First, we carried out a thorough performance tuning of the high-level framework and the docking kernel to produce a fast serial code, which was then ported to shared-memory multi-core CPUs yielding a near-ideal scaling. Further, using Xeon Phi gives 1.9× performance improvement over a dual 10-core Xeon CPU, whereas the best GPU accelerator, GeForce GTX 980, achieves a speedup as high as 3.5×. On that account, GeauxDock can take advantage of modern heterogeneous architectures to considerably accelerate structure-based virtual screening applications. GeauxDock is open-sourced and publicly available at www.brylinski.org/geauxdock and https://figshare.com/articles/geauxdock_tar_gz/3205249. PMID:27420300

  1. 2D and 3D multipactor modeling in dielectric-loaded accelerator structures

    Sinitsyn, Oleksandr; Nusinovich, Gregory; Antonsen, Thomas

    2010-11-01

    Multipactor (MP) is known as the avalanche growth of the number of secondary electrons emitted from a solid surface exposed to an RF electric field under vacuum conditions. MP is a severe problem in modern rf systems and, therefore, theoretical and experimental studies of MP are of great interest to the researchers working in various areas of physics and engineering. In this work we present results of MP studies in dielectric-loaded accelerator (DLA) structures. First, we show simulation results obtained with the use of the 2D self-consistent MP model (O. V. Sinitsyn, et. al., Phys. Plasmas, vol. 16, 073102 (2009)) and compare those to experimental ones obtained during recent extensive studies of DLA structures performed by Argonne National Laboratory, Naval Research Laboratory, SLAC National Accelerator Laboratory and Euclid TechLabs (C. Jing, et al., IEEE Trans. Plasma Sci., vol. 38, pp. 1354-1360 (2010)). Then we present some new results of 3D analysis of MP which include studies of particle trajectories and studies of MP development at the early stage.

  2. Current state of X-band accelerating structure high gradient test. Be held at high energy accelerator organization on April 15, 2005

    XTF (X-band Test Facility, Old name is GLCTA) is the high gradient test facility for X-band acceleration. We have installed an X-band 60cm structure (KX01) in the April 2004 and have been processing it for more than 10 months. Now it is under test on long-term operation. We report here the high gradient test result to date. (author)

  3. Molecular Structure of RADA16-I Designer Self-Assembling Peptide Nanofibers

    Cormier, Ashley R.; Pang, Xiaodong; Zimmerman, Maxwell I.; Zhou, Huan-Xiang; Paravastu, Anant K.

    2013-01-01

    The designer self-assembling peptide RADA16-I forms nanofiber matrices which have shown great promise for regenerative medicine and 3-dimensional cell culture. RADA16-I has a β-strand-promoting alternating hydrophobic/charged motif, but arrangement of β-strands into the nanofiber structure has not been previously determined. Here we present a structural model of RADA16-I nanofibers, based on solid-state NMR measurements on samples with different schemes for 13C isotopic labeling. NMR peak positions and line widths indicate an ordered structure composed of β-strands. The NMR data show that the nanofibers are composed of two stacked β-sheets stabilized by a hydrophobic core formed by alanine sidechains, consistent with previous proposals. However, the previously proposed antiparallel β-sheet structure is ruled out by 13C-13C dipolar couplings. Instead, neighboring β-strands within β-sheets are parallel, with a registry shift that allows for cross-strand staggering of oppositely charged arginine and aspartate sidechains. The resulting structural model is compared to nanofiber dimensions observed via images taken by transmission electron microscopy and atomic force microscopy. Multiple NMR peaks for each alanine sidechain were observed and could be attributed to multiple configurations of sidechain packing within a single scheme for intermolecular packing. PMID:23977885

  4. Deterministic assembly processes govern bacterial community structure in the Fynbos, South Africa.

    Moroenyane, I; Chimphango, S B M; Wang, J; Kim, H-K; Adams, Jonathan Miles

    2016-08-01

    The Mediterranean Fynbos vegetation of South Africa is well known for its high levels of diversity, endemism, and the existence of very distinct plant communities on different soil types. Studies have documented the broad taxonomic classification and diversity patterns of soil microbial diversity, but none has focused on the community assembly processes. We hypothesised that bacterial phylogenetic community structure in the Fynbos is highly governed by deterministic processes. We sampled soils in four Fynbos vegetation types and examined bacterial communities using Illumina HiSeq platform with the 16S rRNA gene marker. UniFrac analysis showed that the community clustered strongly by vegetation type, suggesting a history of evolutionary specialisation in relation to habitats or plant communities. The standardised beta mean nearest taxon distance (ses. β NTD) index showed no association with vegetation type. However, the overall phylogenetic signal indicates that distantly related OTUs do tend to co-occur. Both NTI (nearest taxon index) and ses. β NTD deviated significantly from null models, indicating that deterministic processes were important in the assembly of bacterial communities. Furthermore, ses. β NTD was significantly higher than that of null expectations, indicating that co-occurrence of related bacterial lineages (over-dispersion in phylogenetic beta diversity) is determined by the differences in environmental conditions among the sites, even though the co-occurrence pattern did not correlate with any measured environmental parameter, except for a weak correlation with soil texture. We suggest that in the Fynbos, there are frequent shifts of niches by bacterial lineages, which then become constrained and evolutionary conserved in their new environments. Overall, this study sheds light on the relative roles of both deterministic and neutral processes in governing bacterial communities in the Fynbos. It seems that deterministic processes play a major

  5. Convergence acceleration for partitioned simulations of the fluid-structure interaction in arteries

    Radtke, Lars; Larena-Avellaneda, Axel; Debus, Eike Sebastian; Düster, Alexander

    2016-02-01

    We present a partitioned approach to fluid-structure interaction problems arising in analyses of blood flow in arteries. Several strategies to accelerate the convergence of the fixed-point iteration resulting from the coupling of the fluid and the structural sub-problem are investigated. The Aitken relaxation and variants of the interface quasi-Newton -least-squares method are applied to different test cases. A hybrid variant of two well-known variants of the interface quasi-Newton-least-squares method is found to perform best. The test cases cover the typical boundary value problem faced when simulating the fluid-structure interaction in arteries, including a strong added mass effect and a wet surface which accounts for a large part of the overall surface of each sub-problem. A rubber-like Neo Hookean material model and a soft-tissue-like Holzapfel-Gasser-Ogden material model are used to describe the artery wall and are compared in terms of stability and computational expenses. To avoid any kind of locking, high-order finite elements are used to discretize the structural sub-problem. The finite volume method is employed to discretize the fluid sub-problem. We investigate the influence of mass-proportional damping and the material model chosen for the artery on the performance and stability of the acceleration strategies as well as on the simulation results. To show the applicability of the partitioned approach to clinical relevant studies, the hemodynamics in a pathologically deformed artery are investigated, taking the findings of the test case simulations into account.

  6. Convergence acceleration for partitioned simulations of the fluid-structure interaction in arteries

    Radtke, Lars; Larena-Avellaneda, Axel; Debus, Eike Sebastian; Düster, Alexander

    2016-06-01

    We present a partitioned approach to fluid-structure interaction problems arising in analyses of blood flow in arteries. Several strategies to accelerate the convergence of the fixed-point iteration resulting from the coupling of the fluid and the structural sub-problem are investigated. The Aitken relaxation and variants of the interface quasi-Newton -least-squares method are applied to different test cases. A hybrid variant of two well-known variants of the interface quasi-Newton-least-squares method is found to perform best. The test cases cover the typical boundary value problem faced when simulating the fluid-structure interaction in arteries, including a strong added mass effect and a wet surface which accounts for a large part of the overall surface of each sub-problem. A rubber-like Neo Hookean material model and a soft-tissue-like Holzapfel-Gasser-Ogden material model are used to describe the artery wall and are compared in terms of stability and computational expenses. To avoid any kind of locking, high-order finite elements are used to discretize the structural sub-problem. The finite volume method is employed to discretize the fluid sub-problem. We investigate the influence of mass-proportional damping and the material model chosen for the artery on the performance and stability of the acceleration strategies as well as on the simulation results. To show the applicability of the partitioned approach to clinical relevant studies, the hemodynamics in a pathologically deformed artery are investigated, taking the findings of the test case simulations into account.

  7. Combinatorial and topological modeling of cluster self-assembly of the crystal structure of zeolites

    Ilyushin, G. D.; Blatov, V. A.

    2015-07-01

    Combinatorial and topological modeling of packings of symmetrically connected polyhedral T12 clusters (hexagonal prisms), which are most widespread in crystal structures of zeolites, has been performed. Packings of T12 clusters are periodic 1D chains (11 types) and 2D microlayers (15 types). 2D microlayers that can be involved in the self-assembly of 3D zeolite structures described by tetracoordinated T nets are selected. Computer methods (the ToposPro program package) have been used to establish a correspondence with zeolites CHA (Chabazite, Ca6(H2O)40Al12Si24O72), AEI (AlPO-18, Al24P24O96), SAV ((C18H42N6)2(H2O)7Mg5Al19P24O96), KFI (Na30(H2O)98Al30Si66O192), GME (Gmelinite, (Ca,Na)4(H2O)24Al8Si16O48), AFX (SAPO-56, H3Al23Si5P20O96), and AFT (AlPO-52, Al36P36O144) for 7 out of 11 obtained models of 3D frameworks. Modeling of 3D polytypes of the GME (1L type)- AFX (2L type)- AFT (3L type) family has resulted in a new 3L polytype with the following crystallographic parameters: a =13.75 Å, c = 30.00 Å, V = 4912.0 Å3, sp. gr. P m2 (no. 187). It is established that the 2D self-assembly of known zeolite structures is accompanied by pairwise binding of all (T12 + T12) clusters with the formation of 4C rings, and the number of bonds between complementary chains during the formation of microlayers is maximum. Three types of obtained frameworks, which have no analogs among zeolites, exhibit low chain connectivity during microlayer formation in all cases.

  8. Hierarchical assembly strategy and multiscale structural origin of exceptional mechanical performance in nacre

    Huang, Zaiwang

    Nacre (mother of pearl) is a self-assembled hierarchical nanocomposite in possession of exquisite multiscale architecture and exceptional mechanical properties. Previous work has shown that the highly-ordered brick-mortar-like structure in nacre is assembled via epitaxial growth and the aragonite platelets are pure single-crystals. Our results challenge this conclusion and propose that nacre's individual aragonite platelets are constructed with highly-aligned aragonite nanoparticles mediated by screw dislocation and amorphous aggregation. The underlying physics mechanism why the aragonite nanoparticles choose highly-oriented attachment as its crystallization pathway is rationalized in terms of thermodynamics. The aragonite nanoparticle order-disorder transformation can be triggered by high temperature and mechanical deformation, which in turn confirms that the aragonite nanoparticles are basic building blocks for aragonite platelets. Particularly fascinating is the fracture toughness enhancement of nacre through exquisitely collecting mechanically inferior calcium carbonate (CaCO3) and biomolecules. The sandwich-like microarchitecture with a geometrically staggered arrangement can induce crack deflection along its biopolymer interface, thus significantly enhancing nacre's fracture toughness. Our new findings ambiguously demonstrate that, aside from crack deflection, the advancing crack can invade aragonite platelet, leaving a zigzag crack propagation pathway. These unexpected experimental observations disclose, for the first time, the inevitable structural role of aragonite platelets in enhancing nacre's fracture toughness. Simultaneously, the findings that the crack propagates in a zigzag manner within individual aragonite platelets overturn the previously well-established wisdom that considers aragonite platelets as brittle single-crystals. Moreover, we investigated the dynamical mechanical response of nacre under unixial compression. Our results show that the

  9. Directed self-assembly of large scaffold-free multi-cellular honeycomb structures

    Tejavibulya, Nalin; Youssef, Jacquelyn; Bao, Brian; Ferruccio, Toni-Marie; Morgan, Jeffrey R, E-mail: Jeffrey_Morgan@Brown.edu [Department of Molecular Pharmacology, Physiology and Biotechnology, Center for Biomedical Engineering, Brown University, G-B 393, Biomed Center, 171 Meeting St, Providence, RI 02912 (United States)

    2011-09-15

    A significant challenge to the field of biofabrication is the rapid construction of large three-dimensional (3D) living tissues and organs. Multi-cellular spheroids have been used as building blocks. In this paper, we create large multi-cellular honeycomb building blocks using directed self-assembly, whereby cell-to-cell adhesion, in the context of the shape and obstacles of a micro-mold, drives the formation of a 3D structure. Computer-aided design, rapid prototyping and replica molding were used to fabricate honeycomb-shaped micro-molds. Nonadhesive hydrogels cast from these micro-molds were equilibrated in the cell culture medium and seeded with two types of mammalian cells. The cells settled into the honeycomb recess were unable to attach to the nonadhesive hydrogel and so cell-to-cell adhesion drove the self-assembly of a large multi-cellular honeycomb within 24 h. Distinct morphological changes occurred to the honeycomb and its cells indicating the presence of significant cell-mediated tension. Unlike the spheroid, whose size is constrained by a critical diffusion distance needed to maintain cell viability, the overall size of the honeycomb is not limited. The rapid production of the honeycomb building unit, with its multiple rings of high-density cells and open lumen spaces, offers interesting new possibilities for biofabrication strategies.

  10. Characterization of engineered actin binding proteins that control filament assembly and structure.

    Crista M Brawley

    Full Text Available BACKGROUND: Eukaryotic cells strictly regulate the structure and assembly of their actin filament networks in response to various stimuli. The actin binding proteins that control filament assembly are therefore attractive targets for those who wish to reorganize actin filaments and reengineer the cytoskeleton. Unfortunately, the naturally occurring actin binding proteins include only a limited set of pointed-end cappers, or proteins that will block polymerization from the slow-growing end of actin filaments. Of the few that are known, most are part of large multimeric complexes that are challenging to manipulate. METHODOLOGY/PRINCIPAL FINDINGS: We describe here the use of phage display mutagenesis to generate of a new class of binding protein that can be targeted to the pointed-end of actin. These proteins, called synthetic antigen binders (sABs, are based on an antibody-like scaffold where sequence diversity is introduced into the binding loops using a novel "reduced genetic code" phage display library. We describe effective strategies to select and screen for sABs that ensure the generated sABs bind to the pointed-end surface of actin exclusively. CONCLUSIONS/SIGNIFICANCE: From our set of pointed-end binders, we identify three sABs with particularly useful properties to systematically probe actin dynamics: one protein that caps the pointed end, a second that crosslinks actin filaments, and a third that severs actin filaments and promotes disassembly.

  11. Directed self-assembly of large scaffold-free multi-cellular honeycomb structures

    A significant challenge to the field of biofabrication is the rapid construction of large three-dimensional (3D) living tissues and organs. Multi-cellular spheroids have been used as building blocks. In this paper, we create large multi-cellular honeycomb building blocks using directed self-assembly, whereby cell-to-cell adhesion, in the context of the shape and obstacles of a micro-mold, drives the formation of a 3D structure. Computer-aided design, rapid prototyping and replica molding were used to fabricate honeycomb-shaped micro-molds. Nonadhesive hydrogels cast from these micro-molds were equilibrated in the cell culture medium and seeded with two types of mammalian cells. The cells settled into the honeycomb recess were unable to attach to the nonadhesive hydrogel and so cell-to-cell adhesion drove the self-assembly of a large multi-cellular honeycomb within 24 h. Distinct morphological changes occurred to the honeycomb and its cells indicating the presence of significant cell-mediated tension. Unlike the spheroid, whose size is constrained by a critical diffusion distance needed to maintain cell viability, the overall size of the honeycomb is not limited. The rapid production of the honeycomb building unit, with its multiple rings of high-density cells and open lumen spaces, offers interesting new possibilities for biofabrication strategies.

  12. Ag nanoparticles formed by femtosecond pulse laser ablation in water: self-assembled fractal structures

    Santillán, Jesica M. J. [CONICET La Plata-CIC, Centro de Investigaciones Ópticas (CIOp) (Argentina); Fernández van Raap, Marcela B., E-mail: raap@fisica.unlp.edu.ar; Mendoza Zélis, Pedro; Coral, Diego [CONICET, Instituto de Física La Plata (IFLP) (Argentina); Muraca, Diego [Universidade Estadual de Campinas, Instituto de Física “Gleb Wataghin” (IFGW) (Brazil); Schinca, Daniel C.; Scaffardi, Lucía B., E-mail: lucias@ciop.unlp.edu.ar [CONICET La Plata-CIC, Centro de Investigaciones Ópticas (CIOp) (Argentina)

    2015-02-15

    We report for the first time on the formation of self-assembled fractals of spherical Ag nanoparticles (Nps) fabricated by femtosecond pulse laser ablation of a solid silver target in water. Fractal structures grew both in two and three Euclidean dimensions (d). Ramified-fractal assemblies of 2 nm height and 5–14 μm large, decorated with Ag Nps of 3 nm size, were obtained in a 2d geometry when highly diluted drops of colloidal suspension were dried at a fast heating rate over a mica substrate. When less-diluted drops were dried at slow heating rate, isolated single Nps or rosette-like structures were formed. Fractal aggregates about 31 nm size in 3d geometry were observed in the as-prepared colloidal suspension. Electron diffraction and optical extinction spectroscopy (OES) analyses performed on the samples confirmed the presence of Ag and Ag{sub 2}O. The analysis of the optical extinction spectrum, using the electrostatic approximation of Mie theory for small spheres, showed the existence of Ag bare core, Ag–Ag{sub 2}O and air–Ag core–shell Nps, Ag–Ag{sub 2}O being the most frequent type [69 % relative abundance (r.a.)]. Core-size and shell-thickness distribution was derived from OES. In situ scattering measurements of the Ag colloidal suspension, carried out by small-angle X-ray scattering, indicate a mass fractal composed of packaged 〈D{sub SAXS}〉 = (5 ± 1) nm particles and fractal dimension d{sub f} = 2.5. Ex situ atomic force microscopy imaging displayed well-ramified structures, which, analyzed with box-counting method, yield a fractal dimension d{sub f} = 1.67. The growing behavior of these 2d and 3d self-assembled fractals is consistent with the diffusion-limited aggregation model.

  13. Structure-property relationships for self-assembled zinc chlorin light-harvesting dye aggregates.

    Huber, Valerie; Sengupta, Sanchita; Würthner, Frank

    2008-01-01

    A series of zinc 3(1)-hydroxymethyl chlorins 10 a-e and zinc 3(1)-hydroxyethyl chlorins 17 with varied structural features were synthesized by modifying naturally occurring chlorophyll a. Solvent-, temperature-, and concentration-dependent UV/Vis and CD spectroscopic methods as well as microscopic investigations were performed to explore the importance of particular functional groups and steric effects on the self-assembly behavior of these zinc chlorins. Semisynthetic zinc chlorins 10 a-e possess the three functional units relevant for self-assembly found in their natural bacteriochlorophyll (BChl) counterparts, namely, the 3(1)-OH group, a central metal ion, and the 13(1) C==O moiety along the Qy axis, and they contain various 17(2)-substituents. Depending on whether the zinc chlorins have 17(2)-hydrophobic or hydrophilic side chains, they self-assemble in nonpolar organic solvents or in aqueous media, respectively. Zinc chlorins possessing at least two long side chains provide soluble self-aggregates that are stable in solution for a prolonged time, thus facilitating elucidation of their properties by optical spectroscopy. The morphology of the zinc chlorin aggregates was elucidated by atomic force microscopy (AFM) studies, revealing well-defined nanoscale rod structures for zinc chlorin 10 b with a height of about 6 nm. It is worth noting that this size is in good accordance with a tubular arrangement of the dyes similar to that observed in their natural BChl counterparts in the light-harvesting chlorosomes of green bacteria. Furthermore, for the epimeric 3(1)-hydroxyethyl zinc chlorins 17 with hydrophobic side chains, the influence of the chirality center at the 3(1)-position on the aggregation behavior was studied in detail by UV/Vis and CD spectroscopy. Unlike zinc chlorins 10, the 3(1)-hydroxyethyl zinc chlorins 17 formed only small oligomers and not higher rod aggregate structures, which can be attributed to the steric effect imposed by the additional

  14. ISWI regulates higher-order chromatin structure and histone H1 assembly in vivo.

    Davide F V Corona

    2007-09-01

    Full Text Available Imitation SWI (ISWI and other ATP-dependent chromatin-remodeling factors play key roles in transcription and other processes by altering the structure and positioning of nucleosomes. Recent studies have also implicated ISWI in the regulation of higher-order chromatin structure, but its role in this process remains poorly understood. To clarify the role of ISWI in vivo, we examined defects in chromosome structure and gene expression resulting from the loss of Iswi function in Drosophila. Consistent with a broad role in transcriptional regulation, the expression of a large number of genes is altered in Iswi mutant larvae. The expression of a dominant-negative form of ISWI leads to dramatic alterations in higher-order chromatin structure, including the apparent decondensation of both mitotic and polytene chromosomes. The loss of ISWI function does not cause obvious defects in nucleosome assembly, but results in a significant reduction in the level of histone H1 associated with chromatin in vivo. These findings suggest that ISWI plays a global role in chromatin compaction in vivo by promoting the association of the linker histone H1 with chromatin.

  15. The absence of tertiary interactions in a self-assembled DNA crystal structure.

    Nguyen, Nam; Birktoft, Jens J; Sha, Ruojie; Wang, Tong; Zheng, Jianping; Constantinou, Pamela E; Ginell, Stephan L; Chen, Yi; Mao, Chengde; Seeman, Nadrian C

    2012-04-01

    DNA is a highly effective molecule for controlling nanometer-scale structure. The convenience of using DNA lies in the programmability of Watson-Crick base-paired secondary interactions, useful both to design branched molecular motifs and to connect them through sticky-ended cohesion. Recently, the tensegrity triangle motif has been used to self-assemble three-dimensional crystals whose structures have been determined; sticky ends were reported to be the only intermolecular cohesive elements in those crystals. A recent communication in this journal suggested that tertiary interactions between phosphates and cytosine N(4) groups are responsible for intermolecular cohesion in these crystals, in addition to the secondary and covalent interactions programmed into the motif. To resolve this issue, we report experiments challenging this contention. Gel electrophoresis demonstrates that the tensegrity triangle exists in conditions where cytosine-PO(4) tertiary interactions seem ineffective. Furthermore, we have crystallized a tensegrity triangle using a junction lacking the cytosine suggested for involvement in tertiary interactions. The unit cell is isomorphous with that of a tensegrity triangle crystal reported earlier. This structure has been solved by molecular replacement and refined. The data presented here leave no doubt that the tensegrity triangle crystal structures reported earlier depend only on base pairing and covalent interactions for their formation. PMID:22434713

  16. Animal Hairs as Water-stimulated Shape Memory Materials: Mechanism and Structural Networks in Molecular Assemblies

    Xiao, Xueliang; Hu, Jinlian

    2016-05-01

    Animal hairs consisting of α-keratin biopolymers existing broadly in nature may be responsive to water for recovery to the innate shape from their fixed deformation, thus possess smart behavior, namely shape memory effect (SME). In this article, three typical animal hair fibers were first time investigated for their water-stimulated SME, and therefrom to identify the corresponding net-points and switches in their molecular and morphological structures. Experimentally, the SME manifested a good stability of high shape fixation ratio and reasonable recovery rate after many cycles of deformation programming under water stimulation. The effects of hydration on hair lateral size, recovery kinetics, dynamic mechanical behaviors and structural components (crystal, disulfide and hydrogen bonds) were then systematically studied. SME mechanisms were explored based on the variations of structural components in molecular assemblies of such smart fibers. A hybrid structural network model with single-switch and twin-net-points was thereafter proposed to interpret the water-stimulated shape memory mechanism of animal hairs. This original work is expected to provide inspiration for exploring other natural materials to reveal their smart functions and natural laws in animals including human as well as making more remarkable synthetic smart materials.

  17. Template Syntheses, Crystal Structures and Supramolecular Assembly of Hexaaza Macrocyclic Copper(II) Complexes

    Kim, Taehyung; Kim, Ju Chang [Pukyong National Univ., Busan (Korea, Republic of); Lough, Alan J. [Univ. of Toronto, Toronto (Canada)

    2013-06-15

    Two new hexaaza macrocyclic copper(II) complexes were prepared by a template method and structurally characterized. In the solid state, they were self-assembled by intermolecular interactions to form the corresponding supramolecules 1 and 2, respectively. In the structure of 1, the copper(II) macrocycles are bridged by a tp ligand to form a macrocyclic copper(II) dimer. The dimer extends its structure by intermolecular forces such as hydrogen bonds and C-H···π interactions, resulting in the formation of a double stranded 1D supramolecule. In 2, the basic structure is a monomeric copper(II) macrocycle with deprotonated imidazole pendants. An undulated 1D hydrogen bonded array is achieved through hydrogen bonds between imidazole pendants and secondary amines, where the imidazole pendants act as a hydrogen bond acceptor. The 1D hydrogen bonded supramolecular chain is supported by C-H···π interactions between the methyl groups of acetonitrile ligands and imidazole pendants of the copper(II) macrocycles. In both complexes, the introduction of imidazoles to the macrocycle as a pendant plays an important role for the formation of supramolecules, where they act as intermolecular hydrogen bond donors and/or acceptors, C-H···π and π-π interactions.

  18. Animal Hairs as Water-stimulated Shape Memory Materials: Mechanism and Structural Networks in Molecular Assemblies.

    Xiao, Xueliang; Hu, Jinlian

    2016-01-01

    Animal hairs consisting of α-keratin biopolymers existing broadly in nature may be responsive to water for recovery to the innate shape from their fixed deformation, thus possess smart behavior, namely shape memory effect (SME). In this article, three typical animal hair fibers were first time investigated for their water-stimulated SME, and therefrom to identify the corresponding net-points and switches in their molecular and morphological structures. Experimentally, the SME manifested a good stability of high shape fixation ratio and reasonable recovery rate after many cycles of deformation programming under water stimulation. The effects of hydration on hair lateral size, recovery kinetics, dynamic mechanical behaviors and structural components (crystal, disulfide and hydrogen bonds) were then systematically studied. SME mechanisms were explored based on the variations of structural components in molecular assemblies of such smart fibers. A hybrid structural network model with single-switch and twin-net-points was thereafter proposed to interpret the water-stimulated shape memory mechanism of animal hairs. This original work is expected to provide inspiration for exploring other natural materials to reveal their smart functions and natural laws in animals including human as well as making more remarkable synthetic smart materials. PMID:27230823

  19. Template Syntheses, Crystal Structures and Supramolecular Assembly of Hexaaza Macrocyclic Copper(II) Complexes

    Two new hexaaza macrocyclic copper(II) complexes were prepared by a template method and structurally characterized. In the solid state, they were self-assembled by intermolecular interactions to form the corresponding supramolecules 1 and 2, respectively. In the structure of 1, the copper(II) macrocycles are bridged by a tp ligand to form a macrocyclic copper(II) dimer. The dimer extends its structure by intermolecular forces such as hydrogen bonds and C-H···π interactions, resulting in the formation of a double stranded 1D supramolecule. In 2, the basic structure is a monomeric copper(II) macrocycle with deprotonated imidazole pendants. An undulated 1D hydrogen bonded array is achieved through hydrogen bonds between imidazole pendants and secondary amines, where the imidazole pendants act as a hydrogen bond acceptor. The 1D hydrogen bonded supramolecular chain is supported by C-H···π interactions between the methyl groups of acetonitrile ligands and imidazole pendants of the copper(II) macrocycles. In both complexes, the introduction of imidazoles to the macrocycle as a pendant plays an important role for the formation of supramolecules, where they act as intermolecular hydrogen bond donors and/or acceptors, C-H···π and π-π interactions

  20. Construction and testing of a blower-door assembly for regulation of air pressure within structures

    The Technical Measurements Center is evaluating several methods to decrease the time required to determine an annual average radon-daughter concentration in structures. One method involves stabilizing the air pressure within the structure at a constant pressure with reference to external atmospheric or soil-gas pressure. This report describes the construction and preliminary testing of a blower-door system to maintain a constant differential air pressure within a structure. The blower-door assembly includes a collapsible frame and a large fan to occlude a doorway, a damper with an actuator to control air flow, a controller to drive the damper actuator, and a pressure transducer to measure the differential pressure. Preliminary testing of the system indicates that pressure within the structure in the range of 1 to 20 Pascals can be held to within approximately +-1 Pa of the set point. Further testing of the blower-door system is planned to provide data on the applicability of this method to short-duration tests for annual average radon-daughter concentration estimates. 13 figs., 1 tab