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Sample records for beam modification effects

  1. Ion Beam Modification of Materials

    SciTech Connect

    Averback, B; de la Rubia, T D; Felter, T E; Hamza, A V; Rehn, L E

    2005-10-10

    This volume contains the proceedings of the 14th International Conference on Ion Beam Modification of Materials, IBMM 2004, and is published by Elsevier-Science Publishers as a special issue of Nuclear Instruments and Methods B. The conference series is the major international forum to present and discuss recent research results and future directions in the field of ion beam modification, synthesis and characterization of materials. The first conference in the series was held in Budapest, Hungary, 1978, and subsequent conferences were held every two years at locations around the Globe, most recently in Japan, Brazil, and the Netherlands. The series brings together physicists, materials scientists, and ion beam specialists from all over the world. The official conference language is English. IBMM 2004 was held on September 5-10, 2004. The focus was on materials science involving both basic ion-solid interaction processes and property changes occurring either during or subsequent to ion bombardment and ion beam processing in relation to materials and device applications. Areas of research included Nanostructures, Multiscale Modeling, Patterning of Surfaces, Focused Ion Beams, Defects in Semiconductors, Insulators and Metals, Cluster Beams, Radiation Effects in Materials, Photonic Devices, Ion Implantation, Ion Beams in Biology and Medicine including New Materials, Imaging, and Treatment.

  2. Effects of laser fluence on silicon modification by four-beam laser interference

    SciTech Connect

    Zhao, Le; Li, Dayou; Wang, Zuobin Yue, Yong; Zhang, Jinjin; Yu, Miao; Li, Siwei

    2015-12-21

    This paper discusses the effects of laser fluence on silicon modification by four-beam laser interference. In this work, four-beam laser interference was used to pattern single crystal silicon wafers for the fabrication of surface structures, and the number of laser pulses was applied to the process in air. By controlling the parameters of laser irradiation, different shapes of silicon structures were fabricated. The results were obtained with the single laser fluence of 354 mJ/cm{sup 2}, 495 mJ/cm{sup 2}, and 637 mJ/cm{sup 2}, the pulse repetition rate of 10 Hz, the laser exposure pulses of 30, 100, and 300, the laser wavelength of 1064 nm, and the pulse duration of 7–9 ns. The effects of the heat transfer and the radiation of laser interference plasma on silicon wafer surfaces were investigated. The equations of heat flow and radiation effects of laser plasma of interfering patterns in a four-beam laser interference distribution were proposed to describe their impacts on silicon wafer surfaces. The experimental results have shown that the laser fluence has to be properly selected for the fabrication of well-defined surface structures in a four-beam laser interference process. Laser interference patterns can directly fabricate different shape structures for their corresponding applications.

  3. Ion beam surface modification

    NASA Technical Reports Server (NTRS)

    Dwight, D. W.

    1982-01-01

    The essential details of a study on the practical applications and mechanisms of polymer sputtering via Argon ion impact are summarized. The potential to modify the properties of polymer surfaces to improve their adherence, durability, biocompatibility, or other desirable properties by ion beam sputtering was emphasized. Ion beam milling can be of benefit as an analytical tool to obtain composition versus depth information. Ion impact from a directed ion gun source specifically etches polymer structures according to their morphologies, therefore this technique may be useful to study unknown or new morphological features. Factors addressed were related to: (1) the texture that arises on a polymer target after ion impact; (2) the chemistry of the top surface after ion impact; (3) the chemistry of sputtered films of polymeric material deposited on substrates placed adjacent to targets during ion impact; and (4) practical properties of textured polymer targets, specifically the wettability and adhesive bonding properties.

  4. Neutralized ion beam modification of cellulose membranes for study of ion charge effect on ion-beam-induced DNA transfer

    NASA Astrophysics Data System (ADS)

    Prakrajang, K.; Sangwijit, K.; Anuntalabhochai, S.; Wanichapichart, P.; Yu, L. D.

    2012-02-01

    Low-energy ion beam biotechnology (IBBT) has recently been rapidly developed worldwide. Ion-beam-induced DNA transfer is one of the important applications of IBBT. However, mechanisms involved in this application are not yet well understood. In this study plasma-neutralized ion beam was applied to investigate ion charge effect on induction of DNA transfer. Argon ion beam at 7.5 keV was neutralized by RF-driven plasma in the beam path and then bombarded cellulose membranes which were used as the mimetic plant cell envelope. Electrical properties such as impedance and capacitance of the membranes were measured after the bombardment. An in vitro experiment on plasmid DNA transfer through the cellulose membrane was followed up. The results showed that the ion charge input played an important role in the impedance and capacitance changes which would affect DNA transfer. Generally speaking, neutral particle beam bombardment of biologic cells was more effective in inducing DNA transfer than charged ion beam bombardment.

  5. Beam Distribution Modification by Alfven Modes

    SciTech Connect

    White, R. B.; Gorelenkov, N.; Heidbrink, W. W.; Van Zeeland, M. A.

    2010-04-03

    Modification of a deuterium beam distribution in the presence of low amplitude Toroidal Alfven (TAE) eigenmodes and Reversed Shear Alfven (RSAE) eigenmodes in a toroidal magnetic confinement device is examined. Comparison with experimental data shows that multiple low amplitude modes can account for significant modification of high energy beam particle distributions. It is found that there is a stochastic threshold for beam transport, and that the experimental amplitudes are only slightly above this threshold. The modes produce a substantial central flattening of the beam distribution.

  6. Modification of PVC/ENR blend by electron beam irradiation: effect of crosslinking agents

    NASA Astrophysics Data System (ADS)

    Ratnam, C. T.; Zaman, K.

    1999-05-01

    In order to improve the mechanical properties of PVC/ENR blends, they were irradiated by using a 3.0 MeV electron beam machine with doses ranging from 20 to 200 kGy. Changes in mechanical properties of the blends with increasing irradiation dose were investigated. In an attempt to maximize the beneficial effect of irradiation, the influence of multifunctional acrylates (MFA) such as TMPTA, HDDA and EHA on the 70/30 PVC/ENR blend was investigated. The properties studied include hardness, gel fraction, tensile strength, elongation at break and glass transition temperature. The results revealed that all mechanical properties increased with increasing irradiation dose with exception of elongation at break. The enhancement in blend properties was further improved by addition of MFA. This is attributed to the increase in crosslink density. The steady increase in gel fraction with irradiation dose and the shifting of the irradiation those towards a lower value to achieve 70% gel fraction upon addition of MFA has provided evidence for significant increase in crosslink density. Among the MFA employed in this studies, TMPTA was found to render highest mechanical properties to the blend with irradiation. Thus, TMPTA can be useful as an efficient crosslink enhancer to PVC/ENR blends. Results from Fourier transform infrared spectroscopy (FTIR) indicated radiation-induced crosslinks formed in PVC/ENR blends sensitized by TMPTA. The single glass transition temperature obtained confirms that the blend remains miscible upon irradiation with the presence of TMPTA. The changes in blend properties upon irradiation with the addition of acrylated polyurethene (PU) oligomer are also presented in this paper.

  7. A comparative study on low-energy ion beam and neutralized beam modifications of naked DNA and biological effect on mutation

    NASA Astrophysics Data System (ADS)

    Sarapirom, S.; Thongkumkoon, P.; Prakrajang, K.; Anuntalabhochai, S.; Yu, L. D.

    2012-02-01

    DNA conformation change or damage induced by low-energy ion irradiation has been of great interest owing to research developments in ion beam biotechnology and ion beam application in biomedicine. Mechanisms involved in the induction of DNA damage may account for effect from implanting ion charge. In order to check this effect, we used both ion beam and neutralized beam at keV energy to bombard naked DNA. Argon or nitrogen ion beam was generated and extracted from a radiofrequency (RF) ion source and neutralized by microwave-driven plasma in the beam path. Plasmid DNA pGFP samples were irradiated with the ion or neutralized beam in vacuum, followed by gel electrophoresis to observe changes in the DNA conformations. It was revealed that the ion charge played a certain role in inducing DNA conformation change. The subsequent DNA transfer into bacteria Escherichia coli ( E. coli) for mutation analysis indicated that the charged ion beam induced DNA change had high potential in mutation induction while neutralized beam did not. The intrinsic reason was attributed to additional DNA deformation and contortion caused by ion charge exchange effect so that the ion beam induced DNA damage could hardly be completely repaired, whereas the neutralized beam induced DNA change could be more easily recoverable owing to absence of the additional DNA deformation and contortion.

  8. Ion beam and laser induced surface modifications

    NASA Astrophysics Data System (ADS)

    Appleton, B. R.

    1984-01-01

    The capabilities of energetic ion beam and laser processing of surfaces are reviewed. Ion implantation doping, ion beam mixing, and laser and electron beam processing techniques are capable of producing new and often unique surface properties. The inherent control of these techniques has led to significant advances in our ability to tailor the properties of solids for a wide range of technological applications. Equally important, these techniques have allowed tests of fundamental materials interactions under conditions not heretofore achievable and have resulted in increased understanding of a broad range of materials phenomena. These include new metastable phase formation, rapid nucleation and crystal growth kinetics, amorphous metals and metaglasses, supersaturated solid solutions and substitutional alloys, interface interactions, solute trapping, laser-assisted chemical modifications, and a host of other.

  9. Surface modification using low energy ground state ion beams

    NASA Technical Reports Server (NTRS)

    Chutjian, Ara (Inventor); Hecht, Michael H. (Inventor); Orient, Otto J. (Inventor)

    1990-01-01

    A method of effecting modifications at the surfaces of materials using low energy ion beams of known quantum state, purity, flux, and energy is presented. The ion beam is obtained by bombarding ion-generating molecules with electrons which are also at low energy. The electrons used to bombard the ion generating molecules are separated from the ions thus obtained and the ion beam is directed at the material surface to be modified. Depending on the type of ion generating molecules used, different ions can be obtained for different types of surface modifications such as oxidation and diamond film formation. One area of application is in the manufacture of semiconductor devices from semiconductor wafers.

  10. Surface modification using ionic liquid ion beams

    NASA Astrophysics Data System (ADS)

    Takaoka, Gikan H.; Hamaguchi, Takuya; Takeuchi, Mitsuaki; Ryuto, Hiromichi

    2014-12-01

    We developed an ionic liquid (IL) ion source using 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6) and produced IL ion beams by applying a high electric field between the tip and the extractor. Time-of-flight measurements showed that small cluster and fragment ions were contained in the positive and negative ion beams. The positive and negative cluster ions were deposited on Si(1 0 0) substrates. X-ray photoelectron spectroscopy measurements showed that the composition of the deposited layers was similar to that of an IL solvent. This suggests that a cation (A+) or an anion (B-) was attached to an IL cluster (AB)n, resulting in the formation of positive cluster ions (AB)nA+ or negative cluster ions (AB)nB-, respectively. The surfaces of the IL layers deposited on Si(1 0 0) substrates were flat at an atomic level for positive and negative cluster ion irradiation. Moreover, the contact angles of the deposited layers were similar to that of the IL solvent. Thus, surface modification of Si(1 0 0) substrates was successfully demonstrated with BMIM-PF6 cluster ion beams.

  11. The effect of high-energy electron-beam irradiation on microstructural modification of a high-speed steel roll

    NASA Astrophysics Data System (ADS)

    Suh, Dongwoo; Lee, Sunghak; Koo, Yangmo; Lee, Hui Choon

    1996-10-01

    The purpose of this study is to investigate the microstructural modification in a high-speed steel (HSS) roll irradiated with an accelerated high-energy electron beam. The HSS roll samples were irradiated at the beam travel speeds of 2.5 to 25 mm/s using an electron accelerator (1.4 MeV). The microstructure was examined with a scanning electron microscope (SEM) capable of in situ fracture testing and simultaneous measurement of the apparent fracture toughness. Irradiation changed the matrix phase from tempered martensite to a mixture of retained austenite and martensite. Coarse primary carbides were partially or completely dissolved, depending on the heat input. Irradiation greatly improved the fracture properties because of the presence of retained austenite, which could retard crack propagation, although hardness was decreased. Occasional interior quench cracks were found in the heat-affected region. Appropriate processing methods, such as pre- or postirradiation, were suggested. A heat transfer analysis of the irradiated surface layer was also carried out to elucidate the influence of the irradiation parameters on the microstructure.

  12. Ionospheric modification using relativistic electron beams

    NASA Technical Reports Server (NTRS)

    Banks, Peter M.; Fraser-Smith, Anthony C.; Gilchrist, B. E.

    1990-01-01

    The recent development of comparatively small electron linear accelerators (linacs) now makes possible a new class of ionospheric modification experiments using beams of relativistic electrons. These experiments can potentially provide much new information about the interactions of natural relativistic electrons with other particles in the upper atmosphere, and it may also make possible new forms of ionization structures extending down from the lower ionosphere into the largely un-ionized upper atmosphere. The consequences of firing a pulsed 1 A, 5 Mev electron beam downwards into the upper atmosphere are investigated. If a small pitch angle with respect to the ambient geomagnetic field is selected, the beam produces a narrow column of substantial ionization extending down from the source altitude to altitudes of approximately 40 to 45 km. This column is immediately polarized by the natural middle atmosphere fair weather electric field and an increasingly large potential difference is established between the column and the surrounding atmosphere. In the regions between 40 to 60 km, this potential can amount to many tens of kilovolts and the associated electric field can be greater than the field required for breakdown and discharge. Under these conditions, it may be possible to initiate lightning discharges along the initial ionization channel. Filamentation may also occur at the lower end to drive further currents in the partially ionized gases of the stratosphere. Such discharges would derive their energy from the earth-ionosphere electrical system and would be sustained until plasma depletion and/or electric field reduction brought the discharge under control. It is likely that this artificially-triggered lightning would produce measurable low-frequency radiation.

  13. Ion beam modification of polyacetylene films

    NASA Astrophysics Data System (ADS)

    Lin, Senhao; Sheng, Kanglong; Bao, Jinrong; Rong, Tingwen; Zhou, Zhiyi; Zhang, Lanping; Zhu, Dezhang; Shen, Zhiquan; Yan, Mujie

    1989-03-01

    Low energy ion implantation of polyacetylene films synthesized with rare earth compound catalysts have been studied for potassium, sodium and iodine at the energy region of 15 to 30 keV. Film samples prepared in different ways, thermally treated and/or chemically doped, were irradiated up to 1 × 10 17 ions/cm 2. The resulting surface property modifications of the (CH) x films were examined by various kinds of techniques. Compensation effects of the dopants and electrical conductivity changes in the implanted regions were observed. Some of the implanted film samples exhibited diode like characteristics. Discussions on the experimental results are presented.

  14. Ion beam modification of aromatic polymers

    NASA Astrophysics Data System (ADS)

    Shukushima, Satoshi; Nishikawa, Shinya; Matsumoto, Yasuyo; Hibino, Yutaka

    1993-06-01

    We studied the optical, mechanical and thermal properties of aromatic polymer films which had been irradiated with 1 MeV H +, H 2+ and He + ions. The examined aromatic polymers were polyetherether ketone (PEEK), polyetherimide (PEI), polycther sulfon (PES), polysulfon (PSF), and polyphenylene sulfide (PPS). The optical densities at 300 nm of PES greatly increased after the irradiation. The optical densities at 400 nm of all the examined polymer linearly increased with the irradiation dose. Elongations of all the polymers at room temperature were reduced after irradiation. The PEEK film which had been irradiated with 1 MeV H + was not deformed above the melting point. This demonstrates that cross-linking occurs in PEEK films by ion beam irradiation. As for the effects, depending on the mass of the irradiated ions, it was found that the ions with a high mass induced larger effects on the arematic polymers for the same absorption energy.

  15. Electron beam irradiation modification of collagen membrane.

    PubMed

    Jiang, Bo; Wu, Zhihong; Zhao, Huichuan; Tang, Fangyuan; Lu, Jian; Wei, Qingrong; Zhang, Xingdong

    2006-01-01

    A critical observation of reconstituted collagen membrane radiated by electron beam (EB) indicated that these collagenous fibers become cross-linked network when the irradiation is carried out in greater than melt temperature and nitrogen atmosphere. Studies on the membrane properties showed that glass transformation temperature (Tg) and melt point (Tm) of reconstituted collagen have no changes, but thermal gravity curves and infrared (IR) spectra become obviously different before and after irradiation. Cross-linking density calculated by the equation based on the theory of Flory-Rehner proved further that the densities increase with radiation doses increasing. Resistance to enzymatic digestions in vitro and implantation in vivo were determined to evaluate the physicochemical properties of cross-linked matrices. Based on the above results, it was concluded that EB radiation inducing cross-linking in greater than melt temperature and nitrogen atmosphere condition is an attractive, effective method, which introduce into intermolecular covalent cross-linkings.

  16. Effects of topographical surface modifications of electron beam melted Ti-6Al-4V titanium on human fetal osteoblasts.

    PubMed

    Ponader, Sabine; Vairaktaris, Eleftherios; Heinl, Peter; Wilmowsky, Cornelius V; Rottmair, Andreas; Körner, Carolin; Singer, Robert F; Holst, Stefan; Schlegel, Karl A; Neukam, Friedrich W; Nkenke, Emeka

    2008-03-15

    The aim of the study was to assess the suitability of different Ti-6Al-4V surfaces produced by the electron beam melting (EBM) process as matrices for attachment, proliferation, and differentiation of human fetal osteoblasts (hFOB 1.19). Human osteoblasts were cultured in vitro on smooth and rough-textured Ti-6Al-4V alloy disks. By means of cell number and vitality and SEM micrographs cell attachment and proliferation were observed. The differentiation rate was examined by using quantitative real-time PCR analysis for the gene expression of alkaline phosphatase (ALP), type I collagen (Coll-I), bone sialoprotein (BSP) and osteocalcin (OC). After 3 days of incubation there was a significant higher vitality (p < 0.02) and proliferation (p < 0.02) of hFOB cells on smooth surfaces (R(a) = 0.077 microm) and compact surfaces with adherent partly molten titanium particles on the surface (R(a) /= 56.9 microm) reduced proliferation of hFOB cells. Surface characteristics of titanium can easily be changed by EBM in order to further improve proliferation. (c) 2007 Wiley Periodicals, Inc.

  17. Coherent beam-beam effects, theory & observations

    SciTech Connect

    Yuri I Alexahin

    2003-07-16

    Current theoretical understanding of the coherent beam-beam effect as well as its experimental observations are discussed: conditions under which the coherent beambeam modes may appear, possibility of their resonant interaction (coherent resonances), stability of beam-beam oscillations in the presence of external impedances. A special attention is given to the coherent beam-beam modes of finite length bunches: the synchro-betatron coupling is shown to provide reduction in the coherent tuneshift and--at the synchrotron tune values smaller than the beam-beam parameter--Landau damping by overlapping synchrotron satellites.

  18. Design of an electron beam spectral modification system

    SciTech Connect

    Sheppard, J.C.; York, R.C.; Norum, B.E.; McCarthy, J.S.

    1981-10-01

    We report the design of a spectral modification system (SMS) for use with the proposed NEAL linac-pulse stretcher ring, cw electron beam facility. The SMS allows tailoring of the energy distribution of electrons in beams produced by a pulsed linac operating in the transient beam loading (TBL) regime. Modification of the energy distribution of electrons injected into the pulse strecher ring will increase the duty factor of current extracted from the ring and improve the efficiency of the extraction process. Physically, the SMS consists of an anisochronous, achromatic magnetic lattice followed by a pair of traveling-wave accelerating sections. For beams in the energy range of 500 MeV to 4 GeV, TBL ripple on the energy envelope of microsecond long beam spills is expected to be reduced from 1% peak-peak to less than 0.01% while the desired width of the energy profile due to the phase extent of the microbunches in the beam spill is preserved.

  19. Electron beam induced modification of poly(ethylene terephthalate) films

    NASA Astrophysics Data System (ADS)

    Vasiljeva, I. V.; Mjakin, S. V.; Makarov, A. V.; Krasovsky, A. N.; Varlamov, A. V.

    2006-10-01

    Electron beam processing of poly(ethylene terephthalate) (PET) films is found to promote significant changes in the melting heat, intrinsic viscosity and polymer film-liquid (water, isooctane and toluene) boundary surface tension. These properties are featured with several maximums depending on the absorbed dose and correlating with the modification of PET surface functionality. Studies using adsorption of acid-base indicators and IR-spectroscopy revealed that the increase of PET surface hydrophilicity is determined by the oxidation of methylene and methyne groups. Electron beam treatment of PET films on the surface of N-vinylpyrrolidone aqueous solution provided graft copolymerization with this comonomer at optimum process parameters (energy 700 keV, current 1 mA, absorbed dose 50 kGy).

  20. Module for dielectric surfaces modification by fast neutral particles beams

    NASA Astrophysics Data System (ADS)

    Barchenko, V. T.; Lisenkov, A. A.; Babinov, N. A.

    2014-11-01

    In this paper, we describe the module for dielectric and wide-gap semiconductor surfaces modification by fast neutral beam. The module can be used for cleaning, etching or assisting of films deposition. The surface proceeding by neutral beam can prevent an accumulation of surface charge without using current compensation by inserting electrons to the beam or RF power supply. The module beside cathode and anode contains an electrode with floating potential. Insertion of the additional electrode causes electron retention in an electrostatic trap resulting the reducing of the module operating pressure. Moreover, the electrode with floating potential allows increasing the current efficient of the module. An important feature of the module is that neutralization of the ions extracted from the plasma occurs in the cathode potential well. Thereby ions that have not neutralized cannot leave nearcathode region and there are no fast ions in the output beam. Module does not contain sources of the magnetic fields or elements heated by external sources. Module operates with free cooling. Thus, the module does not need water cooling and can be freely moved in the vacuum chamber.

  1. The effect of near-infrared laser beam on the surface modification of metal complex based on 3D laser scanning system

    NASA Astrophysics Data System (ADS)

    Zhao, Mali; Liu, Tiegen; Jiang, Junfeng; Wang, Meng

    2014-11-01

    High-precision 3-dimensional metallization is difficult to realize in specific nonmetallic areas by using the traditional methods such as wet-chemical and mechanical methods because of the disadvantage that usually they cannot achieve selective modification. In this paper, 3-dimensional laser scanning system was applied to achieve the modification of specific regions of the sample surface. In 3-dimensional laser scanning system, the laser beam, after going through dynamic focusing system, was reflected by galvanometers and then focused by f-theta lens on the sample surface. The changes in surface characteristics of the blends of polycarbonate and acrylonitrile butadiene styrene copolymers (PC/ABS) mixed with Cu-Cr complex by the laser irradiation with the wavelength of 1064nm were investigated. Through analysis it was found that the smooth surface of the original samples was changed to a micro-hole structure accompanied by an increased surface roughness as well as an increased water contact angle. The chemical composition percentage had changed and the metal components of copper and chromium were detected after the laser irradiation. The irradiated areas were degraded into organic ligand fragments, volatile gas and reducing metal ions of copper and chromium. Besides, the thickness of the deposited metal layer and the adhesive force between the metal layer and the substrate after electroless plating varied according to the laser parameters such as frequency and scanning speed. As shown in the experiment, the thickness of deposited copper layer exceeded 11μm and the deposited nickel layer exceeded 2μm respectively.

  2. Ultralow energy ion beam surface modification of low density polyethylene.

    PubMed

    Shenton, Martyn J; Bradley, James W; van den Berg, Jaap A; Armour, David G; Stevens, Gary C

    2005-12-01

    Ultralow energy Ar+ and O+ ion beam irradiation of low density polyethylene has been carried out under controlled dose and monoenergetic conditions. XPS of Ar+-treated surfaces exposed to ambient atmosphere show that the bombardment of 50 eV Ar+ ions at a total dose of 10(16) cm(-2) gives rise to very reactive surfaces with oxygen incorporation at about 50% of the species present in the upper surface layer. Using pure O+ beam irradiation, comparatively low O incorporation is achieved without exposure to atmosphere (approximately 13% O in the upper surface). However, if the surface is activated by Ar+ pretreatment, then large oxygen contents can be achieved under subsequent O+ irradiation (up to 48% O). The results show that for very low energy (20 eV) oxygen ions there is a dose threshold of about 5 x 10(15) cm(-2) before surface oxygen incorporation is observed. It appears that, for both Ar+ and O+ ions in this regime, the degree of surface modification is only very weakly dependent on the ion energy. The results suggest that in the nonequilibrium plasma treatment of polymers, where the ion flux is typically 10(18) m(-2) s(-1), low energy ions (<50 eV) may be responsible for surface chemical modification.

  3. The role of electronic energy loss in ion beam modification of materials

    DOE PAGES

    Weber, William J.; Duffy, Dorothy M.; Thome, Lionel; ...

    2014-10-05

    The interaction of energetic ions with solids results in energy loss to both atomic nuclei and electrons in the solid. In this article, recent advances in understanding and modeling the additive and competitive effects of nuclear and electronic energy loss on the response of materials to ion irradiation are reviewed. Experimental methods and large-scale atomistic simulations are used to study the separate and combined effects of nuclear and electronic energy loss on ion beam modification of materials. The results demonstrate that nuclear and electronic energy loss can lead to additive effects on irradiation damage production in some materials; while inmore » other materials, the competitive effects of electronic energy loss leads to recovery of damage induced by elastic collision cascades. Lastly, these results have significant implications for ion beam modification of materials, non-thermal recovery of ion implantation damage, and the response of materials to extreme radiation environments.« less

  4. The role of electronic energy loss in ion beam modification of materials

    SciTech Connect

    Weber, William J.; Duffy, Dorothy M.; Thome, Lionel; Zhang, Yanwen

    2014-10-05

    The interaction of energetic ions with solids results in energy loss to both atomic nuclei and electrons in the solid. In this article, recent advances in understanding and modeling the additive and competitive effects of nuclear and electronic energy loss on the response of materials to ion irradiation are reviewed. Experimental methods and large-scale atomistic simulations are used to study the separate and combined effects of nuclear and electronic energy loss on ion beam modification of materials. The results demonstrate that nuclear and electronic energy loss can lead to additive effects on irradiation damage production in some materials; while in other materials, the competitive effects of electronic energy loss leads to recovery of damage induced by elastic collision cascades. Lastly, these results have significant implications for ion beam modification of materials, non-thermal recovery of ion implantation damage, and the response of materials to extreme radiation environments.

  5. Reduction of Glass Surface Reflectance by Ion Beam Surface Modification

    SciTech Connect

    Mark Spitzer

    2011-03-11

    This is the final report for DOE contract DE-EE0000590. The purpose of this work was to determine the feasibility of the reduction of the reflection from the front of solar photovoltaic modules. Reflection accounts for a power loss of approximately 4%. A solar module having an area of one square meter with an energy conversion efficiency of 18% generates approximately 180 watts. If reflection loss can be eliminated, the power output can be increased to 187 watts. Since conventional thin-film anti-reflection coatings do not have sufficient environmental stability, we investigated the feasibility of ion beam modification of the glass surface to obtain reduction of reflectance. Our findings are generally applicable to all solar modules that use glass encapsulation, as well as commercial float glass used in windows and other applications. Ion implantation of argon, fluorine, and xenon into commercial low-iron soda lime float glass, standard float glass, and borosilicate glass was studied by implantation, annealing, and measurement of reflectance. The three ions all affected reflectance. The most significant change was obtained by argon implantation into both low-iron and standard soda-lime glass. In this way samples were formed with reflectance lower than can be obtained with a single-layer coatings of magnesium fluoride. Integrated reflectance was reduced from 4% to 1% in low-iron soda lime glass typical of the glass used in solar modules. The reduction of reflectance of borosilicate glass was not as large; however borosilicate glass is not typically used in flat plate solar modules. Unlike conventional semiconductor ion implantation doping, glass reflectance reduction was found to be tolerant to large variations in implant dose, meaning that the process does not require high dopant uniformity. Additionally, glass implantation does not require mass analysis. Simple, high current ion implantation equipment can be developed for this process; however, before the process

  6. Ion beam modification of biological materials in nanoscale

    NASA Astrophysics Data System (ADS)

    Yu, L. D.; Anuntalabhochai, S.

    2012-07-01

    Ion interaction with biological objects in nanoscale is a novel research area stemming from applications of low-energy ion beams in biotechnology and biomedicine. Although the ion beam applications in biotechnology and biomedicine have achieved great successes, many mechanisms remain unclear and many new applications are to be explored. We have carried out some research on exploring the mechanisms and new applications besides attaining ion beam induction of mutation breeding and gene transformation. In the studies on the mechanisms, we focused our investigations on the direct interaction in nanoscale between ions and biological living materials. Our research topics have included the low-energy ion range in DNA, low-energy ion or neutral beam bombardment effect on DNA topological form change and mutation, low-energy ion or neutral beam bombardment effect on the cell envelope and gene transformation, and molecular dynamics simulation of ultra-low-energy ion irradiation of DNA. In the exploration of new applications, we have started experiments on ion irradiation or bombardment, in the nanoscaled depth or area, of human cells for biomedical research. This paper introduces our experiments and reports interesting results.

  7. Chemical modifications at Teflon interfaces induced by MeV ion beams

    NASA Astrophysics Data System (ADS)

    Ingemarsson, P. Anders; Keane, Michael P.; Gelius, Ulrik

    1989-10-01

    The effect of MeV ion beams incident on Teflon surfaces was studied by x-ray photoelectron spectroscopy (XPS). Irradiation with 20-MeV 35Cl4+ was carried out at doses ranging from 1012 to 1014 ions/cm2. Residual gas analysis was performed during irradiation to identify molecular fragments released from the Teflon surface. XPS spectra were recorded before and after ion irradiation. On some substrates, gold thin films were evaporated before and after ion bombardment, respectively, to detect possible modifications in thin-film adhesion. Changes in the XPS spectra were interpreted in terms of chemical and structural shifts, and related to the observed adhesion modifications.

  8. Electron beam surface modifications in reinforcing and recycling of polymers

    NASA Astrophysics Data System (ADS)

    Czvikovszky, T.; Hargitai, H.

    1997-08-01

    Thermoplastic polymers can be fiber-reinforced in the recycling step through a reactive modification of the interface between the polymer matrix and fiber. Recollected automobile bumpers made of polypropylene copolymers have been reinforced during the reprocessing with eight different types of high-strength fibers, with waste cord-yarns of the tire industry. A thin layer reactive interface of acrylic oligomers has been applied and activated through low energy (175 keV) electron beam (EB). The upcycling (upgrading recycling) resulted in a series of extrudable and injection-mouldable, fiber-reinforced thermoplastic of enhanced bending strength, increased modulus of elasticity and acceptable impact strength. EB treatment has been compared with conventional methods.

  9. Ion beam modification of topological insulator bismuth selenide

    NASA Astrophysics Data System (ADS)

    Sharma, P. A.; Lima Sharma, A. L.; Hekmaty, M.; Hattar, K.; Stavila, V.; Goeke, R.; Erickson, K.; Medlin, D. L.; Brahlek, M.; Koirala, N.; Oh, S.

    2014-12-01

    We demonstrate chemical doping of a topological insulator Bi2Se3 using ion implantation. Ion beam-induced structural damage was characterized using grazing incidence X-ray diffraction and transmission electron microscopy. Ion damage was reversed using a simple thermal annealing step. Carrier-type conversion was achieved using ion implantation followed by an activation anneal in Bi2Se3 thin films. These two sets of experiments establish the feasibility of ion implantation for chemical modification of Bi2Se3, a prototypical topological insulator. Ion implantation can, in principle, be used for any topological insulator. The direct implantation of dopants should allow better control over carrier concentrations for the purposes of achieving low bulk conductivity. Ion implantation also enables the fabrication of inhomogeneously doped structures, which in turn should make possible new types of device designs.

  10. Ion beam modification of topological insulator bismuth selenide

    SciTech Connect

    Sharma, Peter Anand; Sharma, A. L. Lima; Hekmaty, Michelle A.; Hattar, Khalid Mikhiel; Stavila, Vitalie; Goeke, Ronald S.; Erickson, K.; Medlin, Douglas L.; Brahlek, M.; Oh, S.; Koirala, N.

    2014-12-17

    In this study, we demonstrate chemical doping of a topological insulator Bi2Se3 using ion implantation. Ion beam-induced structural damage was characterized using grazing incidence X-ray diffraction and transmission electron microscopy. Ion damage was reversed using a simple thermal annealing step. Carrier-type conversion was achieved using ion implantation followed by an activation anneal in Bi2Se3 thin films. These two sets of experiments establish the feasibility of ion implantation for chemical modification of Bi2Se3, a prototypical topological insulator. Ion implantation can, in principle, be used for any topological insulator. The direct implantation of dopants should allow better control over carrier concentrations for the purposes of achieving low bulk conductivity. Ion implantation also enables the fabrication of inhomogeneously doped structures, which in turn should make possible new types of device designs.

  11. Ion beam modification of topological insulator bismuth selenide

    SciTech Connect

    Sharma, P. A. Lima Sharma, A. L.; Hattar, K.; Goeke, R.; Hekmaty, M.; Stavila, V.; Erickson, K.; Medlin, D. L.; Brahlek, M.; Koirala, N.; Oh, S.

    2014-12-15

    We demonstrate chemical doping of a topological insulator Bi{sub 2}Se{sub 3} using ion implantation. Ion beam-induced structural damage was characterized using grazing incidence X-ray diffraction and transmission electron microscopy. Ion damage was reversed using a simple thermal annealing step. Carrier-type conversion was achieved using ion implantation followed by an activation anneal in Bi{sub 2}Se{sub 3} thin films. These two sets of experiments establish the feasibility of ion implantation for chemical modification of Bi{sub 2}Se{sub 3}, a prototypical topological insulator. Ion implantation can, in principle, be used for any topological insulator. The direct implantation of dopants should allow better control over carrier concentrations for the purposes of achieving low bulk conductivity. Ion implantation also enables the fabrication of inhomogeneously doped structures, which in turn should make possible new types of device designs.

  12. Ion beam modification of topological insulator bismuth selenide

    DOE PAGES

    Sharma, Peter Anand; Sharma, A. L. Lima; Hekmaty, Michelle A.; ...

    2014-12-17

    In this study, we demonstrate chemical doping of a topological insulator Bi2Se3 using ion implantation. Ion beam-induced structural damage was characterized using grazing incidence X-ray diffraction and transmission electron microscopy. Ion damage was reversed using a simple thermal annealing step. Carrier-type conversion was achieved using ion implantation followed by an activation anneal in Bi2Se3 thin films. These two sets of experiments establish the feasibility of ion implantation for chemical modification of Bi2Se3, a prototypical topological insulator. Ion implantation can, in principle, be used for any topological insulator. The direct implantation of dopants should allow better control over carrier concentrations formore » the purposes of achieving low bulk conductivity. Ion implantation also enables the fabrication of inhomogeneously doped structures, which in turn should make possible new types of device designs.« less

  13. Structural Modification of Nanocrystalline Ceria using Ion Beams

    SciTech Connect

    Zhang, Yanwen; Edmondson, Philip D; Varga, Tamas; Moll, Sandra; Namavar, Fereydoon; Weber, William J

    2011-01-01

    Exceptional size-dependent electronic-ionic conductivity of nanostructured ceria can significantly alter materials properties in chemical, physical, electronic and optical applications. Using energetic ions, we have demonstrated effective modification of interface volume and grain size in nanocrystalline ceria from a few nm up to ~ 25 nm, which is the critical region for controlling size-dependent material property. The unique self-healing response of radiation damage at grain boundaries is applied to control the grain size at nanoscale as a function of ion dose and irradiation temperature. Structural modification by energetic ions is proposed to achieve disirable electronic-ionic conductivity.

  14. Structural Modification of Nanocrystalline Ceria by Ion Beams

    SciTech Connect

    Zhang, Yanwen; Edmondson, Philip D.; Varga, Tamas; Moll, Sandra J.; Namavar, Fereydoon; Lan, Chune; Weber, William J.

    2011-05-25

    Using energetic ions, we have demonstrated effective modification of grain size in nanocrystalline ceria in the critical region for controlling exceptional size-dependent electronicionic conductivity. The grain size increases and follows an exponential law as a function of ion fluence that increases with temperature, while the cubic phase is stable under the irradiation. The unique self-healing response of radiation damage at grain boundaries is utilized to control the grain size at the nanoscale.

  15. Considerations relating to pulsed-beam modification of materials

    SciTech Connect

    Myers, S.M.; Follstaedt, D.M.; Bourcier, R.J.; Dugger, M.T.; McIntyre, D.C.; Rader, D.J.

    1990-01-01

    Ion implantation has been shown to produce unique improvements in the properties of a wide range of materials. This technology has been extensively used for doping of semiconductors, where the required doses and implantation depths are relatively modest and readily achieved with commercial implanters. Other applications of ion implantation currently being pursued at a commercial level include the synthesis of buried second-phase layers in Si and the improvement of metal surface properties such as hardness, friction, wear rate, and corrosion. However, these applications have been severely constrained by the costs of treating large surface areas with the high ion doses required, and by the need to produce modified layers thicker than the range of the sub-MeV ions available from presently available commercial high-flux ion implanters. It therefore seems worthwhile to consider whether pulsed ion accelerators may offer advantages for such applications by providing high ion fluxes at MeV energies. The previously reported applications of pulsed accelerators to materials modification have used sub-MeV ion energies. The purpose of this article is to being these considerations the perspective of materials scientists who use ion implantation. We comment on needed extensions in implantation capabilities while leaving to others the question of whether these needs can be met with pulsed-beam technology. Further, in order to illustrate the kinds of beneficial materials modifications that can be achieved with implantation, we provide examples from recent work at Sandia National Laboratories, where large improvements have been realized in the tribological properties and strengths of Fe and A{ell} alloys. 10 refs., 6 figs.

  16. Application of electron beam plasma for biopolymers modification

    NASA Astrophysics Data System (ADS)

    Vasilieva, T. M.

    2012-06-01

    The effects of the Electron Beam Plasma treatment on natural polysaccharide chitosan were studied experimentally. Low molecular water-soluble products of chitosan and chitooligosaccharides were obtained by treating the original polymers in the Electron Beam Plasma of oxygen and water vapor. The molecular mass of the products varied from 18 kDa to monomeric fragments. The degradation of the original polymers was due to the action of active oxygen particles (atomic and singlet oxygen) and the particles of the water plasmolysis (hydroxyl radicals, hydrogen peroxides). The 95% yield of low molecular weight chitosans was attained by optimizing the treatment conditions. The studies of the antimicrobial activity of low molecular products showed that they strongly inhibit the multiplication of colon bacillus, aurococcus and yeast-like fungi. The EBP-stimulated degradation of polysaccharides and proteins were found to result from breaking β-1,4 glycosidic bounds and peptide bonds, respectively.

  17. Ion beam modification of single crystal sapphire for high temperature optical waveguiding

    NASA Astrophysics Data System (ADS)

    Spratt, William T.

    High temperature environments (>1000°C) provide a significant challenge for fiber optic based sensing due to the poor physical properties of silica fiber at elevated temperature. Not only does silica soften above 1000°C, but the dopants that are responsible for the refractive index change between the core and cladding diffuse, reducing the fibers effectiveness as a waveguide. Single-crystal sapphire fiber has the potential to supplement fiber sensing at high temperature however sapphire fiber is unclad and no cladding methods exist that withstand high temperatures. In addition to higher losses the lack of a cladding also leads to decreased sensitivity due to the large number of modes. This thesis explores a cladding method for sapphire based on ion beam modification and annealing, which initial results indicate is suitable for high temperature applications. Ion beam modification of planar sapphire using hydrogen is conducted and analyzed using Rutherford backscattering spectroscopy (RBS), nuclear reaction analysis (NRA), and transmission electron microscopy (TEM) to determine the structural changes and prism coupling, spectroscopic ellipsometry (SE), and UV absorption to determine the optical effects. Sapphire fibers are modified through the use of a rotating implant holder and examined using end face coupling. Substantial change in refractive index does not occur until annealing above 600°C and persists to at least 1700°C. From the measurements of planar sapphire the root cause of the refractive index change at high temperature is determined and verified through finite element simulations. Modified sapphire fibers exhibit increased containment of light to the core region and a novel annular waveguide is fabricated with potential for sensing applications. This work adds to the understanding of the optical effects of ion beam modification and high temperature annealing of sapphire, and provides a foundation for future high temperature sensing applications of

  18. Electron beam enhanced surface modification for making highly resolved structures

    DOEpatents

    Pitts, J.R.

    1984-10-10

    A method for forming high resolution submicron structures on a substrate is provided by direct writing with a submicron electron beam in a partial pressure of a selected gas phase characterized by the ability to dissociate under the beam into a stable gaseous leaving group and a reactant fragment that combines with the substrate material under beam energy to form at least a surface compound. Variations of the method provide semiconductor device regions on doped silicon substrates, interconnect lines between active sites, three dimensional electronic chip structures, electron beam and optical read mass storage devices that may include color differentiated data areas, and resist areas for use with selective etching techniques.

  19. Electron beam enhanced surface modification for making highly resolved structures

    DOEpatents

    Pitts, John R.

    1986-01-01

    A method for forming high resolution submicron structures on a substrate is provided by direct writing with a submicron electron beam in a partial pressure of a selected gas phase characterized by the ability to dissociate under the beam into a stable gaseous leaving group and a reactant fragment that combines with the substrate material under beam energy to form at least a surface compound. Variations of the method provide semiconductor device regions on doped silicon substrates, interconnect lines between active sites, three dimensional electronic chip structures, electron beam and optical read mass storage devices that may include color differentiated data areas, and resist areas for use with selective etching techniques.

  20. Polymer metallization: Low energy ion beam surface modification to improve adhesion

    NASA Astrophysics Data System (ADS)

    Bertrand, P.; Lambert, P.; Travaly, Y.

    1997-08-01

    The interface formation between copper and poly(ethylene terephthalate) (PET) and poly(methyl methacrylate) (PMMA) films is studied in situ by Ion Scattering Spectrometry (ISS). Very low metal fluxes (˜ 10 13 atoms/cm 2 s) and hence low deposition rates are obtained by using a Knudsen's effusion cell. This allows to reach very low metal coverages down to the sub-monolayer regime. The results indicate that without surface activation, Cu atoms interact only very weakly with both polymer surfaces. Indeed, the oxygen/carbon ISS intensity ratio remains nearly unaffected by the metal deposition, showing no preferential shadowing effect. Moreover, the ISS polymer signals are still detected after exposure to Cu atom fluences corresponding to several monolayers coverage. Cu diffusion below the polymer surface is evidenced by the presence of an inelastic multiple collision contribution in the ISS spectra. It is observed that 2 keV 3He + ion beam irradiation prior to metallization induces a drastic modification in the interface formation. Ion beam irradiation prevents the metal diffusion into the polymer bulk and leads to an increase of the metal concentration at the surface. In order to explain these results, the surface modifications produced by the ion beam on pristine polymers are studied by ISS and ToF-SIMS. Dehydrogenation and preferential loss of O containing fragments are found. These modifications are associated with the production of radicals leading to the creation of new adsorption sites for the Cu atoms. It is proposed that the reaction between radicals of different macrochains induces a surface crosslinking, that can prevent the diffusion for the deposited metal atoms into the polymer bulk.

  1. Non-ideal axicon-generated Bessel beam application for intra-volume glass modification.

    PubMed

    Dudutis, Juozas; GeČys, Paulius; RaČiukaitis, Gediminas

    2016-12-12

    The extended focal depth of Bessel beams is a very attracting property for glass cutting applications. However, Bessel beam generation with a non-ideal conical lens induces beam pattern distortions. We present our novel results on bulk modifications of soda-lime glass using a non-ideal axicon-generated Bessel beam. Modelling of the Bessel beam pattern and experimental measurements indicated ellipticity of the central core diameter. That resulted in the formation of cracks in a transverse direction inside the bulk of glass. Furthermore, we demonstrate the possibility to control the transverse crack propagation direction, which is crucial in the case of glass cutting applications.

  2. Variable-Energy Ion Beams For Modification Of Surfaces

    NASA Technical Reports Server (NTRS)

    Chutjian, Ara; Hecht, Michael H.; Orient, Otto J.

    1989-01-01

    Beam of low-energy negative oxygen ions used to grow layer of silicon dioxide on silicon. Beam unique both in purity, contains no molecular oxygen or other charged species, and in low energy, which is insufficient to damage silicon by physically displacing atoms. Low-energy growth accomplished with help of ion-beam apparatus. Directs electrons into crosswise stream of gas, generating stream of negative ions. Pair of charged plates separates ions from accompanying electrons and diverts ion beam to target - silicon substrate. Diameter of beam at target 0.5 to 0.75 cm. Promises useful device to study oxidation of semiconductors and, in certain applications, to replace conventional oxidation processes.

  3. Ion beam modification of chitosan and cellulose membranes for simulation of ion bombardment of plant cell envelope

    NASA Astrophysics Data System (ADS)

    Prakrajang, K.; Wanichapichart, P.; Anuntalabhochai, S.; Pitakrattananukool, S.; Yu, L. D.

    2009-05-01

    Ion beam biotechnology has been developed for induction of DNA transfer into biological cells. To separately investigate effects of ion interaction with plant cell envelope for understanding relevant mechanisms, this study used chitosan and cellulose membranes to simulate the cell envelope and characterize behavior of the membranes modified by ion beam. Chitosan and cellulose membranes were bombarded with argon and nitrogen ion beams at energy of 15-25 keV to fluencies in orders of 1015 ion/cm2. Modifications of the membrane surface morphology, contact angle and electric characteristics were investigated. Results showed that subjected to ion bombardment, the membrane surface was roughened, the contact angle of the membrane surface was varied, the membrane impedance was decreased and the conductance and capacitance were increased. These modifications explain effects of ion bombardment of plant cell envelope on induction of DNA transfer.

  4. The modification of spectral characteristics of cytostatics by optical beams

    NASA Astrophysics Data System (ADS)

    Pascu, Mihail Lucian; Brezeanu, Mihail; Carstocea, Benone D.; Voicu, Letitia; Gazdaru, Doina M.; Smarandache, Adriana A.

    2004-10-01

    Besides the biochemical action of methotrexate (MTX) and 5-fluorouracil (FU) their effect in destroying cancer tumours could be enhanced by exposure to light at different doses. Absorption, excitation and emission spectra of 10-4M - 10-5M MTX solutions in natural saline and sodium hydroxide at pH = 8.4 were measured, while their exposure to coherent and uncoherent light in the visible and near ultraviolet (UV) spectral ranges was made (Hg lamps and Nitrogen pulsed laser radiation were used). Absorption spectra exhibit spectral bands in the range 200 nm - 450 nm. The 200 - 450 nm excitation spectra were measured with emission centered on 470 nm; MTX fluorescence excitation was measured at 390 nm and the emission was detected between 400 nm and 600 nm showing a maximum at 470 nm. Spectra modifications, nonlinearly depending on exposure time (varying from 1 min to 20 min), evidenced MTX photo-dissociation to the fluorescent compound 2,4 diamino-formylpteridine. In the 5-FU case the absorption spectra exhibit bands between 200 nm and 450 nm. The emission fluorescence spectra were measured between 400 nm and 600 nm, with λex = 350 nm for UV Hg lamp and with λex = 360 nm for laser irradiated samples; at irradiation with N2 laser emitted radiation the excitation spectra were measured in the range of 200 nm - 400 nm, with λem = 440 nm. New vascularity rapid destruction was observed for conjunctive impregnated with 5-FU solution whilst exposed to incoherent UV and visible light.

  5. Ion beam modification of injection moulded polymere materials

    NASA Astrophysics Data System (ADS)

    Wolf, G. K.; Kersten, H. J.

    1998-05-01

    Ion beam based treatments and processes are an ecologically friendly alternative for the metallization of polymers. Nowadays mainly chemical and electrochemical and plasma assisted techniques are used. In this contribution the copper metallization of high temperature thermoplasts using ion beam assisted deposition (IBAD) was studied. The applications in mind were magnetic shielding of cases for sensors. The influence of ion beam intensity and energy, deposition rate, preconditioning and substrate material on the Cu adhesion was investigated. As materials PPS (Polyphenylene sulfide) and LCP (Liquid Crystal Polymer) with different filling materials were used. It could be shown that the adhesion reacts very critical to the type of polymer and the type and concentration of filling material. The IBAD parameters giving best results are I/A ratios of 0.005-0.01 and energies of 0.5-2 keV. The highest adhesion force (≈27 N/mm 2) was measured on PPS. For LCP thin Ti interlayers increased the adhesion force ≈50% up to values above 10 N/mm 2.

  6. Surface modification by ion implantation and ion beam mixing

    NASA Astrophysics Data System (ADS)

    Rivière, J. P.

    1992-05-01

    After its successful applications in the semiconductor industry, ion implantation is being employed for other technical applications. The main process in ion implantation is the introduction of additive elements to change the composition and properties of the surface region of a material. We present results demonstrating the important improvement of the wear resistance and friction in a NiTi alloy implanted with nitrogen. The formation of hard TiN precipitates embedded in an amorphous layer is responsible for such modifications. The generation of many atomic displacements in collision cascades during implantation can be also employed as a modification process itself. For instance, the chemical disordering in an implanted Fe60Al40 alloy induces a para- to ferromagnetic transition. The formation of an amorphous surface alloy by ion irradiation at a temperature of 15 K has been shown in Ni50Al50 by in situ RBS, channelling and TEM. The new method of dynamic ion mixing (DIM) combines ion bombardment with simultaneous material deposition and allows thicker adherent coatings to be built up, this is shown for both metallic Cu50Ni50 and ceramic TiB2 coatings. Recent results demonstrating a significant increase in fatigue lifetime of a coated 316 L stainless steel are also reported and discussed.

  7. The modification of the structure of multilayer Co/Pt films by the irradiation with a focused helium ion beam

    SciTech Connect

    Gusev, S. A. Drozdov, M. N.; Ermolaeva, O. L.; Fraerman, A. A.; Gusev, N. S.; Sapozhnikov, M. V. Vdovichev, S. N.; Mikhailovskii, V. Yu.; Petrov, Yu. V.

    2016-06-17

    We report here on the possibility of a local modification of Co/Pt multilayered magnetic films by focused ion beam irradiation. The changes of structural and magnetic properties are experimentally investigated as a function of irradiation fluence. The method is used to form lateral structures with the periods up to 100 nm. The magnetic force microscopy accompanied by Hall effect measurements of the structure indicate the formation of magnetic skyrmion lattices in the absence of Dzyaloshinskii-Moriya interaction.

  8. Modification of the radial beam port of ITU TRIGA Mark II research reactor for BNCT applications.

    PubMed

    Akan, Zafer; Türkmen, Mehmet; Çakir, Tahir; Reyhancan, İskender A; Çolak, Üner; Okka, Muhittin; Kiziltaş, Sahip

    2015-05-01

    This paper aims to describe the modification of the radial beam port of ITU (İstanbul Technical University) TRIGA Mark II research reactor for BNCT applications. Radial beam port is modified with Polyethylene and Cerrobend collimators. Neutron flux values are measured by neutron activation analysis (Au-Cd foils). Experimental results are verified with Monte Carlo results. The results of neutron/photon spectrum, thermal/epithermal neutron flux, fast group photon fluence and change of the neutron fluxes with the beam port length are presented.

  9. Computer simulation of surface modification with ion beams

    NASA Astrophysics Data System (ADS)

    Insepov, Z.; Hassanein, A.; Swenson, D.; Terasawa, M.

    2005-12-01

    Interactions of energetic ions with various solid targets including silicon and a few metal surfaces were studied by computer simulation and verified by experiment. Surface sputtering and modification for collisions of Arn (n ∼ 100) cluster ions, with kinetic energies of 12-54 eV/atom, and slow highly charged ions (HCI), with potential energies of 80-3500 eV, have been simulated. Various energy transfer mechanisms of the ion energy into the solid target, such as shock wave generation, hollow atom formation, Coulomb explosion, charge screening and neutralization were studied. Atomistic molecular dynamics (MD), as well as a phenomenological surface dynamics methods were employed and the results of the simulations were compared with the experimental data.

  10. A beam-modification assembly for experimental neutron capture therapy of brain tumors

    SciTech Connect

    Slatkin, D.N.; Kalef-Ezra, J.A.; Saraf, S.K.; Joel, D.D.

    1989-01-01

    Recent attempts to treat intracerebral rat gliomas by boron neutron capture therapy (BNCT) have been somewhat disappointing, perhaps in part because of excessive whole-body and nasopharyngeal irradiation. Intracerebral rat gliomas were treated by BNCT with more success using a new beam-modification assembly. 3 refs., 2 figs.

  11. Ion beam modification of CR-39 (DOP) and polyamide nylon-6 polymers

    NASA Astrophysics Data System (ADS)

    Kumar, Rajesh; Prasad, Rajendra; Vijay, Y. K.; Acharya, N. K.; Verma, K. C.; De, Udayan

    2003-12-01

    Swift heavy ions interact predominantly through inelastic scattering while traversing any polymeric medium and produce excited/ionized atoms. This results into the modification of physical and chemical response of the polymer. CR-39 (DOP) and polyamide nylon-6 polymer samples were irradiated with 70 MeV C 5+ ion beam to the fluences of 10 11, 10 12 and 10 13 ions cm -2. Modifications due to irradiation were studied using Fourier transform infra red (FTIR) spectroscopic and X-ray diffraction (XRD) technique. Considerable deformation has been observed in both the polymers at the fluence of 10 12 and 10 13 ions cm -2. XRD analyses show slight shift of peak position and significant changes in peak width and intensity. Particle size or grain size, calculated by applying Scherrer formula, indicates measurable changes in particle size in the irradiated samples. XRD peaks at d-values of 4.335 Å and 3.838 Å for the virgin polyamide nylon-6 gradually change with increasing fluence into one broad peak. Some difference in the irradiation effect in these two different polymers has been observed.

  12. Precision shape modification of nanodevices with a low-energy electron beam

    DOEpatents

    Zettl, Alex; Yuzvinsky, Thomas David; Fennimore, Adam

    2010-03-09

    Methods of shape modifying a nanodevice by contacting it with a low-energy focused electron beam are disclosed here. In one embodiment, a nanodevice may be permanently reformed to a different geometry through an application of a deforming force and a low-energy focused electron beam. With the addition of an assist gas, material may be removed from the nanodevice through application of the low-energy focused electron beam. The independent methods of shape modification and material removal may be used either individually or simultaneously. Precision cuts with accuracies as high as 10 nm may be achieved through the use of precision low-energy Scanning Electron Microscope scan beams. These methods may be used in an automated system to produce nanodevices of very precise dimensions. These methods may be used to produce nanodevices of carbon-based, silicon-based, or other compositions by varying the assist gas.

  13. Ion beam modification of two-dimensional materials: Characterization, properties, and applications

    NASA Astrophysics Data System (ADS)

    Li, Ziqi; Chen, Feng

    2017-03-01

    The layered two-dimensional (2D) materials, e.g., the well-known graphene, transition metal dichalcogenides, and topological insulators, have attracted great interest of researchers from fundamental research as well as industries owing to their intriguing properties in a number of aspects. In practical applications, the efficient modification of the features of 2D materials is compelling and essential to achieve desired functionalities. Ion implantation has been successfully applied to synthesize graphene. The most exotic advantage of ion beam technology is that it offers distinct options of energetic beams, which has recently shown the unique capability to modify and tailor the properties of versatile 2D materials. To name a few, the energetic ion beams could implement the surface morphology or layer-to-layer structural engineering of 2D materials. At the microcosmic level, the introduction of ion beam induced defects and intentional doping of specific ions are the basis of tailoring properties of 2D materials. By manipulating the parameters of ion beams (energies, species, fluences, incident angles, etc.), the modified 2D materials may possess novel properties, which are unprecedented in pristine ones. Promising applications based on these 2D materials with ion beam tailored features have been realized in a broad range of fields. In this work, we systematically review the latest research progress on the deployed techniques and property modifications of graphene and other 2D materials under the treatment of various ion beams. A few selected applications are presented to indicate the practical potentials of ion beam modified 2D materials in distinct areas. Perspectives on future developments are also provided by focusing on several promising topics.

  14. Ion beam induced optical and surface modification in plasmonic nanostructures

    NASA Astrophysics Data System (ADS)

    Singh, Udai B.; Gautam, Subodh K.; Kumar, Sunil; Hooda, Sonu; Ojha, Sunil; Singh, Fouran

    2016-07-01

    In present work, ion irradiation induced nanostructuring has been exploited as an efficient and effective tool for synthesis of coupled plasmonics nanostructures by using 1.2 MeV Xe ions on Au/ZnO/Au system deposited on glass substrate. The results are correlated on the basis of their optical absorption, surface morphologies and enhanced sensitivity of evolved phonon modes by using UV Visible spectroscopy, scanning electron microscopy (SEM), and Raman spectroscopy (RS), respectively. Optical absorbance spectra of plasmonic nanostructures (NSs) show a decrease in band gap, which may be ascribed to the formation of defects with ion irradiation. The surface morphology reveals the formation of percolated NSs upon ion irradiation and Rutherford backscattering spectrometry (RBS) study clearly shows the formation of multilayer system. Furthermore, RS measurements on samples are studied to understand the enhanced sensitivity of ion irradiation induced phonon mode at 573 cm-1 along with other modes. As compared to pristine sample, a stronger and pronounced evolution of these phonon modes is observed with further ion irradiation, which indicates localized surface plasmon results with enhanced intensity of phonon modes of Zinc oxide (ZnO) material. Thus, such plasmonic NSs can be used as surface enhanced Raman scattering (SERS) substrates.

  15. Surface modifications of hydrogen storage alloy by heavy ion beams with keV to MeV irradiation energies

    NASA Astrophysics Data System (ADS)

    Abe, Hiroshi; Tokuhira, Shinnosuke; Uchida, Hirohisa; Ohshima, Takeshi

    2015-12-01

    This study deals with the effect of surface modifications induced from keV to MeV heavy ion beams on the initial reaction rate of a hydrogen storage alloy (AB5) in electrochemical process. The rare earth based alloys like this sample alloy are widely used as a negative electrode of Ni-MH (Nickel-Metal Hydride) battery. We aimed to improve the initial reaction rate of hydrogen absorption by effective induction of defects such as vacancies, dislocations, micro-cracks or by addition of atoms into the surface region of the metal alloys. Since defective layer near the surface can easily be oxidized, the conductive oxide layer is formed on the sample surface by O+ beams irradiation, and the conductive oxide layer might cause the improvement of initial reaction rate of hydriding. This paper demonstrates an effective surface treatment of heavy ion irradiation, which induces catalytic activities of rare earth oxides in the alloy surface.

  16. Modification of the Structural-Phase State of the Surface Layer of a Cermet Composite Under Electron Beam Irradiation in Inert Gas Plasmas

    NASA Astrophysics Data System (ADS)

    Ovcharenko, V. E.; Ivanov, K. V.; Ivanov, Yu. F.; Mokhovikov, A. A.; Bao Hai, Yu.

    2017-04-01

    The results of investigation of characteristic features of modification of the structural-phase state of the surface layer of a TiC-(Ni-Cr) cermet composite under irradiation by a pulsed electron beam in the discharge plasma of inert gases with different atomic masses and ionization energies are presented. The effect of modification of the structural-phase state of the composite surface layer on its strength is analyzed under conditions of threepoint bending.

  17. Fundamental aspects on ion-beam surface modification: defect production and migration processes

    SciTech Connect

    Rehn, L.E.; Averback, R.S.; Okamoto, P.R.

    1984-09-01

    Ion-beam modification of metals is generating increasing scientific interest not only because it has exciting technological potential, but also because it has raised fundamental questions concerning radiation-induced diffusion processes. In addition to the implanted species, several defect production and migration mechanisms contribute to changes in the near-surface composition of an alloy during ion bombardment, e.g., atoms exchange positions via displacements and replacement sequences; preferential sputtering effects arise; radiation-enhanced diffusion and radiation-induced segregation occur. The latter two defect migration mechanisms are of particular significance since they can alter the composition to depths which are much greater than the implanted ion range. By altering various parameters such as irradiation temperature, ion mass, energy, and current density, and initial alloying distributions, a rich variety of near-surface composition profiles can be created. We have utilized changes in ion mass and energy, and irradiation temperature to distinguish defect production from defect migration effects. Experimental results are presented which provide a guide to the relative efficiencies of different mechanisms under various irradiation conditions. 46 references.

  18. Pore structure modification of diatomite as sulfuric acid catalyst support by high energy electron beam irradiation and hydrothermal treatment

    NASA Astrophysics Data System (ADS)

    Li, Chong; Zhang, Guilong; Wang, Min; Chen, Jianfeng; Cai, Dongqing; Wu, Zhengyan

    2014-08-01

    High energy electron beam (HEEB) irradiation and hydrothermal treatment (HT), were applied in order to remove the impurities and enlarge the pore size of diatomite, making diatomite more suitable to be a catalyst support. The results demonstrated that, through thermal, charge, impact and etching effects, HEEB irradiation could make the impurities in the pores of diatomite loose and remove some of them. Then HT could remove rest of them from the pores and contribute significantly to the modification of the pore size distribution of diatomite due to thermal expansion, water swelling and thermolysis effects. Moreover, the pore structure modification improved the properties (BET (Brunauer-Emmett-Teller) specific surface area, bulk density and pore volume) of diatomite and the catalytic efficiency of the catalyst prepared from the treated diatomite.

  19. Surface modification of structural materials by low-energy high-current pulsed electron beam treatment

    SciTech Connect

    Panin, A. V. E-mail: kms@ms.tsc.ru; Kazachenok, M. S. E-mail: kms@ms.tsc.ru; Sinyakova, E. A.; Borodovitsina, O. M.; Ivanov, Yu. F.; Leontieva-Smirnova, M. V.

    2014-11-14

    Microstructure formation in surface layers of pure titanium and ferritic-martensitic steel subjected to electron beam treatment is studied. It is shown that low energy high-current pulsed electron beam irradiation leads to the martensite structure within the surface layer of pure titanium. Contrary, the columnar ferrite grains grow during solidification of ferritic-martensitic steel. The effect of electron beam energy density on the surface morphology and microstructure of the irradiated metals is demonstrated.

  20. Ion Beam and Plasma Technology Development for Surface Modification at Los Alamos National Laboratory

    SciTech Connect

    Davis, H.A.; Munson, C.P.; Wood, B.P.; Bitteker, L.J.; Nastasi, M.A.; Rej, D.J.; Waganaar, W.J.; Walter, K.C.; Coates, D.M.; Schleinitz, H.M.

    1997-12-31

    We are developing two high-throughput technologies for materials modification. The first is a repetitive intense ion beam source for materials modification through rapid surface melt and resolidification (up to 10{sup 10} deg/sec cooling rates) and for ablative deposition of coatings. The short range of the ions (typically 0.1 to 5 micrometers) allows vaporization or melting at moderate beam energy density (typically 1-50 J/cm{sup 2}). A new repetitive intense ion beam accelerator called CHAMP is under development at Los Alamos. The design beam parameters are: E=200 keV, I=15 kA, {tau}=1 {micro}s, and 1 Hz. This accelerator will enable applications such as film deposition, alloying and mixing, cleaning and polishing, corrosion and wear resistance, polymer surface treatments, and nanophase powder synthesis. The second technology is plasma source ion implantation (PSII) using plasmas generated from both gas phase (using radio frequency excitation) and solid phase (using a cathodic arc) sources. We have used PSII to directly implant ions for surface modification or as method for generating graded interfaces to enhance the adhesion of surface coatings. Surfaces with areas of up to 16 m{sup 2} and weighing more than a thousand kilograms have been treated in the Los Alamos PSII chamber. In addition, PSII in combination with cathodic source deposition has been used to form highly adherent, thick Er{sub 2}O{sub 3} coatings on steel for reactive metal containment in casting. These coatings resist delamination under extreme mechanical and thermal stress.

  1. Possible Quantum Mechanical Effect on Beam Echo

    SciTech Connect

    Chao, Alex

    2000-12-07

    The echo effect in charged particle beams provides a link between macroscopic measurable beam parameters and microscopic phase space motion of the beam. Since quantum mechanics dictates a granularization of the phase space, it influences how the phase space behaves microscopically, and thus potentially affect how the echo effect behaves macroscopically. In this study, we propose to examine the possible measurable macroscopic effects of quantum mechanics on beams through its echo effect.

  2. The potential of electron beam radiation for simultaneous surface modification and bioresorption control of PLLA.

    PubMed

    Cairns, Marie-Louise; Dickson, Glenn R; Orr, John F; Farrar, David; Hardacre, Christopher; Sa, Jacinto; Lemoine, Patrick; Mughal, Muhammad Zeeshan; Buchanan, Fraser J

    2012-09-01

    Bioresorbable polymers have been widely investigated as materials exhibiting significant potential for successful application in the fields of tissue engineering and drug delivery. Further to the ability to control degradation, surface engineering of polymers has been highlighted as a key method central to their development. Previous work has demonstrated the ability of electron beam (e-beam) technology to control the degradation profiles and bioresorption of a number of commercially relevant bioresorbable polymers (poly-l-lactic acid (PLLA), L-lactide/DL-lactide co-polymer (PLDL) and poly(lactic-co-glycolic acid (PLGA)). This work investigates the further potential of e-beam technology to impart added biofunctionality through the manipulation of polymer (PLLA) surface properties. PLLA samples were subjected to e-beam treatments in air, with varying beam energies and doses. Surface characterization was then performed using contact angle analysis, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and atomic force microscopy. Results demonstrated a significant increase in surface wettability post e-beam treatment. In correlation with this, XPS data showed the introduction of oxygen-containing functional groups to the surface of PLLA. Raman spectroscopy indicated chain scission in the near surface region of PLLA (as predicted). However, e-beam effects on surface properties were not shown to be dependent on beam energy or dose. E-beam irradiation did not seem to affect the surface roughness of PLLA as a direct consequence of the treatment.

  3. Ion beam effects in diacetylenes

    NASA Astrophysics Data System (ADS)

    Elman, B. S.; Blackburn, Gary F.; Thakur, M. K.; Sandman, D. J.; Samuelson, L. A.; Kenneson, D. G.

    Due to their unique backbone structure and crystalline organization, polydiacetylenes (PDAs) are considered to be prototype one-dimensional systems. They were shown to have properties considered important to realize concepts of all-optical signal processing. Macroscopic, nearly defect-free, highly anisotropic PDA single crystals are prepared by exposure of diacteylene monomers to various forms of radiation. These materials can also be prepared as thin film crystals and Langmuir-Blodgett (LB) assemblies. We have studied and compared the effects of ion beam irradiation on different configurations of diacetylenes: bulk crystals, thin films and LB structures. Exposure of monomeric diacetylene films to very low fiuence ion beams results in their polymerization and in the formation of good quality anisotropic films of controlled thickness. Significant changes in optical and electrical properties of PDAs were observed and studied by optical absorption and do temperature dependent conductivity measurements.

  4. SCALP, a platform dedicated to material modifications and characterization under ion beam

    NASA Astrophysics Data System (ADS)

    Bacri, C.-O.; Bachelet, C.; Baumier, C.; Bourçois, J.; Delbecq, L.; Ledu, D.; Pauwels, N.; Picard, S.; Renouf, S.; Tanguy, C.

    2017-09-01

    SCALP (Synthesis and Characterization using ion AcceLerators for Pluridisciplinary research) is a platform dedicated to characterization and modification of materials using ion beams. Located at CSNSM, a joint research unit of CNRS and Université Paris-Sud, Orsay-France, it is composed, on the one hand, by a 2 MV Tandem/Van de Graaff accelerator and a 190 kV implanter, both possibly coupled with a Transmission Electron Microscope. On the other hand, a 40 kV separator is dedicated to magnetic isotopic separation and enables either a pure isotope beam to be delivered, or mono-isotopic targets (purity of the order of ppm) to be manufactured by implantation or by deposition. The platform will be described, emphasizing on its originalities. New ongoing developments will also be presented.

  5. New facility for ion beam materials characterization and modification at Los Alamos

    SciTech Connect

    Tesmer, J.R.; Maggiore, C.J.; Parkin, D.M.

    1988-01-01

    The Ion Beam Materials Laboratory (IBML) is a new Los Alamos laboratory devoted to the characterization and modification of the near surfaces of materials. The primary instruments of the IBML are a tandem electrostatic accelerator, a National Electrostatics Corp. Model 9SDH, coupled with a Varian CF-3000 ion implanter. The unique organizational structure of the IBML as well as the operational characteristics of the 9SDH (after approximately 3000 h of operation) and the laboratories' research capabilities will be discussed. Examples of current research results will also be presented. 5 refs., 2 figs.

  6. Proceedings of the 19th International Conference on Ion Beam Modification of Materials (IBMM 2014)

    NASA Astrophysics Data System (ADS)

    Vantomme, André; Temst, Kristiaan

    2015-12-01

    It is our pleasure to present the proceedings of the 19th International Conference on Ion Beam Modification of Materials, which took place from September 14th until September 19th, 2014. The conference was held in the historic center of Leuven, a medieval city in the heart of Europe, a city where centuries-old culture meets frontier science and technology. Among other places, the conference brought us to the University Hall, which has been in use by the university since its foundation in 1425, to the Infirmerie of the Grand Beguinage and to the medieval city of Bruges, the latter two being Unesco World Heritage sites.

  7. Effectiveness of decanter modifications on organic removal

    SciTech Connect

    Lambert, D.P.

    1992-08-20

    A series of runs were planned in the Precipitate Hydrolysis Experimental Facility (PHEF) at the Savannah River Plant to determine the effectiveness of equipment and process modifications on the PHEF decanter organic removal efficiency. Runs 54-59 were planned to test the effectiveness of spray recirculation, a new decanter, heated organic recirculation and aqueous drawoff on organic removal efficiency in the revised HAN flowsheet. Runs 60-63 were planned to provide a comparison of the original and new decanter designs on organic removal efficiency in the late wash flowsheet without organic recirculation. Operational problems were experienced in both the PHEF and IDMS pilot facilities because of the production of high boiling organics and the low organic removal efficiency of the PHEF decanters. To prevent these problems in the DWPF Salt and Chemical Cells, modifications were proposed to the decanter and flowsheet to maximize the organic removal efficiency and minimize production of high boiling organics.

  8. Modifications of the beam profile in the new inclined crystal geometry

    NASA Astrophysics Data System (ADS)

    Lee, W. K.; Macrander, A. T.

    1991-10-01

    The new inclined crystal geometry has been successfully used in high heat load X-ray monochromator tests. The important aspect of this geometry is that from a diffraction point of view, when properly aligned, it is a symmetric Bragg reflection; i.e., b = k(sub i) . n/k(sub out).n = -1. An interesting result of this geometry is that with a single reflection from an inclined crystal, the output X-ray beam shape changes dramatically while maintaining the same beam cross section area. For example, a parallel 8 keV input X-ray beam using Si(111) reflection, with an inclination angle of 70.5 deg, the output beam size is compressed by about a factor of 5.4 in one direction and expanded by the same factor in the other direction. This geometry can therefore, be used to alter the source line profile of in house X-ray generators and in some cases, be used to better match the sample size and the X-ray beam. The effect of this geometry on beam profiles, beam divergences and acceptance angles will be discussed.

  9. Modifications of the beam profile in the new inclined crystal geometry

    NASA Astrophysics Data System (ADS)

    Keat Lee, Wah; Macrander, Albert T.

    1992-08-01

    The new inclined crystal geometry has been successfully used in high heat load X-ray monochromator tests. The important aspect of this geometry is that from a diffraction point of view, when properly aligned, it is a symmetric Bragg reflection, i.e., b= ki· n/ kout· n=-1. An interesting result of this geometry is that with a single reflection from an inclined crystal the output X-ray beam shape changes dramatically, while maintaining the same beam cross sectional area. For example, a parallel 8 keV input X-ray beam using Si(111) reflection, with an inclination angle of 70.5°, the output beam size is compressed by about a factor of 5.6 in one direction and expanded by the same factor in the other direction. This geometry can therefore be used to alter the source line profile of in house X-ray generators, and in some cases to better match the sample size and the X-ray beam. The effect of this geometry on beam profiles, beam divergences and acceptance angles will be discussed.

  10. Pulsed electron-beam technology for surface modification of metallic materials

    SciTech Connect

    Proskurovsky, D.I.; Rotshtein, V.P.; Ozur, G.E.; Markov, A.B.; Nazarov, D.S.; Shulov, V.A.; Ivanov, Y.F.; Buchheit, R.G.

    1998-07-01

    This article concerns the foundations of a new technology for surface modification of metallic materials based on the use of original sources of low-energy, high-current electron beams. The sources contain an electron gun with an explosive-emission cathode and a plasma anode, placed in a guide magnetic field. The acceleration gap and the transportation channel are prefilled with plasma with the use of spark plasma sources or a low-pressure reflected discharge. The electron-beam sources produce electron beams with the parameters as follows: electron energy 10{endash}40 keV; pulse duration 0.5{endash}5 {mu}s; energy density 0.5{endash}40thinspJ/cm{sup 2}, and beam cross-section area 10{endash}50thinspcm{sup 2}. They are simple and reliable in operation. Investigations performed with a variety of constructional and tool materials (steels, aluminum and titanium alloys, hard alloys) have shown that the most pronounced changes of the structure-phase state occur in the near-surface layers quenched from the liquid state, where the crystallization front velocity reaches its maximum. In these layers partial or complete dissolving of second phases and formation of oversaturated solid solutions and ordered nanosized structures may take place. This makes it possible to improve substantially the electrochemical and strength properties of the surface layers. It has been established that the deformation processes occurring in the near-surface layers have the result that the thickness of the modified layer with improved strength properties is significantly greater than that of the heat-affected zone. Some examples of the use of low-energy, high-current electron beams for improving the performance of materials and articles are given. {copyright} {ital 1998 American Vacuum Society.}

  11. Ion beam analysis and modification of thin-film, high-temperature superconductors

    NASA Astrophysics Data System (ADS)

    Nastasi, Michael

    1989-10-01

    The application of ion beams to ceramic processing is a very powerful technique. In particular, ion beams have been shown to be very effective in producing novel material properties through their rather violent interactions with the component atoms of the ceramics. However, in all these cases ions are used to process and produce changes in ceramics, changes that must be monitored by other techniques. This paper shows that, in addition to modifying materials, ion beams can be used in a more gentle but very powerful way to explore what happens to a ceramic thin film as a result of processing. The following discussions are concerned exclusively with a new and exciting class of ceramic: the high-temperature superconductor (HTS). We will discuss the application of various ion beam backscattering techniques as well as examine the use of ion implantation in the processing of these materials.

  12. Health behavior modification after electron beam computed tomography and physician consultation.

    PubMed

    Schwartz, Jennifer; Allison, Mathew; Wright, C Michael

    2011-04-01

    This study aimed to determine whether participants reported altering health behaviors (physical activity, diet, and alcohol consumption) after seeing results from an electron-beam computed tomography (EBCT) scan for coronary artery calcium and reviewing these results with a physician. Clinicians attempt to motivate patients to control cardiovascular risk factors by adopting healthy behaviors and reducing harmful actions. Asymptomatic patients (N = 510) were evaluated by EBCT for the extent of coronary artery calcium. Information pertaining to demographics, health history, and lifestyle/health behaviors was obtained from each participant at the time of the EBCT scan. Patients were given their numerical calcium score, shown images of their coronary arteries, and counseled by a physician for lifestyle and medical risk modification based on their coronary artery calcium score. Approximately 6 years after the scan, participants completed a follow-up questionnaire related to lifestyle modifications. In multivariable analysis, the presence and extent of coronary artery calcium was significantly associated with beneficial health behavior modifications. Specifically, the greater a patient's coronary artery calcium score, the more likely they were to report increasing exercise (odds ratio = 1.34, P = 0.02), changing diet (odds ratio = 1.40, P < 0.01), and changing alcohol intake (odds ratio = 1.46, P = 0.05). This study suggests that seeing and being counseled on the presence and extent of coronary artery calcium is significantly associated with behavior change.

  13. Modification of the sample's surface of hypereutectic silumin by pulsed electron beam

    NASA Astrophysics Data System (ADS)

    Rygina, M. E.; Ivanov, Yu F.; Lasconev, A. P.; Teresov, A. D.; Cherenda, N. N.; Uglov, V. V.; Petricova, E. A.; Astashinskay, M. V.

    2016-04-01

    The article presents the results of the analysis of the elemental and phase composition, defect substructures. It demonstrates strength and tribological characteristics of the aluminium-silicon alloy of the hypereutectic composition in the cast state and after irradiation with a high-intensity pulsed electron beam of a submillisecond exposure duration (a Solo installation, Institute of High Current Electrons of the Siberian Branch of the Russian Academy of Sciences). The research has been conducted using optical and scanning electron microscopy, and the X-ray phase analysis. Mechanical properties have been characterized by microhardness, tribological properties - by wear resistance and the friction coefficient value. Irradiation of silumin with the high-intensity pulsed electron beam has led to the modification of the surface layer up to 1000 microns thick. The surface layer with the thickness of up to 100 microns is characterized by melting of all phases present in the alloy; subsequent highspeed crystallization leads to the formation of a submicro- and nanocrystalline structure in this layer. The hardness of the modified layer decreases with the increasing distance from the surface exposure. The hardness of the surface layer is more than twice the hardness of cast silumin. Durability of silumin treated with a high intensity electron beam is ≈ 1, 2 times as much as the wear resistance of the cast material.

  14. Simulation of beam-induced plasma for the mitigation of beam-beam effects

    SciTech Connect

    Ma, J.; Wang, G.; Samulyak, R.; Yu, K.; Litvinenko, V.

    2015-05-03

    One of the main challenges in the increase of luminosity of circular colliders is the control of the beam-beam effect. In the process of exploring beam-beam mitigation methods using plasma, we evaluated the possibility of plasma generation via ionization of neutral gas by proton beams, and performed highly resolved simulations of the beam-plasma interaction using SPACE, a 3D electromagnetic particle-in-cell code. The process of plasma generation is modelled using experimentally measured cross-section coefficients and a plasma recombination model that takes into account the presence of neutral gas and beam-induced electromagnetic fields. Numerically simulated plasma oscillations are consistent with theoretical analysis. In the beam-plasma interaction process, high-density neutral gas reduces the mean free path of plasma electrons and their acceleration. A numerical model for the drift speed as a limit of plasma electron velocity was developed. Simulations demonstrate a significant reduction of the beam electric field in the presence of plasma. Preliminary simulations using fully-ionized plasma have also been performed and compared with the case of beam-induced plasma.

  15. Ion beam neutralization using three-dimensional electron confinement by surface modification of magnetic poles

    NASA Astrophysics Data System (ADS)

    Nicolaescu, Dan; Sakai, Shigeki; Gotoh, Yasuhito; Ishikawa, Junzo

    2011-07-01

    Advanced implantation systems used for semiconductor processing require transportation of quasi-parallel ion beams, which have low energy (11B+, 31P+,75As+, Eion=200-1000 eV). Divergence of the ion beam due to space charge effects can be compensated through injection of electrons into different regions of the ion beam. The present study shows that electron confinement takes place in regions of strong magnetic field such as collimator magnet provided with surface mirror magnetic fields and that divergence of the ion beam passing through such regions is largely reduced. Modeling results have been obtained using Opera3D/Tosca/Scala. Electrons may be provided by collision between ions and residual gas molecules or may be injected by field emitter arrays. The size of surface magnets is chosen such as not to disturb ion beam collimation, making the approach compatible with ion beam systems. Surface magnets may form thin magnetic layers with thickness h=0.5 mm or less. Conditions for spacing of surface magnet arrays for optimal electron confinement are outlined.

  16. Morphological and structural modifications of multiwalled carbon nanotubes by electron beam irradiation

    NASA Astrophysics Data System (ADS)

    Elsehly, Emad M.; Chechenin, N. G.; Makunin, A. V.; Motaweh, H. A.

    2016-10-01

    Effects of electron beam irradiation on a morphology and structure of multiwalled carbon nanotubes sample in a normal imaging regime of a scanning electron microscope (SEM) were investigated. Direct SEM observations give evidence that irradiation by electron beam in SEM eliminates morphological unevenness, in the form of round spots of white contrast, on the surface of carbon nanotubes (CNTs) and makes the tubes thinner. Electron dispersive analysis and Raman spectroscopy are used to explore the origin and nature of these spots. From this analysis we found that e-beam irradiation improves the CNTs graphitization. The synergy of thermal heating and ionization produced by the irradiation are discussed as possible mechanisms of the observed effects.

  17. Low-damage atomic layer modification of self-assembled monolayer using neutral beam process

    NASA Astrophysics Data System (ADS)

    Ishikawa, Yasushi; Samukawa, Seiji; Ishida, Takao

    2006-09-01

    Damage-free surface nitridation of terphenyl methanethiol self-assembled monolayers (TP1-SAMs) was investigated using a novel low-energy N2 neutral beam (NB) irradiation technique. When a conventional inductively coupled plasma process was used, x-ray photoelectron spectra confirmed that the TP1-SAM was quickly broken because ions or ultraviolet (UV) photons enhance the surface decomposition and molecular desorption. Conversely, with the N2 NB radiation process, which is free of ions and UV photons, there was little difference in the atomic ratios of x-ray photoelectron spectra before and after NB irradiation. These results suggest that low-damage surface modification is possible through the authors' NB technique.

  18. OBSERVATION OF STRONG - STRONG AND OTHER BEAM - BEAM EFFECTS IN RHIC.

    SciTech Connect

    Fischer, W; Brennan, J M; Cameron, P; Connolly, R; Montag, C; Peggs, S; Pilat, F; Ptitsyn, V; Tepikian, S; Trbojevic, D; Van Zeijts, J

    2003-05-12

    RHIC is currently the only hadron collider in which strong-strong beam-beam effects can be seen. For the first time, coherent beam-beam modes were observed in a bunched beam hadron collider. Other beam-beam effects in RHIC were observed in operation and in dedicated experiments with gold ions, deuterons and protons. Observations include measurements of beam-beam induced tune shifts, lifetime and emittance growth measurements with and without beam-beam interaction, and background rates as a function of tunes. During ramps unequal radio frequencies in the two rings cause the crossing points to move longitudinally. Thus bunches experience beam-beam interactions only in intervals and the tunes are modulated. In this article we summarize the most important beam-beam observations made so far.

  19. Efficient modification of floral traits by heavy-ion beam irradiation on transgenic Torenia.

    PubMed

    Ohtsubo, Norihiro; Sasaki, Katsutomo; Aida, Ryutaro; Ryuto, Hiromichi; Ichida, Hiroyuki; Hayashi, Yoriko; Abe, Tomoko

    2012-01-01

    While heavy-ion beam irradiation is becoming popular technology for mutation breeding in Japan, the combination with genetic manipulation makes it more convenient to create greater variation in plant phenotypes. We have succeeded in producing over 200 varieties of transgenic torenia (Torenia fournieri Lind.) from over 2,400 regenerated plants by this procedure in only 2 years. Mutant phenotypes were observed mainly in flowers and showed wide variation in colour and shape. Higher mutation rates in the transgenics compared to those in wild type indicate the synergistic effect of genetic manipulation and heavy-ion beam irradiation, which might be advantageous to create greater variation in floral traits.

  20. Analysis and modification of blue sapphires from Rwanda by ion beam techniques

    NASA Astrophysics Data System (ADS)

    Bootkul, D.; Chaiwai, C.; Tippawan, U.; Wanthanachaisaeng, B.; Intarasiri, S.

    2015-12-01

    Blue sapphire is categorised in a corundum (Al2O3) group. The gems of this group are always amazed by their beauties and thus having high value. In this study, blue sapphires from Rwanda, recently came to Thai gemstone industry, are chosen for investigations. On one hand, we have applied Particle Induced X-ray Emission (PIXE), which is a highly sensitive and precise analytical technique that can be used to identify and quantify trace elements, for chemical analysis of the sapphires. Here we have found that the major element of blue sapphires from Rwanda is Al with trace elements such as Fe, Ti, Cr, Ga and Mg as are commonly found in normal blue sapphire. On the other hand, we have applied low and medium ion implantations for color improvement of the sapphire. It seems that a high amount of energy transferring during cascade collisions have altered the gems properties. We have clearly seen that the blue color of the sapphires have been intensified after nitrogen ion bombardment. In addition, the gems were also having more transparent and luster. The UV-Vis-NIR measurement detected the modification of their absorption properties, implying of the blue color increasing. Here the mechanism of these modifications is postulated and reported. In any point of view, the bombardment by using nitrogen ion beam is a promising technique for quality improvement of the blue sapphire from Rwanda.

  1. A shape-modification strategy of electron-beam direct writing considering circuit performance in LSI interconnects

    NASA Astrophysics Data System (ADS)

    Midoh, Yoshihiro; Osaki, Atsushi; Nakamae, Koji

    2014-03-01

    As the feature size of LSI shrinks, the cost of mask manufacturing and turn-around-time continue to increase. Maskless lithography using electron beam direct writing (EBDW) technology attracts attention. On the other hands, with continuous scaling and the introduction of low-k dielectrics in Cu interconnect technology, reliability degradation caused by time-dependent dielectric breakdown (TDDB) and electromigration has become important issues. Therefore, EBDW in backend process is needed to ensure superior patterning quality and reliability using high-accuracy proximity effect correction (PEC). We have already proposed a dose-modification strategy of EBDW considering reliability for TDDB degradation. In this paper, furthermore, we propose a shape-modification strategy of EBDW considering circuit performance in LSI interconnects for improving EB drawing throughput. We use effectively patterns with rounded corner in order to reduce EB shots increased by PEC and avoid the local high current density at the corner of metal lines. We applied the proposed method to a microprocessor layout synthesized with the Nangate 45nm Open Cell Library. As a result, the drawn pattern by corner rounding and coarse dose adjustment achieved 2.5% higher throughput than that by no corner rounding and fine dose adjustment.

  2. Beam Breakup Effects in Dielectric Based Accelerators

    SciTech Connect

    Schoessow, P.; Kanareykin, A.; Jing, C.; Kustov, A.; Altmark, A.; Power, J. G.; Gai, W.

    2009-01-22

    The dynamics of the beam in structure-based wakefield accelerators leads to beam stability issues not ordinarily found in other machines. In particular, the high current drive beam in an efficient wakefield accelerator loses a large fraction of its energy in the decelerator structure, resulting in physical emittance growth, increased energy spread, and the possibility of head-tail instability for an off axis beam, all of which can lead to severe reduction of beam intensity. Beam breakup (BBU) effects resulting from parasitic wakefields provide a potentially serious limitation to the performance of dielectric structure based wakefield accelerators as well. We report on experimental and numerical investigation of BBU and its mitigation. The experimental program focuses on BBU measurements at the AWA facility in a number of high gradient and high transformer ratio wakefield devices. New pickup-based beam diagnostics will provide methods for studying parasitic wakefields that are currently unavailable. The numerical part of this research is based on a particle-Green's function beam breakup code we are developing that allows rapid, efficient simulation of beam breakup effects in advanced linear accelerators. The goal of this work is to be able to compare the results of detailed experimental measurements with the accurate numerical results and to design an external FODO channel for the control of the beam in the presence of strong transverse wakefields.

  3. Chemical and structural effects of base modifications in messenger RNA

    NASA Astrophysics Data System (ADS)

    Harcourt, Emily M.; Kietrys, Anna M.; Kool, Eric T.

    2017-01-01

    A growing number of nucleobase modifications in messenger RNA have been revealed through advances in detection and RNA sequencing. Although some of the biochemical pathways that involve modified bases have been identified, research into the world of RNA modification -- the epitranscriptome -- is still in an early phase. A variety of chemical tools are being used to characterize base modifications, and the structural effects of known base modifications on RNA pairing, thermodynamics and folding are being determined in relation to their putative biological roles.

  4. Electron beam effects in a UV FEL

    SciTech Connect

    Wong, R.K.; Blau, J.; Colson, W.B.

    1995-12-31

    At the Continuous Electron Beam Accelerator Facility (CEBAF), a free electron laser (FEL) is designed to produce ultraviolet (UV) light. A four-dimensional FEL simulation studies the effects of betatron oscillations, external focusing, and longitudinal pulse compression of the electron beam on the FEL performance.

  5. Compensation of the beam-beam effect in proton-proton colliders

    SciTech Connect

    Tsyganov, E.; Meinke, R.; Nexsen, W.; Zinchenko, A.

    1993-10-01

    Compensation of the beam-beam effect in high-energy proton-proton colliders using a low-energy electron beam is proposed. It is concluded that such compensation looks feasible. Requirements for such a device are formulated.

  6. Disruption effects on the beam size measurement

    SciTech Connect

    Raimondi, P.; Decker, F.J.; Chen, P.

    1995-06-01

    At the SLC Final Focus with higher currents and smaller beam sizes, the disruption parameter D{sub y} is close to one and so the pinch effect should produce a luminosity enhancement. Since a flat beam-beam function is fit to deflection scan data to measure the beam size, disruption can affect the measurement. Here the authors discuss the quantitative effects of disruption for typical SLC beam parameters. With 3.5 10{sup 10} particles per pulse, bunch length of 0.8 mm and beam sizes of 2.1 {mu}m horizontally and 0.55 {mu}m vertically, the measured vertical size can be as much as 25% bigger than the real one. Furthermore during the collision the spot size actually decrease, producing an enhancement factor H{sub D} of about 1.25. This would yield to a true luminosity which is 1.6 times that which is estimated from the beam-beam deflection fit.

  7. Enhancement of the magnetic interfacial exchange energy at a specific interface in NiFe/CoO/Co trilayer thin films via ion-beam modification

    SciTech Connect

    Cortie, D. L.; Ting, Y.-W.; Chen, P.-S.; Lin, K.-W.; Tan, X.; Klose, F.

    2014-02-21

    A series of ferromagnetic Ni{sub 80}Fe{sub 20}(55 nm)/antiferromagnetic CoO (25 to 200 nm)/ferromagnetic Co (55 nm)/SiO{sub 2}(substrate) trilayer thin films were fabricated by ion-beam assisted deposition in order to understand the role of ion beam modification on the interfacial and interlayer coupling. The microstructural study using transmission electron microscopy, X-ray reflectometry, and polarised neutron reflectometry showed that ion-beam modification during the deposition process led to an oxygen-rich Co/CoO nanocomposite interface region at the bottom layer. This interface caused a high exchange bias field for the ferromagnetic cobalt. However, the exchange bias for top permalloy ferromagnet remained low, in line with expectations from the literature for the typical interfacial energy. This suggest that the ion-beam enhancement of the magnetic exchange bias is localized to the Co/CoO interface where local microstructural effects provide the dominant mechanism.

  8. Negative propagation effect in nonparaxial Airy beams.

    PubMed

    Vaveliuk, Pablo; Martinez-Matos, Oscar

    2012-11-19

    Negative propagation is an unusual effect concerning the local sign change in the Poynting vector components of an optical beam under free propagation. We report this effect for finite-energy Airy beams in a subwavelength nonparaxial regime. This effect is due to a coupling process between propagating and evanescent plane waves forming the beam in the spectral domain and it is demonstrated for a single TE or TM mode. This is contrary to what happens for vector Bessel beams and vector X-waves, for which a complex superposition of TE and TM modes is mandatory. We also show that evanescent waves cannot contribute to the energy flux density by themselves such that a pure evanescent Airy beam is not physically realizable. The break of the shape-preserving and diffraction-free properties of Airy beams in a nonparaxial regime is exclusively caused by the propagating waves. The negative propagation effect in subwavelength nonparaxial Airy beams opens new capabilities in optical traps and tweezers, optical detection of invisibility cloacks and selective on-chip manipulation of nanoparticles.

  9. A modification of the laser detonation-type hyperthermal oxygen atom beam source for a long-term operation.

    PubMed

    Kinoshita, Hiroshi; Yamamoto, Shunsuke; Yatani, Hideaki; Ohmae, Nobuo

    2008-07-01

    It has been an impedimental problem, for the laser detonation-type atom beam generator, that a poppet in the pulsed supersonic valve is rapidly eroded by the irradiation of powerful laser light and high temperature plasma. In order to operate the atom beam source for a long duration, a modification was made to hide the poppet from direct irradiation of laser and plasma. The alteration of device configuration resulted in great improvement in endurance of poppet more than 300,000 repetitions. Morphology of a polyimide film exposed to approximately 200,000 pulses of hyperthermal oxygen atom beam showed a shaglike carpet structure, which is a characteristic to that exposed to energetic oxygen atoms. A flux of the oxygen atom beam was estimated to be 5x10(14) atoms/cm2/pulse at a location of 30 cm away from the nozzle throat.

  10. A modification of the laser detonation-type hyperthermal oxygen atom beam source for a long-term operation

    NASA Astrophysics Data System (ADS)

    Kinoshita, Hiroshi; Yamamoto, Shunsuke; Yatani, Hideaki; Ohmae, Nobuo

    2008-07-01

    It has been an impedimental problem, for the laser detonation-type atom beam generator, that a poppet in the pulsed supersonic valve is rapidly eroded by the irradiation of powerful laser light and high temperature plasma. In order to operate the atom beam source for a long duration, a modification was made to hide the poppet from direct irradiation of laser and plasma. The alteration of device configuration resulted in great improvement in endurance of poppet more than 300 000 repetitions. Morphology of a polyimide film exposed to approximately 200 000 pulses of hyperthermal oxygen atom beam showed a shaglike carpet structure, which is a characteristic to that exposed to energetic oxygen atoms. A flux of the oxygen atom beam was estimated to be 5×1014 atoms/cm2/pulse at a location of 30 cm away from the nozzle throat.

  11. Effects of dipole magnet inhomogeneities on the beam ellipsoid

    SciTech Connect

    Tsoupas, N.; Colman, J.; Levine, M.; McKenzie-Wilson, R.; Ward, T.; Grand, P.

    1986-01-01

    The RAYTRACE computer code has been modified to accept magnetic fields measured in the median plane of a dipole magnet. This modification allows one to study the effects of a non-ideal dipole magnet on the beam ellipsoid (as defined by the TRANSPORT code manual). The effects on the beam ellipsoid are due to: field inhomogeneities in the interior region of the dipole, and discrepancies from design conditions of the magnetic field values in the fringe field region. The results of the RAYTRACE code calculations based on experimentally measured fields will be compared with the results derived using both an ideal (no inhomogeneities) dipole with SCOFF boundaries and an ideal dipole with perfect (according to design) fringe fields.

  12. High power ion beam (HPIB) modification of one- and two-layer metal surfaces

    SciTech Connect

    Renk, T.J.; Sorensen, N.R.; Senft, D.C.; Buchheit, R.G.; Thompson, M.O.; Grabowski, K.S.

    1997-11-01

    Intense pulsed high-power ion beams have been demonstrated to produce enhanced surface properties by changes in microstructure caused by rapid heating and cooling of the surface. Additional improvements can be effected by the mixing of a previously deposited thin-film layer (surface alloying or ion beam mixing) into any number of substrate materials. The authors have conducted surface treatment and alloying experiments with Al, Fe, and Ti-based metals on the RHEPP-1 accelerator (0.8 MV, 20 W, 80 ns FHWM, up to 1 Hz repetition rate) at Sandia National Laboratories. Ions are generated by the MAP gas-breakdown active anode, which can yield a number of different beam species including H, N, and Xe, depending upon the injected gas. Enhanced hardness and wear resistance have been produced by treatment of 440C stainless steel, and by the mixing of Pt into Ti-6Al-4V alloy. Mixing of a thin-film Hf layer into Al 6061-T6 alloy (Al-1.0Mg-0.6Si) has improved its corrosion resistance by as much as four orders of magnitude in electrochemical testing, compared with untreated and uncoated Al6061. Experiments are ongoing to further understand the microstructural basis for these surface improvements.

  13. Effect of site-specific modification on restriction endonucleases and DNA modification methyltransferases.

    PubMed Central

    McClelland, M; Nelson, M; Raschke, E

    1994-01-01

    Restriction endonucleases have site-specific interactions with DNA that can often be inhibited by site-specific DNA methylation and other site-specific DNA modifications. However, such inhibition cannot generally be predicted. The empirically acquired data on these effects are tabulated for over 320 restriction endonucleases. In addition, a table of known site-specific DNA modification methyltransferases and their specificities is presented along with EMBL database accession numbers for cloned genes. PMID:7937074

  14. Modification of the titanium alloy surface in electroexplosive alloying with boron carbide and subsequent electron-beam treatment

    SciTech Connect

    Gromov, Victor E. Budovskikh, Evgeniy A. Bashchenko, Lyudmila P. Kobzareva, Tatyana Yu. Semin, Alexander P.; Ivanov, Yurii F.; Wang, Xinli

    2015-10-27

    The modification of the VT6 titanium alloy surface in electroexplosion alloying with plasma being formed in titanium foil with a weighed powder of boron carbide with subsequent irradiation by a pulsed electron beam has been carried out. An electroexplosive alloying zone of a thickness up to 50 μm with a gradient structure is found to form. The subsequent electron-beam treatment of the alloying zone results in smoothing of the alloying surface and is accompanied by the formation of the multilayer structure with alternating layers of various alloying degree at a depth of 30 μm.

  15. EFFECTS OF TRANSFERSE BEAM SIZE IN BEAM POSITIONS MONITORS

    SciTech Connect

    S.S. KURENNOY

    2001-06-01

    The fields produced by a long beam with a given transverse charge distribution in a homogeneous vacuum chamber are studied. Signals induced by the displaced finite-size beam on electrodes of a beam position monitor (BPM) are calculated and compared to those from a pencil beam. The non-linearities and corrections to BPM signals due to a finite transverse beam size are calculated for an arbitrary chamber cross section. Simple analytical expressions are given for a few particular transverse distributions of the beam current in a circular or rectangular chamber. Of particular interest is a general proof that in an arbitrary homogeneous chamber the beam-size corrections vanish for any axisymmetric beam current distribution.

  16. Beam-beam and electron cloud effects in CEPC/FCC-ee

    NASA Astrophysics Data System (ADS)

    Ohmi, Kazuhito

    2016-11-01

    We discuss beam dynamics issues in CEPC/FCC-ee, especially focusing on the beam-beam and electron cloud effects. Beamstrahlung is strong in extreme high energy collision such as Higgs and top factory. Beam-beam simulations considering beamstrahlung are now ready. Several points of beam-beam effects for FCC-ee are presented. Electron cloud effects are serious for high current positron machine, especially in Z factory that many bunches are stored. Analytical estimate for threshold of electron density and electron build-up for CEPC are presented.

  17. Effects of different substrate surface modifications on the epitaxial ZnO/Si

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Jin, Changlian; Zhan, Huahan; Chen, Xiaohang; Xu, Fuchun; Zhou, Yinghui; Wang, Huiqiong; Kang, Junyong

    2013-09-01

    To produce high quality ZnO/Si for the applications in short wavelength optoelectronic devices, the effects of different silicon surface modifications on the overgrown ZnO thin film were investigated. Samples were grown by a plasma assistant molecular beam epitaxy at room temperature, avoiding the oxidation of the Si surface and the thermal stress caused by difference of the thermal expansion coefficients between ZnO and silicon. Different modifications on the Si(100) substrate surface including nitridation, oxidation, and depositions of Mg and Zn, were employed. The effects on the overgrown ZnO layers and the interlayer SiOx were investigated by atomic force microscopy, photoluminescence, X-ray diffraction and auger depth electron spectroscopy. All the modifications were effective in different degrees at reducing the SiOx amorphous layer. However, different mechanisms resulted in distinct performance in crystal structure and optical property.

  18. Chemical and structural effects of base modifications in messenger RNA

    PubMed Central

    Harcourt, Emily M.; Kietrys, Anna M.; Kool, Eric T.

    2017-01-01

    A growing number of nucleobase modifications in messenger RNA have been revealed through advances in detection and RNA sequencing. Although some of the biochemical pathways that involve modified bases have been identified, research into the world of RNA modification — the epitranscriptome — is still in an early phase. A variety of chemical tools are being used to characterize base modifications, and the structural effects of known base modifications on RNA pairing, thermodynamics and folding are being determined in relation to their putative biological roles. PMID:28102265

  19. Electron gun jitter effects on beam bunching

    SciTech Connect

    Liu, M. S.; Iqbal, M.

    2014-02-15

    For routine operation of Beijing Electron Positron Collider II (BEPCII) linac, many factors may affect the beam bunching process directly or indirectly. We present the measurements and analyses of the gun timing jitter, gun high voltage jitter, and beam energy at the exit of the standard acceleration section of the linac quantitatively. Almost 80 mV and more than 200 ps of gun high voltage and time jitters have ever been measured, respectively. It was analyzed that the gun timing jitter produced severe effects on beam energy than the gun high voltage jitter, if the timing jitter exceeded 100 ps which eventually deteriorates both the beam performance and the injection rate to the storage ring.

  20. Experimental Studies of Compensation of Beam-Beam Effects with Tevatron Electron Lenses

    SciTech Connect

    Shiltsev, V.; Alexahin, Yu.; Bishofberger, Kip; Kamerdzhiev, V.; Parkhomchuk, V.; Reva, V.; Solyak, N.; Wildman, D.; Zhang, X.-L.; Zimmermann, F.; /Fermilab /Los Alamos /Novosibirsk, IYF /CERN

    2008-02-01

    Applying the space-charge forces of a low-energy electron beam can lead to a significant improvement of the beam-particle lifetime limit arising from the beam-beam interaction in a high-energy collider [1]. In this article we present the results of various beam experiments with 'electron lenses', novel instruments developed for the beam-beam compensation at the Tevatron, which collides 980-GeV proton and antiproton beams. We study the dependencies of the particle betatron tunes on the electron beam current, energy and position; we explore the effects of electron-beam imperfections and noises; and we quantify the improvements of the high-energy beam intensity and the collider luminosity lifetime obtained by the action of the Tevatron Electron Lenses.

  1. Ion-beam-induced modifications in the structural and electrical properties of copper oxide selenite nanowires

    NASA Astrophysics Data System (ADS)

    Rana, Pallavi; Chauhan, R. P.

    2015-04-01

    Irradiation with swift heavy ions (SHIs) with energy in the MeV range is a unique tool for engineering the properties of materials. In this context, the objective of the present work is to study the conduction of charge carriers in pre- and post-ion-irradiated semiconducting nanowires. Copper oxide selenite nanowires were synthesized using a template-assisted electrodeposition technique from an aqueous solution of 0.8 M CuSO4·5H2O and 8 mM SeO2. The synthesized nanowires were observed to have a monoclinic structure with linear I-V characteristics (IVC). The effect of irradiation with 160 MeV Ni+12 ions on the properties of the copper oxide selenite nanowires was investigated for fluences varying from 1011 to 1013 ions/cm2. XRD spectra confirmed no change in the phase of the swift-heavy-ion-irradiated nanowires, but a modification in the orientation of the planes was observed that depended on the ion fluence. The electrical resistivity of the semiconducting nanowires also varied with the ion fluence. Simultaneous irradiation-induced modifications to the electro-chemical potential gradient and the granular properties of the material may have been the origin of the alteration in the structural and electrical properties of the nanowires.

  2. Effect of crossed beams irradiation on parametric instabilities

    SciTech Connect

    Labaune, C., Ecole Polytechnique, France

    1998-04-27

    Modification of the growth of scattering processes in the case of multiple beam irradiation compared to single beam irradiation has been investigated in a preformed plasma using Thomson scattrering of a short wavelength probe beam, and spectral and temporal analysis of reflected and transmitted light. First observations of the reduction of the amplitude of ion acoustic waves associated with stimulated Brillouin scattering, amplification of the amplitude of electron plasma waves associated with stimulated Raman scattering, and transfer of energy between crqssing beams with same frequency in a flowing plasma under crossed beam irradiation are reported.

  3. Propagation of charge-neutral beams in space - Modifications when negative ions are present

    NASA Technical Reports Server (NTRS)

    Winglee, R. M.; Pritchett, P. L.

    1987-01-01

    Two-dimensional (three velocity component) electrostatic simulations are used to investigate the properties of a charge-neutral beam consisting of H(+), H(-), and electrons which will be used in the Beams on Rockets (BEAR) experiment to be launched in late 1987 or early 1988. For cross-field injection and beam densities much greater than the ambient plasma density, the beam splits into two approximately charge-neutral beams: a H(+)-e(-) beam that propagates down the field lines and a H(+)-H(-) beam that propagates at nearly the initial beam velocity on time scales less than the ion gyroperiod. Because of this splitting, space-charge oscillations are induced in the H(+)-H(-) component, which lead to its breakup. At lower beam densities, particularly when the beam electron density is less than about the density of the ambient plasma, the ambient plasma response reduces the space-charge fields as the beam splits and the space-charge oscillations are suppressed.

  4. Ion beam irradiation of cuprate high-temperature superconductors: Systematic modification of the electrical properties and fabrication of nanopatterns

    NASA Astrophysics Data System (ADS)

    Lang, W.; Marksteiner, M.; Bodea, M. A.; Siraj, K.; Pedarnig, J. D.; Kolarova, R.; Bauer, P.; Haselgrübler, K.; Hasenfuss, C.; Beinik, I.; Teichert, C.

    2012-02-01

    Irradiation of thin films of the cuprate high-temperature superconductor YBaCuO (YBCO) with 75 keV He ions leads to an exponential increase of the resistivity and a non-linear decrease of the critical temperature. At a fluence above 3×1015 cm the material becomes semiconducting. Calculations of ion-target interactions using the MARLOWE code indicated that these effects are due to the creation of point defects, primarily by displacing oxygen atoms, and that the lateral broadening of the ion's collision cascades is smaller than 10 nm in a 100 nm thick YBCO film. Irradiating a YBCO film through a silicon stencil mask with minimum aperture of 125 nm placed on top of the sample results in a local modification of its electrical properties. We demonstrate that this technique can be used to produce patterns of sub-100 nm size, visualized by scanning electron microscopy and conductive atomic force microscopy. This simple one-step process does not require the removal of target material and avoids the contamination problems associated with chemical etching and focused ion beam techniques.

  5. Magnetic modification at sub-surface of FeRh bulk by energetic ion beam irradiation

    SciTech Connect

    Koide, T.; Iwase, A.; Uno, H.; Sakane, H.; Sakamaki, M.; Amemiya, K.; Matsui, T.

    2015-05-07

    Ferromagnetic layered structure has been made at sub-surface of the antiferromagnetic FeRh bulk samples by high energy He ion beam irradiation. In accordance with the Transport of Ions in Matter simulation, such ion beam can effectively deposit the elastic collision energy in several μm regions in the depth from the surface. Measurement with a superconducting quantum interference device reveals the irradiated samples to be ferromagnetic. Assuming that only the part the energy deposited can be modified to be ferromagnetic, the corresponding irradiation induced magnetization is consistent with the data that we previously reported. On the other hand, the X-ray magnetic circular dichroism (XMCD) spectra for the irradiated samples are totally unchanged as those for the unirradiated samples. Since XMCD signal in total emission yield method is considered to be surface sensitive with a typical probing depth of several nm, the surface magnetic state is maintained to be antiferromagnetic. By utilizing these phenomena, three-dimensional magnetic patterning of FeRh can be realized, which may potentially be used for future magnetic exchange device application such as nano-scale sensors and memories.

  6. Magnetic modification at sub-surface of FeRh bulk by energetic ion beam irradiation

    NASA Astrophysics Data System (ADS)

    Koide, T.; Uno, H.; Sakane, H.; Sakamaki, M.; Amemiya, K.; Iwase, A.; Matsui, T.

    2015-05-01

    Ferromagnetic layered structure has been made at sub-surface of the antiferromagnetic FeRh bulk samples by high energy He ion beam irradiation. In accordance with the Transport of Ions in Matter simulation, such ion beam can effectively deposit the elastic collision energy in several μm regions in the depth from the surface. Measurement with a superconducting quantum interference device reveals the irradiated samples to be ferromagnetic. Assuming that only the part the energy deposited can be modified to be ferromagnetic, the corresponding irradiation induced magnetization is consistent with the data that we previously reported. On the other hand, the X-ray magnetic circular dichroism (XMCD) spectra for the irradiated samples are totally unchanged as those for the unirradiated samples. Since XMCD signal in total emission yield method is considered to be surface sensitive with a typical probing depth of several nm, the surface magnetic state is maintained to be antiferromagnetic. By utilizing these phenomena, three-dimensional magnetic patterning of FeRh can be realized, which may potentially be used for future magnetic exchange device application such as nano-scale sensors and memories.

  7. Modelling of local modification of chemical composition generated by artificial beam injection in stratosphere

    NASA Astrophysics Data System (ADS)

    Oraevsky, V.; Ruzhin, Y.; Borisov, N.; Nesterov, I.

    The physical/chemical processes that are occurring in the middle atmosphere, are very complex and knowledge of them are obviously poor. At the same time the understanding of these processes is necessary, in particular, for an explanation of ozone dynamics and influencing on it of the different factors, for example, impurities of anthropogenous nature. In the present activity the capability of creation of noticeable local disturbances of concentration of ozone and other minor neutral components in stratosphere si theoretically modeled for artificial injection of high energy electron beams from a high-altitude balloon. With the help of numerical simulations (31 reactions) the quantitative assessments of expected effect for different altitudes (range of 35-45 km) and different values of eddy diffusion factor are obtained and presented. It is shown the considered means has a number of advantages in comparison with method of artificial action on stratosphere ozone by VHF generation of ionized area in atmosphere. At first, it is much more friend and precisely to conduct diagnostic of effect, which one arises due to "in -situ" onboard measurements from a balloon. Secondly, it is possible to inject any impurities (freons) to study directly in stratosphere their affect on ozone. The method, tendered here, requires considerably smaller material costs and can be realized already now. Based on presented modeling results it is important to note that in our method an integral disturbance in stratosphere (full quantity of created molecules of ozone, nitric oxides etc.) is rather insignificant, as the effect is localized near to injected electron beam. Therefore there is no hazard of deposition of unchecked injury to environment. At the same time realization of tendered experiment will allow essentially to deepen our representations about composite physical/chemical processes occurring in middle atmosphere (stratosphere).

  8. Effect Modification and Interaction Terms: It Takes Two to Tango.

    PubMed

    Jupiter, Daniel C

    2016-01-01

    In this Investigators' Corner I look more deeply into the previously discussed phenomenon of effect modification. I revisit an explanation and examples of the phenomenon and then examine how to account for it statistically. Specifically, I show, in detail, how to write a regression equation that includes interaction terms that account for the effect modification. Finally, I look at interpretation of regression coefficients both with and without the presence of effect modification, and the associated interaction terms. Copyright © 2016 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

  9. Fluorine-ion-beam modification of magnetic properties of thin GaMnAs films

    SciTech Connect

    Mello, S. L. A. E-mail: mms@if.ufrj.br; Sant'Anna, M. M. E-mail: mms@if.ufrj.br Codeço, C. F. S.; Dong, S. N.; Liu, X.; Furdyna, J. K. E-mail: mms@if.ufrj.br; Yoo, T.

    2015-05-07

    Magnetic and electrical transport properties of fluorine-ion-beam irradiated GaMnAs films were studied as a function of ion fluence and energy of impinging ions. The different nature of defects created by ions of low- and high-energies is explored in this work by means of transport and magnetization measurements. Our results show that the saturation magnetization of the irradiated samples is suppressed as the ion fluence is increased. Interestingly, however, the same effect is not observed in the case of critical temperature, which remains nearly the same for irradiated and non-irradiated samples measured by superconducting quantum interference device. Magnetotransport measurements appear to provide more reliable results regarding the critical temperature, since they are consistent with the ion-irradiation-induced disorder in the GaMnAs film, quantified here as the increase of the resistivity. We discuss this behavior based on the inhomogeneity of damages caused by the irradiation process.

  10. Increasing Extracted Beam Current Density in Ion Thrusters through Plasma Potential Modification

    NASA Astrophysics Data System (ADS)

    Arthur, Neil; Foster, John

    2015-09-01

    A gridded ion thruster's maximum extractable beam current is determined by the space charge limit. The classical formulation does not take into account finite ion drift into the acceleration gap. It can be shown that extractable beam current can be increased beyond the conventional Child-Langmuir law if the ions enter the gap at a finite drift speed. In this work, ion drift in a 10 cm thruster is varied by adjusting the plasma potential relative to the potential at the extraction plane. Internal plasma potential variations are achieved using a novel approach involving biasing the magnetic cusps. Ion flow variations are assessed using simulated beam extraction in conjunction with a retarding potential analyzer. Ion beam current density changes at a given total beam voltage in full beam extraction tests are characterized as a function of induced ion drift velocity as well.

  11. Build-up modification of commercial diodes for entrance dose measurements in 'higher energy' photon beams.

    PubMed

    Georg, D; De Ost, B; Hoornaert, M T; Pilette, P; Van Dam, J; Van Dycke, M; Huyskens, D

    1999-06-01

    Several commercially available p-type diodes do not provide sufficient build-up for in-vivo dosimetry in 'higher' energy photon beams, and only limited information could be found in the literature describing the correction factor variation and/or the achievable accuracy for in-vivo dosimetry methods in this energy range. The first aim of this study is to assess and analyze the variation of diode correction factors for entrance dose measurements at higher photon energies. In a second step the total build up thickness of the diode has been modified in order to minimize the correction factor variation. Diode correction factors accounting for non-reference conditions (field size, source surface distance, tray, wedge, and block) are determined in 18-25 MV photon beams provided by different treatment units for Scanditronix p-type diodes recommended for higher energy photon beams: old type and new type EDP-20, and EDP-30 diodes. Hemispherical build-up caps of different materials (copper, iron, lead) are used to increase the total build-up thickness. Perturbation effects with and without additional build-up caps are assessed for the three diode types. For unmodified diodes field size correction factors (C(FS)) vary between 1.7% and 6%, dependent on diode type and treatment unit. For example, for an old type EDP-20 the C(FS) variation at 18 MV is much higher on a GE linac (5%) as compared to the Philips machine (1.7%). Depending on diode type, this variation can be reduced to 1-2% when adding additional build-up. The variation of source to surface distance correction factors is almost independent of build-up thickness. By adding additional build-up the influence of trays and blocks can be almost eliminated. The correction factor variation of unmodified diodes reflects the variation of the electron contamination with treatment geometry. A total build-up thickness of 30 mm is found to be the 'best compromise' for the three types of diodes investigated when measuring entrance

  12. Simulations and Experiments of Beam-Beam Effects in e+e- Storage Rings

    SciTech Connect

    Cai, Y.; Seeman, J.; Kozanecki, W.; Ohmi, K.; Tawada, M.; /KEK, Tsukuba

    2005-05-16

    Over the past decade, extensive simulations of beam-beam effects in e{sup +}e{sup -} colliders, based on the particle-in-cell method, were developed to explain many complex experimental observations. Recently, such simulations were used to predict the future luminosity performance of e{sup +}e{sup -} colliders. Some predictions have been proven to be correct in the existing accelerators. In this paper, many effects such as the beam-beam limit, crossing angle, parasitic collisions, betatron spectrum, and the beam-beam lifetime, will be directly compared between simulations and experiments.

  13. Implementation of depolarization due to beam-beam effects in the beam-beam interaction simulation tool GUINEA-PIG++

    NASA Astrophysics Data System (ADS)

    Rimbault, C.; Le Meur, G.; Blampuy, F.; Bambade, P.; Schulte, D.

    2009-12-01

    Depolarization is a new feature in the beam-beam simulation tool GUINEA-PIG++ (GP++). The results of this simulation are studied and compared with another beam-beam simulation tool, CAIN, considering different beam parameters for the International Linear Collider (ILC) with a centre-of-mass energy of 500 GeV.

  14. High luminosity operation, beam-beam effects and their compensation in Tevatron

    SciTech Connect

    Shiltsev, V.; /Fermilab

    2008-06-01

    Over the past 2 years the Tevatron peak luminosity steadily progressed and reached the level of 3.15 {center_dot} 10{sup 32} cm{sup -2} s{sup -1} which exceeds the Run II Upgrade goal. We discuss the collider performance, illustrate limitations and understanding of beam-beam effects and present experimental results of compensation of the beam-beam effects by electron lenses--a technique of great interest for the LHC.

  15. Simulations of coherent beam-beam effects with head-on compensation

    SciTech Connect

    White S.; Fischer, W.; Luo. Y.

    2012-05-20

    Electron lenses are under construction for installation in RHIC in order to mitigate the head-on beam-beam effects. This would allow operation with higher bunch intensity and result in a significant increase in luminosity. We report on recent strong-strong simulations and experiments that were carried out using the RHIC upgrade parameters to assess the impact of coherent beam-beam effects in the presence of head-on compensation.

  16. Lifetime and Tail Simulations for Beam-Beam Effects in PEP-II B Factory

    SciTech Connect

    Shatilov, D.N.; Zholents, A.A.

    1994-12-01

    A fast tracking technique for doing beam tail simulations has been applied to a study of beam-beam effects in the SLAC/LBL/LLNL PEP-II B Factory. In particular, the dependence of beam lifetime and particle density distribution due to vacuum pressure, damping times, machine nonlinearity and parasitic crossings has been analyzed. Effects of accidental orbit separation and dispersion function at the interaction point (IP) have also been considered.

  17. Modification of Ag containing photo-thermo-refractive glasses induced by electron-beam irradiation

    NASA Astrophysics Data System (ADS)

    Podsvirov, O. A.; Ignatiev, A. I.; Nashchekin, A. V.; Nikonorov, N. V.; Sidorov, A. I.; Tsekhomsky, V. A.; Usov, O. A.; Vostokov, A. V.

    2010-10-01

    We present the experimental investigation of formation and growth of Ag nanocrystals in silica photo-thermo-refractive glasses under the electron-beam irradiation and subsequent thermal treatment. The influence of electron irradiation fluence, current density and thermal treatment conditions on nanocrystal growth dynamic has been investigated. Theoretical models and computer simulation of main processes which take place during electron-beam irradiation are presented.

  18. Electron beam modification of anode materials for high-rate lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Park, Yiseul; Park, Jung Soo; Baek, Seong-Ho; Kim, Jae Hyun

    2015-11-01

    The rate capability of a Li4Ti5O12 (LTO)-based anode in a lithium ion battery can be easily improved by electron beam (EB) irradiation without the need for complicated synthetic procedures. The electrode prepared with EB-irradiated LTO at a 50 kGy dose has an enhanced rate capability while retaining a discharge capacity of 100 mAh g-1, even at the 20 C-rate. The effect of EB irradiation on the properties of the anode materials (i.e., LTO, poly(vinylidene fluoride) (PVDF), super P carbon) is examined in detail through systematic experiments. Both LTO and PVDF are affected by EB irradiation and dependent on the exposed electron dose, but super P is affected negligibly. EB irradiation partially reduces LTO with forming Tix+ (2 < x < 4) which is attributed to the enhanced electrical conductivity. EB irradiation causes dehydrofluorination and cross-linking in PVDF, resulting in the formation of carbon-carbon double bonds. The conjugated structure of PVDF is formed by the further dehydrofluorination during mixing with LTO via ball-milling, and this is accelerated in the presence of EB-PVDF. This conjugated structure enhances the electrical conductivity and is responsible for the improved rate capability.

  19. Scrape-off layer-induced beam density fluctuations and their effect on beam emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Moulton, D.; Marandet, Y.; Tamain, P.; Dif-Pradalier, G.

    2015-07-01

    A statistical model is presented to calculate the magnitude of beam density fluctuations generated by a turbulent scrape-off layer (SOL). It is shown that the SOL can induce neutral beam density fluctuations of a similar magnitude to the plasma density fluctuations in the core, potentially corrupting beam emission spectroscopy measurements. The degree of corruption is quantified by combining simulations of beam and plasma density fluctuations inside a simulated measurement window. A change in pitch angle from the separatrix to the measurement window is found to reduce the effect of beam fluctuations, whose largest effect is to significantly reduce the measured correlation time.

  20. Ion-beam-sputter modification of the surface morphology of biological implants

    NASA Technical Reports Server (NTRS)

    Weigand, A. J.; Banks, B. A.

    1977-01-01

    The surface chemistry and texture of materials used for biological implants may significantly influence their performance and biocompatibility. Recent interest in the microscopic control of implant surface texture has led to the evaluation of ion-beam sputtering as a potentially useful surface roughening technique. Ion sources, similar to electron-bombardment ion thrusters designed for propulsive applications, are used to roughen the surfaces of various biocompatible alloys or polymer materials. These materials are typically used for dental implants, orthopedic prostheses, vascular prostheses, and artificial heart components. Masking techniques and resulting surface textures are described along with progress concerning evaluation of the biological response to the ion-beam-sputtered surfaces.

  1. Ion beam sputter modification of the surface morphology of biological implants

    NASA Technical Reports Server (NTRS)

    Weigand, A. J.; Banks, B. A.

    1976-01-01

    The surface chemistry and texture of materials used for biological implants may significantly influence their performance and biocompatibility. Recent interest in the microscopic control of implant surface texture has led to the evaluation of ion beam sputtering as a potentially useful surface roughening technique. Ion sources, similar to electron bombardment ion thrusters designed for propulsive applications, are used to roughen the surfaces of various biocompatible alloys or polymer materials. These materials are typically used for dental implants, orthopedic prostheses, vascular prostheses, and artificial heart components. Masking techniques and resulting surface textures are described along with progress concerning evaluation of the biological response to the ion beam sputtered surfaces.

  2. Ion-beam-sputter modification of the surface morphology of biological implants

    NASA Technical Reports Server (NTRS)

    Weigand, A. J.; Banks, B. A.

    1977-01-01

    The surface chemistry and texture of materials used for biological implants may significantly influence their performance and biocompatibility. Recent interest in the microscopic control of implant surface texture has led to the evaluation of ion-beam sputtering as a potentially useful surface roughening technique. Ion sources, similar to electron-bombardment ion thrusters designed for propulsive applications, are used to roughen the surfaces of various biocompatible alloys or polymer materials. These materials are typically used for dental implants, orthopedic prostheses, vascular prostheses, and artificial heart components. Masking techniques and resulting surface textures are described along with progress concerning evaluation of the biological response to the ion-beam-sputtered surfaces.

  3. Modifications in the structural and optical properties of nanocrystalline CaWO4 induced by 8 MeV electron beam irradiation

    NASA Astrophysics Data System (ADS)

    Aloysius Sabu, N.; Priyanka, K. P.; Ganesh, Sanjeev; Varghese, Thomas

    2016-06-01

    In this article we report the post irradiation effects in the structural and optical properties of nanocrystalline calcium tungstate synthesized by chemical precipitation and heat treatment. The samples were subjected to different doses of high-energy electron beam obtained from an 8 MeV Microton. Investigations using X-ray diffraction, scanning electron microscopy and Raman spectra confirmed changes in particle size and structural parameters. However, no phase change was detected for irradiated samples. The stretching/compressive strain caused by high energy electrons is responsible for the slight shift in the XRD peaks of irradiated samples. Modifications in the morphology of different samples were confirmed by scanning electron microscopy. Ultraviolet-visible absorption studies showed variations in the optical band gap (4.08-4.25 eV) upon electron-beam irradiation. New photoluminescence behaviour in electron beam irradiated nanocrystalline CaWO4 was evidenced. A blue shift of the PL peak with increase in intensity was observed in all the irradiated samples.

  4. Surface Modification of AISI-4620 Steel With Intense Pulsed Ion Beams

    SciTech Connect

    Rej, D.J.; Davis, H.A.; Nastasi, M.; Olson, J.C.; Peterson, E.J.; Reiswig, R.D.; Walter, K.C.; Stinnett, R.W.; Remnev, G.E.; Struts, V.K.

    1996-09-01

    A 300-keV, 30-kA, 1-{micro}s intense beam of carbon, oxygen, and hydrogen ions is used for the surface treatment of AISI-4620 steel coupons, a common material used in automotive gear applications. The beam is extracted from a magnetically-insulated vacuum diode and deposited into the top 1 {micro}m of the target surface. The beam-solid interaction causes a rapid melt and resolidification with heating and cooling rates of up to 10{sup 10} K/sec. Treated surfaces are smoothed over 1-{micro}m scale-lengths, but are accompanied by 1-{micro}m diameter craters and larger-scale roughening over >=10 {micro}m, depending on beam fluence and number of pulses. Treated surfaces are up to 1.8 x harder with no discernible change in modulus over depths of 1 {micro}m or more Qualitative improvements in the wear morphology of treated surfaces are reported.

  5. GPU-optimized Code for Long-term Simulations of Beam-beam Effects in Colliders

    SciTech Connect

    Roblin, Yves; Morozov, Vasiliy; Terzic, Balsa; Aturban, Mohamed A.; Ranjan, D.; Zubair, Mohammed

    2013-06-01

    We report on the development of the new code for long-term simulation of beam-beam effects in particle colliders. The underlying physical model relies on a matrix-based arbitrary-order symplectic particle tracking for beam transport and the Bassetti-Erskine approximation for beam-beam interaction. The computations are accelerated through a parallel implementation on a hybrid GPU/CPU platform. With the new code, a previously computationally prohibitive long-term simulations become tractable. We use the new code to model the proposed medium-energy electron-ion collider (MEIC) at Jefferson Lab.

  6. Disparity modifications and the emotional effects of stereoscopic images

    NASA Astrophysics Data System (ADS)

    Kawai, Takashi; Atsuta, Daiki; Tomiyama, Yuya; Kim, Sanghyun; Morikawa, Hiroyuki; Mitsuya, Reiko; Häkkinen, Jukka

    2014-03-01

    This paper describes a study that focuses on disparity changes in emotional scenes of stereoscopic (3D) images, in which an examination of the effects on pleasant and arousal was carried out by adding binocular disparity to 2D images that evoke specific emotions, and applying disparity modification based on the disparity analysis of famous 3D movies. From the results of the experiment, for pleasant, a significant difference was found only for the main effect of the emotions. On the other hand, for arousal, there was a trend of increasing the evaluation values in the order 2D condition, 3D condition and 3D condition applied the disparity modification for happiness, surprise, and fear. This suggests the possibility that binocular disparity and the modification affect arousal.

  7. Effective beam method for element concentrations

    PubMed Central

    Tolhurst, Thomas; Barbi, Mauricio; Tokaryk, Tim

    2015-01-01

    There is a great diversity of research being conducted at synchrotron facilities around the world and a diverse set of beamlines to accommodate this research. Time is a precious commodity at synchrotron facilities; therefore, methods that can maximize the time spent collecting data are of value. At the same time the incident radiation spectrum, necessary for some research, may not be known on a given beamline. A preliminary presentation of a method applicable to X-ray fluorescence spectrocopic analyses that overcomes the lack of information about the incident beam spectrum that addresses both of these concerns is given here. The method is equally applicable for other X-ray sources so long as local conditions are considered. It relies on replacing the polychromatic spectrum in a standard fundamental parameters analysis with a set of effective monochromatic photon beams. A beam is associated with each element and can be described by an analytical function allowing extension to elements not included in the necessary calibration measurement(s). PMID:25723941

  8. Modification of a metal nanoparticle beam by a hollow electrode discharge

    SciTech Connect

    Ahadi, Amir Mohammad Hinz, Alexander; Polonskyi, Oleksandr; Strunskus, Thomas; Faupel, Franz; Trottenberg, Thomas; Kersten, Holger

    2016-03-15

    Treatment of nanoparticles (NPs) in complex environments, such as plasmas, is of interest for the fabrication of advanced nanomaterials with desired properties and also from a physical point of view. Here, the authors investigate the mutual interaction between silver NPs and a radio frequency (RF) plasma at different conditions by combining a cylindrical hollow electrode with a gas aggregation source. The investigation of the NP deposits and the morphology of the casted films shows that the applied RF discharge significantly changes the path of the NPs as well as the NP size distribution in the beam. Starting from a neutral NP beam, it is observed that most of the NPs leave the plasma region with negative charge(s), yet the fraction of positively charged NPs grows with power. Furthermore, the plasma characteristics are slightly influenced by the NP flux since the passing NPs collect the plasma charge carriers.

  9. Modifications of optical properties of PC/ABS by dual ions beam irradiation

    NASA Astrophysics Data System (ADS)

    Park, Jae-Won; Lee, Jae-Sang; Lee, Byung-hoon; Kim, Min-kyu; Moon, Byung-Sik; Lee, Chan-Young; Choi, Byung-Ho

    2013-03-01

    Polycarbonate (PC)/acrylonitrile butadien styrene (ABS) blends used in the inner parts of automobiles require a glossy and metallic colored optical property. Such a surface can be produced by ion beam irradiation, but the surface treated by a single ion species irradiation tends to be degraded upon a long term exposure under UV and visible lights, which includes the loss of glossiness and the delamination of the irradiated layer. Such degradations can be prevented or greatly reduced by a combined irradiation of heavy and light ions such as N and He ions. This may be attributable to a graded interface between the irradiation affected layer and the base materials by overlapping penetration depths of the heavy and light ions. This work is motivated by an effort to substitute the conventional Cr plating process with the ion beam process in the automobile industry.

  10. Surface modification of Ti alloy by electro-explosive alloying and electron-beam treatment

    SciTech Connect

    Gromov, Victor Kobzareva, Tatiana Budovskikh, Evgeniy Baschenko, Lyudmila; Ivanov, Yuryi

    2016-01-15

    By methods of modern physical metallurgy the analysis of structure phase states of titanium alloy VT6 is carried out after electric explosion alloying with boron carbide and subsequent irradiation by pulsed electron beam. The formation of an electro-explosive alloying zone of a thickness up to 50 µm, having a gradient structure, characterized by decrease in the concentration of carbon and boron with increasing distance to the treatable surface has been revealed. Subsequent electron-beam treatment of alloying zone leads to smoothing of the alloying area surface and is accompanied by the multilayer structure formation at the depth of 30 µm with alternating layers with different alloying degrees having the structure of submicro - and nanoscale level.

  11. Surface modification of Ti alloy by electro-explosive alloying and electron-beam treatment

    NASA Astrophysics Data System (ADS)

    Gromov, Victor; Kobzareva, Tatiana; Ivanov, Yuryi; Budovskikh, Evgeniy; Baschenko, Lyudmila

    2016-01-01

    By methods of modern physical metallurgy the analysis of structure phase states of titanium alloy VT6 is carried out after electric explosion alloying with boron carbide and subsequent irradiation by pulsed electron beam. The formation of an electro-explosive alloying zone of a thickness up to 50 µm, having a gradient structure, characterized by decrease in the concentration of carbon and boron with increasing distance to the treatable surface has been revealed. Subsequent electron-beam treatment of alloying zone leads to smoothing of the alloying area surface and is accompanied by the multilayer structure formation at the depth of 30 µm with alternating layers with different alloying degrees having the structure of submicro - and nanoscale level.

  12. Protective effects in radiation modification of elastomers

    NASA Astrophysics Data System (ADS)

    Głuszewski, Wojciech; Zagórski, Zbigniew P.; Rajkiewicz, Maria

    2014-12-01

    Saturated character of ethylene/octene thermoplastic elastomers demands an application of nonconventional methods of crosslinking connections between chains of molecules. These are organic peroxides, usually in the presence of coagents or an application of ionizing radiation. Several approaches (radiation, peroxide, peroxide/plus radiation and radiation/plus peroxide) were applied in crosslinking of elastomere Engage 8200. Attention was directed to the protection effects by aromatic peroxides and by photo- and thermostabilizers on radiolysis of elastomers. Role of dose of radiation, dose rate of radiation as well as the role of composition of elastomere on the radiation yield of hydrogen and absorbtion of oxygen was investigated. DRS method was used to follow postirradiation degradation. Influence of crosslinking methods on properties of elastomers is described. Results were interpreted from the point of view of protective actions of aromatic compounds.

  13. In situ ion-beam analysis and modification of sol-gel zirconia thin films

    SciTech Connect

    Levine, T.E.; Yu, Ning; Kodali, P.; Walter, K.C.; Nastasi, M.; Tesmer, J.R.; Maggiore, C.J.; Mayer, J.W.

    1995-05-01

    We report the investigation of ion-beam-induced densification of sol-gel zirconia thin films via in situ ion backscattering spectrometry. We have irradiated three regions of a sample with neon, argon, and krypton ions. For each ion species, a series of irradiation and analysis steps were performed using an interconnected 3 MV tandem accelerator. The technique offers the advantages of minimizing the variation of experimental parameters and sequentially monitoring the densification phenomenon with increasing ion dose.

  14. Application of pulsed electron beam for modification of ion-plasma multi-element coatings

    NASA Astrophysics Data System (ADS)

    Koval, N. N.; Eremin, E. N.; Yurov, V. M.; Krysina, O. V.; Teresov, A. D.; Guchenko, S. A.; Laurynas, V. Ch.

    2017-08-01

    It is established that coating irradiation by electron beam leads to coating structure dispersion, to microhardness increase and to friction coefficient decrease. The surface energy is enlarged too. That leads to wear resistance growth. The obtained operational characteristics results for ion-plasma multi-element coatings show their usage expediency for the equipment hardening which is applied in the oil production and refining systems.

  15. Effect of beam emittance on self-modulation of long beams in plasma wakefield accelerators

    SciTech Connect

    Lotov, K. V.

    2015-12-15

    The initial beam emittance determines the maximum wakefield amplitude that can be reached as a result of beam self-modulation in the plasma. The wakefield excited by the fully self-modulated beam decreases linearly with the increase in the beam emittance. There is a value of initial emittance beyond which the self-modulation does not develop even if the instability is initiated by a strong seed perturbation. The emittance scale at which the wakefield is suppressed by a factor of two with respect to the zero-emittance case (the so called critical emittance) is determined by inability of the excited wave to confine beam particles radially and is related to beam and plasma parameters by a simple formula. The effect of beam emittance can be observed in several discussed self-modulation experiments.

  16. Analysis of multiwavelength coherent beam combining effect.

    PubMed

    Kai, Han; Xiaojun, Xu; Zejin, Liu

    2012-12-01

    The combination effect of multiwavelength active coherent beam combination (CBC) is investigated theoretically. The dependence of the combination effect on the optical path control precision, spectral width, wavelength number, and channel number is revealed. In the case of small optical path variance, the combination effect approximately decreases in quadratic form with wavelength number N, spectral width Δν, and optical path variance σ increasing. In the case of large optical path variance, the combination effect is independent of the optical path variance and the spectral width. The larger the wavelength number is, the smaller the Strehl ratio expectation is, and it finally degenerates to the incoherent combination. The necessity of optical path control is discussed. This study is helpful for multiwavelength CBC system design and the combination effect estimation.

  17. Effects of Cognitive Bias Modification Training via Smartphones.

    PubMed

    Yang, Ranming; Cui, Lixia; Li, Feng; Xiao, Jing; Zhang, Qin; Oei, Tian P S

    2017-01-01

    Background and Objectives: Negative cognitive biases have been linked to anxiety and mood problems. Accumulated data from laboratory studies show that positive and negative interpretation styles with accompanying changes in mood can be induced through cognitive bias modification (CBM) paradigms. Despite the therapeutic potential of positive training effects, few studies have explored training paradigms administered via smartphones. The current study aimed to compare the effectiveness of three different types of training programmes (cognitive bias modification-attention, CBM-A; cognitive bias modification-interpretation, CBM-I; attention and interpretation modification, AIM) administered via smart-phones by using a control condition (CC). Methods:Seventy-six undergraduate participants with high social anxiety (Liebowitz Social Anxiety Scale, LSAS ≥ 30) were randomly assigned to four groups: CBM-A (n = 20), CBM-I (n = 20), AIM (n = 16), and CC (n = 20). Results: The results showed that the effects of CBM training, CBM-I training, or AIM training vs. CC for attention yielded no significant differences in dot-probe attention bias scores. The CBM-I group showed significantly less threat interpretation and more benign interpretation than the CC group on interpretation bias scores. Conclusions: The present results supported the feasibility of delivering CBM-I via smartphones, but the effectiveness of CBM-A and AIM training via smartphones was limited.

  18. Learner Interaction Using Email: The Effects of Task Modification

    ERIC Educational Resources Information Center

    Knight, Paul

    2005-01-01

    This paper outlines the findings of a research project studying the effects of task modification on learner interaction when using email. Taking as its starting point interactionalist theories of SLA, it argues that if those interactional features characteristic of negotiation of meaning which have been identified as promoting SLA are to be…

  19. Effects of beam irregularity on uniform scanning

    NASA Astrophysics Data System (ADS)

    Kim, Chang Hyeuk; Jang, Sea duk; Yang, Tae-Keun

    2016-09-01

    An active scanning beam delivery method has many advantages in particle beam applications. For the beam is to be successfully delivered to the target volume by using the active scanning technique, the dose uniformity must be considered and should be at least 2.5% in the case of therapy application. During beam irradiation, many beam parameters affect the 2-dimensional uniformity at the target layer. A basic assumption in the beam irradiation planning stage is that the shape of the beam is symmetric and follows a Gaussian distribution. In this study, a pure Gaussian-shaped beam distribution was distorted by adding parasitic Gaussian distribution. An appropriate uniform scanning condition was deduced by using a quantitative analysis based on the gamma value of the distorted beam and 2-dimensional uniformities.

  20. Microstructure and property modifications of an AISI H13 (4Cr5MoSiV) steel induced by pulsed electron beam treatment

    SciTech Connect

    Zhang Kemin; Zou Jianxin; Grosdidier, Thierry; Dong Chuang

    2010-11-15

    In the present work, surface modifications generated by the low energy high current pulsed electron beam (LEHCPEB) treatments have been investigated on an AISI H13 (4Cr5MoSiV) steel. From the observations of scanning electron microscopy, x-ray diffraction, and electron back scattering diffraction determinations, it could be established that the final structure in the melted layer is a mixture of ultrafine {delta} phase, martensite, and residual austenite. The formation of the heterogeneous microstructures on the surface layer is related to the very rapid heating, melting, solidification, and cooling induced by the LEHCPEB irradiation. After the LEHCPEB treatment, the wear resistance of the steel effectively improved. This can be mainly attributed to the higher hardness of the ultrafine structures formed on the top surface and the hardened subsurface layers after the treatment.

  1. Numerical Simulation of Beam-Beam Effects in the Proposed Electron-Ion Colider at Jefferson Lab

    SciTech Connect

    Balsa Terzic, Yuhong Zhang

    2010-05-01

    One key limiting factor to a collider luminosity is beam-beam interactions which usually can cause serious emittance growth of colliding beams and fast reduction of luminosity. Such nonlinear collective beam effect can be a very serious design challenge when the machine parameters are pushed into a new regime. In this paper, we present simulation studies of the beam-beam effect for a medium energy ring-ring electron-ion collider based on CEBAF.

  2. Electron beam fracturing of ZnO nanostructures and modification in optical band gap

    NASA Astrophysics Data System (ADS)

    Siraj, K.; Kanwal, M.; Saleem, S.; Pedarnig, J. D.; Rafique, M. S.; Naseem, S.

    2016-12-01

    In our previous work Siraj et al (J Alloys Comp 563:280, 2013), the electron beam irradiation at high energies (6-15 MeV) at constant dose of 30 Gy produced Zinc oxide elongated nanostructures and modified the optical band gap energies accordingly. In present work, those nanostructures are fractured to smaller sizes by increasing the electron doses to 100 and 200 Gy. The very high temperature gradient induced stresses are responsible for further fracturing of ZnO nanostructures. The optical properties such as refractive index, extinction coefficient and optical band gap energy have also modified when higher cumulative electron doses are used. The optical band gap energies are found to decrease by increasing electron doses at all used electron energies, which is attributed to the production of different defects like vacancies, unpaired bonds, nanovoids, nanocavities, nanocracks and high strains. The electron beam irradiation of ZnO thin films at used parameters (doses and energies) is found to be plausible technique to produce nanostructures of different sizes and accordingly modify the optical band gap energies. The results can be beneficial for optical and optoelectronic industries.

  3. Accelerator-based electron beam technologies for modification of bipolar semiconductor devices

    NASA Astrophysics Data System (ADS)

    Pavlov, Y. S.; Surma, A. M.; Lagov, P. B.; Fomenko, Y. L.; Geifman, E. M.

    2016-09-01

    Radiation processing technologies for static and dynamic parameters modification of silicon bipolar semiconductor devices implemented. Devices of different classes with wide range of operating currents (from a few mA to tens kA) and voltages (from a few volts to 8 kV) were processed in large scale including power diodes and thyristors, high-frequency bipolar and IGBT transistors, fast recovery diodes, pulsed switching diodes, precise temperature- compensated Zener diodes (in general more than fifty 50 device types), produced by different enterprises. The necessary changes in electrical parameters and characteristics of devices caused by formation in the device structures of electrically active and stable in the operating temperature range sub-nanoscale recombination centres. Technologies implemented in the air with high efficiency and controllability, and are an alternative to diffusion doping of Au or Pt, γ-ray, proton and low-Z ion irradiation.

  4. Effects of beam-driven poloidal rotation on the neoclassical bootstrap current

    SciTech Connect

    Lin-Liu, Y.R.; Hinton, F.L.

    1996-12-31

    Unbalanced neutral beam injection drives toroidal and poloidal rotations in a tokamak plasma. The beam toroidal momentum input drives the toroidal rotation, and the parallel friction between the thermal ions and fast ions induces the poloidal rotation. A theory of the beam-driven poloidal rotation and its effects on energy transport was given recently by Hinton and Kim. In this work, we extend their considerations to the effects on the neoclassical bootstrap current. For parameters of interest in present neutral beam heated tokamaks, the magnitude of the beam-driven poloidal rotation can be significantly larger than that of the standard neoclassical value due to the ion temperature gradient. The presence of this driven poloidal rotation will manifest itself in modification of the neoclassical bootstrap current. In the case of coinjection, the driven poloidal rotation is in the opposite direction to the rotation driven by the temperature gradient, therefore it enhances the bootstrap current. In comparison with the standard theoretical predictions of the neutral beam-driven current, that enhancement in the bootstrap current varies with the beam and plasma parameters. A calculation of the parallel transport coefficients associated with the driven poloidal flow in finite-aspect ratio tokamaks will be presented. Experimental conditions for observing the enhancement in bootstrap current will be discussed.

  5. DSC characterization of ion beam modifications in ion conducting PEO salt polymers

    NASA Astrophysics Data System (ADS)

    Maitra, Minakshi; Verma, K. C.; Sinha, Mrinal; Kumar, Rajesh; Middya, T. R.; Tarafdar, S.; Sen, P.; Bandyopadhyay, S. K.; De, Udayan

    2006-03-01

    Ion conducting polymer films have been prepared by complexing non-conducting poly-(ethylene-oxide), PEO, with x fraction of NH4ClO4 salt. Since its electrical conductivity showed a maximum at x somewhere between 0.18 and 0.19, such polymer films having 17 and 19 wt% salt, have been chosen and irradiated by 160 MeV Ne6+ beam. The films have been investigated by differential scanning calorimetry (DSC) and ac impedance spectroscopy before and after the irradiations. Irradiation-induced shift of an endotherm in our DSC indicates a rise in the melting temperature from 54.6 °C to 57.9 °C for the 19% film. Cross-linking by the Ne-irradiation making the polymer structure more rigid can explain this as well as our other observation of a decrease in electrical conductivity.

  6. The effects of betatron phase advances on beam-beam and its compensation in RHIC

    SciTech Connect

    Luo, Y.; Fischer, W.; Gu, X.; Tepikian, S.; Trbojevic, D.

    2011-03-28

    In this article we perform simulation studies to investigate the effects of betatron phase advances between the beam-beam interaction points on half-integer resonance driving term, second order chromaticty and dynamic aperture in RHIC. The betatron phase advances are adjusted with artificial matrices inserted in the middle of arcs. The lattices for the 2011 RHIC polarized proton (p-p) run and 2010 RHIC Au-Au runs are used in this study. We also scan the betatron phase advances between IP8 and the electron lens for the proposed Blue ring lattice with head-on beam-beam compensation.

  7. TRANSIENT BEAM LOADING EFFECTS IN RF SYSTEMS IN JLEIC

    SciTech Connect

    Wang, Haipeng; Guo, Jiquan; Rimmer, Robert A.; Wang, Shaoheng

    2016-05-01

    The pulsed electron bunch trains generated from the Continuous Electron Beam Accelerator Facility (CEBAF) linac to inject into the proposed Jefferson Lab Electron Ion Collider (JLEIC) e-ring will produce transient beam loading effects in the Superconducting Radio Frequency (SRF) systems that, if not mitigated, could cause unacceptably large beam energy deviation in the injection capture, or exceed the energy acceptance of CEBAF’s recirculating arcs. In the electron storage ring, the beam abort or ion clearing gaps or uneven bucket filling can cause large beam phase transients in the (S)RF cavity control systems and even beam loss due to Robinson instability. We have first analysed the beam stability criteria in steady state and estimated the transient effect in Feedforward and Feedback RF controls. Initial analytical models for these effects are shown for the design of the JLEIC e-ring from 3GeV to 12GeV.

  8. Creep Effects in Pultruded FRP Beams

    NASA Astrophysics Data System (ADS)

    Boscato, G.; Casalegno, C.; Russo, S.

    2016-03-01

    The paper presents results of two creep tests on pultruded open-section GFRP beams aimed to evaluate the long-term deformations, the residual deflection after unloading, and the influence of creep strains on the flexuraltorsional buckling phenomenon. Two beams were subjected to a constant load for about one year. Then one of the beams was unloaded to evaluate its residual deflection. For the other beam, the load was increased up to failure, and the residual buckling strength was compared with that of a similar beam tested up to failure. The parameters of the Findley power law are evaluated, and the experimental results are compared with those of numerical analyses and with available formulations for prediction of the time-dependent properties of composite beams. Results of the investigation testify, in particular, to a noninsignificant time-dependent increment in deflections of the beams and to a significant reduction in their buckling strength due to creep deformations.

  9. REVIEW ARTICLE: Optical pumping-induced spatio-temporal modifications to propagation, polarization and intensity of laser beams in sodium vapour

    NASA Astrophysics Data System (ADS)

    Holzner, R.; Dangel, S.

    1998-02-01

    Circularly polarized laser beams propagating through sodium vapour and tuned to the buffer-gas-broadened atomic 1355-5111/10/1/003/img1 transition can optically pump sodium atoms into a non-absorbing ground state. This causes an intensity-dependent refractive index gradient along as well as transverse to the laser beam propagation direction, giving rise to a number of nonlinear spatio-temporal intensity and polarization pattern creating processes. In the case of a single circularly polarized laser beam we have observed self-focusing and defocusing, the transformation of the incident Gaussian beam intensity profiles into ring profiles, a large shift of about 5 GHz of the maximum of the absorption profile when suitable magnetic fields are applied and the deflection of a beam by the inhomogeneous transverse magnetic field of a current-carrying wire. When two beams of opposite circular polarization are superimposed, astonishing effects such as the mutual deflection of both beams (beam bouncing), the mutual extinction of both beams (beam switching), the separation of initially overlapping beams (beam splitting) and the mutual attraction of both beams (beam attraction) can be observed. While most of the effects can be well described for the stationary state by a 1355-5111/10/1/003/img2 to 1355-5111/10/1/003/img3 atomic transition model, the correct description of the dynamics requires the consideration of all hyperfine states.

  10. Undulator Beam Pipe Magnetic Shielding Effect Tests

    SciTech Connect

    Fisher, Andrew; Wolf, Zachary; /SLAC

    2010-11-23

    The proposed stainless steel beampipe for the LCLS undulator has a measurable shielding effect on the magnetic field of the LCLS undulators. This note describes the tests used to determine the magnitude of the shielding effect, as well as deviations in the shielding effect caused by placing different phase shims in the undulator gap. The effect of the proposed Steel strongback which will be used to support the beam pipe, was also studied. A hall probe on a 3 axis movement system was set up to measure the main component of the magnetic field in the Prototype Undulator. To account for temperature variations of the magnetic field of the undulator for successive tests, a correction is applied which is described in this technical note. Using this method, we found the shielding effect, the amount which the field inside the gap was reduced due to the placement of the beampipe, to be {approx}10 Gauss. A series of tests was also performed to determine the effect of phase shims and X and Y correction shims on the shielding. The largest effect on shielding was found for the .3 mm phase shims. The effect of the .3 mm phase shims was to increase the shielding effect {approx}4 Gauss. The tolerance for the shielding effect of the phase shims is less than 1 gauss. The effect of the strongback was seen in its permanent magnetic field. It introduced a dipole field across the measured section of the undulator of {approx}3 gauss. This note documents the tests performed to determine these effects, as well as the results of those tests.

  11. Effect of beam arrangement on oral cavity dose in external beam radiotherapy of nasopharyngeal carcinoma

    SciTech Connect

    Wu, Vincent W.C.; Yang Zhining; Zhang Wuzhe; Wu Lili; Lin Zhixiong

    2012-07-01

    This study compared the oral cavity dose between the routine 7-beam intensity-modulated radiotherapy (IMRT) beam arrangement and 2 other 7-beam IMRT with the conventional radiotherapy beam arrangements in the treatment of nasopharyngeal carcinoma (NPC). Ten NPC patients treated by the 7-beam routine IMRT technique (IMRT-7R) between April 2009 and June 2009 were recruited. Using the same computed tomography data, target information, and dose constraints for all the contoured structures, 2 IMRT plans with alternative beam arrangements (IMRT-7M and IMRT-7P) by avoiding the anterior facial beam and 1 conventional radiotherapy plan (CONRT) were computed using the Pinnacle treatment planning system. Dose-volume histograms were generated for the planning target volumes (PTVs) and oral cavity from which the dose parameters and the conformity index of the PTV were recorded for dosimetric comparisons among the plans with different beam arrangements. The dose distributions to the PTVs were similar among the 3 IMRT beam arrangements, whereas the differences were significant between IMRT-7R and CONRT plans. For the oral cavity dose, the 3 IMRT beam arrangements did not show significant difference. Compared with IMRT-7R, CONRT plan showed a significantly lower mean dose, V30 and V-40, whereas the V-60 was significantly higher. The 2 suggested alternative beam arrangements did not significantly reduce the oral cavity dose. The impact of varying the beam angles in IMRT of NPC did not give noticeable effect on the target and oral cavity. Compared with IMRT, the 2-D conventional radiotherapy irradiated a greater high-dose volume in the oral cavity.

  12. Effect of beam arrangement on oral cavity dose in external beam radiotherapy of nasopharyngeal carcinoma.

    PubMed

    Wu, Vincent W C; Yang, Zhi-Ning; Zhang, Wu-Zhe; Wu, Li-li; Lin, Zhi-xiong

    2012-01-01

    This study compared the oral cavity dose between the routine 7-beam intensity-modulated radiotherapy (IMRT) beam arrangement and 2 other 7-beam IMRT with the conventional radiotherapy beam arrangements in the treatment of nasopharyngeal carcinoma (NPC). Ten NPC patients treated by the 7-beam routine IMRT technique (IMRT-7R) between April 2009 and June 2009 were recruited. Using the same computed tomography data, target information, and dose constraints for all the contoured structures, 2 IMRT plans with alternative beam arrangements (IMRT-7M and IMRT-7P) by avoiding the anterior facial beam and 1 conventional radiotherapy plan (CONRT) were computed using the Pinnacle treatment planning system. Dose-volume histograms were generated for the planning target volumes (PTVs) and oral cavity from which the dose parameters and the conformity index of the PTV were recorded for dosimetric comparisons among the plans with different beam arrangements. The dose distributions to the PTVs were similar among the 3 IMRT beam arrangements, whereas the differences were significant between IMRT-7R and CONRT plans. For the oral cavity dose, the 3 IMRT beam arrangements did not show significant difference. Compared with IMRT-7R, CONRT plan showed a significantly lower mean dose, V30 and V-40, whereas the V-60 was significantly higher. The 2 suggested alternative beam arrangements did not significantly reduce the oral cavity dose. The impact of varying the beam angles in IMRT of NPC did not give noticeable effect on the target and oral cavity. Compared with IMRT, the 2-D conventional radiotherapy irradiated a greater high-dose volume in the oral cavity.

  13. Assessment and modification of an ion source grid design in KSTAR neutral beam system.

    PubMed

    Lee, Dong Won; Shin, Kyu In; Jin, Hyung Gon; Choi, Bo Guen; Kim, Tae-Seong; Jeong, Seung Ho

    2014-02-01

    A new 2 MW NB (Neutral Beam) ion source for supplying 3.5 MW NB heating for the KSTAR campaign was developed in 2012 and its grid was made from OFHC (Oxygen Free High Conductivity) copper with rectangular cooling channels. However, the plastic deformation such as a bulging in the plasma grid of the ion source was found during the overhaul period after the 2012 campaign. A thermal-hydraulic and a thermo-mechanical analysis using the conventional code, ANSYS, were carried out and the thermal fatigue life assessment was evaluated. It was found that the thermal fatigue life of the OFHC copper grid was about 335 cycles in case of 0.165 MW/m(2) heat flux and it gave too short fatigue life to be used as a KSTAR NB ion source grid. To overcome the limited fatigue life of the current design, the following methods were proposed in the present study: (1) changing the OHFC copper to CuCrZr, copper-alloy or (2) adopting a new design with a pure Mo metal grid and CuCrZr tubes. It is confirmed that the proposed methods meet the requirements by performing the same assessment.

  14. Wettability modification of human tooth surface by water and UV and electron-beam radiation.

    PubMed

    Tiznado-Orozco, Gaby E; Reyes-Gasga, José; Elefterie, Florina; Beyens, Christophe; Maschke, Ulrich; Brès, Etienne F

    2015-12-01

    The wettability of the human tooth enamel and dentin was analyzed by measuring the contact angles of a drop of distilled water deposited on the surface. The samples were cut along the transverse and longitudinal directions, and their surfaces were subjected to metallographic mirror-finish polishing. Some samples were also acid etched until their microstructure became exposed. Wettability measurements of the samples were done in dry and wet conditions and after ultraviolet (UV) and electron beam (EB) irradiations. The results indicate that water by itself was able to increase the hydrophobicity of these materials. The UV irradiation momentarily reduced the contact angle values, but they recovered after a short time. EB irradiation raised the contact angle and maintained it for a long time. Both enamel and dentin surfaces showed a wide range of contact angles, from approximately 10° (hydrophilic) to 90° (hydrophobic), although the contact angle showed more variability on enamel than on dentin surfaces. Whether the sample's surface had been polished or etched did not influence the contact angle value in wet conditions.

  15. Increased tensile strength of carbon nanotube yarns and sheets through chemical modification and electron beam irradiation.

    PubMed

    Miller, Sandi G; Williams, Tiffany S; Baker, James S; Solá, Francisco; Lebron-Colon, Marisabel; McCorkle, Linda S; Wilmoth, Nathan G; Gaier, James; Chen, Michelle; Meador, Michael A

    2014-05-14

    The inherent strength of individual carbon nanotubes (CNTs) offers considerable opportunity for the development of advanced, lightweight composite structures. Recent work in the fabrication and application of CNT forms such as yarns and sheets has addressed early nanocomposite limitations with respect to nanotube dispersion and loading and has pushed the technology toward structural composite applications. However, the high tensile strength of an individual CNT has not directly translated into that of sheets and yarns, where the bulk material strength is limited by intertube electrostatic attractions and slippage. The focus of this work was to assess postprocessing of CNT sheets and yarns to improve the macro-scale strength of these material forms. Both small-molecule functionalization and electron-beam irradiation were evaluated as means to enhance the tensile strength and Young's modulus of the bulk CNT materials. Mechanical testing revealed a 57% increase in tensile strength of CNT sheets upon functionalization compared with unfunctionalized sheets, while an additional 48% increase in tensile strength was observed when functionalized sheets were irradiated. Similarly, small-molecule functionalization increased tensile strength of yarn by up to 25%, whereas irradiation of the functionalized yarns pushed the tensile strength to 88% beyond that of the baseline yarn.

  16. Improvement of surface properties by modification and alloying with high-power ion beams

    NASA Astrophysics Data System (ADS)

    Renk, T. J.; Buchheit, R. G.; Sorensen, N. R.; Cowell Senft, D.; Thompson, M. O.; Grabowski, K. S.

    1998-05-01

    Surface treatment and alloying experiments with Al, Fe, and Ti-based metals as well as Si wafers were conducted on the Repetitive High Energy Pulsed Power-I (RHEPP-I) accelerator [0.8 MV, 20 Ω, 80 ns full width at half maximum (FWHM) pulse width, up to 1 Hz repetition rate] at Sandia National Laboratories. Ions are generated by the magnetically confined anode plasma (MAP) gas-breakdown active anode, which can yield a number of different beam species including H, C, N, O, Kr, and Xe, depending upon the injected gas. Enhanced hardness and wear resistance have been produced by treatment of 440C stainless steel, by the mixing of a thin-film Pt coating into Ti-6Al-4V alloy, and of a Si coating into Al 6061-T6 alloy (Al-1.0Mg-0.6Si). Mixing of a thin-film Hf layer into Al 6061-T6 has improved its corrosion resistance by as much as four orders of magnitude in electrochemical testing, compared with untreated and uncoated Al6061. Processing of Si was used to validate simulation codes. When treated with nitrogen ions, melt and full epitaxial growth was observed to depths of 4-6 μm. Experiments are ongoing to further understand the microstructural basis for these surface improvements.

  17. Improvement of surface properties by modification and alloying with high-power ion beams

    SciTech Connect

    Renk, T.J.; Buchheit, R.G.; Sorensen, N.R.; Cowell Senft, D.; Thompson, M.O.; Grabowski, K.S.

    1998-05-01

    Surface treatment and alloying experiments with Al, Fe, and Ti-based metals as well as Si wafers were conducted on the Repetitive High Energy Pulsed Power-I (RHEPP-I) accelerator [0.8 MV, 20 {Omega}, 80 ns full width at half maximum (FWHM) pulse width, up to 1 Hz repetition rate] at Sandia National Laboratories. Ions are generated by the magnetically confined anode plasma (MAP) gas-breakdown active anode, which can yield a number of different beam species including H, C, N, O, Kr, and Xe, depending upon the injected gas. Enhanced hardness and wear resistance have been produced by treatment of 440C stainless steel, by the mixing of a thin-film Pt coating into Ti-6Al-4V alloy, and of a Si coating into Al 6061-T6 alloy (Al-1.0Mg-0.6Si). Mixing of a thin-film Hf layer into Al 6061-T6 has improved its corrosion resistance by as much as four orders of magnitude in electrochemical testing, compared with untreated and uncoated Al6061. Processing of Si was used to validate simulation codes. When treated with nitrogen ions, melt and full epitaxial growth was observed to depths of 4{endash}6 {mu}m. Experiments are ongoing to further understand the microstructural basis for these surface improvements. {copyright} {ital 1998 American Institute of Physics.}

  18. Surface modification and adhesion improvement of PTFE film by ion beam irradiation

    NASA Astrophysics Data System (ADS)

    Lee, S. W.; Hong, J. W.; Wye, M. Y.; Kim, J. H.; Kang, H. J.; Lee, Y. S.

    2004-06-01

    The polytetrafluoroethylene (PTFE) surfaces, modified by 1 kV Ar + or O 2+ ion beam irradiation, was investigated with in-situ X-ray photoelectron spectroscopy (XPS), scanning electron micrographs (SEM), atomic force microscopy (AFM) measurements. The surface of PTFE films modified by Ar + ion irradiation was carbonized and the surface roughness increased with increasing ion doses. The surface of PTFE films modified by both Ar + ion in O 2 atmosphere and O 2+ ion irradiation formed the oxygen function group on PTFE surface, and the surface roughness change was relatively small. The adhesion improvement in Ar + ion irradiated PTFE surface is attributed to mechanical interlocking due to the surface roughness and CF-radical, but that in Ar + ion irradiation in an O 2 atmosphere was contributed by the CO complex and CF-radical with mechanical interlocking. The CO complex and CF-radical in O 2+ ion irradiated surface contributed to the adhesion.

  19. Increased Tensile Strength of Carbon Nanotube Yarns and Sheets through Chemical Modification and Electron Beam Irradiation

    NASA Technical Reports Server (NTRS)

    Miller, Sandi G.; Williams, Tiffany S.; Baker, James S.; Sola, Francisco; Lebron-Colon, Marisabel; McCorkle, Linda S.; Wilmoth, Nathan G.; Gaier, James; Chen, Michelle; Meador, Michael A.

    2014-01-01

    The inherent strength of individual carbon nanotubes offers considerable opportunity for the development of advanced, lightweight composite structures. Recent work in the fabrication and application of carbon nanotube (CNT) forms such as yarns and sheets has addressed early nanocomposite limitations with respect to nanotube dispersion and loading; and has pushed the technology toward structural composite applications. However, the high tensile strength of an individual CNT has not directly translated to macro-scale CNT forms where bulk material strength is limited by inter-tube electrostatic attraction and slippage. The focus of this work was to assess post processing of CNT sheet and yarn to improve the macro-scale strength of these material forms. Both small molecule functionalization and e-beam irradiation was evaluated as a means to enhance tensile strength and Youngs modulus of the bulk CNT material. Mechanical testing results revealed a tensile strength increase in CNT sheets by 57 when functionalized, while an additional 48 increase in tensile strength was observed when functionalized sheets were irradiated; compared to unfunctionalized sheets. Similarly, small molecule functionalization increased yarn tensile strength up to 25, whereas irradiation of the functionalized yarns pushed the tensile strength to 88 beyond that of the baseline yarn.

  20. Interplay of space-charge and beam-beam effects in a collider

    SciTech Connect

    Fedotov, A.V.; Blaskiewicz, M.; Fischer, W.; Satogata, T.; Tepikian, S.

    2010-09-27

    Operation of a collider at low energy or use of cooling techniques to increase beam density may result in luminosity limitation due to the space-charge effects. Understanding of such limitation became important for Low-Energy RHIC physics program with heavy ions at the center of mass energies of 5-20 GeV/nucleon. For a collider, we are interested in a long beam lifetime, which limits the allowable space-charge tune shift. An additional complication comes from the fact that ion beams are colliding, which requires careful consideration of the interplay of direct space-charge and beam-beam effects. This paper summarizes the initial observations during experimental studies in RHIC at low energies.

  1. Modifications of thick-target model: re-acceleration of electron beams by static and stochastic electric fields

    NASA Astrophysics Data System (ADS)

    Varady, M.; Karlický, M.; Moravec, Z.; Kašparová, J.

    2014-03-01

    Context. The collisional thick-target model (CTTM) of the impulsive phase of solar flares, together with the famous Carmichael, Sturrock, Hirayama, and Kopp-Pneuman (CSHKP) model, presented for many years a "standard" model, which straightforwardly explained many observational aspects of flares. On the other hand, many critical issues appear when the concept is scrutinised theoretically or with the new generation of hard X-ray (HXR) observations. The famous "electron number problem" or problems related to transport of enormous particle fluxes though the corona represent only two of them. To resolve the discrepancies, several modifications of the CTTM appeared. Aims: We study two of them based on the global and local re-acceleration of non-thermal electrons by static and stochastic electric fields during their transport from the coronal acceleration site to the thick-target region in the chromosphere. We concentrate on a comparison of the non-thermal electron distribution functions, chromospheric energy deposits, and HXR spectra obtained for both considered modifications with the CTTM itself. Methods: The results were obtained using a relativistic test-particle approach. We simulated the transport of non-thermal electrons with a power-law spectrum including the influence of scattering, energy losses, magnetic mirroring, and also the effects of the electric fields corresponding to both modifications of the CTTM. Results: We show that both modifications of the CTTM change the outcome of the chromospheric bombardment in several aspects. The modifications lead to an increase in chromospheric energy deposit, change of its spatial distribution, and a substantial increase in the corresponding HXR spectrum intensity. Conclusions: The re-acceleration in both models reduces the demands on the efficiency of the primary coronal accelerator, on the electron fluxes transported from the corona downwards, and on the total number of accelerated coronal electrons during flares.

  2. Effect of surface modification on semiconductor nanocrystal fluorescence lifetime.

    PubMed

    Ruedas-Rama, Maria J; Orte, Angel; Hall, Elizabeth A H; Alvarez-Pez, Jose M; Talavera, Eva M

    2011-04-04

    Semiconductor nanocrystals, namely, quantum dots (QDs), present a set of unique photoluminescence properties, which has led to increased interest in using them as advantageous alternatives to conventional organic dyes. Many applications of QDs involve surface modification to enhance the solubility or biocompatibility of the QDs. One of the least exploited properties of QDs is the very long photoluminescence lifetime that usually has complex kinetics owing to the effect of quantum confinement. Herein, we describe the effect of different surface modifications on the photoluminescence decay kinetics of QDs. The different surface modifications were carefully chosen to provide lipophilic or water-soluble QDs with either positive or negative surface net charges. We also survey the effect on the QD lifetime of several ligands that interact with the QD surface, such as organic chromophores or fluorescent proteins. The results obtained demonstrate that time-resolved fluorescence is a useful tool for QD-based sensing to set the basis for the development of time-resolved-based nanosensors.

  3. Thermal effects in orthotropic porous elastic beams

    NASA Astrophysics Data System (ADS)

    Iaşan, D.

    2009-01-01

    This paper is concerned with the linear theory of anisotropic porous elastic bodies. The extension and bending of orthotropic porous elastic cylinders subjected to a plane temperature field is investigated. The work is motivated by the recent interest in the using of the orthotropic porous elastic solid as model for bones and various engineering materials. First, the thermoelastic deformation of inhomogeneous beams whose constitutive coefficients are independent of the axial coordinate is studied. Then, the extension and bending effects in orthotropic cylinders reinforced by longitudinal rods are investigated. The three-dimensional problem is reduced to the study of two-dimensional problems. The method is used to solve the problem of an orthotropic porous circular cylinder with a special kind of inhomogeneity.

  4. The effects of inlet flow modification on cavitating inducer performance

    NASA Technical Reports Server (NTRS)

    Del Valle, J.; Braisted, D. M.; Brennen, C. E.

    1992-01-01

    This paper explores the effect of inlet flow modification on the cavitating and noncavitating performance of two cavitating inducers, one of simple helical design and the other a model of the low-pressure LOX pump in the Space Shuttle Main Engine. The modifications were generated by sections of honeycomb, both uniform and nonuniform. Significant improvement in the performance over a wide range of flow coefficients resulted from the use of either honeycomb section. Measurements of the axial and swirl velocity profiles of the flows entering the inducers were made in order to try to understand the nature of the inlet flow and the manner in which it is modified by the honeycomb sections.

  5. Effect of depth span ratio on the behaviour of beams

    NASA Astrophysics Data System (ADS)

    Patel, Rakesh; Dubey, S. K.; Pathak, K. K.

    2014-06-01

    Behaviour of beam depends on its depth. A beam is considered as deep, if the depth span ratio is 0.5 or more. In the available beam theories, we have to apply correction in case of deep beams. In the present work, method of initial functions (MIF) is used to study the effect of depth on the behaviour of concrete beam. The MIF is an analytical method of elasticity theory. It gives exact solutions of different types of problems without the use of assumptions about the character of stress and strain. In this method, no correction factor is required for beams having larger depth. Results are obtained for three different cases of depth span ratios and compared with available theory and finite element method-based software ANSYS. It is observed that deep beam action starts at depth span ratio equal to 0.25.

  6. Slenderness effects in the free vibration of laminated magnetoelectroelastic beams

    NASA Astrophysics Data System (ADS)

    Jiang, Chao; Heyliger, Paul R.

    2017-08-01

    A semi-analytical discrete-layer approach is used to evaluate slenderness effects in the free vibration of laminated magnetoelectroelastic beams under various boundary conditions. Piecewise continuous approximations are used through the thickness direction of the beam and either continuous polynomial or trigonometric functions are used in the axial direction. Conventional beam models, including those of Euler-Bernoulli and Timoshenko, can be recovered to predict frequency estimates and are compared with results of the present model. Numerical examples are used to show the effects of beam slenderness on frequency and modal order for beams under simply-supported, fixed-fixed, and cantilever conditions. The results of these analyses clearly illustrate the thickness effects for axial, torsional, and bending modes and also provide some results useful for comparison for theses laminated beams.

  7. Simulation Studies of Beam-Beam Effects of a Ring-Ring Electron-Ion Collider Based on CEBAF

    SciTech Connect

    Yuhong Zhang,Ji Qiang

    2009-05-01

    The collective beam-beam effect can potentially cause a rapid growth of beam sizes and reduce the luminosity of a collider to an unacceptably low level. The ELIC, a proposed ultra high luminosity electron-ion collider based on CEBAF, employs high repetition rate crab crossing colliding beams with very small bunch transverse sizes and very short bunch lengths, and collides them at up to 4 interaction points with strong final focusing. All of these features can make the beam-beam effect challenging. In this paper, we present simulation studies of the beam-beam effect in ELIC using a self-consistent strong-strong beam-beam simulation code developed at Lawrence Berkeley National Laboratory. This simulation study is used for validating the ELIC design and for searching for an optimal parameter set.

  8. The effectiveness of workplace dietary modification interventions: a systematic review.

    PubMed

    Geaney, F; Kelly, C; Greiner, B A; Harrington, J M; Perry, I J; Beirne, P

    2013-11-01

    To evaluate the effectiveness of workplace dietary modification interventions alone or in combination with nutrition education on employees' dietary behaviour, health status, self-efficacy, perceived health, determinants of food choice, nutrition knowledge, co-worker support, job satisfaction, economic cost and food-purchasing patterns. Data sources included PubMed, Medline, Embase, Psych Info., Web of Knowledge and Cochrane Library (November 2011). This review was guided by the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement. Studies were randomised controlled trials and controlled studies. Interventions were implemented for at least three months. Cochrane Collaboration's risk of bias tool measured potential biases. Heterogeneity precluded meta-analysis. Results were presented in a narrative summary. Six studies conducted in Brazil, the USA, Netherlands and Belgium met the inclusion criteria. Four studies reported small increases in fruit and vegetable consumption (≤half serving/day). These studies involved workplace dietary modifications and three incorporated nutrition education. Other outcomes reported included health status, co-worker support, job satisfaction, perceived health, self-efficacy and food-purchasing patterns. All studies had methodological limitations that weakened confidence in the results. Limited evidence suggests that workplace dietary modification interventions alone and in combination with nutrition education increase fruit and vegetable intakes. These interventions should be developed with recommended guidelines, workplace characteristics, long-term follow-up and objective outcomes for diet, health and cost. © 2013.

  9. Space Charge Effect in the Sheet and Solid Electron Beam

    NASA Astrophysics Data System (ADS)

    Song, Ho Young; Kim, Hyoung Suk; Ahn, Saeyoung

    1998-11-01

    We analyze the space charge effect of two different types of electron beam ; sheet and solid electron beam. Electron gun simulations are carried out using shadow and control grids for high and low perveance. Rectangular and cylindrical geometries are used for sheet and solid electron beam in planar and disk type cathode. The E-gun code is used to study the limiting current and space charge loading in each geometries.

  10. An overview of the facilities, activities, and developments at the University of North Texas Ion Beam Modification and Analysis Laboratory (IBMAL)

    NASA Astrophysics Data System (ADS)

    Rout, Bibhudutta; Dhoubhadel, Mangal S.; Poudel, Prakash R.; Kummari, Venkata C.; Pandey, Bimal; Deoli, Naresh T.; Lakshantha, Wickramaarachchige J.; Mulware, Stephen J.; Baxley, Jacob; Manuel, Jack E.; Pacheco, Jose L.; Szilasi, Szabolcs; Weathers, Duncan L.; Reinert, Tilo; Glass, Gary A.; Duggan, Jerry L.; McDaniel, Floyd D.

    2013-07-01

    The Ion Beam Modification and Analysis Laboratory (IBMAL) at the University of North Texas includes several accelerator facilities with capabilities of producing a variety of ion beams from tens of keV to several MeV in energy. The four accelerators are used for research, graduate and undergraduate education, and industrial applications. The NEC 3MV Pelletron tandem accelerator has three ion sources for negative ions: He Alphatross and two different SNICS-type sputter ion sources. Presently, the tandem accelerator has four high-energy beam transport lines and one low-energy beam transport line directly taken from the negative ion sources for different research experiments. For the low-energy beam line, the ion energy can be varied from ˜20 to 80 keV for ion implantation/modification of materials. The four post-acceleration beam lines include a heavy-ion nuclear microprobe; multi-purpose PIXE, RBS, ERD, NRA, and broad-beam single-event upset; high-energy ion implantation line; and trace-element accelerator mass spectrometry. The NEC 3MV single-ended Pelletron accelerator has an RF ion source mainly for hydrogen, helium and heavier inert gases. We recently installed a capacitive liner to the terminal potential stabilization system for high terminal voltage stability and high-resolution microprobe analysis. The accelerator serves a beam line for standard RBS and RBS/C. Another beamline for high energy focused ion beam application using a magnetic quadrupole lens system is currently under construction. This beam line will also serve for developmental work on an electrostatic lens system. The third accelerator is a 200 kV Cockcroft-Walton accelerator with an RF ion source. The fourth accelerator is a 2.5 MV Van de Graaff accelerator, which was in operation for last several decades is currently planned to be used mainly for educational purpose. Research projects that will be briefly discussed include materials synthesis/modification for photonic, electronic, and

  11. An overview of the facilities, activities, and developments at the University of North Texas Ion Beam Modification and Analysis Laboratory (IBMAL)

    SciTech Connect

    Rout, Bibhudutta; Dhoubhadel, Mangal S.; Poudel, Prakash R.; Kummari, Venkata C.; Pandey, Bimal; Deoli, Naresh T.; Lakshantha, Wickramaarachchige J.; Mulware, Stephen J.; Baxley, Jacob; Manuel, Jack E.; Pacheco, Jose L.; Szilasi, Szabolcs; Weathers, Duncan L.; Reinert, Tilo; Glass, Gary A.; Duggan, Jerry L.; McDaniel, Floyd D.

    2013-07-03

    The Ion Beam Modification and Analysis Laboratory (IBMAL) at the University of North Texas includes several accelerator facilities with capabilities of producing a variety of ion beams from tens of keV to several MeV in energy. The four accelerators are used for research, graduate and undergraduate education, and industrial applications. The NEC 3MV Pelletron tandem accelerator has three ion sources for negative ions: He Alphatross and two different SNICS-type sputter ion sources. Presently, the tandem accelerator has four high-energy beam transport lines and one low-energy beam transport line directly taken from the negative ion sources for different research experiments. For the low-energy beam line, the ion energy can be varied from {approx}20 to 80 keV for ion implantation/modification of materials. The four post-acceleration beam lines include a heavy-ion nuclear microprobe; multi-purpose PIXE, RBS, ERD, NRA, and broad-beam single-event upset; high-energy ion implantation line; and trace-element accelerator mass spectrometry. The NEC 3MV single-ended Pelletron accelerator has an RF ion source mainly for hydrogen, helium and heavier inert gases. We recently installed a capacitive liner to the terminal potential stabilization system for high terminal voltage stability and high-resolution microprobe analysis. The accelerator serves a beam line for standard RBS and RBS/C. Another beamline for high energy focused ion beam application using a magnetic quadrupole lens system is currently under construction. This beam line will also serve for developmental work on an electrostatic lens system. The third accelerator is a 200 kV Cockcroft-Walton accelerator with an RF ion source. The fourth accelerator is a 2.5 MV Van de Graaff accelerator, which was in operation for last several decades is currently planned to be used mainly for educational purpose. Research projects that will be briefly discussed include materials synthesis/modification for photonic, electronic, and

  12. Chemical modification of the poly(vinylidene fluoride-trifluoroethylene) copolymer surface through fluorocarbon ion beam deposition

    SciTech Connect

    Hsu, W.-D.; Jang, Inkook; Sinnott, Susan B.

    2007-07-15

    Classical molecular dynamics simulations are used to study the effects of continuous fluorocarbon ion beam deposition on a poly(vinylidene fluoride-trifluoroethylene) [P(VDF-trFE)] surface, a polymer with electromechanical properties. Fluorocarbon plasma processing is widely used to chemically modify surfaces and deposit thin films. It is well accepted that polyatomic ions and neutrals within low-energy plasmas have a significant effect on the surface chemistry induced by the plasma. The deposition of mass selected fluorocarbon ions is useful to isolate the effects specific to polyatomic ions. Here, the differences in the chemical interactions of C{sub 3}F{sub 5}{sup +} and CF{sub 3}{sup +} ions with the P(VDF-trFE) surface are examined. The incident energy of the ions in both beams is 50 eV. The CF{sub 3}{sup +} ions are predicted to be more effective at fluorinating the P(VDF-trFE) surface than C{sub 3}F{sub 5}{sup +} ions. At the same time, the C{sub 3}F{sub 5}{sup +} ions are predicted to be more effective at growing fluorocarbon thin films. The simulations also reveal how the deposition process might ultimately modify the electromechanical properties of this polymer surface.

  13. Effects of parasitic beam-beam interaction during the injection process at the PEP-II B Factory

    SciTech Connect

    Chin, Y.H.

    1992-06-01

    This paper is concerned with beam-beam effects during the injection process at the proposed asymmetric SLAC/LBL/LLNL B-Factory, PEP-II. It is shown that the parasitic beam-beam interaction can lead to a significant blowup in the vertical size of the injected beam. Simulation results for the horizontal and the vertical injection schemes are presented, and their performances are studied.

  14. Future e/sup +/e/sup -/ linear colliders and beam-beam effects

    SciTech Connect

    Wilson, P.B.

    1986-05-01

    Numerous concepts, ranging from conventional to highly exotic, hae been proposed for the acceleration of electrons and positrons to very high energies. For any such concept to be viable, it must be possible to produce from it a set of consistent parameters for one of these ''benchmark'' machines. Attention is directed to the choice of parameters for a collider in the 300 GeV energy range, operating at a gradient on the order of 200 MV/m, using X-band power sources to drive a conventional disk-loaded accelerating structure. These rf power sources, while not completely conventional represent a reasonable extrapolation from present technology. The choice of linac parameters is strongly coupled to various beam-beam effects which take place when the electron and positron bunches collide. We summarize these beam-beam effects, and then return to the rf design of a 650 GeV center-of-mass collider. 14 refs.

  15. Beam-beam effects of single ring and partial double ring scheme in CEPC

    NASA Astrophysics Data System (ADS)

    Zhang, Yuan

    2016-11-01

    After the Higgs discovery, it is believed that a circular e+e- collider could serve as a Higgs factory. The high energy physics community in China launched a study of a 50-100 km ring collider. A preliminary conceptual design report (Pre-CDR) has been published in early 2015. This report is based on a 54-km ring design. Some progress on beam-beam effect study after Pre-CDR is shown in the paper. We estimate the beamstrahlung lifetime using a pure strong-strong code as a comparison with the result obtained using a quasi-strong-strong method. The effect of parasitic crossing in the pretzel scheme is also estimated for the very first time. The feasibility of the main parameters for partial double ring scheme are evaluated from the point view of beam-beam interaction.

  16. Induction of apoptosis by accelerated heavy-ion beams in cultured fetal rat testes and its modification

    NASA Astrophysics Data System (ADS)

    Wang, Bing; Tanaka, Kaoru; Shang, Yi; Fujita, Kazuko; Ninomiya, Yasuharu; Moreno, Stephanie G.; Coffigny, Herve; Hayata, Isamu; Murakami, Masahiro; Eguchi-Kasai, Kiyomi; Nenoi, Mitsuru

    The increasing human activities in space missions make the study on effects from high-LET ionizing radiation an important issue to be addressed. We reported previously that prenatal irradiations with heavy-ion beams on gestation day 15 generally induced markedly detrimental effects on prenatal gonads, postnatal testicular development and male breeding activity in rats. To explore the mechanisms involved in radiation-induced gonocyte apoptosis in fetal gonads, which played a critical role in the fate of postnatal testis development, accelerated heavy-ion irradiations and organotypic culture of Wistar fetal rat testes were applied to investigations focused on cellular and molecular events after irradiations with or without chemical addition. Results showed that, in addition to the clustered distribution, both the time course and the percentage of apoptosis in gonocytes on gestation day 15 equivalent in vitro appeared similar to that in utero after exposure to either carbon-ion beams with a LET value of about 13 keV/µm or neon-ion beams with a LET value of about 30 keV/µm. Irradiations induced increased p53 expression in a dose dependent manner and decreased expressions of p21 and Bcl- 2 by Western Blot examination. Administration of pan-caspase inhibitor prior to irradiations effectively inhibited apoptosis occurrence and reduced the extent of clustered apoptosis, while such effects were not observed with the presence of p53 inhibitor, gap junction inhibitor, or nitric oxide specific scavenger. These findings indicated that irradiations of cultured fetal rat testes manifested pathologically similar apoptosis induction in gonocytes to that in utero. P53 expression was possibly responsible for the response to radiation damage rather than induction of apoptosis. The syncytial organization of gonocytes played a key role in formation of the clustered apoptosis, an event that both gap junction inhibitor and nitric oxide specific scavenger were incapable of preventing.

  17. Effect of crosstalk on combined beam characteristics in spectral beam combining systems

    NASA Astrophysics Data System (ADS)

    Yang, Lei; Wu, Zhen; Zhong, Zheqiang; Zhang, Bin

    2017-02-01

    In a spectral beam combining (SBC) system, crosstalk always happens because stray lights are inevitable due to fabrication errors of optical components and 'smile' effect of laser arrays. Two kinds of crosstalk, including the crosstalk generated between two adjacent emitters of the laser array (ad-crosstalk) and that generated between two non-adjacent emitters (non-ad-crosstalk), have been analyzed. The equivalent light of the crosstalk model has been proposed, and the propagation model of the SBC system with the crosstalk has been built up. On this basis, influences of above two kinds of the crosstalk on the combined beam have been numerically simulated and discussed in detail. The results show that the wavelength composition of the combined beam varies evidently owing to the existence of the crosstalk. With the increasing of the crosstalk intensity, the beam quality of the combined beam degrades, and the side lobes of intensity distribution of the combined beam become more and more obvious. Furthermore, the influence of the non-ad-crosstalk on the beam quality is more serious than that of the ad-crosstalk.

  18. Effects of the circularly polarized beam of linearized gravitational waves

    NASA Astrophysics Data System (ADS)

    Barker, W.

    2017-08-01

    Solutions of the linearized Einstein equations are found that describe a transversely confined beam of circularly polarized gravitational waves on a Minkowski backdrop. By evaluating the cycle-averaged stress-energy-momentum pseudotensor of Landau & Lifshitz it is found that the angular momentum density is concentrated in the ‘skin’ at the edge of the beam where the intensity falls, and that the ratio of angular momentum to energy per unit length of the beam is 2/ω , where ω is the wave frequency, as expected for a beam of spin-2 gravitons. For sharply-defined, uniform, axisymmetric beams, the induced background metric is shown to produce the gravitomagnetic field and frame-dragging effects of a gravitational solenoid, whilst the angular momentum current helically twists the space at infinite radius along the beam axis.

  19. Effect of layer length on deflection in sandwich beams

    NASA Astrophysics Data System (ADS)

    Abbu, Muthanna A.; AL-Ameri, Riyadh

    2017-09-01

    A theoretical study has been carried out on sandwich beams strengthened mechanically by two external steel plates attached to their tension and compression sides with so-called "shear connectors ". This study is based on the individual behaviour of each component of the composite sandwich section (i.e. reinforced concrete beam and upper steel plate and lower steel plate). The approach has been developed to simulate the behaviour of such beams, and is based on neglecting the separation between the three layers; i.e., the deflections are equal in each element through the same section. The differential equations reached were solved analytically. Deflection was calculated by using the approach for several beams, tested in two series, and close agreements were obtained with the experimental values. Furthermore, the interaction efficiency between the three elements in a composite sandwich beam has been considered thoroughly, from which the effect of some parameters, such as plate length upon the behaviour of such beams, were studied.

  20. Effects of energetic particle phase space modifications by instabilities on integrated modeling

    NASA Astrophysics Data System (ADS)

    Podestà, M.; Gorelenkova, M.; Fredrickson, E. D.; Gorelenkov, N. N.; White, R. B.

    2016-11-01

    Tokamak plasmas can feature a large population of energetic particles (EP) from neutral beam injection or fusion reactions. In turn, energetic particles can drive instabilities, which affect the driving EP population leading to a distortion of the original EP distribution function and of quantities that depend on it. The latter include, for example, neutral beam (NB) current drive and plasma heating through EP thermalization. Those effects must be taken into account to enable reliable and quantitative simulations of discharges for present devices as well as predictions for future burning plasmas. Reduced models for EP transport are emerging as an effective tool for long time-scale integrated simulations of tokamak plasmas, possibly including the effects of instabilities on EP dynamics. Available models differ in how EP distribution properties are modified by instabilities, e.g. in terms of gradients in real or phase space. It is therefore crucial to assess to what extent different assumptions in the transport models affect predicted quantities such as EP profile, energy distribution, NB driven current and energy/momentum transfer to the thermal populations. A newly developed kick model, which includes modifications of the EP distribution by instabilities in both real and velocity space, is used in this work to investigate these issues. Coupled to TRANSP simulations, the kick model is used to analyze NB-heated NSTX and DIII-D discharges featuring unstable Alfvén eigenmodes (AEs). Results show that instabilities can strongly affect the EP distribution function, and modifications propagate to macroscopic quantities such as NB-driven current profile and NB power transferred to the thermal plasma species. Those important aspects are only qualitatively captured by simpler fast ion transport models that are based on radial diffusion of energetic ions only.

  1. Effects of energetic particle phase space modifications by instabilities on integrated modeling

    SciTech Connect

    Podesta, M.; Gorelenkova, M.; Fredrickson, E. D.; Gorelenkov, N. N.; White, R. B.

    2016-07-22

    Tokamak plasmas can feature a large population of energetic particles (EP) from neutral beam injection or fusion reactions. In turn, energetic particles can drive instabilities, which affect the driving EP population leading to a distortion of the original EP distribution function and of quantities that depend on it. The latter include, for example, neutral beam (NB) current drive and plasma heating through EP thermalization. Those effects must be taken into account to enable reliable and quantitative simulations of discharges for present devices as well as predictions for future burning plasmas. Reduced models for EP transport are emerging as an effective tool for long time-scale integrated simulations of tokamak plasmas, possibly including the effects of instabilities on EP dynamics. Available models differ in how EP distribution properties are modified by instabilities, e.g. in terms of gradients in real or phase space. It is therefore crucial to assess to what extent different assumptions in the transport models affect predicted quantities such as EP profile, energy distribution, NB driven current and energy/momentum transfer to the thermal populations. A newly developed kick model, which includes modifications of the EP distribution by instabilities in both real and velocity space, is used in this work to investigate these issues. Coupled to TRANSP simulations, the kick model is used to analyze NB-heated NSTX and DIII-D discharges featuring unstable Alfvén eigenmodes (AEs). Results show that instabilities can strongly affect the EP distribution function, and modifications propagate to macroscopic quantities such as NB-driven current profile and NB power transferred to the thermal plasma species. Furthermore, those important aspects are only qualitatively captured by simpler fast ion transport models that are based on radial diffusion of energetic ions only.

  2. Effects of energetic particle phase space modifications by instabilities on integrated modeling

    SciTech Connect

    Podesta, M.; Gorelenkova, M.; Fredrickson, E. D.; Gorelenkov, N. N.; White, R. B.

    2016-07-22

    Tokamak plasmas can feature a large population of energetic particles (EP) from neutral beam injection or fusion reactions. In turn, energetic particles can drive instabilities, which affect the driving EP population leading to a distortion of the original EP distribution function and of quantities that depend on it. The latter include, for example, neutral beam (NB) current drive and plasma heating through EP thermalization. Those effects must be taken into account to enable reliable and quantitative simulations of discharges for present devices as well as predictions for future burning plasmas. Reduced models for EP transport are emerging as an effective tool for long time-scale integrated simulations of tokamak plasmas, possibly including the effects of instabilities on EP dynamics. Available models differ in how EP distribution properties are modified by instabilities, e.g. in terms of gradients in real or phase space. It is therefore crucial to assess to what extent different assumptions in the transport models affect predicted quantities such as EP profile, energy distribution, NB driven current and energy/momentum transfer to the thermal populations. A newly developed kick model, which includes modifications of the EP distribution by instabilities in both real and velocity space, is used in this work to investigate these issues. Coupled to TRANSP simulations, the kick model is used to analyze NB-heated NSTX and DIII-D discharges featuring unstable Alfvén eigenmodes (AEs). Results show that instabilities can strongly affect the EP distribution function, and modifications propagate to macroscopic quantities such as NB-driven current profile and NB power transferred to the thermal plasma species. Furthermore, those important aspects are only qualitatively captured by simpler fast ion transport models that are based on radial diffusion of energetic ions only.

  3. Correction of beam-beam effects in luminosity measurement in the forward region at CLIC

    NASA Astrophysics Data System (ADS)

    Lukić, S.; Božović-Jelisavčić, I.; Pandurović, M.; Smiljanić, I.

    2013-05-01

    Procedures for correcting the beam-beam effects in luminosity measurements at CLIC at 3 TeV center-of-mass energy are described and tested using Monte Carlo simulations. The angular counting loss due to the combined Beamstrahlung and initial-state radiation effects is corrected based on the reconstructed velocity of the collision frame of the Bhabha scattering. The distortion of the luminosity spectrum due to the initial-state radiation is corrected by deconvolution. At the end, the counting bias due to the finite calorimeter energy resolution is numerically corrected. To test the procedures, BHLUMI Bhabha event generator, and Guinea-Pig beam-beam simulation were used to generate the outgoing momenta of Bhabha particles in the bunch collisions at CLIC. The systematic effects of the beam-beam interaction on the luminosity measurement are corrected with precision of 1.4 permille in the upper 5% of the energy, and 2.7 permille in the range between 80 and 90% of the nominal center-of-mass energy.

  4. Structural and optical investigation of the effect of electron beam irradiation in a PM-355 nuclear track detector

    NASA Astrophysics Data System (ADS)

    Nouh, S. A.; Bahammam, S.

    2012-05-01

    The effect of electron beam irradiation on the structure and optical properties of a PM-355 solid-state nuclear track detector has been investigated. Samples from PM-355 were irradiated with electron beams with different doses ranging from 20 to 250 kGy. The structural and optical modifications in the electron beam-irradiated PM-355 samples have been studied as a function of dose using different characterization techniques such as Fourier transform infrared spectroscopy, Vickers hardness, refractive index and color difference measurements. The Commission International de E'Claire (CIE units x, y and z) methodology was used in this work for the description of colored samples. In addition, the color differences between the non-irradiated sample and those irradiated with different electron beam doses were calculated. The results indicate that the PM-355 detector acquires color changes under electron beam irradiation.

  5. Effect of Electron Beam Irradiation on Tensile Strength of Polypropylene

    NASA Astrophysics Data System (ADS)

    Yamada, Hiroshi; Ikeda, Masayuki; Shimbo, Minoru; Miyano, Yasushi

    In this paper, the effects of the intensity of electron beam and the variation with time after irradiation of electron beam on the tensile strength of the polypropylene (PP), which is widely used as medicine containers, were investigated. PP with and without colorants were used first and samples irradiated under various intensity of EB. A tensile test on the irradiated samples with elapsed time after the irradiation of the electron beam was carried out. The effects of those factors on the tensile strength were discussed. The following results were obtained (1) The tensile strength of PP decreased due to the influence of the electron beam irradiation, however the rate of the decrease in strength was small compared with the original one. Furthermore, the rate of the decrease in strength was very small owing to the variation with time after the EB irradiation. (2) The tensile rupture strength of PP increased and the rupture strain owing to the influence of the electron beam irradiation compared with the original one. In addition, these rupture strength increased and the rupture strain decreased along with time after the irradiation of the electron beam. (3) The tensile rupture strain energy of PP decreased owing to the influence of the electron beam irradiation compared with the original one. In addition, the strain energy decreases with time after the irradiation of the electron beam. Moreover, the strength characteristics of PP with colorants received greater influence of electron beam compared with the one without colorants.

  6. Structural and kinetic modification of aqueous hydroxypropylmethylcellulose (HPMC) induced by electron beam irradiation

    NASA Astrophysics Data System (ADS)

    Furusawa, Kazuya; Dobashi, Toshiaki; Morishita, Satoshi; Oyama, Mikio; Hashimoto, Tadashi; Shinyashiki, Naoki; Yagihara, Shin; Nagasawa, Naotsugu

    2005-08-01

    Aqueous solutions of 10 and 20 wt% hydroxypropylmethylcellulose (HPMC) were irradiated with different doses to make gel films. The gel fraction of the film increased sharply above a critical dose upon increase of the dose and then decreased gradually after passing a maximum. The scission/cross-linking ratio and the critical dose were determined with the aid of Charlesby-Rosiak equation as 0.52 and 9 kGy for the 10 wt% gel and 0.43 and 14 kGy for the 20 wt% gel, respectively. The gel fraction for the 20 wt% HPMC film was lower at low dose and higher at high dose than that for the 10 wt% film. The behavior of the swelling ratio of the gel film was just opposite to that of the gel fraction. The cross-linking density of the gel estimated from the Flory theory increased linearly with the irradiation dose at low dose, passed through a maximum around 100 and 160 kGy for 10% and 20% films, respectively, and decreased at high dose. These results suggest a competition of scission and cross-linking induced by the indirect effect of irradiation. Dielectric-relaxation measurements by time-domain reflectometry and RF impedance/material analyzer revealed two characteristic relaxations of chain motions around 100 MHz and of orientation of free water around 20 GHz. From the dose dependence of the dielectric-relaxation parameters determined by fitting to a combined equation of the Cole-Cole type and of the KWW type, a coupling of motions of HPMC molecules and water molecules was strongly suggested. The critical dose for gelation was coincident with the dose for the maximum of τ and the minimum of Δε together with the minimum of τ and the maximum of Δε, where τ and Δε denote the relaxation time and the relaxation strength for water molecular motion and τ and Δε the corresponding ones for HPMC molecular motion. The characteristic behavior is discussed in terms of an increase of the affinity between HPMC and water and the constrained molecular motion in the gel network.

  7. Ecological Effects of Weather Modification: A Problem Analysis.

    ERIC Educational Resources Information Center

    Cooper, Charles F.; Jolly, William C.

    This publication reviews the potential hazards to the environment of weather modification techniques as they eventually become capable of producing large scale weather pattern modifications. Such weather modifications could result in ecological changes which would generally require several years to be fully evident, including the alteration of…

  8. Effects of energetic particle phase space modifications by instabilities on integrated modeling

    DOE PAGES

    Podesta, M.; Gorelenkova, M.; Fredrickson, E. D.; ...

    2016-07-22

    Tokamak plasmas can feature a large population of energetic particles (EP) from neutral beam injection or fusion reactions. In turn, energetic particles can drive instabilities, which affect the driving EP population leading to a distortion of the original EP distribution function and of quantities that depend on it. The latter include, for example, neutral beam (NB) current drive and plasma heating through EP thermalization. Those effects must be taken into account to enable reliable and quantitative simulations of discharges for present devices as well as predictions for future burning plasmas. Reduced models for EP transport are emerging as an effectivemore » tool for long time-scale integrated simulations of tokamak plasmas, possibly including the effects of instabilities on EP dynamics. Available models differ in how EP distribution properties are modified by instabilities, e.g. in terms of gradients in real or phase space. It is therefore crucial to assess to what extent different assumptions in the transport models affect predicted quantities such as EP profile, energy distribution, NB driven current and energy/momentum transfer to the thermal populations. A newly developed kick model, which includes modifications of the EP distribution by instabilities in both real and velocity space, is used in this work to investigate these issues. Coupled to TRANSP simulations, the kick model is used to analyze NB-heated NSTX and DIII-D discharges featuring unstable Alfvén eigenmodes (AEs). Results show that instabilities can strongly affect the EP distribution function, and modifications propagate to macroscopic quantities such as NB-driven current profile and NB power transferred to the thermal plasma species. Furthermore, those important aspects are only qualitatively captured by simpler fast ion transport models that are based on radial diffusion of energetic ions only.« less

  9. Ultra-low-energy (<10 eV/u) ion beam bombardment effect on naked DNA

    NASA Astrophysics Data System (ADS)

    Thopan, P.; Thongkumkoon, P.; Prakrajang, K.; Suwannakachorn, D.; Yu, L. D.

    2014-05-01

    Since ion energy deposition in the ion-bombarded materials dominantly occurs in the low-energy range, it is very interesting to know effects from ultra-low-energy ion interaction with DNA for understanding ion-beam-induced genetic mutation. Tens-keV Ar- and N-ion beams were decelerated to ultra-low energy ranging from 20 to 100 eV, or only a few to 10 eV/u, to bombard naked plasmid DNA. The bombarded DNA was analyzed using gel electrophoresis for DNA form changes. The original DNA supercoiled form was found to change to relaxed and linear forms, indicating single or double strand breaks after bombarded by tens-eV ion beam. N-ion beam was found more effective in inducing DNA change and mutation than Ar-ion beam. The study demonstrated that the ion bombardment with energy as low as several-tens eV was able to break DNA strands and thus potentially to cause genetic modification of biological cells. The experimental results were discussed in terms of direct atomic collision between the ions and DNA atoms.

  10. Effect of ABCD transformations on beam paraxiality.

    PubMed

    Vaveliuk, Pablo; Martinez-Matos, Oscar

    2011-12-19

    The limits of the paraxial approximation for a laser beam under ABCD transformations is established through the relationship between a parameter concerning the beam paraxiality, the paraxial estimator, and the beam second-order moments. The applicability of such an estimator is extended to an optical system composed by optical elements as mirrors and lenses and sections of free space, what completes the analysis early performed for free-space propagation solely. As an example, the paraxiality of a system composed by free space and a spherical thin lens under the propagation of Hermite-Gauss and Laguerre-Gauss modes is established. The results show that the the paraxial approximation fails for a certain feasible range of values of main parameters. In this sense, the paraxial estimator is an useful tool to monitor the limits of the paraxial optics theory under ABCD transformations.

  11. Image effects of cylindrical pipes on continuous beams

    SciTech Connect

    Allen, C.K.; Reiser, M.

    1996-09-01

    We analyze the image effects of a cylindrical pipe on continuous beams with elliptical symmetry. Differential equations involving the second-order spatial moments of a particle distribution are given. From the moment equations, a set of Kapchinskij-Vladimirskij-type equations is developed, which include the image effects of a cylindrical beam pipe. These equations are used to analyze the image effects for focusing, drift, defocusing, drift channels, sheet beams, and a magnetic quadrupole matching section. {copyright} {ital 1996 The American Physical Society.}

  12. Imaging the neural effects of cognitive bias modification training.

    PubMed

    Wiers, Corinde E; Wiers, Reinout W

    2017-05-01

    Cognitive bias modification (CBM) was first developed as an experimental tool to examine the causal role of cognitive biases, and later developed into complementary interventions in experimental psychopathology research. CBM involves the "re-training" of implicit biases by means of multiple trials of computerized tasks, and has been demonstrated to change anxious, depressive and drug-seeking behavior, including clinically relevant effects. Recently, the field has progressed by combining CBM with neuroimaging techniques, which provides insight into neural mechanisms underlying how CBM affects implicit biases in anxiety, depression, and addiction, and potentially other pathologies. This narrative literature review summarizes the state of the art of studies on the neural effects of CBM and provides directions for future research in the field. A total of 13 published studies were found and discussed: n=9 in anxiety, n=2 in depressive behavior, and n=2 in addiction. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. Effect of epigenetic modification of maspin on extravillous trophoblastic function.

    PubMed

    Shi, Xinwei; Wu, Yuanyuan; Liu, Haiyi; Gong, Xun; Du, Hui; Li, Yuqi; Zhao, Jun; Chen, Ping; Tang, Guiju; Qiao, Fuyuan

    2012-12-01

    This study investigated the effect of epigenetic modification of maspin on extravillous trophoblastic function. The mRNA expression of maspin in placentae from normotensive and preeclamptic pregnant women was detected by RT-PCR. TEV-1 cells, a human first-trimester extravillous trophoblast cell line, were cultured and treated with CoCl(2) (300 μmol/L) to induce chemical hypoxia and with 5-aza (500 nmol/L) to induce demethylation. The mRNA expression of maspin in TEV-1 cells subjected to different treatments was determined by RT-PCR, and the proliferative and migratory abilities of TEV-1 cells were assessed by cell counting kit-8 (CCK-8) and Transwell assays. Our results showed that the maspin mRNA expression level in placentae from preeclamptic women was much higher than that from normotensive women. CoCl(2) or 5-aza could up-regulate the mRNA expression of maspin and significantly suppress the proliferation and migration of TEV-1 cells. It was concluded that the epigenetic modification in promoter region of maspin contributes to incomplete trophoblast invasion, which offers a novel approach for predicting and treating placental dysfunction.

  14. Effect of thermal modification on rheological properties of polyethylene blends

    SciTech Connect

    Siriprumpoonthum, Monchai; Nobukawa, Shogo; Yamaguchi, Masayuki; Satoh, Yasuo; Sasaki, Hiroko

    2014-03-15

    We examined the effects of thermal modification under flow field on the rheological properties of linear low-density polyethylene (LLDPE) with high molecular weight, low-density polyethylene (LDPE), and their blends, without thermal stabilizer. Although structural changes during processing are not detected by size extrusion chromatography or nuclear magnetic resonance spectroscopy, linear viscoelastic properties changed greatly, especially for the LLDPE. A cross-linking reaction took place, leading to, presumably, star-shaped long-chain branches. Consequently, the modified LLDPE, having high zero-shear viscosity, became a thermorheologically complex melt. Moreover, it should be noted that the drawdown force, defined as the uniaxial elongational force at a constant draw ratio, was significantly enhanced for the blends. Enhancement of elongational viscosity was also detected. The drawdown force and elongational viscosity are marked for the thermally modified blend as compared with those for the blend of thermally modified pure components. Intermolecular cross-linking reactions between LDPE and LLDPE, yielding polymers with more than two branch points per chain, result in marked strain-hardening in the elongational viscosity behavior even at small strain. The recovery curve of the oscillatory modulus after the shear modification is further evidence of a branched structure.

  15. Near-field modification of femtosecond laser beam to enhance single-shot pulse filamentation in glass medium

    NASA Astrophysics Data System (ADS)

    Ahmed, Farid; Shamim Ahsan, M.; Seop Lee, Man; Jun, Martin B. G.

    2014-03-01

    In this paper, a study of the effect of a transparent dielectric medium (soda-lime glass placed after an objective lens) on femtosecond pulse filamentation in Corning Eagle2000 glass is presented. The dielectric medium placed after the objective lens increases the effective numerical aperture of the focusing lens and tightly focuses the beam to elevate the power density in a tiny focal volume. A single-shot narrow filamentary void of diameter 3.8 μm is observed to propagate as long as 700 μm in Corning Eagle2000 glass. Elevated optical intensity confined in the small focal volume and low ionization losses per unit length in the narrow plasma column collectively enhance the filamentary propagation of the ultra-short pulse in bulk glass. The applied technique also offers an approach to control the length and width of a filamentary void structure in a transparent dielectric medium.

  16. Artificial domain structures realized by local gallium focused Ion-beam modification of Pt /Co/Pt trilayer transport structure

    NASA Astrophysics Data System (ADS)

    Aziz, A.; Bending, S. J.; Roberts, H.; Crampin, S.; Heard, P. J.; Marrows, C. H.

    2005-12-01

    We demonstrate that a high-resolution Ga focused ion beam can be used to introduce artificial domain structures in Pt(1.6nm )/Co(0.5nm)/Pt(3.5nm) trilayer transport structures. We have used thin SiO2 overlayers to control the effective energy and dose of Ga ions at the Pt /Co interface. The extraordinary Hall effect (EHE) was used to characterize the magnetic properties of the patterned films. Using 30keV Ga ions and SiO2 overlayer thicknesses in the range of 0-24nm, we achieve complete control of the coercive field of our Pt /Co/Pt trilayer structures. The magnetization reversal mechanism for an artificial domain of size of 3×0.5μm2 is investigated using EHE.

  17. Detector dose response in megavoltage small photon beams. II. Pencil beam perturbation effects.

    PubMed

    Bouchard, Hugo; Kamio, Yuji; Palmans, Hugo; Seuntjens, Jan; Duane, Simon

    2015-10-01

    To quantify detector perturbation effects in megavoltage small photon fields and support the theoretical explanation on the nature of quality correction factors in these conditions. In this second paper, a modern approach to radiation dosimetry is defined for any detector and applied to small photon fields. Fano's theorem is adapted in the form of a cavity theory and applied in the context of nonstandard beams to express four main effects in the form of perturbation factors. The pencil-beam decomposition method is detailed and adapted to the calculation of perturbation factors and quality correction factors. The approach defines a perturbation function which, for a given field size or beam modulation, entirely determines these dosimetric factors. Monte Carlo calculations are performed in different cavity sizes for different detection materials, electron densities, and extracameral components. Perturbation effects are detailed with calculated perturbation functions, showing the relative magnitude of the effects as well as the geometrical extent to which collimating or modulating the beam impacts the dosimetric factors. The existence of a perturbation zone around the detector cavity is demonstrated and the approach is discussed and linked to previous approaches in the literature to determine critical field sizes. Monte Carlo simulations are valuable to describe pencil beam perturbation effects and detail the nature of dosimetric factors in megavoltage small photon fields. In practice, it is shown that dosimetric factors could be avoided if the field size remains larger than the detector perturbation zone. However, given a detector and beam quality, a full account for the detector geometry is necessary to determine critical field sizes.

  18. Detector dose response in megavoltage small photon beams. II. Pencil beam perturbation effects

    SciTech Connect

    Bouchard, Hugo Duane, Simon; Kamio, Yuji; Palmans, Hugo; Seuntjens, Jan

    2015-10-15

    Purpose: To quantify detector perturbation effects in megavoltage small photon fields and support the theoretical explanation on the nature of quality correction factors in these conditions. Methods: In this second paper, a modern approach to radiation dosimetry is defined for any detector and applied to small photon fields. Fano’s theorem is adapted in the form of a cavity theory and applied in the context of nonstandard beams to express four main effects in the form of perturbation factors. The pencil-beam decomposition method is detailed and adapted to the calculation of perturbation factors and quality correction factors. The approach defines a perturbation function which, for a given field size or beam modulation, entirely determines these dosimetric factors. Monte Carlo calculations are performed in different cavity sizes for different detection materials, electron densities, and extracameral components. Results: Perturbation effects are detailed with calculated perturbation functions, showing the relative magnitude of the effects as well as the geometrical extent to which collimating or modulating the beam impacts the dosimetric factors. The existence of a perturbation zone around the detector cavity is demonstrated and the approach is discussed and linked to previous approaches in the literature to determine critical field sizes. Conclusions: Monte Carlo simulations are valuable to describe pencil beam perturbation effects and detail the nature of dosimetric factors in megavoltage small photon fields. In practice, it is shown that dosimetric factors could be avoided if the field size remains larger than the detector perturbation zone. However, given a detector and beam quality, a full account for the detector geometry is necessary to determine critical field sizes.

  19. Quantum effects in electron beam pumped GaAs

    SciTech Connect

    Yahia, M. E.; Azzouz, I. M.; Moslem, W. M.

    2013-08-19

    Propagation of waves in nano-sized GaAs semiconductor induced by electron beam are investigated. A dispersion relation is derived by using quantum hydrodynamics equations including the electrons and holes quantum recoil effects, exchange-correlation potentials, and degenerate pressures. It is found that the propagating modes are instable and strongly depend on the electron beam parameters, as well as the quantum recoil effects and degenerate pressures. The instability region shrinks with the increase of the semiconductor number density. The instability arises because of the energetic electron beam produces electron-hole pairs, which do not keep in phase with the electrostatic potential arising from the pair plasma.

  20. BEAM-BEAM 2003 SUMMARY.

    SciTech Connect

    FISCHER,W.SEN,T.

    2003-05-19

    This paper summarizes the presentations and discussions of the Beam-Beam'03 workshop, held in Montauk, Long Island, from May 19 to 23, 2003. Presentations and discussions focused on halo generation from beam-beam interactions; beam-beam limits, especially coherent limits and their effects on existing and future hadron colliders; beam-beam compensation techniques, particularly for long-range interactions; and beam-beam study tools in theory, simulation, and experiment.

  1. Thermal effect on prebunched two-beam free electron laser

    NASA Astrophysics Data System (ADS)

    Mirian, N. S.; Maraghechi, B.

    2013-08-01

    A numerical simulation in one-dimension is conducted to study the two-beam free electron laser. The fundamental resonance of the fast electron beam coincides with the fifth harmonic of the slow electron beam in order to generate extreme ultraviolet radiation. Thermal effect in the form of the longitudinal velocity spread is included in the analysis. In order to reduce the length of the wiggler, prebunched slow electron beam is considered. The evaluation of the radiation power, bunching parameter, distribution function of energy, and the distribution function of the pondermotive phase is studied. Sensitivity of the power of the fifth harmonic to the jitter in the energy difference between the two beams is also studied. A phase space is presented that shows the trapped electrons at the saturation point.

  2. Closed Form Expression for the Geometric Effect of a Beam Scraper on the Transverse Beam Distribution

    SciTech Connect

    Decker, Franz-Josef

    2000-08-08

    The geometric effect of a beam scraper on the transverse and longitudinal properties of a charged bunch has been extensively investigated. Analytical expressions have been derived for various asymptotic limits such as small offsets of the beam through the scraper and/or very short or very long bunch lengths compared to the scraper gap. A more general, semi-analytical approach that is valid in the asymptotic limits, and for the intermediate cases is presented in this paper. The relative expressions are compact and easy to evaluate. A comparison is made with numerical simulation results from MAFIA. In addition, estimates of the effect on the higher order moments of the beam distributions are provided for typical SLC parameters.

  3. Closed Form Expression for the Effect of a Beam Scraper on the transverse Beam Distributions

    NASA Astrophysics Data System (ADS)

    Raimondi, P.; Decker, F. J.; Ng, C. K.

    1997-05-01

    The effect of a beam scraper on the transverse and longitudinal properties of a charged bunch has been extensively investigated. Analytical expressions have been derived for various asymptotic limits such as small offset of the beam through the scraper and/or very short or very long bunch lengths compared to the scraper gap. A more general, semi-analytical approach that is valid for almost all cases is presented in this paper. The relative expressions are compact and easy to evaluate. A comparison is made with numerical simulation results from MAFIA and TBCI. In addition, estimates of the effect on the higher order moments of the beam distributions are provided for typical SLC parameters.

  4. Effect of dispersion on the spectrum of partially coherent beams.

    PubMed

    Pan, Liuzhan; Yuan, Xiao; Ding, Chaoliang; Lü, Baida

    2008-08-01

    Taking the Gaussian Schell-model (GSM) beam as a typical example of partially coherent beams, the analytical expressions of the spectrum of GSM beams propagating in dispersive media are derived, and the spectral properties are studied in detail. It is shown that, in comparison with propagation in free space and in turbulence, whether or not GSM beams satisfy the scaling law, the normalized spectrum of GSM beams in dispersive media changes on propagation in general, because the dispersive medium affects different spectral components differently. As compared with the free-space propagation, for the scaling-law GSM beams the dispersion results in spectrum change, and for the nonscaling-law GSM beams the dispersion gives rise to a further increase in spectral changes. The structure constant of the dispersive property of the media, the transverse coordinate of the observation point, the spatial correlation length of the source, and the propagation distance affect the spectral behavior of GSM beams; this effect is illustrated numerically.

  5. 120 MeV Ni Ion beam induced modifications in poly (ethylene terephthalate) used in commercial bottled water

    SciTech Connect

    Kumar, Vijay; Sonkawade, R. G.; Ali, Yasir; Dhaliwal, A. S.

    2012-06-05

    We report the effects of heavy ion irradiation on the optical, structural, and chemical properties of polyethylene terephthalate (PET) film used in commercial bottled water. PET bottles were exposed with 120 MeV Ni ions at fluences varying from 3 x 10{sup 10} to 3 x 10{sup 12} ion/cm{sup 2}. The modifications so induced were analyzed by using UV-Vis, X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. Substantial decrease in optical band gap is observed with the increase in ion fluence. In the FTIR spectra, most of bands are decreased due the degradation of the molecular structure. XRD measurements show the decrease in peak intensity, which reflects the loss of crystallinity after irradiation.

  6. Polarized beam splitting effect in inhomogeneously magnetized magnetooptic films.

    PubMed

    Waring, M

    1989-10-15

    Linearly polarized light passing through a several micron thick magnetooptic film in the inhomogeneous magnetization state is split into a linearly polarized central beam and linearly polarized first and higher order diverging rings. The polarization of the central output beam lies in the same direction as the linearly polarized input, while the polarization of the diverging rings lies in a direction orthogonal to the input plane of polarization. The effect is described, and applications of the effect are discussed.

  7. Effects of Particle Beams on Explosives

    DTIC Science & Technology

    1991-12-01

    azide) and secondary (HMX, RDX, TATB, HNS , NTO and TNT) explosives as well as the oxidizer ammonium perchlorate. During each experiment the explosive...out with HMX, RDX, TNT, TATB, HNS and NTO. During this study, the rate of energy deposition was approximately 1-1.5 cal/gm-s, yielding a temperature...RECRYSTALLIZED HMX PRIMARY EXPLOSIVE - PROTON BEAMS When experiments on primary explosives such as lead azide, lead styphnate, PETN and ammonium perchlorate were

  8. Simulating Electron Cloud Effects in Heavy-Ion Beams

    SciTech Connect

    Cohen, R.H.; Friedman, A.; Lund, S.W.; Molvik, A.W.; Azevedo, T.; Vay, J.-L.; Stoltz, P.; Veitzer, S.

    2004-08-04

    Stray electrons can be introduced in heavy ion fusion accelerators as a result of ionization of ambient gas or gas released from walls due to halo-ion impact, or as a result of secondary-electron emission. We summarize here results from several studies of electron-cloud accumulation and effects: (1) Calculation of the electron cloud produced by electron desorption from computed beam ion loss; the importance of ion scattering is shown; (2) Simulation of the effect of specified electron cloud distributions on ion beam dynamics. We find electron cloud variations that are resonant with the breathing mode of the beam have the biggest impact on the beam (larger than other resonant and random variations), and that the ion beam is surprisingly robust, with an electron density several percent of the beam density required to produce significant beam degradation in a 200-quadrupole system. We identify a possible instability associated with desorption and resonance with the breathing mode. (3) Preliminary investigations of a long-timestep algorithm for electron dynamics in arbitrary magnetic fields.

  9. HOLLOW ELECTRON BEAM COLLIMATION FOR HL-LHC - EFFECT ON THE BEAM CORE

    SciTech Connect

    Fitterer, M.; Stancari, G.; Valishev, A.; Bruce, R.; Papadopoulou, S.; Papotti, G.; Pellegrini, D.; Pellegrini, S.; Valuch, D.; Wagner, J. F.

    2016-10-05

    Collimation with hollow electron beams or lenses (HEL) is currently one of the most promising concepts for active halo control in HL-LHC. In previous studies it has been shown that the halo can be efficiently removed with a hollow electron lens. Equally important as an efficient removal of the halo, is also to demonstrate that the core stays unperturbed. In this paper, we present a summary of the experiment at the LHC and simulations in view of the effect of the HEL on the beam core in case of a pulsed operation.

  10. Analysis of KrF excimer laser beam modification resulting from ablation under closed thick film flowing filtered water

    NASA Astrophysics Data System (ADS)

    Dowding, Colin; Lawrence, Jonathan

    2011-09-01

    The application of a closed thick film flowing filtered water to immerse the ablation etching mechanism of an excimer laser poses interesting possibilities concerning debris control, modification of machined feature topography and modification of the ablation rate. Furthermore, these parameters have been shown to be dependent on flow velocity; hence, offering further user control of machining characteristics. However, the impact of this technique requires investigation. This contribution offers comparison of the calculated ablation pressure and the effect on feature surface characteristics given for laser ablation of bisphenol A polycarbonate using KrF excimer laser radiation in ambient air against laser ablation of the same substrate under closed thick film flowing filtered water immersion. Also, an impact of such immersion equipment on the optical performance of the micromachining centre used is quantified and reviewed. The pressure is calculated to have risen by a magnitude of 48, when using the liquid immersed ablation technique. This increase in pressure is proposed to have an increased surface roughness, promoting the number of asperities with a surface area lower than 16 μm 2; resulting in a diffuse reflection of light and an apparent darkening of features. The focal length of the optical system was accurately predicted to increase by 2.958 mm, when using the closed flowing liquid immersion equipment. This equipment is predicted to have increased the optical depth of focus via reduction in the angle of convergence of the two defining image rays; yet the perceived focus, measured discretely by mean feature wall angle, was found to be 25% smaller when using the closed thick film flowing filtered water immersion technique instead of similar laser ablation in ambient air. A compressed plume interaction is proposed as a contributing factor in this change.

  11. Ground cloud related weather modification effects. [heavy lift launch vehicles

    NASA Technical Reports Server (NTRS)

    Lee, J.

    1980-01-01

    The principal concerns about inadvertent weather modification by the solar power satellite system rocket effluents are discussed, namely the possibility that the ground cloud might temporarily modify local weather and the cumulative effects of nearly 500 launches per year. These issues are discussed through the consideration of (1) the possible alteration of the microphysical processes of clouds in the general area due to rocket effluents and debris and cooling water entrained during the launch and (2) the direct dynamical and thermodynamical responses to the inputs of thermal energy and moisture from the rocket exhaust for given ambient meteorological conditions. The huge amount of thermal energy contained in the exhaust of the proposed launch vehicle would in some situations induce a saturated, wet convective cloud or enhance an existing convective activity. Nevertheless, the effects would be limited to the general area of the launch site. The observed long lasting high concentrations of cloud condensation nuclei produced during and after a rocket launch may appreciably affect the frequency of occurrence and persistence of fogs and haze. In view of the high mission frequency proposed for the vehicle launches, a potential exists for a cumulative effect.

  12. Microstructural and plasmonic modifications in Ag–TiO2 and Au–TiO2 nanocomposites through ion beam irradiation

    PubMed Central

    Chakravadhanula, Venkata Sai Kiran; Mishra, Yogendra Kumar; Kotnur, Venkata Girish; Avasthi, Devesh Kumar; Strunskus, Thomas; Zaporotchenko, Vladimir; Fink, Dietmar; Kienle, Lorenz

    2014-01-01

    Summary The development of new fabrication techniques of plasmonic nanocomposites with specific properties is an ongoing issue in the plasmonic and nanophotonics community. In this paper we report detailed investigations on the modifications of the microstructural and plasmonic properties of metal–titania nanocomposite films induced by swift heavy ions. Au–TiO2 and Ag–TiO2 nanocomposite thin films with varying metal volume fractions were deposited by co-sputtering and were subsequently irradiated by 100 MeV Ag8+ ions at various ion fluences. The morphology of these nanocomposite thin films before and after ion beam irradiation has been investigated in detail by transmission electron microscopy studies, which showed interesting changes in the titania matrix. Additionally, interesting modifications in the plasmonic absorption behavior for both Au–TiO2 and Ag–TiO2 nanocomposites were observed, which have been discussed in terms of ion beam induced growth of nanoparticles and structural modifications in the titania matrix. PMID:25247124

  13. Beam hardening and partial beam hardening of the bowtie filter: Effects on dosimetric applications in CT

    NASA Astrophysics Data System (ADS)

    Lopez-Rendon, X.; Zhang, G.; Bosmans, H.; Oyen, R.; Zanca, F.

    2014-03-01

    Purpose: To estimate the consequences on dosimetric applications when a CT bowtie filter is modeled by means of full beam hardening versus partial beam hardening. Method: A model of source and filtration for a CT scanner as developed by Turner et. al. [1] was implemented. Specific exposures were measured with the stationary CT X-ray tube in order to assess the equivalent thickness of Al of the bowtie filter as a function of the fan angle. Using these thicknesses, the primary beam attenuation factors were calculated from the energy dependent photon mass attenuation coefficients and used to include beam hardening in the spectrum. This was compared to a potentially less computationally intensive approach, which accounts only partially for beam hardening, by giving the photon spectrum a global (energy independent) fan angle specific weighting factor. Percentage differences between the two methods were quantified by calculating the dose in air after passing several water equivalent thicknesses representative for patients having different BMI. Specifically, the maximum water equivalent thickness of the lateral and anterior-posterior dimension and of the corresponding (half) effective diameter were assessed. Results: The largest percentage differences were found for the thickest part of the bowtie filter and they increased with patient size. For a normal size patient they ranged from 5.5% at half effective diameter to 16.1% for the lateral dimension; for the most obese patient they ranged from 7.7% to 19.3%, respectively. For a complete simulation of one rotation of the x-ray tube, the proposed method was 12% faster than the complete simulation of the bowtie filter. Conclusion: The need for simulating the beam hardening of the bow tie filter in Monte Carlo platforms for CT dosimetry will depend on the required accuracy.

  14. Ion Beam Materials Analysis and Modifications at keV to MeV Energies at the University of North Texas

    NASA Astrophysics Data System (ADS)

    Rout, Bibhudutta; Dhoubhadel, Mangal S.; Poudel, Prakash R.; Kummari, Venkata C.; Lakshantha, Wickramaarachchige J.; Manuel, Jack E.; Bohara, Gyanendra; Szilasi, Szabolcs Z.; Glass, Gary A.; McDaniel, Floyd D.

    2014-02-01

    The University of North Texas (UNT) Ion Beam Modification and Analysis Laboratory (IBMAL) has four particle accelerators including a National Electrostatics Corporation (NEC) 9SDH-2 3 MV tandem Pelletron, a NEC 9SH 3 MV single-ended Pelletron, and a 200 kV Cockcroft-Walton. A fourth HVEC AK 2.5 MV Van de Graaff accelerator is presently being refurbished as an educational training facility. These accelerators can produce and accelerate almost any ion in the periodic table at energies from a few keV to tens of MeV. They are used to modify materials by ion implantation and to analyze materials by numerous atomic and nuclear physics techniques. The NEC 9SH accelerator was recently installed in the IBMAL and subsequently upgraded with the addition of a capacitive-liner and terminal potential stabilization system to reduce ion energy spread and therefore improve spatial resolution of the probing ion beam to hundreds of nanometers. Research involves materials modification and synthesis by ion implantation for photonic, electronic, and magnetic applications, micro-fabrication by high energy (MeV) ion beam lithography, microanalysis of biomedical and semiconductor materials, development of highenergy ion nanoprobe focusing systems, and educational and outreach activities. An overview of the IBMAL facilities and some of the current research projects are discussed.

  15. Magnetic zenith effect in the ionospheric modification by an X-mode HF heater wave

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskaya, N. F.; Borisova, T. D.; Haggstrom, I.; Rietveld, M. T.; Yeoman, T. K.

    2013-12-01

    We report experimental results aimed at an investigation of the magnetic zenith effect in the high latitude ionosphere F region from ionospheric modification by powerful HF heater wave with X-polarization. The ionospheric modification was produced by the HF heating facility at Tromsø (Norway) using the phased array with a narrow beam with of 6 degrees. Effective radiated power was varied between 450 and 1000 MW. The HF pump wave radiated in different directions relative to the magnetic field from 90 degrees (vertical) to 78 degrees (magnetic zenith) at frequencies near or above the ordinary-mode critical frequency. The response of the ionosphere plasma to the HF pump wave impact was checked by the UHF incoherent scatter radar located in the immediate vicinity of the HF heater. UHF radar was probing the plasma parameters, such as electron density and temperature (Ne and Te), HF-induced plasma and ion lines in the altitude range from 90 to 600 km. It was running in a scanning mode when UHF radar look angles were changed from 74 to 90 degrees by 1 or 2 degree step. It was clearly demonstrated that the strongest heater-induced effects took place in the magnetic field-aligned direction when HF pointing was also to the magnetic zenith. It was found that strong Ne enhancement of up to 80 % along magnetic field (artificial density ducts) were excited only under HF pumping towards magnetic zenith. The width of the artificial ducts comes to only 2 degrees. The Ne increases were accompanied by the Te enhancements of up to about 50 %. Less pronounced Te increases were also observed in the directions of 84 and 90 degrees. Strong Ne enhancements can be accompanied by excitation of strong HF-induced plasma and ion lines. Thus experimental results obtained points to the strong magnetic zenith effect due to self-focusing powerful HF radio wave with X-mode polarization.

  16. Effective shielding to measure beam current from an ion source

    SciTech Connect

    Bayle, H.; Delferrière, O.; Gobin, R.; Harrault, F.; Marroncle, J.; Senée, F.; Simon, C.; Tuske, O.

    2014-02-15

    To avoid saturation, beam current transformers must be shielded from solenoid, quad, and RFQ high stray fields. Good understanding of field distribution, shielding materials, and techniques is required. Space availability imposes compact shields along the beam pipe. This paper describes compact effective concatenated magnetic shields for IFMIF-EVEDA LIPAc LEBT and MEBT and for FAIR Proton Linac injector. They protect the ACCT Current Transformers beyond 37 mT radial external fields. Measurements made at Saclay on the SILHI source are presented.

  17. Effects of positive interpretive bias modification in highly anxious individuals.

    PubMed

    Salemink, Elske; van den Hout, Marcel; Kindt, Merel

    2009-06-01

    Over the past 20 years evidence has accumulated that individuals suffering from anxiety tend to interpret ambiguous information as threatening. Considering the causal role of this interpretive bias in anxiety, it was recently established that modifying interpretive biases influences anxiety. This suggests that anxiety can be clinically treated by directly targeting this interpretive bias. The present study was designed to modify a negative interpretive bias in highly anxious individuals, and subsequently assess the hypothesized beneficial effects on clinical measures. High trait-anxious participants were randomly assigned to one of two conditions: a positive interpretational Cognitive Bias Modification (CBM-I) or a control condition (n=2 x 17). The program was offered online for eight consecutive days. Upon completing the program, participants who had followed positive CBM-I were less state and trait-anxious compared to the control group. Additionally, positively trained participants scored lower on a measure of general psychopathology (SCL-90). No effects were observed on social anxiety and stress vulnerability. The mixed pattern of findings renders them rather inconclusive, leaving interpretations of the potential therapeutic merits of CBM-I open for future research.

  18. Electron-Cloud Effects on Heavy-Ion Beams

    SciTech Connect

    Azevedo, T; Friedman, A; Cohen, R; Vay, J

    2004-03-29

    Stray electrons can be introduced in positive-charge accelerators for heavy ion fusion (or other applications) as a result of ionization of ambient gas or gas released from walls due to halo-ion impact, or as a result of secondary-electron emission. We are developing a capability for self-consistent simulation of ion beams with the electron clouds they produce. We report on an ingredient in this capability, the effect of specified electron cloud distributions on the dynamics of a coasting ion beam. We consider here electron distributions with axially varying density, centroid location, or radial shape, and examine both random and sinusoidally varying perturbations. We find that amplitude variations are most effective in spoiling ion beam quality, though for sinusoidal variations which match the natural ion beam centroid oscillation or breathing mode frequencies, the centroid and shape perturbations can also be effective. We identify a possible instability associated with resonance with the beam-envelope ''breathing'' mode. One conclusion from this study is that heavy-ion beams are surprisingly robust to electron clouds, compared to a priori expectations.

  19. Stability studies of plasma modification effects of polylactide and polycaprolactone surface layers

    NASA Astrophysics Data System (ADS)

    Moraczewski, Krzysztof; Stepczyńska, Magdalena; Malinowski, Rafał; Rytlewski, Piotr; Jagodziński, Bartłomiej; Żenkiewicz, Marian

    2016-07-01

    The article presents results of research on the stability of oxygen plasma modification effects of polylactide and polycaprolactone surface layers. The modified samples were aged for three, six or nine weeks. The studies were carried out using scanning electron microscopy, goniometry and Fourier transform infrared spectroscopy. Studies have shown that the plasma modification has significant impact on the geometric structure and chemical composition of the surface, wettability and surface energy of tested polymers. The modification effects are not permanent. It has been observed that over time the effects of plasma modification fade. Studies have shown that modifying effect lasts longer in the case of polycaprolactone.

  20. Single Bunch Electron Cloud Effects in the NLC Beam Delivery System(LCC-0126)

    SciTech Connect

    Chen, D

    2003-12-08

    A positron beam passing through a linear collider beam delivery beam line is finely focused to desired specifications during collimation and especially in Final Focusing (FFS). Undesired additional focusing is generated by beam-electron cloud interactions, which typically leads to beam size increases at high cloud densities. This paper examines the severity of the electron cloud effects and assesses the critical cloud density.

  1. Effect of noncircularity of experimental beam on CMB parameter estimation

    SciTech Connect

    Das, Santanu; Mitra, Sanjit; Paulson, Sonu Tabitha E-mail: sanjit@iucaa.ernet.in

    2015-03-01

    Measurement of Cosmic Microwave Background (CMB) anisotropies has been playing a lead role in precision cosmology by providing some of the tightest constrains on cosmological models and parameters. However, precision can only be meaningful when all major systematic effects are taken into account. Non-circular beams in CMB experiments can cause large systematic deviation in the angular power spectrum, not only by modifying the measurement at a given multipole, but also introducing coupling between different multipoles through a deterministic bias matrix. Here we add a mechanism for emulating the effect of a full bias matrix to the PLANCK likelihood code through the parameter estimation code SCoPE. We show that if the angular power spectrum was measured with a non-circular beam, the assumption of circular Gaussian beam or considering only the diagonal part of the bias matrix can lead to huge error in parameter estimation. We demonstrate that, at least for elliptical Gaussian beams, use of scalar beam window functions obtained via Monte Carlo simulations starting from a fiducial spectrum, as implemented in PLANCK analyses for example, leads to only few percent of sigma deviation of the best-fit parameters. However, we notice more significant differences in the posterior distributions for some of the parameters, which would in turn lead to incorrect errorbars. These differences can be reduced, so that the errorbars match within few percent, by adding an iterative reanalysis step, where the beam window function would be recomputed using the best-fit spectrum estimated in the first step.

  2. 78 FR 20137 - Probable Economic Effect of Certain Modifications to the North American Free Trade Agreement...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-03

    ... COMMISSION Probable Economic Effect of Certain Modifications to the North American Free Trade Agreement Rules.... 3313), the Commission instituted investigation No. TA-103-027, Probable Economic Effect of Certain... provide advice on the probable economic effect of the proposed modifications on U.S. trade under the...

  3. Nanometer-scale modification and welding of silicon and metallic nanowires with a high-intensity electron beam.

    PubMed

    Xu, Shengyong; Tian, Mingliang; Wang, Jinguo; Xu, Jian; Redwing, Joan M; Chan, Moses H W

    2005-12-01

    We demonstrate that a high-intensity electron beam can be applied to create holes, gaps, and other patterns of atomic and nanometer dimensions on a single nanowire, to weld individual nanowires to form metal-metal or metal-semiconductor junctions, and to remove the oxide shell from a crystalline nanowire. In single-crystalline Si nanowires, the beam induces instant local vaporization and local amorphization. In metallic Au, Ag, Cu, and Sn nanowires, the beam induces rapid local surface melting and enhanced surface diffusion, in addition to local vaporization. These studies open up a novel approach for patterning and connecting nanomaterials in devices and circuits at the nanometer scale.

  4. Effect of Chemical Modifications on Aptamer Stability in Serum.

    PubMed

    Kratschmer, Christina; Levy, Matthew

    2017-09-25

    There is increasing interest in the use of aptamers for the development of therapeutics. However, as oligonucleotides, aptamers are susceptible to nuclease degradation; poor serum stability is likely to negatively affect in vivo function. Modified nucleotides have been used to thwart nuclease degradation. However, few studies report the serum stability of selected aptamers. In this study, we examined the effect of various chemical modifications (2'-deoxy, 2'-hydroxyl, 2'-fluoro, and 2'-O-methyl) on the stability of a control oligonucleotide sequence following incubation in frozen human, fresh mouse, and fresh human serum. We also assessed the effect of the 3' inverted dT cap on stability. Surprisingly, we found that fYrR (2'-fluoro RNA) is only roughly as stable as DNA (2'-deoxy). Interestingly, the inclusion of a 3' inverted dT cap had only a modest effect on serum stability, if any. In one instance, the addition of a 3' inverted dT cap rendered a molecule composed of DNA more stable than its fYrR counterpart. By far, fully modified oligonucleotides (100% 2-O-Methyl or 2'-O-methyl A, C, and U in combination with 2'-fluoro G, termed fGmH) had the longest half-lives. These compositions demonstrated little degradation in human serum even after prolonged incubation. Together these results support the need for using fully modified aptamers for in vivo applications and should encourage those in the field to exploit newer polymerase variants capable of directly generating such polymers.

  5. Effects of neutral gas releases on electron beam injection from electrically tethered spacecraft

    NASA Technical Reports Server (NTRS)

    Winglee, R. M.

    1990-01-01

    The presence of high neutral densities at low altitudes and/or during thruster firings is known to modify the spacecraft potential during active electron beam injection. Two-dimensional (three velocity) particle simulations are used to investigate the ionization processes including the neutral density required, the modification of the spacecraft potential, beam profile and spatial distribution of the return current into the spacecraft. Three processes are identified: (1) beam-induced ionization, (2) vehicle-induced ionization, and (3) beam plasma discharge. Only in the first two cases does the beam propagate away with little distortion.

  6. Ionization chamber gradient effects in nonstandard beam configurations

    SciTech Connect

    Bouchard, Hugo; Seuntjens, Jan; Carrier, Jean-Francois; Kawrakow, Iwan

    2009-10-15

    Purpose: For the purpose of nonstandard beam reference dosimetry, the current concept of reporting absorbed dose at a point in water located at a representative position in the chamber volume is investigated in detail. As new nonstandard beam reference dosimetry protocols are under development, an evaluation of the role played by the definition of point of measurement could lead to conceptual improvements prior to establishing measurement procedures. Methods: The present study uses the current definition of reporting absorbed dose to calculate ionization chamber perturbation factors for two cylindrical chamber models (Exradin A12 and A14) using the Monte Carlo method. The EGSnrc based user-code EGS lowbar chamber is used to calculate chamber dose responses of 14 IMRT beams chosen to cause considerable dose gradients over the chamber volume as previously used by Bouchard and Seuntjens [''Ionization chamber-based reference dosimetry of intensity modulated radiation beams,'' Med. Phys. 31(9), 2454-5465 (2004)]. Results: The study shows conclusively the relative importance of each physical effect involved in the nonstandard beam correction factors of 14 IMRT beams. Of all correction factors involved in the dosimetry of the beams studied, the gradient perturbation correction factor has the highest magnitude, on average, 11% higher compared to reference conditions for the Exradin A12 chamber and about 5% higher for the Extradin A14 chamber. Other perturbation correction factors (i.e., P{sub wall}, P{sub stem}, and P{sub cel}) are, on average, less than 0.8% different from reference conditions for the chambers and beams studied. The current approach of reporting measured absorbed dose at a point in water coinciding with the location of the centroid of the chamber is the main factor responsible for large correction factors in nonstandard beam deliveries (e.g., intensity modulated radiation therapy) reported in literature. Conclusions: To reduce or eliminate the magnitude

  7. Modification of Structure and Strength Properties of Permanent Joints Under Laser Beam Welding with Application of Nanopowder Modifiers

    NASA Astrophysics Data System (ADS)

    Cherepanov, A. N.; Orishich, A. M.; Malikov, A. G.; Ovcharenko, V. E.

    2016-08-01

    In the paper we present the results of experimental study of specially prepared nanosize metal-ceramic compositions impact upon structure, microhardness and mechanical properties of permanent joints produced by laser-beam welding of steel and titanium alloy plates.

  8. Investigation of artificial domains realized by local gallium focused ion-beam modification of Pt/Co/Pt trilayer structures

    NASA Astrophysics Data System (ADS)

    Aziz, A.; Bending, S. J.; Roberts, H.; Crampin, S.; Heard, P. J.; Marrows, C. H.

    2006-04-01

    We present the results of experimental investigations of magnetic switching and magnetotransport in a generation of magnetic devices containing artificially patterned domains. Our devices are realized by locally reducing the coercive field of a perpendicularly magnetized Pt(3.5 nm)/Co(0.5 nm)/Pt(1.6 nm) trilayer structure using a gallium focused ion beam. Artificial domain walls are created at the interfaces between dosed and undosed regions when an external magnetic field switches the former but not the latter. We have exploited this property to create stripelike domains with widths down to submicron length scales, separated by undosed regions. Using the extraordinary Hall effect to monitor the local magnetization we have investigated the reversal dynamics of these artificial domains by measuring major and minor hysteresis loops. The coercive field of regions irradiated with identical doses systematically increases as their size decreases. In the lower branch of minor loops, reversal is seen to occur via a few large Barkhausen events. Preliminary measurements of transport across domain walls reveal a positive domain-wall resistance, that does not change sign from 4.2 to 300 K.

  9. Surface Modification Energized by Focused Ion Beam: The Influence of Etch Rates & Aspect Ratio on Ripple Wavelengths.

    SciTech Connect

    MoberlyChan, W J

    2006-11-15

    Ion beams have been used to modify surface topography, producing nanometer-scale modulations (and even subnanometer ripples in this work) that have potential uses ranging from designing self-assembly structures, to controlling stiction of micromachined surfaces, to providing imprint templates for patterned media. Modern computer-controlled Focused Ion Beam tools enable alternating submicron patterned zones of such ion-eroded surfaces, as well as dramatically increasing the rate of ion beam processing. The DualBeam FIB/SEM also expedites process development while minimizing the use of materials that may be precious (Diamond) and/or produce hazardous byproducts (Beryllium). A FIB engineer can prototype a 3-by-3-by-3 matrix of variables in tens of minutes and consume as little as zeptoliters of material; whereas traditional ion beam processing would require tens of days and tens of precious wafers. Saturation wavelengths have been reported for ripples on materials such as single crystal silicon or diamond ({approx}200nm); however this work achieves wavelengths >400nm on natural diamond. Conversely, Be can provide a stable and ordered 2-dimensional array of <40nm periodicity; and ripples <0.4nm are also fabricated on carbon surfaces and quantified by HR-TEM and electron diffraction. Rippling is a function of material, ion beam, and angle; but is also controlled by chemical environment, redeposition, and aspect ratio. Ideally a material exhibits a constant yield (atoms sputtered off per incident ion); however, pragmatic FIB processes, coupled with the direct metrological feedback in a DualBeam tool, reveal etch rates do not remain constant for nanometer-scale processing. Control of rippling requires controlled metrology, and robust software tools are developed to enhance metrology. In situ monitoring of the influence of aspect ratio and redeposition at the micron scale correlates to the rippling fundamentals that occur at the nanometer scale and are controlled by the

  10. Neutral Beam Propagation Effects in the Upper Atmosphere.

    DTIC Science & Technology

    1984-10-01

    I 7 -AA74 6 NEUTRAL BEAR PROPAGAT ION EFFECTS IN THE UPPER7~ATMOSPHERE(U) B STON C LL CHESTNUT HILL MA DEPT OF~PHYSICS P CARINI ET AL 01 OCT 84...BUREAU OF STANDARDS 2963 A t %. -_- ’o N, r ,._ .~ , AD-A 174 896 AFGL-TR-85-0038 NEUTRAL BEAM PROPAGATION EFFECTS IN THE UPPER ATMOSPHERE P. Carini...ZIP Code) 10 SOURCE OF FUNDING NOS PROGRAM PROJECT TASK( WORK UNIT ELEMENT NO NO. NO. NO 1j 1 TITLE (Include secuit’iy ClawficaiJon) Neutral Beam

  11. Effects of porous carbon additives and induced fluorine on low dielectric constant polyimide synthesized with an e-beam

    SciTech Connect

    Im, Ji Sun; Bae, Tae-Sung; Lee, Sung Kyu; Lee, Sei-Hyun; Jeong, Euigyung; Kang, Phil Hyun; Lee, Young-Seak

    2010-11-15

    We report the synthesis of a polyimide matrix with a low dielectric constant for application as an intercalation material between metal interconnections in electronic devices. Porous activated carbon was embedded in the polyimide to reduce the dielectric constant, and a thin film of the complex was obtained using the spin-coating and e-beam irradiation methods. The surface of the thin film was modified with fluorine functional groups to impart water resistance and reduce the dielectric constant further. The water resistance was significantly improved by the modification with hydrophobic fluorine groups. The dielectric constant was effectively decreased by porous activated carbon. The fluorine modification also resulted in a low dielectric constant on the polyimide surface by reducing the polar surface free energy. The dielectric constant of polyimide film decreased from 2.98 to 1.9 by effects of porous activated carbon additive and fluorine surface modification.

  12. Polycation binding to glomerular basement membrane. Effect of biochemical modification.

    PubMed

    Bertolatus, J A; Hunsicker, L G

    1987-02-01

    The polycation hexadimethrine (HDM) binds to anionic sites in the glomerular basement membrane (GBM) and causes heavy proteinuria when infused in vivo. An in vitro assay of 3H-HDM binding to isolated dog GBM was developed, to permit further analysis of the GBM components binding HDM. 3H-HDM binding to isolated GBM was saturable, reversible in dose-dependent fashion by competing polycations, and inhibited by increasing salt concentration and low pH. The pH dependence of binding suggested that most of the HDM binds to carboxyl groups rather than to the sulfate groups of proteoglycans. Removal of heparan sulfate by heparinase or purified heparatinase had no detectable effect on HDM binding. Treatment of GBM with neuraminidase, hyaluronidase, or chondroitinase reduced binding of HDM by a maximum of 20 to 38%. However, substitution of carboxyl anions with nonionizable glycine methyl ester residues resulted in complete elimination of HDM binding. Parallel results were obtained in studies of glomerular localization of cationized ferritin (CatF), pI 8.5. After carboxyl substitution, GBM did not bind CatF; heparinase-treated GBM bound CatF in a distribution not demonstrably different from normal. Cellulose acetate electrophoresis of glycosaminoglycan fractions prepared from treated GBM confirmed that carboxyl modification did not alter the content or charge of the heparan sulfate of GBM, but heparinase treatment removed at least 90% of heparan sulfate. The results indicate that carboxyl groups are quantitatively more important than heparan sulfate for binding of HDM in vitro. Since HDM causes proteinuria in vivo, carboxyl groups may be important for maintenance of normal permselectivity.

  13. Effective parameters in beam acoustic metamaterials based on energy band structures

    NASA Astrophysics Data System (ADS)

    Jing, Li; Wu, Jiu Hui; Guan, Dong; Hou, Mingming; Kuan, Lu; Shen, Li

    2016-07-01

    We present a method to calculate the effective material parameters of beam acoustic metamaterials. The effective material parameters of a periodic beam are calculated as an example. The dispersion relations and energy band structures of this beam are calculated. Subsequently, the effective material parameters of the beam are investigated by using the energy band structures. Then, the modal analysis and transmission properties of the beams with finite cells are simulated in order to confirm the correctness of effective approximation. The results show that the periodic beam can be equivalent to the homogeneous beam with dynamic effective material parameters in passband.

  14. Effects of Flux and Energy of Neutral Beam on Hydrogenation of Graphene

    NASA Astrophysics Data System (ADS)

    Okada, Takeru; Samukawa, Seiji

    2015-09-01

    Hydrogen modification, hydrogenation, of graphene, has attracted due to the possibility of hydrogen storage. Chemisorbed hydrogen has strong interaction with graphene surface and sp3 bond forms. Surprisingly, ideal structure of graphene shows reversible absorption of hydrogen and it leads to effective designing of hydrogen storage material. In this paper, we have demonstrated neutral beam (NB) technique for hydrogenation of graphene instead of conventional plasma method. NB system consists of a plasma generation chamber and a process chamber, which are separated by a carbon plate with many apertures. The charged particles can be effectively neutralized by collision with the sidewall of the apertures when passing through them to the process chamber. Development of the D-band and blue shift of G-band were observed after hydrogen NB irradiation by Raman spectroscopy. FTIR analysis reveals CH bending mode was appeared and it depends on beam energy, thus CH formation has reaction threshold and potential to control it. In addition, it is shown that beam flux affects hydrogenation and additional effect is also included in reaction process. We believe our investigation will provide development of hydrogenated graphene applications.

  15. Scattering effects in passive foil focusing of ion beams

    DOE PAGES

    Yuen, Albert; Lund, Steven M.; Barnard, John J.; ...

    2015-09-11

    A stack of thin, closely spaced conducting foils has been investigated by Lund et al. [Phys. Rev. ST Accel. Beams 16, 044202 (2013)] as a passive focusing lens for intense ion beams. The foils mitigate space-charge defocusing forces to enable the beam self-magnetic field to focus. In this study, we analyze possible degradation of focusing due to scattering of beam ions resulting from finite foil thickness using an envelope model and numerical simulations with the particle-in-cell code WARP. Ranges of kinetic energy where scattering effects are sufficient to destroy passive focusing are quantified. The scheme may be utilized to focusmore » protons produced in intense laser-solid accelerator schemes. The spot size of an initially collimated 30 MeV proton beam with initial rms radius 200 μm, perveance Q=1.8×10-2, and initial transverse emittance ϵx,rms=0.87 mm mrad propagating through a stack of 6.4 μm thick foils, spaced 100 μm apart, gives a 127.5 μm spot with scattering and a 81.0 μm spot without scattering, illustrating the importance of including scattering effects.« less

  16. Irradiation Effects on RIA Fragmentation CU Beam Dump

    SciTech Connect

    Reyes, S; Boles, J L; Ahle, L E; Stein, W; Wirth, B D

    2005-05-09

    Within the scope of conceptual research and development (R&D) activities in support of the Rare Isotope Accelerator (RIA) facility, high priority is given to the development of high-power fragmentation beam dumps. A pre-study was made of a static water-cooled Cu beam dump that can meet requirements for a 400 MeV/u uranium beam. The issue of beam sputtering was addressed and found to be insignificant. Preliminary radiation transport simulations show significant damage (in displacements per atom, DPA) in the vicinity of the Bragg peak of the uranium ions. Experimental data show that defects in Cu following neutron or high-energy particle irradiation tend to saturate at doses between 1 and 5 DPA, and this saturation in defect density also results in saturation of mechanical property degradation. However, effects of swift heavy ion irradiation and the production of gaseous and solid transmutant elements still need to be addressed. Initial calculations indicate that He concentrations on the order of 400 appm are produced in the beam dump after several weeks of continuous operation and He embrittlement may be a concern. Recommendations are made for further investigation of Cu irradiation effects for RIA-relevant conditions.

  17. Irradiation Effects on RIA Fragmentation CU Beam Dump

    SciTech Connect

    Reyes, S; Boles, J L; Ahle, L E; Stein, W; Wirth, B D

    2005-05-20

    Within the scope of conceptual research and development (R&D) activities in support of the Rare Isotope Accelerator (RIA) facility, high priority is given to the development of high-power fragmentation beam dumps. A pre-study was made of a static water-cooled Cu beam dump that can meet requirements for a 400 MeV/u uranium beam. The issue of beam sputtering was addressed and found to be insignificant. Preliminary radiation transport simulations show significant damage (in displacements per atom, DPA) in the vicinity of the Bragg peak of the uranium ions. Experimental data show that defects in Cu following neutron or high-energy particle irradiation tend to saturate at doses between 1 and 5 DPA, and this saturation in defect density also results in saturation of mechanical property degradation. However, effects of swift heavy ion irradiation and the production of gaseous and solid transmutant elements still need to be addressed. Initial calculations indicate that He concentrations on the order of 400 appm are produced in the beam dump after several weeks of continuous operation and He embrittlement may be a concern. Recommendations are made for further investigation of Cu irradiation effects for RIA-relevant conditions.

  18. Modification of the velocity distribution of H(2) molecules in a supersonic beam by intense pulsed optical gradients.

    PubMed

    Ramirez-Serrano, Jaime; Strecker, Kevin E; Chandler, David W

    2006-07-07

    We report the acceleration and deceleration of H(2) molecules in a supersonic molecular beam by means of its interaction with an intense optical gradient from a nanosecond far-off-resonant optical pulse. The strong optical gradients are formed in the interference pattern of two intense optical pulses at 532 nm. The velocity distribution of the molecular beam, before and after the applied optical pulse, is measured by a velocity-mapped ion imaging technique. Changes in velocity up to 202 m s(-1)+/- 61 m s(-1) are observed in a molecular beam initially travelling at a mean speed of 563 m s(-1). We report the dependence of this change in velocity with the strength of the optical gradient applied.

  19. Advanced carbon-based material C{sub 60} modification using partially ionized cluster and energetic beams

    SciTech Connect

    Du Yuancheng; Ren Zhongmin; Ning Zhifeng; Xu Ning; Li Fuming

    1997-06-20

    Two processes have been undertaken using Partially ionized cluster deposition (PICBD) and energetic ion bombardment beams deposition (IBD) respectively. C{sub 60} films deposited by PICBD at V=0 and 65 V, which result in highly textured close-packed structure in orientation (110) and being more polycrystalline respectively, the resistance of C{sub 60} films to oxygen diffusion contamination will be improved. In the case of PICBD, the ionized C{sub 60} soccer-balls molecules in the evaporation beams will be fragmented in collision with the substrate under the elevated accelerating fields Va. As a new synthetic IBD processing, two low energy (400 and 1000 eV) nitrogen ion beams have been used to bombard C{sub 60} films to synthesize the carbon nitride films.

  20. Computer-Assisted Accent Modification: A Report on Practice Effects.

    ERIC Educational Resources Information Center

    Ferrier, Linda J.; Reid, Lawry N.; Chenausky, Karen

    1999-01-01

    This study evaluated the use of the computer-assisted accent-modification program, Speech Works, with beginning college students of English as a second language with a non-speech-language pathologist trainer. Students who had weekly one-on-one sessions with a teacher and independent practice, especially when the practice was computer monitored,…

  1. Modification of the Coherence Properties of a Laser Beam Propagating through a Plasma and its Consequences for Stimulated Scattering Instabilities

    SciTech Connect

    Labaune, C; Baldis, H A; Bandulet, H; Depierreux, S; Fuchs, J; Michel, P; Pesme, D

    2002-11-19

    The control of coherence is a critical issue for the high-power lasers used in inertial confinement fusion (ICF). The level of coherence is an important parameter for the control of the light intensity distribution as well as the growth rate of parametric instabilities. Over the past few years, experimental and theoretical studies have evidenced the ability of an underdense plasma to reduce the spatial and temporal coherence of an intense laser beam propagating through it. As any process affecting laser propagation, plasma-induced incoherence appears fundamental for ICF for it can impact on wave-coupling conditions. We present results obtained with the six-beam LULI laser facility, in the nanosecond regime, showing direct evidences of the reduction of spatial and temporal coherence of an initially RPP-smoothed laser beam after propagation through a preformed plasma. Plasma induced incoherence (PII) proceeds from several mechanisms which include self-focusing and filament instabilities and non-linear coupling between self-focusing and forward stimulated Brillouin scattering (FSBS). Part of these experiments was dedicated to the understanding of the physical mechanisms involved in PII, as the break up of a single hot spot and the existence of ion acoustic waves having small wave vectors transverse to the interaction beam which are produced in the PII processes. The spatial and temporal characteristics of these waves give a unique access to the influence of PII on stimulated Brillouin and Raman scattering.

  2. Return Current Effects on Electron Beam Focusing in Plasma Lenses

    NASA Astrophysics Data System (ADS)

    Govil, R.; Backhaus, E. Y.; Wurtele, J. S.; Leemans, W. P.

    1998-11-01

    Relativistic electron beams can be focused in field-free plasmas due to magnetic self-pinching(P. Chen, Particle Accelerators, 20, p. 171 (1987).). If the plasma density is sufficiently high, plasma return current can weaken the beam self-pinching by reducing the net current. The return current effect is important when the plasma wavelength is small compared to transverse beam size, namely, k_pσr agt 1. An overdense plasma lens experiment(R. Govil and W.P. Leemans, Proc. of the Advanced Accelerator Workshop, Baltimore, MD (1998), to be published.) was conducted at the Beam Test Facility(W.P. Leemans et al., Proc. of the Particle Accelerator Conference, p. 83 (1993).) at LBNL to examine the reduction in focusing due to return currents induced in the plasma. In the experiment, plasma lenses were produced with k_pσr ranging from 0.3 to 1.1. Simulation results, based on beam envelope model, are shown to agree with measurements in both regimes. In addition, focusing is examined in plasmas with dimensions comparable to transverse bunch size and plasma wavelength.

  3. Nonlinear effects in photothermal-optical-beam-deflection imaging

    NASA Astrophysics Data System (ADS)

    Wetsel, G. C., Jr.; Spicer, J. B.

    1986-09-01

    Nonlinear phenomena have been observed during photothermal-optical-beam-deflection imaging experiments on samples of both high-purity aluminum and aluminum alloys. Evidence for nonlinear optical and thermal effects have been measured. Theoretical models have been developed as aids in understanding the different contrast mechanisms observed in linear and nonlinear photothermal images.

  4. Radii effect on the translation spring constant of force transducer beams

    NASA Technical Reports Server (NTRS)

    Scott, C. E.

    1992-01-01

    Multi-component strain-gage force transducer design requires the designer to determine the spring constant of the numerous beams or flexures incorporated in the transducer. The classical beam deflection formulae that are used in calculating these spring constants typically assume that the beam has a uniform moment of inertia along the entire beam length. In practice all beams have a radius at the end where the beam interfaces with the shoulder of the transducer, and on short beams in particular this increases the beam spring constant considerably. A Basic computer program utilizing numerical integration is presented to determine this effect.

  5. Burner modifications for cost effective NO{sub x} control

    SciTech Connect

    Melick, T.A.; Hensley, M.E.; Gustafson, D.A.

    1998-07-01

    The development of commercial low NO{sub x} burners has provided Energy and Environmental Research Corporation (EER) with the expertise to modify existing burner equipment to provide the controlled fuel/air mixing conditions required for low NO{sub x} combustion. This approach represents a viable lower cost alternative to a full burner retrofit for many applications. EER has modified burners to lower NO{sub x} emissions at Louisville Gas and Electric's (LG and E) Cane Run Station and at Jamestown Board of Public Utilities (JBPU). This paper will discuss the method and results of these burner modifications on a 180 and 170 Mwe boiler for LG and E and four boilers at JBPU. NO{sub x} reductions of greater than 50% have been demonstrated with burner modifications only that have achieved NO{sub x} compliance on these six boilers. EER will also be modifying cell burners for Dayton Power and Light at their JM Stuart Station. Unit {number_sign}3 is a 605 Mwe B and W universal pressure opposed wall fired boiler. EER will retrofit the burners this October through November and results will be available by the first of December. With deregulation of the utility industry approaching, many utilities are looking for lower cost alternatives to satisfy NO{sub x} regulations. Justifying new low NO{sub x} burners on a boiler that is 30 to 40 years old and has limited remaining life is also difficult. Performing modifications to the existing burners provides the utility an option. Modifications are usually 2 to 4 times less expensive than new low NO{sub x} burners.

  6. Effect of electron beams during solar flares

    NASA Astrophysics Data System (ADS)

    Aboudarham, J.; Henoux, J. C.; Brown, J. C.; van den Oord, J.; van Driel-Gesztelyi, L.

    1990-12-01

    Electron bombardment of the solar atmosphere has two effects: one is to enhance hydrogen recombination emission, the other is to increase the opacity via an increase of H(-) population. The first effect is the most important in the upper part of the atmosphere, and the second in the lower part. It is predicted that, when enhanced absorption dominates in the part of the atmosphere where radiation originates, there will be a decrease in the white-light emission, leading to a 'negative flare', or 'black-light flare' short duration, not more than about 20 sec.

  7. Mass spectrometer with electron source for reducing space charge effects in sample beam

    DOEpatents

    Houk, Robert S.; Praphairaksit, Narong

    2003-10-14

    A mass spectrometer includes an ion source which generates a beam including positive ions, a sampling interface which extracts a portion of the beam from the ion source to form a sample beam that travels along a path and has an excess of positive ions over at least part of the path, thereby causing space charge effects to occur in the sample beam due to the excess of positive ions in the sample beam, an electron source which adds electrons to the sample beam to reduce space charge repulsion between the positive ions in the sample beam, thereby reducing the space charge effects in the sample beam and producing a sample beam having reduced space charge effects, and a mass analyzer which analyzes the sample beam having reduced space charge effects.

  8. Thermal effects in high power cavities for photoneutralization of D- beams in future neutral beam injectors

    NASA Astrophysics Data System (ADS)

    Fiorucci, Donatella; Feng, Jiatai; Pichot, Mikhaël; Chaibi, Walid

    2015-04-01

    Photoneutralization may represent a key issue in the neutral beam injectors for future fusion reactors. In fact, photodetachment based neutralization combined with an energy recovery system increase the injector overall efficiency up to 60%. This is the SIPHORE injector concept in which photoneutralization is realized in a refolded cavity [1]. However, about 1 W of the several megaWatts intracavity power is absorbed by the mirrors coatings and gives rise to important thermoelastic distortions. This is expected to change the optical behavior of the mirrors and reduce the enhancement factor of the cavity. In this paper, we estimate these effects and we propose a thermal system to compensate it.

  9. A comparative study of the effect of gamma and electron beam irradiation on the optical and structural properties of polyurethane

    NASA Astrophysics Data System (ADS)

    Nouh, S. A.; Abutalib, M. M.

    2011-03-01

    The effects of both gamma and electron beam irradiation on the color changes of polyurethane were investigated. Samples from polyurethane were classified into two groups. The first group was exposed to gamma doses at levels between 20 and 200 kGy. The second group was exposed to an electron beam with similar doses. The transmission of these samples in the wavelength range 370-780 nm, as well as any color changes, was studied. The Commission International de E'Claire (CIE units X, Y and Z) methodology is used in this work for the description of the colored samples. Additionally, the color differences between the non-irradiated sample and those irradiated with different gamma or electron beam doses were calculated. The results indicate that the polyurethane polymer acquires color changes under gamma or electron beam irradiation, but the response of polyurethane to color changes by electron beam irradiation is higher than the response to gamma irradiation. The structural modifications in the gamma and electron beam-irradiated polyurethane samples have also been studied as a function of the dose using the refractive index and Fourier transform infrared (FTIR) spectroscopy.

  10. Statistical effects in high-power microwave beam propagation

    NASA Astrophysics Data System (ADS)

    Alvarez, R. A.; Bolton, P. R.; Sieger, G. E.

    1988-06-01

    At very high power levels pulsed microwave beams can generate air-breakdown plasmas which may limit the fluence that the beam can transport through the atmosphere. Conventional air breakdown is an avalanche process wherein free electrons, driven by the microwave fields, produce ionization through collisions with air molecules. Propagation of a beam is affected when the plasma electron density approaches the critical density for the particular microwave frequency. The rate of growth of the plasma depends on the competition between the ionization probability and electron loss processes such as attachment and diffusion. The physics of the avalanche process is reasonably well understood, and fluence limits can be fairly accurately predicted, so long as there are free seed electrons to initiate the breakdown. At sea level and low altitudes, seed electrons are, in fact, expected to be fairly rare, and air breakdown, and the consequences for beam propagation, must be treated as a statistical problem; the effective fluence limit may be much greater than would be predicted on the basis of conventional breakdown thresholds. The statistical effects are currently being investigated.

  11. Burner modifications for cost effective NO{sub x} control

    SciTech Connect

    Melick, T.A.; Hensley, M.E.; Gustafson, D.A.

    1998-12-31

    The development of commercial Low NO{sub x} Burners has provided Energy and Environmental Research Corporation (EER) with the expertise to modify existing burner equipment to provide the controlled fuel/air mixing conditions required for low NO{sub x} contribution. This approach represents a viable alternative to a full burner retrofit for many applications. EER has modified burners to lower NO{sub x} emissions at Louisville Gas and Electric`s (LG and E) Cane Run Station and at Jamestown Board of Public Utilities (JBPU). This paper discusses the method and results of these burner modifications.

  12. Ion bunch length effects on the beam-beam interaction and its compensation in a high-luminosity ring-ring electron-ion collider

    SciTech Connect

    Montag C.; Oeftiger, A.; Fischer, W.

    2012-05-20

    One of the luminosity limits in a ring-ring electron-ion collider is the beam-beam effect on the electrons. In the limit of short ion bunches, simulation studies have shown that this limit can be significantly increased by head-on beam-beam compensation with an electron lens. However, with an ion bunch length comparable to the beta-function at the IP in conjunction with a large beam-beam parameter, the electrons perform a sizeable fraction of a betatron oscillation period inside the long ion bunches. We present recent simulation results on the compensation of this beam-beam interaction with multiple electron lenses.

  13. Ion beam mixing effects in Ag precipitates embedded in MgO crystals

    NASA Astrophysics Data System (ADS)

    Fuchs, G.; Abouchacra, G.; Treilleux, M.; Thevenard, P.; Serughetti, J.

    1988-05-01

    MgO single crystals have been implanted at room temperature with 8 × 10 16 Ag cm -2 of 180 keV energy. After 973 K thermal annealing, Ag atoms precipitate in the MgO matrix. The MgOAg samples were then irradiated at 77 K with 800 keV xenon up to 1.7 × 10 16 ions cm -2. The modification of the metallic precipitated phase induced by such ionic bombardment, has been characterized by optical absorption spectroscopy (OAS) and transmission electron microscopy (TEM). The evolution of the optical spectra with xenon bombardment has been interpreted in terms of silver precipitate dispersion induced by ion beam mixing effects. The inhibition of atomic diffusion or radiation induced diffusion, due the low sample temperature during irradiation, increases the efficiency of atomic mixing effects. TEM observations confirm this assumption.

  14. Focused Ion Beam Induced Effects on MOS Transistor Parameters

    SciTech Connect

    Abramo, Marsha T.; Antoniou, Nicholas; Campbell, Ann N.; Fleetwood, Daniel M.; Hembree, Charles E.; Jessing, Jeffrey R.; Soden, Jerry M.; Swanson, Scot E.; Tangyunyong, Paiboon; Vanderlinde, William E.

    1999-07-28

    We report on recent studies of the effects of 50 keV focused ion beam (FIB) exposure on MOS transistors. We demonstrate that the changes in value of transistor parameters (such as threshold voltage, V{sub t}) are essentially the same for exposure to a Ga+ ion beam at 30 and 50 keV under the same exposure conditions. We characterize the effects of FIB exposure on test transistors fabricated in both 0.5 {micro}m and 0.225 {micro}m technologies from two different vendors. We report on the effectiveness of overlying metal layers in screening MOS transistors from FIB-induced damage and examine the importance of ion dose rate and the physical dimensions of the exposed area.

  15. A Study of Effects of Tissue Inhomogeneity on HIFU Beam

    NASA Astrophysics Data System (ADS)

    Amin, Viren; Roberts, Ron; Long, Tao; Thompson, R. B.; Ryken, Timothy

    2006-05-01

    The potential of high-intensity focused ultrasound (HIFU) will not be realized unless the effects of overlaying tissues are understood in such a way that allows for estimation of HIFU dose distribution at a target tissue. We employ computational models to examine the impact of phase aberration on tissue ablation. Thompson and Roberts have recently studied the effects of phase aberration on ultrasound focusing in aerospace engine materials such as titanium alloy, and have developed a computational model to examine these effects. The ultrasound beam observed after transmission through the fused quartz (homogeneous) and that observed after transmission through the titanium (inhomogeneous) demonstrate the severe beam wavefield amplitude distortion introduced by the velocity inhomogeneity-induced phase aberration. We study applicability of this approach to model phase aberration in inhomogeneous tissues and its effect on HIFU dose distribution around the focus. It is hypothesized that the ill-effects of phase aberration accumulate during propagation through intervening tissue in which field intensities are substantially lower than that in the focal zone, and it is therefore appropriate to use a linear acoustic model to describe the transport of energy from the transducer to the volume targeted for ablation. We present initial results of the simulation and experiments of beam measurements under water without and with different tissue layers.

  16. The dose delivery effect of the different Beam ON interval in FFF SBRT: TrueBEAM

    NASA Astrophysics Data System (ADS)

    Tawonwong, T.; Suriyapee, S.; Oonsiri, S.; Sanghangthum, T.; Oonsiri, P.

    2016-03-01

    The purpose of this study is to determine the dose delivery effect of the different Beam ON interval in Flattening Filter Free Stereotactic Body Radiation Therapy (FFF-SBRT). The three 10MV-FFF SBRT plans (2 half rotating Rapid Arc, 9 to10 Gray/Fraction) were selected and irradiated in three different intervals (100%, 50% and 25%) using the RPM gating system. The plan verification was performed by the ArcCHECK for gamma analysis and the ionization chamber for point dose measurement. The dose delivery time of each interval were observed. For gamma analysis (2%&2mm criteria), the average percent pass of all plans for 100%, 50% and 25% intervals were 86.1±3.3%, 86.0±3.0% and 86.1±3.3%, respectively. For point dose measurement, the average ratios of each interval to the treatment planning were 1.012±0.015, 1.011±0.014 and 1.011±0.013 for 100%, 50% and 25% interval, respectively. The average dose delivery time was increasing from 74.3±5.0 second for 100% interval to 154.3±12.6 and 347.9±20.3 second for 50% and 25% interval, respectively. The same quality of the dose delivery from different Beam ON intervals in FFF-SBRT by TrueBEAM was illustrated. While the 100% interval represents the breath-hold treatment technique, the differences for the free-breathing using RPM gating system can be treated confidently.

  17. [Modification of the effects of microwave irradiation on biochemical processes by using foreign protein].

    PubMed

    Podkovkin, V G; Uglova, I B

    1998-01-01

    The biochemical data on the influence of electromagnetic fields in microwave range on the hormonal-mediator regulation systems are presented. The possibility of biological effects modification under combined action of microwave radiation and foreign protein is discussed.

  18. Inhibitory effects of aromatic herbs on lipid peroxidation and protein oxidative modification by copper.

    PubMed

    Toda, Shizuo

    2003-05-01

    Aromatic herbs have been used as carminatives. Oxygen free radicals are generated in ischaemia/reperfusion injury in the stomach, and induce lipid peroxidation or protein oxidative modification. Several aromatic herbs were shown to have inhibitory effects on the generation of oxygen free radicals. It was shown that several aromatic herbs, Caryophylli Flos, Cinnamomi Cortex, Foeniculi Fructus and Zedoariae Rhizoma, have inhibitory effects on lipid peroxidation or protein oxidative modification by copper.

  19. Effect of electron beam misalignments on the gyrotron efficiency

    SciTech Connect

    Dumbrajs, O.; Nusinovich, G. S.

    2013-07-15

    The theory describing the operation of gyrotrons with tilted and shifted electron beams has been developed. Effects of the tilt and shift are studied for a 1 MW, 170 GHz gyrotron, which is presently under development in Europe for electron cyclotron resonance plasma heating and current drive in the International Thermonuclear Experimental Reactor. It is shown that one should expect significant deterioration of gyrotron operation in such gyrotrons when the tilt angle exceeds 0.4°–0.5° and the parallel shift of the beam axis with respect to the axis of a microwave circuit is larger than 0.4–0.5 mm. At the same time, simultaneous tilting and shifting in a proper manner can mitigate this deteriorating effect.

  20. Effect of 8 MeV electron beam irradiation on the structural and optical properties of CeO{sub 2} nanoparticles

    SciTech Connect

    Babitha, K.K.; Priyanka, K.P.; Sreedevi, A.; Ganesh, S.; Varghese, Thomas

    2014-12-15

    The effect of 8 MeV electron beam irradiation on the structural and optical properties of cerium oxide nanoparticles was investigated. Ceria nanoparticles were synthesized by chemical precipitation method, and characterized by X-ray diffraction, transmission electron microscopy, ultraviolet–visible, photoluminescence and Raman spectroscopy. Ultraviolet–visible absorption spectra, photoluminescence and Raman spectra of beam irradiated samples were modified, and shifted to blue region, which were attributed to quantum size effect. Systematic observations found that nonstoichiometry, defects and size reduction caused by beam irradiation have great influence on optical band gap, blue shift, photoluminescence and Raman band modifications. Moreover, electron beam irradiation is a suitable technique to enhance the structural and optical properties of nanoceria by controlling the particle size, which may lead to potentially useful technological applications. - Highlights: • Investigated effect of beam irradiation on CeO{sub 2} nanoparticles • Beam irradiation caused size reduction and surface modification. • It increases microstrain, decreases d-spacing and broadens XRD peaks. • It also modifies optical band gap, absorption, PL and Raman bands.

  1. Skin-sparing effects of neutron beam filtering materials.

    PubMed

    Otte, V A; Almond, P R; Smathers, J B; Attix, F H

    1987-01-01

    The skin-sparing effects of several filtering materials for fast neutron beams were studied under various conditions. A parallel-plate ionization chamber was used for the measurements. The parameters which were studied included field size, distance from filter to ion chamber, filter material, and filter thickness. On the basis of this work, Teflon (polytetrafluoroethylene) was chosen for fabrication of flattening filters and wedges.

  2. Temperature effects in high fluence ion modification of HOPG

    NASA Astrophysics Data System (ADS)

    Andrianova, N. N.; Avilkina, V. S.; Borisov, A. M.; Mashkova, E. S.

    2012-02-01

    The ion-induced processes of HOPG (UPV-1T) modification under high-fluence (10 18-10 19 ion/cm 2) 30 keV Ar + and Ne + ion irradiation have been studied from room temperature till 400 °C. The temperature dependences of ion-induced electron emission yield have been found, in contrary to isotropic graphite MPG-8, the essentially different for HOPG between heating and following cooling measurements. For Ar + irradiation only in the 150-300 °C temperature range anomalously large depth of ion-modified surface layer with developed morphology have been found. The results are discussed in frame of the Ehrlich-Schwoebel instability.

  3. The effect of habitat modification on plant-pollinator network

    NASA Astrophysics Data System (ADS)

    Aminatun, Tien; Putra, Nugroho Susetya

    2017-08-01

    The research aimed to determine; (1) the mutualism interaction pattern of plant-pollinator on several habitat modifications; and (2) the habitat modification which showed the most stable pattern of interaction. The study was conducted in one planting season with 20 plots which each plot had 2x2 m2 width and 2 m spacing among plots, and each plot was planted with the same variety of tomato plants, i.e. "intan". Nitrogen manipulation treatment was conducted with four kinds of fertilizers, i.e. NPK (code PU), compost (code PKM), vermicompost (code PC), and manure (code PK). Each treatment had 5 plot replications. We observed the growth of tomato plants, weed and arthropod populationstwo weekly while pollinator visitation twice a week during tomato plant flowering with counting population and visitation frequence of each pollinator on each sample of tomato plants. The nectar of tomato plant flower of each treatment was tested in laboratory to see its reducing sugar and sucrose. Oganic matter and nitrogen of the soil samples of each treatment were tested in laboratory in the beginning and the end of this research. We analized the plant-pollinator network with bipartite program in R-statistics, and the abiotic and other biotic factors with descriptive analysis. The results of the research were; (1) the mutualism interaction pattern of plant-pollinator network of four treatments were varied, and (2) The pattern of plant-pollinator network of NPK fertilizer treatment showed the more stable interaction based on analysis of interaction evenness, Shannon diversity, frequency and longevity of pollinator visitation.

  4. [Effects of posttranslational modification on the activity of cytochrome P450: current progress].

    PubMed

    Li, Yu-hua; Bi, Hui-chang; Huang, Min

    2011-05-01

    Regulation of the activity of CYP450 has always been research focus of drug metabolism. The effect of compounds on the mRNA and protein expression level of CYP450 is the main purpose of most of the existing reports. In recent years, the protein modification in the posttranslation level has been found to participate in maintaining the proper function of CYP450, thus effect of posttranslational modification on the enzyme activity has been paid more and more attention. Posttranslational modifications including phosphorylation, nitration, and ubiquitination have been described to regulate the activity of CYP450. In this paper, recent developments in the effects of posttranslational modifications on the activity of CYP450 have been reviewed.

  5. Investigation of the effects of beam scattering and beam wandering on laser beams passing thorough the off-gas duct of an Electric Arc Furnace

    NASA Astrophysics Data System (ADS)

    Alikhanzadeh, Amirhossein

    The project sets to determine the effects of scattering and beam wandering on light that passes through the off-gas of EAF. The effects of light scattering from metallic dust and beam wandering due to temperature gradient and turbulence in the medium are investigated. Using Matlab, a model was developed based on Mie theory to calculate light transmission when the optical properties are known; most importantly refractive index of the dust as well as incident wavelength, particle size and concentration of the particles per cm 3 of the gas. The model was validated and was used to show that as the particle size parameter increases, the scattering losses decreases. Turbulence and temperature gradients in the air cause the laser beam to change shape. Using a big collection lens can minimize the signal fluctuation caused by the beam wandering. A thorough understanding of these phenomena helps in designing optical sensors in the industry.

  6. Effects of tRNA modification on translational accuracy depend on intrinsic codon-anticodon strength.

    PubMed

    Manickam, Nandini; Joshi, Kartikeya; Bhatt, Monika J; Farabaugh, Philip J

    2016-02-29

    Cellular health and growth requires protein synthesis to be both efficient to ensure sufficient production, and accurate to avoid producing defective or unstable proteins. The background of misreading error frequency by individual tRNAs is as low as 2 × 10(-6) per codon but is codon-specific with some error frequencies above 10(-3) per codon. Here we test the effect on error frequency of blocking post-transcriptional modifications of the anticodon loops of four tRNAs in Escherichia coli. We find two types of responses to removing modification. Blocking modification of tRNA(UUC)(Glu) and tRNA(QUC)(Asp) increases errors, suggesting that the modifications act at least in part to maintain accuracy. Blocking even identical modifications of tRNA(UUU)(Lys) and tRNA(QUA)(Tyr) has the opposite effect of decreasing errors. One explanation could be that the modifications play opposite roles in modulating misreading by the two classes of tRNAs. Given available evidence that modifications help preorder the anticodon to allow it to recognize the codons, however, the simpler explanation is that unmodified 'weak' tRNAs decode too inefficiently to compete against cognate tRNAs that normally decode target codons, which would reduce the frequency of misreading. © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.

  7. Effect of the spiral phase element on the radial-polarization (0, 1) ∗ LG beam

    NASA Astrophysics Data System (ADS)

    Machavariani, G.; Lumer, Y.; Moshe, I.; Jackel, S.

    2007-03-01

    Radially-polarized beams can be strongly amplified without significant birefringent-induced aberrations. However, radially-polarized beam is a high-order beam, and therefore has to be transformed into a fundamental Gaussian beam for reduction the beam-propagation factor M2. In effort to transform the radially-polarized beam to a nearly-Gaussian beam, we consider effect of a spiral phase element (SPE) on the Laguerre-Gaussian (LG) (0, 1)∗ beam with radial polarization, and compare this with the case when the input beam is a LG (0, 1)∗ beam with spiral phase and uniform or random polarization. The LG (0, 1)∗ beam with radial polarization, despite its identity in intensity profile to the beam with spiral phase, has distinctly different properties when interacting with the SPE. With the SPE and spatial filter, we transformed the radially-polarized (0, 1)∗ mode with M2 = 2.8 to a nearly-Gaussian beam with M2 = 1.7. Measured transformation efficiency was 50%, and the beam brightness P/(M2)2 was practically unchanged. The SPE affects polarization state of the radially-polarized beam, leading to appearance of spin angular momentum in the beam center at the far-field.

  8. Effect of electron-beam irradiation on graphene field effect devices

    NASA Astrophysics Data System (ADS)

    Childres, Isaac; Jauregui, Luis A.; Foxe, Michael; Tian, Jifa; Jalilian, Romaneh; Jovanovic, Igor; Chen, Yong P.

    2010-10-01

    Electron beam exposure is a commonly used tool for fabricating and imaging graphene-based devices. Here, we present a study of the effects of electron-beam irradiation on the electronic transport properties of graphene and the operation of graphene field-effect transistors (GFETs). Exposure to a 30 keV electron-beam caused negative shifts in the charge-neutral point (CNP) of the GFET, interpreted as due to n-doping in the graphene from the interaction of the energetic electron beam with the substrate. The shift in the CNP is substantially reduced for suspended graphene devices. The electron beam is seen to also decrease the carrier mobilities and minimum conductivity, indicating defects created in the graphene. The findings are valuable for understanding the effects of radiation damage on graphene and for the development of radiation-hard graphene-based electronics.

  9. Beam flatness perturbation effects of a perforated thermoplastic immobilization device on 6 and 12 MeV electron beams.

    PubMed

    Van Way, R L; Williams, R O; Johnstone, P A; Papin, P J

    1996-12-01

    Perforated thermoplastic masks are widely used in radiotherapy of head and neck malignancies. They provide for patient immobilization and increase setup reproducibility. Some oncology treatment centers cut mask portals (windows) for the beam to pass through; for those centers that do not, the mask affects beam fluence. The extent to which beam flatness is altered by such a mask is investigated. The effects of perforated thermoplastic on 6 MeV and 12 MeV electron beams was described in terms of optical density differences in a comparative film study. Variations of beam flatness were documented of up to 11.8% at 5 mm depth for 6 MeV, and 8.1% for 12 MeV electrons. The depth at which this effect may be considered insignificant (mean optical density differences < 2%) is approximately 10 mm for both beam energies. For clinical situations where the target volume is superficial, some consideration should be given to beam inhomogeneity caused by the mask.

  10. Effects on focused ion beam irradiation on MOS transistors

    SciTech Connect

    Campbell, A.N.; Peterson, K.A.; Fleetwood, D.M.; Soden, J.M.

    1997-04-01

    The effects of irradiation from a focused ion beam (FIB) system on MOS transistors are reported systematically for the first time. Three MOS transistor technologies, with 0.5, 1, and 3 {mu}m minimum feature sizes and with gate oxide thicknesses ranging from 11 to 50 nm, were analyzed. Significant shifts in transistor parameters (such as threshold voltage, transconductance, and mobility) were observed following irradiation with a 30 keV Ga{sup +} focused ion beam with ion doses varying by over 5 orders of magnitude. The apparent damage mechanism (which involved the creation of interface traps, oxide trapped charge, or both) and extent of damage were different for each of the three technologies investigated.

  11. Attosecond Lighthouse Effect: from tilted waves to isolated harmonic beams

    NASA Astrophysics Data System (ADS)

    Wheeler, Jonathan; Borot, Antonin; Vincenti, Henri; Monchoce, Sylvain; Ricci, Aurelien; Jullien, Aurelie; Malvache, Arnaud; Quere, Fabien; Lopez-Martens, Rodrigo

    2012-06-01

    Spatio-temporal coupling (STC) within a laser pulse is normally a negative feature to be avoided as it leads to non-uniform pulse characteristics and reduced intensity at focus. In this study, STC is purposefully introduced into the laser pulse leading to wavefront rotation at the focus. When such a modified focus is applied to plasma mirror harmonic generation, each harmonic pulse produced from cycle to cycle has a shifted propagation direction. Dependant on the degree of wavefront rotation introduced, this can lead from tilted harmonic spectra due to small displacements of the overlapping beams to fully isolated, individual pulses arising from each cycle of the driving laser pulse, the so-called Attosecond Lighthouse effect. This work discusses the recently measured results of spatially-separated, single harmonic beams from a solid target source obtained with 1kHz, CEP-locked, 800nm laser pulses of both 25 and 5 fs duration.

  12. Effect of beam quality on tilt measurement using cyclic interferometer

    NASA Astrophysics Data System (ADS)

    Pretheesh Kumar, V. C.; Ganesan, A. R.; Joenathan, C.; Somasundaram, U.

    2016-08-01

    Accurate measurement of angles is extremely important in various metrological applications. Interferometry has always been an excellent technique for accurate measurements. Several methods have been proposed for accurate tilt measurement using interferometric techniques. Almost all of them use the Michelson configuration which is extremely sensitive to environmental vibrations and turbulences. We know that a cyclic interferometer is extremely stable. Even though it is not sensitive to displacement changes, it is twice sensitive to tilt compared to that of a Michelson interferometer. We have enhanced the sensitivity to measure tilt using multiple reflections in a cyclic interferometer. Since the input beam is collimated, we have studied the effect of aberration of the input beam on the accuracy of tilt measurement. Experimental results on this study are presented in this paper.

  13. Beam experiments related to the head-on beam-beam compensation project at RHIC

    SciTech Connect

    Montag, C.; Bai, M.; Drees, A.; Fischer, W.; Marusic, A.; Wang, G.

    2011-03-28

    Beam experiments have been performed in RHIC to determine some key parameters of the RHIC electron lenses, and to test the capability of verifying lattice modifications by beam measurements. We report the status and recent results of these experiments. The Relativistic Heavy Ion Collider (RHIC) consists of two superconducting storage rings that intersect at six locations around its circumference. Beams collide in interaction points (IPs) 6 and 8, which are equipped with the detectors STAR and PHENIX, respectively (Fig. 1). With the polarized proton working point constrained between 2/3 and 7/10 to achieve good luminosity lifetime and maintain polarization, the proton bunch intensity is limited to 2 {center_dot} 10{sup 11} protons per bunch by the resulting beam-beam tuneshift. To overcome this limitation, installation of an electron lens in IP 10 is foreseen to partially compensate the beam-beam effect and reduce the beam-beam tuneshift parameter. As part of this project, beam experiments are being performed at RHIC to determine key parameters of the electron lens as well as to verify lattice modifications.

  14. 75 FR 11559 - Certain Combed Cotton Yarns: Effect of Modification of U.S.-Bahrain FTA Rules of Origin

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-11

    ... COMMISSION Certain Combed Cotton Yarns: Effect of Modification of U.S.- Bahrain FTA Rules of Origin AGENCY...-103-025, Certain Combed Cotton Yarns: Effect of Modification of U.S.-Bahrain FTA Rules Of Origin... government of Bahrain on certain modifications to the rules of origin to the FTA for certain combed...

  15. Effects of wing modification on an aircraft's aerodynamic parameters as determined from flight data

    NASA Technical Reports Server (NTRS)

    Hess, R. A.

    1986-01-01

    A study of the effects of four wing-leading-edge modifications on a general aviation aircraft's stability and control parameters is presented. Flight data from the basic aircraft configuration and configurations with wing modifications are analyzed to determine each wing geometry's stability and control parameters. The parameter estimates and aerodynamic model forms are obtained using the stepwise regression and maximum likelihood techniques. The resulting parameter estimates and aerodynamic models are verified using vortex-lattice theory and by analysis of each model's ability to predict aircraft behavior. Comparisons of the stability and control derivative estimates from the basic wing and the four leading-edge modifications are accomplished so that the effects of each modification on aircraft stability and control derivatives can be determined.

  16. Effect of the transverse parasitic mode on beam performance for the ADS driver linac in China

    NASA Astrophysics Data System (ADS)

    Cheng, Peng; Pei, Shi-Lun; Wang, Jiu-Qing; Li, Zhi-Hui

    2015-05-01

    The ADS (Accelerator Driven subcritical System) driver linac in China is designed to run in CW (Continuous Wave) mode with 10 mA designed beam current. In this scenario, the beam-induced parasitic modes in the ADS driver linac may make the beam unstable or deteriorate the beam performance. To evaluate the parasitic mode effect on the beam dynamics systematically, simulation studies using the ROOT-based numerical code SMD have been conducted. The longitudinal beam instability induced by the HOMs (High Order Modes) and SOMs (Same Order Modes) has little effect on the longitudinal beam performance for the current ADS driver linac design based on the 10 MeV/325 MHz injector I from previous studies. Here the transverse parasitic mode (i.e., dipole HOM) effect on the transverse beam performance at the ADS driver linac exit is investigated. To more reasonably quantify the dipole mode effect, the multi-bunch effective emittance is introduced in this paper.

  17. Effect of electron beam radio sterilization on cyclic olefin copolymers used as pharmaceutical storage materials

    NASA Astrophysics Data System (ADS)

    Barakat, Hala; Aymes-Chodur, Caroline; Saunier, Johanna; Yagoubi, Najet

    2013-03-01

    The aim of this work was to study the effect of radio-sterilization on cyclo olefin copolymers (COC), that can be used as pharmaceutical storage materials, both on the surface and in the volume of the material, and to investigate the impact of the presence of a lubricant. A cyclo olefin copolymer (TOPAS® 8007) was treated with an electron beam radio-sterilization at different doses ranging from 25 to 150 kGy. Polymer structure and bulk properties were evaluated by Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and Size Exclusion Chromatography (SEC). A good correlation between those analytical techniques was observed: oxidation products were formed and crosslinking of chains occured. Although these modifications were important, the effect on the thermal properties was weak. The analysis by Reversed Phase High Performance Liquid Chromatography (RP-HPLC) of extraction's solutions of COC after irradiation showed both a remarkable decrease of the extractable amount of polyphenolic antioxidant (Irganox 1010®) initially present in the matrix, and a generation of an important number of degradation products that represent potential migrants for pharmaceutical formulations. Surface modifications were evidenced by both (FTIR/ATR) and contact angle measurements of COC films. An increase in surface polarity of COC after radio-sterilization was observed.

  18. Theoretical modeling on the laser induced effect of liquid crystal optical phased beam steering

    NASA Astrophysics Data System (ADS)

    He, Xiaoxian; Wang, Xiangru; Wu, Liang; Tan, Qinggui; Li, Man; Shang, Jiyang; Wu, Shuanghong; Huang, Ziqiang

    2017-01-01

    Non-mechanical laser beam steering has been reported previously in liquid crystal array devices. To be one of the most promising candidates to be practical non-mechanical laser deflector, its laser induced effect still has few theoretical model. In this paper, we propose a theoretical model to analyze this laser induced effect of LC-OPA to evaluate the deterioration on phased beam steering. The model has three parts: laser induced thermal distribution; temperature dependence of material parameters and beam steering deterioration. After these three steps, the far field of laser beam is obtained to demonstrate the steering performance with the respect to the incident laser beam power and beam waist.

  19. Effect of ultrasound on silver electrodeposition: Crystalline structure modification.

    PubMed

    Nevers, Aymeric; Hallez, Loïc; Touyeras, Francis; Hihn, Jean-Yves

    2017-02-27

    An attractive possibility for influencing microstructures of electrodeposited coatings, and therefore their properties such as hardness, brightness etc. resides in the use of ultrasound. This method is particularly competitive as it may result in a reduction of chemical use, or even in the complete suppression of chemicals. This paper deals with silver coatings depending strongly on current density, with two main categories identified by X-ray diffraction: one poorly structured and the other following the [110] orientation. It is interesting to note that, while changing from still to mechanically stirred conditions, the value of the current density threshold moves from 2.5mAcm(-2) to 5mAcm(-2). When ultrasound is used (575kHz or 20kHz), this coating microstructure modification threshold occurs at higher current density values when coatings are produced under sonication, while agitation is kept constant. In both cases, the shift is about 15mAcm(-2). It is noteworthy that silver electrodeposits elaborated under 20kHz ultrasound conditions appear to be less oriented than those obtained under high frequency conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Study of the thermal effect on silicon surface induced by ion beam from plasma focus device

    NASA Astrophysics Data System (ADS)

    Ahmad, Z.; Ahmad, M.; Al-Hawat, Sh.; Akel, M.

    2017-04-01

    Structural modifications in form of ripples and cracks are induced by nitrogen ions from plasma focus on silicon surface. The investigation of such structures reveals correlation between ripples and cracks formation in peripheral region of the melt spot. The reason of such correlation and structure formation is explained as result of thermal effect. Melting and resolidification of the center of irradiated area occur within one micro second of time. This is supported by a numerical simulation used to investigate the thermal effect induced by the plasma focus ion beams on the silicon surface. This simulation provides information about the temperature profile as well as the dynamic of the thermal propagation in depth and lateral directions. In accordance with the experimental observations, that ripples are formed in latter stage after the arrival of last ion, the simulation shows that the thermal relaxation takes place in few microseconds after the end of the ion beam arrival. Additionally, the dependency of thermal propagation and relaxation on the distance of the silicon surface from the anode is presented.

  1. The effects of magnetic fringe fields on beam dynamics in a beam transport line of a terahertz FEL source

    NASA Astrophysics Data System (ADS)

    Zeng, Han; Xiong, Yongqian; Pei, Yuanji

    2014-11-01

    The transport line used in a terahertz FEL device has to transport electron beam through the entire system efficiently and meet the requirements of the beam parameters at the undulator entrance. Due to space limitations, the size of the magnets (five quadrupoles and two bending magnets) employed in the transport line was limited, and some devices were densely packed. In this paper, analyses of the effect of fringe fields and magnetic interference of magnets are presented. 3D models of these magnets are built and their linear optical properties are compared with those obtained by hard edge models. The results indicated that the effects of these factors are significant and they would cause a mismatch of the beam at the exit of the transport line under the preliminary lattice design. To solve this problem, the beam was re-matched using the particle swarm optimization algorithm.

  2. Beam-Beam Interactions

    SciTech Connect

    Sramek, Christopher

    2003-09-05

    At the interaction point of a particle accelerator, various phenomena occur which are known as beam-beam effects. Incident bunches of electrons (or positrons) experience strong electromagnetic fields from the opposing bunches, which leads to electron deflection, beamstrahlung and the creation of electron/positron pairs and hadrons due to two-photon exchange. In addition, the beams experience a ''pinch effect'' which focuses each beam and results in either a reduction or expansion of their vertical size. Finally, if a beam's disruption parameter is too large, the beam can develop a sinusoidal distortion, or two-stream (kink) instability. This project simulated and studied these effects as they relate to luminosity, deflection angles and energy loss in order to optimize beam parameters for the Next Linear Collider (NLC). Using the simulation program Guinea-Pig, luminosity, deflection angle and beam energy data was acquired for different levels of beam offset and distortion. Standard deflection curves and luminosity plots agreed with theoretical models but also made clear the difficulties of e-e- feedback. Simulations emphasizing kink instability in modulated and straight beam collisions followed qualitative behavioral predictions and roughly fit recent analytic calculations. Finally, a study of e-e- collisions under design constraints for the NLC provided new estimates of how luminosity, beamstrahlung energy loss, upsilon parameter and deflection curve width scale with beam spotsizes.

  3. Modeling of dynamic effects of a low power laser beam

    NASA Technical Reports Server (NTRS)

    Lawrence, George N.; Scholl, Marija S.; Khatib, AL

    1988-01-01

    Methods of modeling some of the dynamic effects involved in laser beam propagation through the atmosphere are addressed with emphasis on the development of simple but accurate models which are readily implemented in a physical optics code. A space relay system with a ground based laser facility is considered as an example. The modeling of such characteristic phenomena as laser output distribution, flat and curved mirrors, diffraction propagation, atmospheric effects (aberration and wind shear), adaptive mirrors, jitter, and time integration of power on target, is discussed.

  4. Coherent beam-beam effects observation and mitigation at the RHIC collider

    SciTech Connect

    White S.; Fischer, W.; Luo, Y.

    2012-05-20

    In polarized proton operation in RHIC coherent beam-beam modes are routinely observed with beam transfer function measurements in the vertical plane. With the existence of coherent modes a larger space is required in the tune diagram than without them and stable conditions can be compromised for operation with high intensity beams as foreseen for future luminosity upgrades. We report on experiments and simulations carried out to understand the existence of coherent modes in the vertical plane and their absence in the horizontal plane, and investigate possible mitigation strategies.

  5. Generation of dynamic Bessel beams and dynamic bottle beams using acousto-optic effect.

    PubMed

    Szulzycki, Krzysztof; Savaryn, Viktoriya; Grulkowski, Ireneusz

    2016-10-17

    We present a novel optical configuration that allows for generation of ultra-high speed dynamic Bessel beams and dynamic bottle beams. The method is based on combination of the axisymmetric acousto-optic device and the spatial filtering enabled by a mask or a digital micromirror device. Selected features of dynamic non-diffracting beams and bottle beams are investigated using time-resolved approach with stroboscopic pulsed illumination, including spatial intensity distribution, spatial modulation factors, MHz-range temporal modulation, and scalability. The numerical simulations based on Fourier optics as well as experimental realizations are demonstrated.

  6. Medium effect on the nuclear modification factor of protons and pions in intermediate-energy heavy ion collisions

    NASA Astrophysics Data System (ADS)

    Lv, M.; Ma, Y. G.; Chen, J. H.; Fang, D. Q.; Zhang, G. Q.

    2017-02-01

    Nuclear modification factors Rcp of protons and pions are investigated by simulating Au+Au collisions from 0.8 A to 1.8 A GeV in a framework of an isospin-dependent quantum molecular dynamics (IQMD) model. The Rcp of protons rise with an increase in the transverse particle momentum pT at different beam energies owing to radial flow and the multiple-collision effect. The rate of increase of Rcp is suppressed at higher beam energies. While the Rcp of pions display weaker pT dependence. By changing the in-medium nucleon-nucleon cross section, the Rcp of protons change a lot, while the Rcp of pions do not. In addition, by deactivating the N Δ →N N and π N →Δ channels, the Rcp of protons change slightly in their increasing rates compared with the "original" case (with these two channels). However, the Rcp of pions is shifted down for the "no N Δ →N N " case and has an inverse trend for the "no π N →Δ " case. Based on these observations, we argue that the observable Rcp is a suitable tool to better distinguish in-medium effects of protons and pions.

  7. Effects of heat waves on mortality: effect modification and confounding by air pollutants.

    PubMed

    Analitis, Antonis; Michelozzi, Paola; D'Ippoliti, Daniela; De'Donato, Francesca; Menne, Bettina; Matthies, Franziska; Atkinson, Richard W; Iñiguez, Carmen; Basagaña, Xavier; Schneider, Alexandra; Lefranc, Agnès; Paldy, Anna; Bisanti, Luigi; Katsouyanni, Klea

    2014-01-01

    Heat waves and air pollution are both associated with increased mortality. Their joint effects are less well understood. We explored the role of air pollution in modifying the effects of heat waves on mortality, within the EuroHEAT project. Daily mortality, meteorologic, and air pollution data from nine European cities for the years 1990-2004 were assembled. We defined heat waves by taking both intensity and duration into account. The city-specific effects of heat wave episodes were estimated using generalized estimating equation models, adjusting for potential confounders with and without inclusion of air pollutants (particles, ozone, nitrogen dioxide, sulphur dioxide, carbon monoxide). To investigate effect modification, we introduced an interaction term between heat waves and each single pollutant in the models. Random effects meta-analysis was used to summarize the city-specific results. The increase in the number of daily deaths during heat wave episodes was 54% higher on high ozone days compared with low, among people age 75-84 years. The heat wave effect on high PM10 days was increased by 36% and 106% in the 75-84 year and 85+ year age groups, respectively. A similar pattern was observed for effects on cardiovascular mortality. Effect modification was less evident for respiratory mortality, although the heat wave effect itself was greater for this cause of death. The heat wave effect was smaller (15-30%) after adjustment for ozone or PM10. The heat wave effect on mortality was larger during high ozone or high PM10 days. When assessing the effect of heat waves on mortality, lack of adjustment for ozone and especially PM10 overestimates effect parameters. This bias has implications for public health policy.

  8. Effective dose range for dental cone beam computed tomography scanners.

    PubMed

    Pauwels, Ruben; Beinsberger, Jilke; Collaert, Bruno; Theodorakou, Chrysoula; Rogers, Jessica; Walker, Anne; Cockmartin, Lesley; Bosmans, Hilde; Jacobs, Reinhilde; Bogaerts, Ria; Horner, Keith

    2012-02-01

    To estimate the absorbed organ dose and effective dose for a wide range of cone beam computed tomography scanners, using different exposure protocols and geometries. Two Alderson Radiation Therapy anthropomorphic phantoms were loaded with LiF detectors (TLD-100 and TLD-100 H) which were evenly distributed throughout the head and neck, covering all radiosensitive organs. Measurements were performed on 14 CBCT devices: 3D Accuitomo 170, Galileos Comfort, i-CAT Next Generation, Iluma Elite, Kodak 9000 3D, Kodak 9500, NewTom VG, NewTom VGi, Pax-Uni3D, Picasso Trio, ProMax 3D, Scanora 3D, SkyView, Veraviewepocs 3D. Effective dose was calculated using the ICRP 103 (2007) tissue weighting factors. Effective dose ranged between 19 and 368 μSv. The largest contributions to the effective dose were from the remainder tissues (37%), salivary glands (24%), and thyroid gland (21%). For all organs, there was a wide range of measured values apparent, due to differences in exposure factors, diameter and height of the primary beam, and positioning of the beam relative to the radiosensitive organs. The effective dose for different CBCT devices showed a 20-fold range. The results show that a distinction is needed between small-, medium-, and large-field CBCT scanners and protocols, as they are applied to different indication groups, the dose received being strongly related to field size. Furthermore, the dose should always be considered relative to technical and diagnostic image quality, seeing that image quality requirements also differ for patient groups. The results from the current study indicate that the optimisation of dose should be performed by an appropriate selection of exposure parameters and field size, depending on the diagnostic requirements. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

  9. Effects of shutter transients in molecular beam epitaxy.

    PubMed

    Gozu, Shin-Ichiro; Mozume, Teruo; Kuwatsuka, Haruhiko; Ishikawa, Hiroshi

    2012-11-12

    : We have studied the effects of shutter transients (STs) in molecular beam epitaxy (MBE). Two series of samples were grown by MBE and evaluated by X-ray diffraction (XRD) and X-ray reflectivity (XRR) measurements. The effects of STs were evaluated by growth rate (GR) analysis using a combination of growth time (GT) and thickness evaluated by XRD and XRR measurements. We revealed two opposite effects of STs: (1) overshoot of GR and (2) increase in GR with GT and subsequent saturation. Each effect was consistent with the previous studies; however, the previous studies showed no relationships between these two effects. By considering closing time of the shutter, the two opposite effects were well understood.

  10. Reduction of metal artifacts: beam hardening and photon starvation effects

    NASA Astrophysics Data System (ADS)

    Yadava, Girijesh K.; Pal, Debashish; Hsieh, Jiang

    2014-03-01

    The presence of metal-artifacts in CT imaging can obscure relevant anatomy and interfere with disease diagnosis. The cause and occurrence of metal-artifacts are primarily due to beam hardening, scatter, partial volume and photon starvation; however, the contribution to the artifacts from each of them depends on the type of hardware. A comparison of CT images obtained with different metallic hardware in various applications, along with acquisition and reconstruction parameters, helps understand methods for reducing or overcoming such artifacts. In this work, a metal beam hardening correction (BHC) and a projection-completion based metal artifact reduction (MAR) algorithms were developed, and applied on phantom and clinical CT scans with various metallic implants. Stainless-steel and Titanium were used to model and correct for metal beam hardening effect. In the MAR algorithm, the corrupted projection samples are replaced by the combination of original projections and in-painted data obtained by forward projecting a prior image. The data included spine fixation screws, hip-implants, dental-filling, and body extremity fixations, covering range of clinically used metal implants. Comparison of BHC and MAR on different metallic implants was used to characterize dominant source of the artifacts, and conceivable methods to overcome those. Results of the study indicate that beam hardening could be a dominant source of artifact in many spine and extremity fixations, whereas dental and hip implants could be dominant source of photon starvation. The BHC algorithm could significantly improve image quality in CT scans with metallic screws, whereas MAR algorithm could alleviate artifacts in hip-implants and dentalfillings.

  11. Self-effect in expanding electron beam plasma

    SciTech Connect

    Garcia, M

    1999-05-07

    An analytical model of plasma flow from a metal plate hit by an intense, pulsed, electron beam aims to bridge the gap between radiation-hydrodynamics simulations and experiments, and to quantify the self-effect of the electron beam penetrating the flow. Does the flow disrupt the tight focus of the initial electron bunch, or later pulses in a train? This work aims to model the spatial distribution of plasma speed, density, degree of ionization, and magnetization to inquire. The initial solid density, several eV plasma expands to 1 cm and 10{sup {minus}4} relative density by 2 {micro}s, beyond which numerical simulations are imprecise. Yet, a Faraday cup detector at the ETA-II facility is at 25 cm from the target and observes the flow after 50 {micro}s. The model helps bridge this gap. The expansion of the target plasma into vacuum is so rapid that the ionized portion of the flow departs from local thermodynamic equilibrium. When the temperature (in eV) in a parcel of fluid drops below V{sub i} x [(2{gamma} - 2)/(5{gamma} + 17)], where V{sub i} is the ionization potential of the target metal (7.8 eV for tantalum), and {gamma} is the ratio of specific heats (5/3 for atoms), then the fractional ionization and electron temperature in that parcel remain fixed during subsequent expansion. The freezing temperature as defined here is V{sub i}/19. The balance between the self-pinching force and the space charge repulsion of an electron beam changes on penetrating a flow: (i) the target plasma cancels the space-charge field, (ii) internal eddy currents arise to counter the magnetization of relativistic electrons, and (iii) electron beam heating alters the flow magnetization by changing the plasma density gradient and the magnitude of the conductivity.

  12. Effects of chemical modification on the conformation and biological activity of peanut agglutinin.

    PubMed

    Nonnenmacher, D; Brossmer, R

    1981-03-27

    The effect of chemical modifications on the biological properties of peanut agglutinin was investigated. The free amino groups were modified with succinic anhydride and 1-isothiocyanato-4-benzenesulfonic acid. Though the extent of modification was 95 and 85%, respectively, these derivatives did not lose their sugar binding capacity. The agglutinating activity with neuraminidase-treated human erythrocytes and various tumor cells was reduced. The mitogenic activity tested with neuraminidase-treated human lymphocytes was also diminished The tyrosine residues were modified with tetranitromethane and further with 4-aminophenyl-alpha-D-glucopyranoside and the negatively charged 2-(4-amino-benzyl)-alpha-D-neuraminic acid. The extent of modification was 30, 28 and 6%, respectively. The agglutinating and mitogenic activities were in this case not severely changed. The influence of all these modifications on the conformation was investigated by means of CD studies in the far and near ultraviolet regions.

  13. Fundamental Proximity Effects in Focused electron Beam Induced Deposition

    SciTech Connect

    Plank, Harald; Smith, Daryl; Haber, Thomas; Rack, Philip D; Hofer, Ferdinand

    2012-01-01

    Fundamental proximity effects for electron beam induced deposition processes on nonflat surfaces were studied experimentally and via simulation. Two specific effects were elucidated and exploited to considerably increase the volumetric growth rate of this nanoscale direct write method: (1) increasing the scanning electron pitch to the scale of the lateral electron straggle increased the volumetric growth rate by 250% by enhancing the effective forward scattered, backscattered, and secondary electron coefficients as well as by strong recollection effects of adjacent features; and (2) strategic patterning sequences are introduced to reduce precursor depletion effects which increase volumetric growth rates by more than 90%, demonstrating the strong influence of patterning parameters on the final performance of this powerful direct write technique.

  14. Surface modification of solids

    SciTech Connect

    Appleton, B.R.

    1984-05-01

    The use of ion beam and pulsed laser processing is reviewed for the near-surface modification of a wide range of materials. The techniques of ion implantation doping, ion beam and laser mixing, and pulsed-laser annealing are stressed with particular emphasis on the nonequilibrium aspects of these processing techniques and on new materials properties which can result. Examples are presented illustrating the utility of these techniques for fundamental materials research as well as practical surface modifications.

  15. Effects of Instruction on Adolescent Beginners' Acquisition of Request Modification

    ERIC Educational Resources Information Center

    Li, Qingping

    2012-01-01

    This quasiexperimental study examined the effects of different focus-on-form techniques, and the durability of such effects, on adolescent beginners' acquisition of request supportive moves. Three treatments were implemented: (1) the incidental group was exposed to input and involved in meaningful output activities; (2) the implicit group was…

  16. Effects of Instruction on Adolescent Beginners' Acquisition of Request Modification

    ERIC Educational Resources Information Center

    Li, Qingping

    2012-01-01

    This quasiexperimental study examined the effects of different focus-on-form techniques, and the durability of such effects, on adolescent beginners' acquisition of request supportive moves. Three treatments were implemented: (1) the incidental group was exposed to input and involved in meaningful output activities; (2) the implicit group was…

  17. Fundamental edge broadening effects during focused electron beam induced nanosynthesis.

    PubMed

    Schmied, Roland; Fowlkes, Jason D; Winkler, Robert; Rack, Phillip D; Plank, Harald

    2015-01-01

    The present study explores lateral broadening effects of 3D structures fabricated through focused electron beam induced deposition using MeCpPt(IV)Me3 precursor. In particular, the scaling behavior of proximity effects as a function of the primary electron energy and the deposit height is investigated through experiments and validated through simulations. Correlated Kelvin force microscopy and conductive atomic force microscopy measurements identified conductive and non-conductive proximity regions. It was determined that the highest primary electron energies enable the highest edge sharpness while lower energies contain a complex convolution of broadening effects. Moreover, it is demonstrated that intermediate energies lead to even more complex proximity effects that significantly reduce lateral edge sharpness and thus should be avoided if desiring high lateral resolution.

  18. Fundamental edge broadening effects during focused electron beam induced nanosynthesis

    DOE PAGES

    Schmied, Roland; Fowlkes, Jason Davidson; Winkler, Robert; ...

    2015-01-01

    In this study, we explore lateral broadening effects of 3D structures fabricated through focused electron beam induced deposition using MeCpPt(IV)Me3 precursor. In particular, the scaling behavior of proximity effects as a function of the primary electron energy and the deposit height is investigated through experiments and validated through simulations. Correlated Kelvin force microscopy and conductive atomic force microscopy measurements identified conductive and non-conductive proximity regions. It was determined that the highest primary electron energies enable the highest edge sharpness while lower energies contain a complex convolution of broadening effects. In addition, it is demonstrated that intermediate energies lead to evenmore » more complex proximity effects that significantly reduce lateral edge sharpness and thus should be avoided if desiring high lateral resolution.« less

  19. Fundamental edge broadening effects during focused electron beam induced nanosynthesis

    SciTech Connect

    Schmied, Roland; Fowlkes, Jason Davidson; Winkler, Robert; Rack, Phillip D.; Plank, Harald

    2015-01-01

    In this study, we explore lateral broadening effects of 3D structures fabricated through focused electron beam induced deposition using MeCpPt(IV)Me3 precursor. In particular, the scaling behavior of proximity effects as a function of the primary electron energy and the deposit height is investigated through experiments and validated through simulations. Correlated Kelvin force microscopy and conductive atomic force microscopy measurements identified conductive and non-conductive proximity regions. It was determined that the highest primary electron energies enable the highest edge sharpness while lower energies contain a complex convolution of broadening effects. In addition, it is demonstrated that intermediate energies lead to even more complex proximity effects that significantly reduce lateral edge sharpness and thus should be avoided if desiring high lateral resolution.

  20. Effects of cytosine modifications on DNA flexibility and nucleosome mechanical stability

    NASA Astrophysics Data System (ADS)

    Ngo, Thuy T. M.; Yoo, Jejoong; Dai, Qing; Zhang, Qiucen; He, Chuan; Aksimentiev, Aleksei; Ha, Taekjip

    2016-02-01

    Cytosine can undergo modifications, forming 5-methylcytosine (5-mC) and its oxidized products 5-hydroxymethylcytosine (5-hmC), 5-formylcytosine (5-fC) and 5-carboxylcytosine (5-caC). Despite their importance as epigenetic markers and as central players in cellular processes, it is not well understood how these modifications influence physical properties of DNA and chromatin. Here we report a comprehensive survey of the effect of cytosine modifications on DNA flexibility. We find that even a single copy of 5-fC increases DNA flexibility markedly. 5-mC reduces and 5-hmC enhances flexibility, and 5-caC does not have a measurable effect. Molecular dynamics simulations show that these modifications promote or dampen structural fluctuations, likely through competing effects of base polarity and steric hindrance, without changing the average structure. The increase in DNA flexibility increases the mechanical stability of the nucleosome and vice versa, suggesting a gene regulation mechanism where cytosine modifications change the accessibility of nucleosomal DNA through their effects on DNA flexibility.

  1. Effects of e-beam parameters on coherent electron cooling

    SciTech Connect

    Webb, S.D.; Litvinenko, V.N.; Wang, G.

    2011-03-28

    Coherent Electron Cooling (CeC) requires detailed control of the phase between the hadron an the FEL-amplified wave packet. This phase depends on local electron beam parameters such as the energy spread and the peak current. In this paper, we examine the effects of local density variations on the cooling rates for CeC. Coherent Electron Cooling (CeC) [1] is a new concept in intense, high energy hadron beamcooling, in which the Debye screened charge perturbation calculated in [2] is used to seed a high-gain free electron laser (FEL). Using delays to give the perturbing hadron an energy-dependent longitudinal displacement relative to its frequencymodulated charge perturbation, the hadron receives an energy-dependent kick which reduces its energy variation from the design energy. The equations of motion in [1] assume that the electron bunch is the same physical size as the hadron bunch, and has a homogeneous charge density across the entire bunch. In practice, the electron bunches will be much shorter than the hadron bunch, and this local spacial inhomogeneity in the charge distribution will alter the gain length of the FEL, resulting in both a change in the amplification of the initial signal and a phase shift. In this paper we consider these inhomogeneity effects, determining cooling equations for bunched beam CeC consistent with these effects and determining thresholds for the cooling parameters.

  2. Effect of Beam Oscillation on Microstructure and Mechanical Properties of AISI 316L Electron Beam Welds

    NASA Astrophysics Data System (ADS)

    Kar, Jyotirmaya; Roy, Sanat Kumar; Roy, Gour Gopal

    2017-04-01

    The properties of electron beam-welded AISI 316L stainless steel butt joints prepared with and without beam oscillation were evaluated by microstructural analysis, mechanical testing like microhardness measurements, tensile tests at room and elevated temperature 973 K (700 °C), three-point bend, and Charpy impact tests. All joints, irrespective of being prepared with or without beam oscillation, were found to be defect free. Welds produced by beam oscillation exhibited narrower fusion zone (FZ) with lathy ferrite morphology, while the weld without beam oscillation was characterized by wider FZ and skeletal ferrite morphology. During tensile tests at room and elevated temperature 973 K (700 °C), all samples fractured in the base metal (BM) and showed almost the same tensile properties as that of the BM. However, the notch tensile tests at room temperature demonstrated higher strength for joints prepared with the oscillating beam. Besides, face and root bend tests, as well as Charpy impact tests, showed higher bending strength and notch toughness, respectively, for joints prepared with beam oscillation.

  3. Effect of Beam Oscillation on Microstructure and Mechanical Properties of AISI 316L Electron Beam Welds

    NASA Astrophysics Data System (ADS)

    Kar, Jyotirmaya; Roy, Sanat Kumar; Roy, Gour Gopal

    2017-02-01

    The properties of electron beam-welded AISI 316L stainless steel butt joints prepared with and without beam oscillation were evaluated by microstructural analysis, mechanical testing like microhardness measurements, tensile tests at room and elevated temperature 973 K (700 °C), three-point bend, and Charpy impact tests. All joints, irrespective of being prepared with or without beam oscillation, were found to be defect free. Welds produced by beam oscillation exhibited narrower fusion zone (FZ) with lathy ferrite morphology, while the weld without beam oscillation was characterized by wider FZ and skeletal ferrite morphology. During tensile tests at room and elevated temperature 973 K (700 °C), all samples fractured in the base metal (BM) and showed almost the same tensile properties as that of the BM. However, the notch tensile tests at room temperature demonstrated higher strength for joints prepared with the oscillating beam. Besides, face and root bend tests, as well as Charpy impact tests, showed higher bending strength and notch toughness, respectively, for joints prepared with beam oscillation.

  4. Surface Modifications and Their Effects on Titanium Dental Implants

    PubMed Central

    Jemat, A.; Ghazali, M. J.; Razali, M.; Otsuka, Y.

    2015-01-01

    This review covers several basic methodologies of surface treatment and their effects on titanium (Ti) implants. The importance of each treatment and its effects will be discussed in detail in order to compare their effectiveness in promoting osseointegration. Published literature for the last 18 years was selected with the use of keywords like titanium dental implant, surface roughness, coating, and osseointegration. Significant surface roughness played an important role in providing effective surface for bone implant contact, cell proliferation, and removal torque, despite having good mechanical properties. Overall, published studies indicated that an acid etched surface-modified and a coating application on commercial pure titanium implant was most preferable in producing the good surface roughness. Thus, a combination of a good surface roughness and mechanical properties of titanium could lead to successful dental implants. PMID:26436097

  5. Surface Modifications and Their Effects on Titanium Dental Implants.

    PubMed

    Jemat, A; Ghazali, M J; Razali, M; Otsuka, Y

    2015-01-01

    This review covers several basic methodologies of surface treatment and their effects on titanium (Ti) implants. The importance of each treatment and its effects will be discussed in detail in order to compare their effectiveness in promoting osseointegration. Published literature for the last 18 years was selected with the use of keywords like titanium dental implant, surface roughness, coating, and osseointegration. Significant surface roughness played an important role in providing effective surface for bone implant contact, cell proliferation, and removal torque, despite having good mechanical properties. Overall, published studies indicated that an acid etched surface-modified and a coating application on commercial pure titanium implant was most preferable in producing the good surface roughness. Thus, a combination of a good surface roughness and mechanical properties of titanium could lead to successful dental implants.

  6. Modification of magnetohydrodynamic waves by the relativistic Hall effect

    NASA Astrophysics Data System (ADS)

    Kawazura, Yohei

    2017-07-01

    This study shows that a relativistic Hall effect significantly changes the properties of wave propagation by deriving a linear dispersion relation for relativistic Hall magnetohydrodynamics (HMHD). Whereas, in nonrelativistic HMHD, the phase and group velocities of fast magnetosonic wave become anisotropic with an increasing Hall effect, the relativistic Hall effect brings upper bounds to the anisotropies. The Alfvén wave group velocity with strong Hall effect also becomes less anisotropic than the nonrelativistic case. Moreover, the group velocity surfaces of Alfvén and fast waves coalesce into a single surface in the direction other than near perpendicular to the ambient magnetic field. It is also remarkable that a characteristic scale length of the relativistic HMHD depends on ion temperature, magnetic field strength, and density while the nonrelativistic HMHD scale length, i.e., ion skin depth, depends only on density. The modified characteristic scale length increases as the ion temperature increases and decreases as the magnetic field strength increases.

  7. Modification of Tamoxifen Effectiveness by Gene Polymorphisms and Other Drugs

    DTIC Science & Technology

    2009-05-01

    effectiveness, and (3) effects of functional polymorphisms in the UDP-glucuronosyltransferase (UGT) enzymes on breast cancer recurrence in Danish women...nested within a population-based case-control study of breast cancer recurrence among Danish women (PI: Timothy L. Lash, Chair of Mr. Ahern’s Doctoral...roster of study participants, breast cancer diagnosis and treatment data were extracted from the Danish Breast Cancer Cooperative Group (DBCG) database

  8. Effect of Beam Motion on Observed Image at Imaging Station C

    SciTech Connect

    Schulze, Martin E.

    2014-01-17

    Imaging Station C on the DARHT II accelerator is used to measure beam spot sizes. Solenoid scans are used to measure the spot sizes as a function of the solenoid current and infer the beam emittance. Beam motion is observed during the measurement window and can contribute to the measured spot size. The effect of beam motion on the observed images at Station C is examined in this note. The variation in the beam position during the kicked beam pulse contributes to the beam spot size as measured at Station C. The beam motion is primarily in the vertical plane and is due to the kicker voltage rise time prior to the solenoid magnet. The effect of beam motion on the spot size is studied using LAMDA. From the measured beam position at BPM28 and BPM29 we determine the beam position and angle at the start of the LAMDA simulation. We then calculate the beam motion at Station C as a function of the S4 solenoid magnet current. The shot-to-shot variation in the beam motion is very small.

  9. Effect of forming stresses on the strength of curved laminated beams of loblolly pine

    Treesearch

    George E. Woodson; Frederick F. Wangaard

    1969-01-01

    Curvature-stress factors reflecting the effect of forming stresses in producing curved beams of thin vertical-grain laminations of clear wood have been determined for loblolly pine. Strength retention of curved beams decreases with increasing severity of curvature but not to the degree suggested by the Wilson equation commonly used in design. Curved beams loaded on the...

  10. Thermomechanical assessment of the effects of a jaw-beam angle during beam impact on Large Hadron Collider collimators

    NASA Astrophysics Data System (ADS)

    Cauchi, Marija; Assmann, R. W.; Bertarelli, A.; Carra, F.; Lari, L.; Rossi, A.; Mollicone, P.; Sammut, N.

    2015-02-01

    The correct functioning of a collimation system is crucial to safely and successfully operate high-energy particle accelerators, such as the Large Hadron Collider (LHC). However, the requirements to handle high-intensity beams can be demanding, and accident scenarios must be well studied in order to assess if the collimator design is robust against possible error scenarios. One of the catastrophic, though not very probable, accident scenarios identified within the LHC is an asynchronous beam dump. In this case, one (or more) of the 15 precharged kicker circuits fires out of time with the abort gap, spraying beam pulses onto LHC machine elements before the machine protection system can fire the remaining kicker circuits and bring the beam to the dump. If a proton bunch directly hits a collimator during such an event, severe beam-induced damage such as magnet quenches and other equipment damage might result, with consequent downtime for the machine. This study investigates a number of newly defined jaw error cases, which include angular misalignment errors of the collimator jaw. A numerical finite element method approach is presented in order to precisely evaluate the thermomechanical response of tertiary collimators to beam impact. We identify the most critical and interesting cases, and show that a tilt of the jaw can actually mitigate the effect of an asynchronous dump on the collimators. Relevant collimator damage limits are taken into account, with the aim to identify optimal operational conditions for the LHC.

  11. Dim waters: side effects of geoengineering using ocean albedo modification

    NASA Astrophysics Data System (ADS)

    Piskozub, J.; Neumann, T.

    2012-04-01

    We use a Monte Carlo radiative transfer code to check how the recently proposed geoengineering by injection of clean or coated microbubbles into the ocean mixed layer would impact in-water light fields. We show that due to massive multiscattering inside a bubble cloud, coating the bubbles with surfactant, needed to stabilize them, would not increase their albedo change effectiveness as much as expected basing on their backscattering coefficients. However, the bubble effect on reflectance is larger than estimated previously using a discrete ordinate method of solving the radiative transfer problem. We show significant side effects of ocean albedo change needed to counter global warming expected in this century and beyond (reduction of euphotic zone depth by respectively 20% and 50% in the case of global ocean albedo change corresponding to -1.25 K and -6 K global surface temperature change and irradiance decrease at 10 m depth by respectively 40% and over 80%) even if all ocean surface was "brightened". We discuss the possible negative side effect of such in-water light dimming on marine life. We conclude that the proposed "ocean brightening" is in fact "ocean dimming" as concerns the marine environment, on a scale that in any other circumstances would be called catastrophic. Finally, we briefly discuss other possible side effect of making the surface ocean waters turbid (both optically and acoustically), of adding large amounts of surfactants to the surface ocean layers and of surface cooling of the ocean, especially within the tropics.

  12. Propeller modulation effects on a scanning beam microwave landing system

    NASA Technical Reports Server (NTRS)

    Pope, J. M.; Staehle, W. H.

    1974-01-01

    An investigation to assess the modulation effects on microwave signals transmitted through rotating propeller blades. Interruption of the antenna line-of-sight signal by the rotating propeller causes a variation of path loss, which produces essentially an amplitude modulation of the received signal. This interruption or blockage effect is generally only partial because of edge diffraction around the particular interfering propeller blade. Signals reflected from the rotating propeller will also cause Doppler frequency shifts to be present in the received signals. A scanning beam microwave landing system (MLS) known as MODILS (modular instrument landing system) was used to process the received signals for display. The effects of propeller modulation were studied by varying the following parameters: (1) spacing between propeller and receiving antenna, (2) propeller dimensions, (3) propeller speed (rpm), (4) number of propeller blades, (5) system data rate, (6) receiver response time, and (7) receiver antenna aperture.

  13. Plasma effects on fast pair beams. III. Oblique electrostatic growth rates for perpendicular Maxwellian pair beams

    SciTech Connect

    Supsar, Markus; Schlickeiser, Reinhard E-mail: rsch@tp4.rub.de

    2014-03-10

    The distant universe is opaque to γ radiation from blazars due to gamma-gamma attenuation with extragalactic background light. This process produces electron-positron pair beams that interact with the intergalactic medium and are unstable to linear instabilities, particularly the electrostatic and Weibel instabilities. The electrostatic instability grows faster and so determines the dissipation of the free energy of the beam. Here, we generalize the calculation of the electrostatic growth rate to a beam plasma system with a Maxwellian perpendicular momentum spread and allow for oblique propagation directions. We show that the growth rate for the oblique electrostatic mode has a maximum value that is even higher than for a cold beam or for one with a constant perpendicular momentum spread.

  14. Beam manipulation techniques, nonlinear beam dynamics, and space charge effect in high energy high power accelerators

    SciTech Connect

    Lee, S. Y.

    2014-04-07

    We had carried out a design of an ultimate storage ring with beam emittance less than 10 picometer for the feasibility of coherent light source at X-ray wavelength. The accelerator has an inherent small dynamic aperture. We study method to improve the dynamic aperture and collective instability for an ultimate storage ring. Beam measurement and accelerator modeling are an integral part of accelerator physics. We develop the independent component analysis (ICA) and the orbit response matrix method for improving accelerator reliability and performance. In collaboration with scientists in National Laboratories, we also carry out experimental and theoretical studies on beam dynamics. Our proposed research topics are relevant to nuclear and particle physics using high brightness particle and photon beams.

  15. The effects of beta-endorphin: state change modification.

    PubMed

    Veening, Jan G; Barendregt, Henk P

    2015-01-29

    Beta-endorphin (β-END) is an opioid neuropeptide which has an important role in the development of hypotheses concerning the non-synaptic or paracrine communication of brain messages. This kind of communication between neurons has been designated volume transmission (VT) to differentiate it clearly from synaptic communication. VT occurs over short as well as long distances via the extracellular space in the brain, as well as via the cerebrospinal fluid (CSF) flowing through the ventricular spaces inside the brain and the arachnoid space surrounding the central nervous system (CNS). To understand how β-END can have specific behavioral effects, we use the notion behavioral state, inspired by the concept of machine state, coming from Turing (Proc London Math Soc, Series 2,42:230-265, 1937). In section 1.4 the sequential organization of male rat behavior is explained showing that an animal is not free to switch into another state at any given moment. Funneling-constraints restrict the number of possible behavioral transitions in specific phases while at other moments in the sequence the transition to other behavioral states is almost completely open. The effects of β-END on behaviors like food intake and sexual behavior, and the mechanisms involved in reward, meditation and pain control are discussed in detail. The effects on the sequential organization of behavior and on state transitions dominate the description of these effects.

  16. Modifications in Children's Cognitive Styles: Some Effects of Peer Modeling.

    ERIC Educational Resources Information Center

    Cohen, Stewart; Przybycien, Collette A.

    An extension of previous attempts at modifying children's cognitive styles is discussed. Specifically, the present study employed sociometric peer models in order to ascertain whether: (1) impulsivity is modifiable through observation of salient models, and (2) sociometrically selected peer models are more effective than unselected models in the…

  17. Semiparametric regression models for detecting effect modification in matched case-crossover studies.

    PubMed

    Kim, Inyoung; Cheong, Hae-Kwan; Kim, Ho

    2011-07-10

    In matched case-crossover studies, it is generally accepted that covariates on which a case and associated controls are matched cannot exert a confounding effect on independent predictors included in the conditional logistic regression model because any stratum effect is removed by the conditioning on the fixed number of sets of a case and controls in the stratum. Hence, the conditional logistic regression model is not able to detect any effects associated with the matching covariates by stratum. In addition, the matching covariates may be effect modification and the methods for assessing and characterizing effect modification by matching covariates are quite limited. In this article, we propose a unified approach in its ability to detect both parametric and nonparametric relationships between the predictor and the relative risk of disease or binary outcome, as well as potential effect modifications by matching covariates. Two methods are developed using two semiparametric models: (1) the regression spline varying coefficients model and (2) the regression spline interaction model. Simulation results show that the two approaches are comparable. These methods can be used in any matched case-control study and extend to multilevel effect modification studies. We demonstrate the advantage of our approach using an epidemiological example of a 1-4 bi-directional case-crossover study of childhood aseptic meningitis associated with drinking water turbidity. Copyright © 2011 John Wiley & Sons, Ltd.

  18. The effect of exit beam phase aberrations on parallel beam coherent x-ray reconstructions

    SciTech Connect

    Hruszkewycz, S. O.; Fuoss, P. H.; Harder, R.; Xiao, X.

    2010-12-15

    Diffraction artifacts from imperfect x-ray windows near the sample are an important consideration in the design of coherent x-ray diffraction measurements. In this study, we used simulated and experimental diffraction patterns in two and three dimensions to explore the effect of phase imperfections in a beryllium window (such as a void or inclusion) on the convergence behavior of phasing algorithms and on the ultimate reconstruction. A predictive relationship between beam wavelength, sample size, and window position was derived to explain the dependence of reconstruction quality on beryllium defect size. Defects corresponding to this prediction cause the most damage to the sample exit wave and induce signature error oscillations during phasing that can be used as a fingerprint of experimental x-ray window artifacts. The relationship between x-ray window imperfection size and coherent x-ray diffractive imaging reconstruction quality explored in this work can play an important role in designing high-resolution in situ coherent imaging instrumentation and will help interpret the phasing behavior of coherent diffraction measured in these in situ environments.

  19. The effect of exit beam phase aberrations on parallel beam coherent x-ray reconstructions.

    SciTech Connect

    Hruszkewycz, S. O.; Harder, R.; Xiao, X.; Fuoss, P. H.

    2010-12-01

    Diffraction artifacts from imperfect x-ray windows near the sample are an important consideration in the design of coherent x-ray diffraction measurements. In this study, we used simulated and experimental diffraction patterns in two and three dimensions to explore the effect of phase imperfections in a beryllium window (such as a void or inclusion) on the convergence behavior of phasing algorithms and on the ultimate reconstruction. A predictive relationship between beam wavelength, sample size, and window position was derived to explain the dependence of reconstruction quality on beryllium defect size. Defects corresponding to this prediction cause the most damage to the sample exit wave and induce signature error oscillations during phasing that can be used as a fingerprint of experimental x-ray window artifacts. The relationship between x-ray window imperfection size and coherent x-ray diffractive imaging reconstruction quality explored in this work can play an important role in designing high-resolution in situ coherent imaging instrumentation and will help interpret the phasing behavior of coherent diffraction measured in these in situ environments.

  20. (Pulsed electron beam precharger)

    SciTech Connect

    Finney, W.C.; Shelton, W.N.

    1990-01-01

    This report discusses the following topics on electron beam guns: Precharger Modification; Installation of Charge vs. Radius Apparatus; High Concentration Aerosol Generation; and Data Acquisition and Analysis System.

  1. Effect of ITO surface modification on the OLED device lifetime.

    PubMed

    Yu, Szu-Yen; Chang, Jung-Hung; Wang, Po-Sheng; Wu, Chi-I; Tao, Yu-Tai

    2014-07-01

    Pretreatment of the indium tin oxide (ITO) surface is generally adopted to improve the charge injection and device performance in the fabrication of organic light-emitting diodes (OLEDs). For the common approaches of surface treatment, such as oxygen plasma treatment, self-assembled monolayer (SAM) adsorption, and the PEDOT:PSS coating, different effects on the device lifetime were observed. A distinctly different driving voltage change with device operation time was obtained and was correlated with the device lifetime. The fast increase in driving voltage for devices based on oxygen-plasma-treated ITO is attributed to the work function change as a result of the change in the composition of the interface with device operation, whereas a rather stable work function for SAM-modified ITO is suggested due to the permanent dipoles associated with the monolayer and the protecting effect of the covalently bound monolayer on the surface composition.

  2. Inflammatory Effects of Edwardsiella ictaluri Lipopolysaccharide Modifications in Catfish Gut

    PubMed Central

    Kilbourne, Jacquelyn; Park, Jie-Yeun; Martin, Taylor; Loh, Amanda; Diaz, Ignacia; Rojas, Robert; Segovia, Cristopher; DeNardo, Dale; Curtiss, Roy

    2014-01-01

    Bacterial lipopolysaccharides (LPS) are structural components of the outer membranes of Gram-negative bacteria and also are potent inducers of inflammation in mammals. Higher vertebrates are extremely sensitive to LPS, but lower vertebrates, like fish, are resistant to their systemic toxic effects. However, the effects of LPS on the fish intestinal mucosa remain unknown. Edwardsiella ictaluri is a primitive member of the Enterobacteriaceae family that causes enteric septicemia in channel catfish (Ictalurus punctatus). E. ictaluri infects and colonizes deep lymphoid tissues upon oral or immersion infection. Both gut and olfactory organs are the primary sites of invasion. At the systemic level, E. ictaluri pathogenesis is relatively well characterized, but our knowledge about E. ictaluri intestinal interaction is limited. Recently, we observed that E. ictaluri oligo-polysaccharide (O-PS) LPS mutants have differential effects on the intestinal epithelia of orally inoculated catfish. Here we evaluate the effects of E. ictaluri O-PS LPS mutants by using a novel catfish intestinal loop model and compare it to the rabbit ileal loop model inoculated with Salmonella enterica serovar Typhimurium LPS. We found evident differences in rabbit ileal loop and catfish ileal loop responses to E. ictaluri and S. Typhimurium LPS. We determined that catfish respond to E. ictaluri LPS but not to S. Typhimurium LPS. We also determined that E. ictaluri inhibits cytokine production and induces disruption of the intestinal fish epithelia in an O-PS-dependent fashion. The E. ictaluri wild type and ΔwibT LPS mutant caused intestinal tissue damage and inhibited proinflammatory cytokine synthesis, in contrast to E. ictaluri Δgne and Δugd LPS mutants. We concluded that the E. ictaluri O-PS subunits play a major role during pathogenesis, since they influence the recognition of the LPS by the intestinal mucosal immune system of the catfish. The LPS structure of E. ictaluri mutants is needed to

  3. Modifications in the metabolism and myeloclastogenic effect of benzene

    SciTech Connect

    Gad-El Karim, M.M.; Harper, B.L.; Ramanujam, S.V.M.; Legator, M.S.

    1982-02-01

    Benzene was studied in its target organ of effect, the bone marrow, with the micronucleus test and metaphase analysis. In a series of experiments, male and female CD-1 mice were subjected to various pretreatments: phenobarbital (PB) (0.1% in drinking water x 7 days or 80 mg/kg/day (I.P.) x 3 days before treatment), 3-methylcholanthrene (3-MCA) (30 mg/kg/day (I.P.) x 2 days), SKF-525A (80 mg/kg (I.P.) 2 hours before each treatment dose), or Aroclor-1254 (100 mg/kg) (I.P.) once, 5 days before treatment. The animals were then treated with benzene (440 or 880 mg/kg) or toluene (860 or 1720 mg/kg) or their mixture in 2 doses 24 hours apart and sacrificed 6 hours or 24 hours after the second dose. Toluene showed no clastogenic activity and reduced the clastogenic effect of benzene when the mixture was given. None of the pretreatments protected against the clastogenic effect of benzene. 3-MCA pretreatment caused a tremendous enhancement of benzene myeloclastogenicity. The sex difference, with females constantly more resistant than males to benzene, was retained among the 3-MCA pretreated group. Toluene, in mixture with benzene, lowered the clastogenic effect in 3-MCA pretreated mice. Dose-response curves with benzene treatment alone and with 3-MCA induced groups were generated in which the former curve was lower for each dose than the latter. Urine fractions were collected at 12-hour intervals from 3-groups of 10 males gavaged with benzene, either non-induced, PB- or 3MCA induced. Catechol was the major metabolite, phenol the minor one, and hydroquinone and semiquinones were present in trace amounts.

  4. Radiation effects of ion and electron beams on poly(methylphenylsilane)

    NASA Astrophysics Data System (ADS)

    Seki, Shu; Shibata, Hiromi; Ban, Hiroshi; Ishigure, Kenkichi; Tagawa, Seiichi

    1996-11-01

    Radiation effects of ion beams on poly(methylphenylsilane), PMPS are described in the present paper. PMPS solid films irradiated by high energy H +, He +, N + ion beams and electron beams show changes of solubility with a large LET effects. Ion (2 MeV) and electron (20 and 30 keV) beams induce mainly crosslinking of PMPS, while it was reported that UV light and γ-rays caused predominantly main chain scission on PMPS. The G-values of crosslinking increase with the values of LET of incident beams.

  5. Advanced computations of multi-physics, multi-scale effects in beam dynamics

    SciTech Connect

    Amundson, J.F.; Macridin, A.; Spentzouris, P.; Stern, E.G.; /Fermilab

    2009-01-01

    Current state-of-the-art beam dynamics simulations include multiple physical effects and multiple physical length and/or time scales. We present recent developments in Synergia2, an accelerator modeling framework designed for multi-physics, multi-scale simulations. We summarize recent several recent results in multi-physics beam dynamics, including simulations of three Fermilab accelerators: the Tevatron, the Main Injector and the Debuncher. Early accelerator simulations focused on single-particle dynamics. To a first approximation, the forces on the particles in an accelerator beam are dominated by the external fields due to magnets, RF cavities, etc., so the single-particle dynamics are the leading physical effects. Detailed simulations of accelerators must include collective effects such as the space-charge repulsion of the beam particles, the effects of wake fields in the beam pipe walls and beam-beam interactions in colliders. These simulations require the sort of massively parallel computers that have only become available in recent times. We give an overview of the accelerator framework Synergia2, which was designed to take advantage of the capabilities of modern computational resources and enable simulations of multiple physical effects. We also summarize some recent results utilizing Synergia2 and BeamBeam3d, a tool specialized for beam-beam simulations.

  6. The Effects of Approach-Avoidance Modification on Social Anxiety Disorder: A Pilot Study

    PubMed Central

    Asnaani, Anu; Rinck, Mike; Becker, Eni; Hofmann, Stefan G.

    2014-01-01

    Cognitive bias modification has recently been discussed as a possible intervention for mental disorders. A specific form of this novel treatment approach is approach-avoidance modification. In order to examine the efficacy of approach-avoidance modification for positive stimuli associated with social anxiety, we recruited 43 individuals with social anxiety disorder and randomly assigned them to a training (implicit training to approach smiling faces) or a control (equal approach and avoidance of smiling faces) condition in three sessions over the course of a one-week period. Dependent measures included clinician ratings, self-report measures of social anxiety, and overt behavior during behavioral approach tasks. No group differences in any of the outcome measures were observed after training. In addition, while individuals in the training group showed increased approach tendency in one of the sessions, this effect was inconsistent across the three sessions and did not result in long-term changes in implicit approach tendencies between the groups over the course of the entire study. These results suggest that approach-avoidance modification might result in short-lasting effects on implicit approach tendencies towards feared positive stimuli, but this modification may not result in meaningful behavioral change or symptom reduction in individuals with social anxiety disorder. PMID:24659832

  7. The Effects of Approach-Avoidance Modification on Social Anxiety Disorder: A Pilot Study.

    PubMed

    Asnaani, Anu; Rinck, Mike; Becker, Eni; Hofmann, Stefan G

    2014-04-01

    Cognitive bias modification has recently been discussed as a possible intervention for mental disorders. A specific form of this novel treatment approach is approach-avoidance modification. In order to examine the efficacy of approach-avoidance modification for positive stimuli associated with social anxiety, we recruited 43 individuals with social anxiety disorder and randomly assigned them to a training (implicit training to approach smiling faces) or a control (equal approach and avoidance of smiling faces) condition in three sessions over the course of a one-week period. Dependent measures included clinician ratings, self-report measures of social anxiety, and overt behavior during behavioral approach tasks. No group differences in any of the outcome measures were observed after training. In addition, while individuals in the training group showed increased approach tendency in one of the sessions, this effect was inconsistent across the three sessions and did not result in long-term changes in implicit approach tendencies between the groups over the course of the entire study. These results suggest that approach-avoidance modification might result in short-lasting effects on implicit approach tendencies towards feared positive stimuli, but this modification may not result in meaningful behavioral change or symptom reduction in individuals with social anxiety disorder.

  8. Bentonite modification with hexadecylpyridinium and aluminum polyoxy cations and its effectiveness in Se(IV) removal.

    PubMed

    Orucoglu, Esra; Haciyakupoglu, Sevilay

    2015-09-01

    Usage of bentonite as a buffer material is suggested in radioactive waste repositories. Although bentonites have higher sorption ability to cations, they cannot adsorp anions due to negative surface charge. Nowadays, ongoing researches focus on increasing anion adsorption ability of the bentonites with modification. Organic-pillared bentonite (OPBent) was produced by modification of sodium bentonite with aluminum polyoxy and hexadecylpyridinium cations in this study. Variation in structure after modification was demonstrated by using different characterization techniques. Se removal efficiency of OPBent is investigated by using (75)Se, since selenium (Se) is one of the important long lived fission products found in radioactive waste and has toxic anionic species in an aqueous environment. The effect of reaction time, solid/liquid ratio, pH and concentration on the adsorption performance were examined. Se speciation and its effect onto adsorption were also investigated by measuring Eh-pH values under certain experimental conditions. Additionally, importance of the amount of Al-polyoxy cations used in modification was investigated by comparing these results with the results of other organic-pillared bentonite produced in our previous research. Experimental results confirmed that both cations were successfully placed into the bentonite interlayer and significant change in the host structure leads to increase Se adsorption. Consequently, bentonite modification improves its Se adsorption ability and further investigations are needed related to the usage of this adsorbent in other remediation studies especially in sorption of other anionic pollutants.

  9. Differential effect of three base modifications on DNA thermostability revealed by high resolution melting.

    PubMed

    López, Carlos M Rodríguez; Lloyd, Amanda J; Leonard, Kate; Wilkinson, Mike J

    2012-09-04

    High resolution melting (HRM) can detect and quantify the presence of 5-methylcytosine (5mC) in DNA samples, but the ability of HRM to diagnose other DNA modifications remains unexplored. The DNA bases N6-methyladenine and 5-hydroxymethylcytosine occur across almost all phyla. While their function remains controversial, their presence perturbs DNA structure. Such modifications could affect gene regulation, chromatin condensation and DNA packaging. Here, we reveal that DNA containing N6-methyladenine or 5-hydroxymethylcytosine exhibits reduced thermal stability compared to cytosine-methylated DNA. These thermostability changes are sufficiently divergent to allow detection and quantification by HRM analysis. Thus, we report that HRM distinguishes between sequence-identical DNA differing only in the modification type of one base. This approach is also able to distinguish between two DNA fragments carrying both N6-methyladenine and 5-methylcytosine but differing only in the distance separating the modified bases. This finding provides scope for the development of new methods to characterize DNA chemically and to allow for low cost screening of mutant populations of genes involved in base modification. More fundamentally, contrast between the thermostabilizing effects of 5mC on dsDNA compared with the destabilizing effects of N6-methyladenine (m6A) and 5-hydroxymethylcytosine (5hmC) raises the intriguing possibility of an antagonistic relationship between modification types with functional significance.

  10. Effects of cementation surface modifications on fracture resistance of zirconia.

    PubMed

    Srikanth, Ramanathan; Kosmac, Tomaz; Della Bona, Alvaro; Yin, Ling; Zhang, Yu

    2015-04-01

    To examine the effects of glass infiltration (GI) and alumina coating (AC) on the indentation flexural load and four-point bending strength of monolithic zirconia. Plate-shaped (12 mm × 12 mm × 1.0 mm or 1.5 or 2.0 mm) and bar-shaped (4 mm × 3 mm × 25 mm) monolithic zirconia specimens were fabricated. In addition to monolithic zirconia (group Z), zirconia monoliths were glass-infiltrated or alumina-coated on their tensile surfaces to form groups ZGI and ZAC, respectively. They were also glass-infiltrated on their upper surfaces, and glass-infiltrated or alumina-coated on their lower (tensile) surfaces to make groups ZGI2 and ZAC2, respectively. For comparison, porcelain-veneered zirconia (group PVZ) and monolithic lithium disilicate glass-ceramic (group LiDi) specimens were also fabricated. The plate-shaped specimens were cemented onto a restorative composite base for Hertzian indentation using a tungsten carbide spherical indenter with a radius of 3.2mm. Critical loads for indentation flexural fracture at the zirconia cementation surface were measured. Strengths of bar-shaped specimens were evaluated in four-point bending. Glass infiltration on zirconia tensile surfaces increased indentation flexural loads by 32% in Hertzian contact and flexural strength by 24% in four-point bending. Alumina coating showed no significant effect on resistance to flexural damage of zirconia. Monolithic zirconia outperformed porcelain-veneered zirconia and monolithic lithium disilicate glass-ceramics in terms of both indentation flexural load and flexural strength. While both alumina coating and glass infiltration can be used to effectively modify the cementation surface of zirconia, glass infiltration can further increase the flexural fracture resistance of zirconia. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  11. Effects of cementation surface modifications on fracture resistance of zirconia

    PubMed Central

    Srikanth, Ramanathan; Kosmac, Tomaz; Bona, Alvaro Della; Yin, Ling; Zhang, Yu

    2015-01-01

    Objectives To examine the effects of glass infiltration (GI) and alumina coating (AC) on the indentation flexural load and four-point bending strength of monolithic zirconia. Methods Plate-shaped (12 mm × 12 mm × 1.0 mm or 1.5 mm or 2.0 mm) and bar-shaped (4 mm × 3 mm × 25 mm) monolithic zirconia specimens were fabricated. In addition to monolithic zirconia (group Z), zirconia monoliths were glass-infiltrated or alumina-coated on their tensile surfaces to form groups ZGI and ZAC, respectively. They were also glass-infiltrated on their upper surfaces, and glass-infiltrated or alumina-coated on their lower (tensile) surfaces to make groups ZGI2 and ZAC2, respectively. For comparison, porcelain-veneered zirconia (group PVZ) and monolithic lithium disilicate glass-ceramic (group LiDi) specimens were also fabricated. The plate-shaped specimens were cemented onto a restorative composite base for Hertzian indentation using a tungsten carbide spherical indenter with a radius of 3.2 mm. Critical loads for indentation flexural fracture at the zirconia cementation surface were measured. Strengths of bar-shaped specimens were evaluated in four-point bending. Results Glass infiltration on zirconia tensile surfaces increased indentation flexural loads by 32% in Hertzian contact and flexural strength by 24% in four-point bending. Alumina coating showed no significant effect on resistance to flexural damage of zirconia. Monolithic zirconia outperformed porcelain-veneered zirconia and monolithic lithium disilicate glass-ceramics in terms of both indentation flexural load and flexural strength. Significance While both alumina coating and glass infiltration can be used to effectively modify the cementation surface of zirconia, glass infiltration can further increase the flexural fracture resistance of zirconia. PMID:25687628

  12. Effects of flux modifications on high strength steel weld metal

    SciTech Connect

    Franke, G.L.

    1994-12-31

    The performance of high strength steel welds is sensitive to the weld metal chemistry, and that, in turn, is dependent on the composition of the welding consumables. In the case of submerged arc welding, the flux plays an important role in determining the chemistry of the resulting weld metal. The u.S. Navy is conducting a program to gain a basic understanding of fluxes used for welding high strength steels in an effort to be able to better select the appropriate flux, or design a new flux, for a given application. The objective of the present work is to analyze the effects of a systematic chance in flux composition on weld metal chemistry and properties The dry mix of a commercial flux was modified with additions of MnO to produce a series of four experimental flux mixes with target MnO levels from 1 wt% to 4 wt%. A fifth experimental flux mix was produced with an addition of 1/2 wt% CeO{sub 2} to examine the effect of rare earth additions to the flux. Tensile and impact properties and weld metal chemistry were tested for each weldment, and correlations were made with flux composition. Weld metal Mn levels from 1.37 wt% (0.76 wt% flux MnO) to 1.75 wt% (4.26 wt% flux MnO) were achieved with the MnO-added fluxes.The small CeO{sub 2} addition appeared to improve weld metal impact performance it was concluded that a more basic knowledge of welding fluxes can be used in selecting or designing appropriate fluxes for Navy applications. Further work is required to characterize the specific effects of other flux constituents and their interactions on weld metal performance.

  13. International Workshop on Ion Beam Modification and Processing of High Tc- Superconductors: Physics and Devices: Program and Abstracts

    DTIC Science & Technology

    1989-04-12

    handled by standard rate theory. A stochastic treatment of the problem, based on a Fokker Planck approximation of the relevant master equation is summarized...talk, I will attempt to summarize the key differences between the oxide superconductors and niobium alloys that have caused this delay in...commercialization. These differences range from crystal structure and anisotropy, to the sensitivity of Tc to chemical doping, to the effects of damage and

  14. Effect of structural modification on second harmonic generation in collagen

    NASA Astrophysics Data System (ADS)

    Stoller, Patrick C.; Reiser, Karen M.; Celliers, Peter M.; Rubenchik, Alexander M.

    2003-07-01

    The effects of structural perturbation on second harmonic generation in collagen were investigated. Type I collagen fascicles obtained from rat tails were structurally modified by increasing nonenzymatic cross-linking, by thermal denaturation, by collagenase digestion, or by dehydration. Changes in polarization dependence were observed in the dehydrated samples. Surprisingly, no changes in polarization dependence were observed in highly crosslinked samples, despite significant alterations in packing structure. Complete thermal denaturation and collagenase digestion produced samples with no detectable second harmonic signal. Prior to loss of signal, no change in polarization dependence was observed in partially heated or digested collagen.

  15. Effect of Structural Modification on Second Harmonic Generation in Collagen

    SciTech Connect

    Stoller, P C; Reiser, K M; Celliers, P M; Rubenchik, A M

    2003-04-04

    The effects of structural perturbation on second harmonic generation in collagen were investigated. Type I collagen fascicles obtained from rat tails were structurally modified by increasing nonenzymatic cross-linking, by thermal denaturation, by collagenase digestion, or by dehydration. Changes in polarization dependence were observed in the dehydrated samples. Surprisingly, no changes in polarization dependence were observed in highly crosslinked samples, despite significant alterations in packing structure. Complete thermal denaturation and collagenase digestion produced samples with no detectable second harmonic signal. Prior to loss of signal, no change in polarization dependence was observed in partially heated or digested collagen.

  16. Numerical Simulation of the Self-Heating Effect Induced by Electron Beam Plasma in Atmosphere

    NASA Astrophysics Data System (ADS)

    Deng, Yongfeng; Tan, Chang; Han, Xianwei; Tan, Yonghua

    2012-02-01

    For exploiting advantages of electron beam air plasma in some unusual applications, a Monte Carlo (MC) model coupled with heat transfer model is established to simulate the characteristics of electron beam air plasma by considering the self-heating effect. Based on the model, the electron beam induced temperature field and the related plasma properties are investigated. The results indicate that a nonuniform temperature field is formed in the electron beam plasma region and the average temperature is of the order of 600 K. Moreover, much larger volume pear-shaped electron beam plasma is produced in hot state rather than in cold state. The beam ranges can, with beam energies of 75 keV and 80 keV, exceed 1.0 m and 1.2 m in air at pressure of 100 torr, respectively. Finally, a well verified formula is obtained for calculating the range of high energy electron beam in atmosphere.

  17. Effects of electron beam irradiation on tribological and physico-chemical properties of Polyoxymethylene copolymer (POM-C)

    NASA Astrophysics Data System (ADS)

    Rahman, Md. Shahinur; Shaislamov, Ulugbek; Yang, Jong-Keun; Kim, Jong-Kuk; Yu, Young Hun; Choi, Sooseok; Lee, Heon-Ju

    2016-11-01

    Polyoxymethylene copolymer (POM-C) is an attractive and widely used engineering thermoplastic across many industrial sectors owing to outstanding physical, mechanical, self-lubricating and chemical properties. In this research work, the POM-C blocks were irradiated with 1 MeV electron beam energy in five doses (100, 200, 300, 500 and 700 kGy) in vacuum condition at room temperature. The tribological and physico-chemical properties of electron beam irradiated POM-C blocks have been analyzed using pin on disk tribometer, Raman spectroscopy, FTIR-ATR, gel content analysis, SEM-EDS (scanning electron microscopy-energy dispersive spectroscopy), surface profiler and contact angle analyzer. Electron beam irradiation at a dose of 100 kGy resulted in decrease of the friction coefficient of POM-C block due to well suited carbonization, cross-linking, free radicals formation and partial physical modification. It also showed the lowest surface roughness and highest water contact angle among all unirradiated and irradiated POM-C blocks. The irradiation dose at 200 kGy resulted in increase of friction coefficient due to less effective cross-linking, but the irradiation doses at 300, 500 and 700 kGy resulted in increase of the friction coefficient as compared to unirradiated POM-C block due to severe chain scission, chemical and physical structural degradation. The degree of improvement for tribological attribute relies on the electron beam surface dose delivered (energy and dose rate).

  18. Modifications in the metabolism and myeloclastogenic effect of benzene

    SciTech Connect

    Gad-El-Karim, M.; Harper, B.L.; Sadagopa Ramanujam, V.M.; Legator, M.S.

    1982-01-01

    Toxicity of benzene was studied in the bone marrow with the micronucleus test and metaphase analysis. Male and female CD-1 mice were subjected to pretreatments with phenobarbital, 3-methylcholanthrene (3-MCA), SKF-525A, or Aroclor-1254. The animals were then treated with benzene (440 or 880 mg/kg), or toluene (860 or 1720 mg/kg), or their mixture by gavage or I.P. in 2 doses 24 hours apart and sacrificed 6 hours or 24 hours after the second dose. Toluene showed no clastogenic activity and reduced the clastogenic effect of benzene when mixture was given. None of the pretreatments protected against the clastogenic effect of benzene. 3-MCA pretreatment caused a tremendous enhancement of benzene myeloclastogenicity. Dose-response curves with benzene treatment alone and with 3-MCA induced groups were generated. Urine fractions were collected from animals gavaged with benzene, either non-induced, PB- or 3MCA induced. The metabolites were quantitated by HPLC, and confirmed by GC/MS.

  19. Effect of desiccation of marine environment on beam structure

    NASA Astrophysics Data System (ADS)

    Chen, Da; Wang, Na; Hou, Li-jun; Liao, Ying-di

    2013-03-01

    This paper presents the study on the effect of desiccation for different part of offshore structure corresponding to the water level. A coupled elastoplastic damage model is proposed to describe the mechanical behavior of cement-based materials under external loading and desiccation, in which both the plastic and damage behaviors under multi-axial stress are considered in composition with the desiccation effect. The comparison between numerical simulation and experimental data indicates that the proposed model can well predict the mechanical characteristics of cement-based materials with different saturations. In addition, a series of small beams subjected to desiccation are further analyzed to reveal the response of structure in the drying process.

  20. Effect of Surface Modification and Macrophage Phenotype on Particle Internalization

    SciTech Connect

    Wang, Daniel; Phan, Ngoc; Isely, Christopher; Bruene, Lucas; Bratlie, Kaitlin M

    2014-11-10

    Material properties play a key role in the cellular internalization of polymeric particles. In the present study, we have investigated the effects of material characteristics such as water contact angle, zeta potential, melting temperature, and alternative activation of complement on particle internalization for pro-inflammatory, pro-angiogenic, and naïve macrophages by using biopolymers (~600 nm), functionalized with 13 different molecules. Understanding how material parameters influence particle internalization for different macrophage phenotypes is important for targeted delivery to specific cell populations. Here, we demonstrate that material parameters affect the alternative pathway of complement activation as well as particle internalization for different macrophage phenotypes. Here, we show that the quantitative structure–activity relationship method (QSAR) previously used to predict physiochemical properties of materials can be applied to targeting different macrophage phenotypes. These findings demonstrated that targeted drug delivery to macrophages could be achieved by exploiting material parameters.

  1. Scalar Modifications to Gravity from Unparticle Effects May Be Testable

    SciTech Connect

    Goldberg, Haim; Nath, Pran

    2008-01-25

    Interest has focused recently on low energy implications of a nontrivial scale invariant sector of an effective field theory with an IR fixed point, manifest in terms of 'unparticles' with peculiar properties. If unparticle stuff exists it could couple to the stress tensor and mediate a new 'fifth' force ('ungravity'). Under the assumption of strict conformal invariance in the hidden sector down to low energies, we compute the lowest order ungravity correction to the Newtonian gravitational potential and find scale invariant power law corrections of type (R{sub G}/r){sup 2d{sub U}-1}, where d{sub U} is an anomalous unparticle dimension and R{sub G} is a characteristic length scale where the ungravity interactions become significant. It is shown that a discrimination between extra dimension models and ungravity is possible in future improved submillimeter tests of gravity.

  2. Dual-effect laser handpiece for modification of tissue permeability

    NASA Astrophysics Data System (ADS)

    McMillan, Kathleen

    2011-03-01

    A new approach for improving the availability of topically applied drugs by reducing the permeability of dermis has been evaluated. The premise of this work is that photothermal vascular injury will reduce vascular uptake of drug in the dermis. The dermal distribution of two topically applied drugs, 5-fluorouracil and mitomycin C, is calculated, considering molecular diffusion and vascular uptake according to a distributed model, in the presence and absence of vascular injury. Intradermal drug exposures obtained are compared to exposures known to be effective in killing tumor cells. Combining the reduction in dermal permeability with fractional photothermal epidermal ablation to increase epidermal permeability may allow higher drug concentrations to be achieved in the skin. A newly developed laser handpiece for implementing the technique is described.

  3. [Modification of placenta blood serum proteins under low temperature effect].

    PubMed

    Fal'ko, O V; Zemlianskikh, N G; Lipina, O V; Prokopiuk, O S

    2013-01-01

    Changes in environmental physical and chemical factors upon freeze-thawing and low temperature storage of biological samples can result in impairments of protein structures. This work specifies spontaneous and diamide-induced protein aggregations of placenta blood serum stored at -20 degrees and -196 degrees C during 2 years with SDS-PAGE. It was shown that storage of placenta blood serum at low temperatures did not cause any quantitative and qualitative changes in fraction distribution of proteins denatured with SDS in comparison to the native samples which were not frozen. Application of beta-mercaptoethanol revealed that placenta blood serum proteins upon freeze-thawing did not form spontaneous aggregates linked by disulphide bridges. Oxidation of amino acid sulfhydryl groups induced by diamide and accompanied by high molecular aggregate formation proved to be a quite effective way for indirect estimation of structural changes in protein upon low temperature effects. In samples thawed after low temperature storage the protein aggregation with 4 microM diamide was significantly higher than in native serum. These discrepancies between native and frozen-thawed samples are stipulated by impairments of protein structure under low temperature and increased in accessibility of reactive SH-groups of proteins for oxidation with diamide. Structural changes in placenta blood serum proteins, which caused by low temperatures and revealed by elevated sensibility to diamide-induced aggregate formation, did not depend on temperature (-20 degrees and -196 degrees C) and storage terms (2 years and 3 weeks). They reflect protein reaction to freeze-thawing processes and could be sequence of ice crystal formation which takes place in unprotected media.

  4. Depletion region surface effects in electron beam induced current measurements

    PubMed Central

    Haney, Paul M.; Yoon, Heayoung P.; Gaury, Benoit; Zhitenev, Nikolai B.

    2016-01-01

    Electron beam induced current (EBIC) is a powerful characterization technique which offers the high spatial resolution needed to study polycrystalline solar cells. Current models of EBIC assume that excitations in the p-n junction depletion region result in perfect charge collection efficiency. However we find that in CdTe and Si samples prepared by focused ion beam (FIB) milling, there is a reduced and nonuniform EBIC lineshape for excitations in the depletion region. Motivated by this, we present a model of the EBIC response for excitations in the depletion region which includes the effects of surface recombination from both charge-neutral and charged surfaces. For neutral surfaces we present a simple analytical formula which describes the numerical data well, while the charged surface response depends qualitatively on the location of the surface Fermi level relative to the bulk Fermi level. We find the experimental data on FIB-prepared Si solar cells is most consistent with a charged surface, and discuss the implications for EBIC experiments on polycrystalline materials. PMID:27881882

  5. Depletion region surface effects in electron beam induced current measurements

    SciTech Connect

    Haney, Paul M.; Zhitenev, Nikolai B.; Yoon, Heayoung P.; Gaury, Benoit

    2016-09-07

    Electron beam induced current (EBIC) is a powerful characterization technique which offers the high spatial resolution needed to study polycrystalline solar cells. Current models of EBIC assume that excitations in the p-n junction depletion region result in perfect charge collection efficiency. However, we find that in CdTe and Si samples prepared by focused ion beam (FIB) milling, there is a reduced and nonuniform EBIC lineshape for excitations in the depletion region. Motivated by this, we present a model of the EBIC response for excitations in the depletion region which includes the effects of surface recombination from both charge-neutral and charged surfaces. For neutral surfaces, we present a simple analytical formula which describes the numerical data well, while the charged surface response depends qualitatively on the location of the surface Fermi level relative to the bulk Fermi level. We find that the experimental data on FIB-prepared Si solar cells are most consistent with a charged surface and discuss the implications for EBIC experiments on polycrystalline materials.

  6. Generalized Hall effect as a modification of ideal magnetohydrodynamics

    SciTech Connect

    Goodman, M.L.

    1986-01-01

    The generalized Hall effect (GHE) in the generalized Hall model (GHM) is studied as a correction to ideal magnetohydrodynamics (MHD) in the context of how it affects the linear stability of cylindrically symmetric equilibria and how it changes helically symmetric equilibria. The GHM differs from what is usually called the Hall model by including the electron pressure in the electron-momentum equations. This gives the GHM some aspects of a two-fluid model, whereas the Hall model is a one-fluid model. In both cases of cylindrical and helical symmetry, the presence of the electron pressure gradient as part of the GHE gives rise to an electric field tangent to the boundary of the plasma. This introduces an additional boundary condition in the case of a perfectly conducting plasma boundary. In the case of helical symmetry, the equilibrium equations are a generalization of the Grad-Shafranov equation to equilibria with flow and GHE. In the case of cylindrical symmetry, a class of Alfven-wave solutions that do not exist in ideal MHD is obtained and the accumulation point, with respect to large radial wavenumber, of the slow magnetoacoustic wave is shown to be changed from a finite nonzero value in ideal MHD to infinity by the GHE>

  7. Effect of plasma surface modification on the biocompatibility of UHMWPE.

    PubMed

    Kaklamani, G; Mehrban, N; Chen, J; Bowen, J; Dong, H; Grover, L; Stamboulis, A

    2010-10-01

    In this paper active screen plasma nitriding (ASPN) is used to chemically modify the surface of UHMWPE. This is an unexplored and new area of research. ASPN allows the homogeneous treatment of any shape or surface at low temperature; therefore, it was thought that ASPN would be an effective technique to modify organic polymer surfaces. ASPN experiments were carried out at 120 °C using a dc plasma nitriding unit with a 25% N(2) and 75% H(2) atmosphere at 2.5 mbar of pressure. UHMWPE samples treated for different time periods were characterized by nanoindentation, FTIR, XPS, interferometry and SEM. A 3T3 fibroblast cell line was used for in vitro cell culture experiments. Nanoindentation of UHMWPE showed that hardness and elastic modulus increased with ASPN treatment compared to the untreated material. FTIR spectra did not show significant differences between the untreated and treated samples; however, some changes were observed at 30 min of treatment in the range of 1500-1700 cm(-1) associated mainly with the presence of N-H groups. XPS studies showed that nitrogen was present on the surface and its amount increased with treatment time. Interferometry showed that no significant changes were observed on the surfaces after the treatment. Finally, cell culture experiments and SEM showed that fibroblasts attached and proliferated to a greater extent on the plasma-treated surfaces leading to the conclusion that ASPN surface treatment can potentially significantly improve the biocompatibility behaviour of polymeric materials.

  8. Effect of landfill cover layer modification on methane oxidation.

    PubMed

    Hu, Lifang; Long, Yuyang

    2016-12-01

    Levels of methane (CH4) oxidation in materials used for landfill cover attained in the laboratory are not often replicated in the field due to effects from the surrounding environment. This study investigates the three dominant factors affecting CH4 oxidation in the cover layer, namely, the thickness of cover layer, the methanotroph spraying manner, and the osmotic coefficient of the cover material. Results show that improved CH4 emission performance of the cover layer can be realized if methanotroph are introduced, meaning that a thinner cover layer is required. The highest CH4 emission reduction can be realized by spraying methanotroph into the top, middle, and bottom layers of a 30-cm thick cover layer with an osmotic coefficient of 7.76 × 10(-5) cm s(-1). Comparing results on cover layer thickness, methane monooxygenase (MMO) activity was much lower with increasing thickness meaning that the thicker cover could reduce O2 availability, thus inhibiting MMO activity. This suggests that MMO may be responsible for differences in CH4 emission reduction and/or oxidation making the osmotic coefficient an important factor for cover layer material.

  9. Cost-effective surface modification for Galinstan® lyophobicity.

    PubMed

    Kadlaskar, Shantanu Shrikant; Yoo, Jun Hyeon; Abhijeet; Lee, Jeong Bong; Choi, Wonjae

    2017-04-15

    In this paper we investigate the feasibility of using a cost-effective fabrication method based on sandblasting, chemical etching and spray coating processes, to render common surfaces to be non-wettable by Galinstan®. Although Galinstan® is a non-toxic liquid metal alternative to mercury, the viscoelastic and extremely wetting characteristics of Galinstan® have been the major bottleneck limiting the wide applicability of the gallium-based liquid metal. This paper tries to accomplish non-wettability to Galinstan® by combining surface texture and chemistry with the unique property of Galinstan®, that is, its high surface tension and yield strength that prevent the penetration of the liquid metal into surface asperities. Fabricated surfaces resemble traditional superhydrophobic (water-repellent) surfaces, and exhibit a superior non-wettability to Galinstan® as quantified by high static and dynamic contact angles, small hysteresis, as well as impact resistance. Reported fabrication method based on sandblasting, etching and spray coating is easily applicable to various surfaces ranging from metals, ceramics, to plastics and is scalable to large surfaces. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. Effect of modification substrate on the microstructure of hydroxyapatite coating

    NASA Astrophysics Data System (ADS)

    Realpe-Jaramillo, J.; Morales-Morales, J. A.; González-Sánchez, J. A.; Cabanzo, R.; Mejía-Ospino, E.; Rodríguez-Pereira, J.

    2017-01-01

    Bioactive hydroxyapatite (HA) coatings were fabricated by a precipitation, sol-gel and dip-coating method. The effects of the aging time and the base used to adjust pH and substrate materials on the phases and microstructures of HA coatings were studied by field emission scanning electron microscopy FESEM, energy dispersive spectroscopy EDS, X-ray photoelectron spectroscopy XPS, and the vibrations of the phosphate groups were determined by Raman spectroscopy. The results showed that all the films were composed of the phases of TiO2 and HA. With coated titanium substrate with TiO2, the crystallinity of the HA coating increases, the structure became more compact and the Ca/P ratio increased because of the loss of P in the films. The addition of sodium hydroxide (adjusting the pH level to about 10) can increase the HA content in the coating. XPS and EDS results for steel substrate and titanium showed poor calcium content as obtained with a Ca/P ratio of 1.38 and 1.58, respectively, composition is similar to that of natural apatite. However, spectroscopic results suggest the presence of a mixture of hydroxyapatite and octacalcium phosphate. The different substrate materials have a high influence on the microstructure of the separated double films. However, hydroxyapatite nanopowders coatings were obtained using a simple method, with potential biomedical applications.

  11. Magnetoresistive sensors for measurements of DNA hybridization kinetics – effect of TINA modifications

    PubMed Central

    Rizzi, G.; Dufva, M.; Hansen, M. F.

    2017-01-01

    We present the use of magnetoresistive sensors integrated in a microfluidic system for real-time studies of the hybridization kinetics of DNA labeled with magnetic nanoparticles to an array of surface-tethered probes. The nanoparticles were magnetized by the magnetic field from the sensor current. A local negative reference ensured that only the specific binding signal was measured. Analysis of the real-time hybridization using a two-compartment model yielded both the association and dissociation constants kon, and koff. The effect of probe modifications with ortho-Twisted Intercalating Nucleic Acid (TINA) was studied. Such modifications have been demonstrated to increase the melting temperature of DNA hybrids in solution and are also relevant for surface-based DNA sensing. Kinetic data for DNA probes with no TINA modification or with TINA modifications at the 5′ end (1 × TINA) or at both the 5′ and 3′ ends (2 × TINA) were compared. TINA modifications were found to provide a relative decrease of koff by a factor of 6-20 at temperatures from 57.5 °C to 60 °C. The values of kon were generally in the range between 0.5-2 × 105 M−1s−1 and showed lower values for the unmodified probe than for the TINA modified probes. The observations correlated well with measured melting temperatures of the DNA hybrids. PMID:28167835

  12. Elastic-plastic deformations of a beam with the SD-effect

    SciTech Connect

    Pavilaynen, Galina V.

    2015-03-10

    The results for the bending of a cantilever beam with the SD-effect under a concentrated load are discussed. To solve this problem, the standard Bernoulli-Euler hypotheses for beams and the Ilyushin model of perfect plasticity are used. The problem is solved analytically for structural steel A40X. The SD-effect for elastic-plastic deformations is studied. The solutions for beam made of isotropic material and material with the SD-effect are compared.

  13. Numerical Investigation of Statistical Turbulence Effects on Beam Propagation through 2-D Shear Mixing Layer

    DTIC Science & Technology

    2010-03-01

    NUMERICAL INVESTIGATION OF STATISTICAL TURBULENCE EFFECTS ON BEAM PROPAGATION THROUGH 2-D SHEAR MIXING LAYER THESIS James C. Bowers, Captain, USAF...STATISTICAL TURBULENCE EFFECTS ON BEAM PROPAGATION THROUGH 2-D SHEAR MIXING LAYER THESIS Presented to the Faculty Department of Engineering Physics...robust method for calculating atmospheric turbulence effects on optical beam propagation, which could simplify similar approaches to chaotic aero-optical

  14. Effect of adipic dihydrazide modification on the performance of collagen/hyaluronic acid scaffold.

    PubMed

    Zhang, Ling; Xiao, Yumei; Jiang, Bo; Fan, Hongsong; Zhang, Xingdong

    2010-02-01

    Collagen and hydrazide-functionalized hyaluronic acid derivatives were hybridized by gelating and genipin crosslinking to form composite hydrogel. The study contributed to the understanding of the effects of adipic dihydrazide modification on the physicochemical and biological properties of the collagen/hyaluronic acid scaffold. The investigation included morphology observation, mechanical measurement, swelling evaluation, and collagenase degradation. The results revealed that the stability of composites was increased through adipic dihydrazide modification and genipin crosslinking. The improved biocompatibility and retention of hyaluronic acid made the composite material more favorable to chondrocytes growing, suggesting the prepared scaffold might be high potential for chondrogenesis.

  15. The effect of transverse flow on the nuclear modification factor at RHIC and LHC

    SciTech Connect

    Betz, Barbara; Gyulassy, Miklos

    2016-01-22

    We determine the nuclear modification factor at RHIC and LHC energies using a generic jet-energy loss model that is expanded by an additional flow factor accounting for the impact of transverse flow. We consider a pQCD-based ansatz with and without jet-energy loss fluctuations that is coupled to a state-of-the-art hydrodynamic prescription and includes a running coupling effect. We show that the nuclear modification factor is a rather insensitive quantity that is barely affected by the flow dynamics of the medium created in a heavy-ion collision.

  16. Meta-Analysis of the Effects of Academic Interventions and Modifications on Student Behavior Outcomes

    ERIC Educational Resources Information Center

    Warmbold-Brann, Kristy; Burns, Matthew K.; Preast, June L.; Taylor, Crystal N.; Aguilar, Lisa N.

    2017-01-01

    The current study examined the effect of academic interventions and modifications on behavioral outcomes in a meta-analysis of 32 single-case design studies. Academic interventions included modifying task difficulty, providing instruction in reading, mathematics, or writing, and contingent reinforcement for academic performance. There was an…

  17. Effects of Lexical Modification on Incidental Vocabulary Acquisition of Iranian EFL Students

    ERIC Educational Resources Information Center

    Negari, Giti Mousapour; Rouhi, Mahdieh

    2012-01-01

    The present article reports on the results of a study designed to investigate the effects of two types of lexical modification i.e., lexical simplification and elaboration, on incidental vocabulary acquisition of Iranian EFL learners.To this end, four versions of experimental texts containing 20 target words were created: baseline and simplified…

  18. High energy cocktail beams for radiation effects studies

    SciTech Connect

    McMahan, M.A.; Argento, D.A.; Gimpel, T.; Guy, A.; Morel, J.; Osborne, K.; Siero, R.; Thatcher, R.; Wutte, D.; Xie, X.Q.; Lyneis, C.M.

    2001-01-01

    The 88-Inch Cyclotron facility consists of a sector-focused, variable energy cyclotron fed by two Electron Cyclotron Resonance (ECR) high charge-state sources. The combination of cyclotron and ECR source provides the ability to run ''cocktails'' of ions, mixtures of ions of near-identical charge-to-mass ratio. This concept was developed for detector calibrations soon after the first ECR source came on line. [1] The ions are tuned out of the source together and the cyclotron frequency--acting as a mass analyzer--separates them. This means that within the components of the cocktail, the accelerated ion can be changed in approximately one minute. Intensity variations are compensated for with a series of attenuator grids at the ion source, which allow ion beam intensity adjustments over nine orders of magnitude. The cocktail beam soon became the mainstay of the heavy ion radiation effects program at the Cyclotron, an applied program which is run on a recharge basis and which accounts for about 10% of the annual usage. The largest component of this program is directed at measuring single event effects--a variety of effects, which can occur when a heavy ion traverses a transistor, memory chip or other piece of microelectronics. It can then be determined whether the device is appropriate for use in a satellite or space vehicle in a particular orbit, knowing the distribution of heavy ions expected at that orbit. To first order, the observed single event effects are atomic processes, which depend only on the linear energy transfer (LET), or stopping power, of the ion. The range of the ion is important only to ensure that the ion reaches the correct interaction depth. In the early 90's, two cocktails were developed at the Cyclotron for standard use: a ''light ion'' cocktail for ions up to {sup 36}Ar at high energy and large range, and a ''heavy ion'' cocktail at 4.5 MeV/nucleon, with LETs ranging from 3-60 MeV/mg/cm{sup 2} and ranges from 43-69 {micro}. Using the AECR, Bi

  19. The effects of linguistic modification on ESL students' comprehension of nursing course test items.

    PubMed

    Bosher, Susan; Bowles, Melissa

    2008-01-01

    Recent research has indicated that language may be a source of construct-irrelevant variance for non-native speakers of English, or English as a second language (ESL) students, when they take exams. As a result, exams may not accurately measure knowledge of nursing content. One accommodation often used to level the playing field for ESL students is linguistic modification, a process by which the reading load of test items is reduced while the content and integrity of the item are maintained. Research on the effects of linguistic modification has been conducted on examinees in the K-12 population, but is just beginning in other areas. This study describes the collaborative process by which items from a pathophysiology exam were linguistically modified and subsequently evaluated for comprehensibility by ESL students. Findings indicate that in a majority of cases, modification improved examinees' comprehension of test items. Implications for test item writing and future research are discussed.

  20. Collective effects on the wakefield and stopping power of an ion beam pulse in plasmas

    SciTech Connect

    Zhang, Ling-yu; Zhao, Xiao-ying; Qi, Xin E-mail: duanws@nwnu.edu.cn Duan, Wen-shan E-mail: duanws@nwnu.edu.cn Xiao, Guo-qing; Yang, Lei E-mail: duanws@nwnu.edu.cn

    2015-05-15

    A two-dimensional (2D) particle-in-cell simulation is carried out to study the collective effects on the wakefield and stopping power for a hydrogen ion beam pulse propagation in hydrogen plasmas. The dependence of collective effects on the beam velocity and density is obtained and discussed. For the beam velocity, it is found that the collective effects have the strongest impact on the wakefield as well as the stopping power in the case of the intermediate beam velocities, in which the stopping power is also the largest. For the beam density, it is found that at low beam densities, the collective contribution to the stopping power increase linearly with the increase of the beam density, which corresponds well to the results calculated using the dielectric theory. However, at high beam densities, our results show that after reaching a maximum value, the collective contribution to the stopping power starts to decrease significantly with the increase of the beam density. Besides, at high beam densities, the wakefield loses typical V-shaped cone structures, and the wavelength of the oscillation wakefield increases as the beam density increases.

  1. The quantum measurement effect of interaction without interaction for an atomic beam

    NASA Astrophysics Data System (ADS)

    Huang, Yong-Yi

    When an atomic beam collectively and harmonically vibrates perpendicular to the wave vector of the beam, the number of atoms reaching the atomic detector will have a vibrant factor Δt / T if the measurement time interval Δt is shorter than the period T. This new quantum mechanical measurement effect for an atomic beam is called interaction without interaction: though the translational motion of the atomic beam does not interact with its collective and transverse harmonic vibration, the latter will have an effect on the measured number of atoms associated with the former. From the new measurement effect the classical harmonic vibration's period is evaluated. We give a clear physical picture and a satisfactory physical interpretation for the measurement effect based on the Copenhagen interpretation of quantum mechanics. We present an experimental proposal to verify this measurement effect for an ion beam instead of an atomic beam.

  2. Smith-Purcell radiation from a ribbon beam as effective THz and X-ray source

    NASA Astrophysics Data System (ADS)

    Tishchenko, A. A.; Sergeeva, D. Yu.; Ponomarenko, A. A.; Strikhanov, M. N.

    2017-07-01

    We investigate the possibility to enhance the THz and X-ray sources based on interaction between an electron beam and a grating using a ribbon beam. Making the beam ribbon, we increase the area of effective interaction between the beam and the grating, which can lead to increasing the number of photons radiated through Smith-Purcell mechanism. The theory of this process is constructed; the fully analytical description is given; the numerical analysis shows that the radiation can be enhanced considerably with use of ribbon beams instead of cylindrical one in case when transversal part of coherent form-factor plays a role.

  3. Incident-beam effects in electron-stimulated Auger-electron diffraction

    NASA Astrophysics Data System (ADS)

    Gao, Y.; Cao, Jianming

    1991-04-01

    We have examined incident-beam effects in electron-stimulated Auger-electron diffraction (AED) on a cleaved GaAs(110) surface. The results indicate that incident-beam diffraction is significant in an AED experiment, and that the dissipative nature of the incident beam in contributing to the Auger process must be accounted for. We have developed a qualitative model that describes the trend of the polar-angle dependence of the Auger intensity for both the incident and exit beams. In calculating the diffraction features, we used a zeroth-order approximation to simulate the dissipation of the incident beam, which is found to adequately describe the experimental data.

  4. Effects of cognitive bias modification training on neural alcohol cue reactivity in alcohol dependence.

    PubMed

    Wiers, Corinde E; Stelzel, Christine; Gladwin, Thomas E; Park, Soyoung Q; Pawelczack, Steffen; Gawron, Christiane K; Stuke, Heiner; Heinz, Andreas; Wiers, Reinout W; Rinck, Mike; Lindenmeyer, Johannes; Walter, Henrik; Bermpohl, Felix

    2015-04-01

    In alcohol-dependent patients, alcohol cues evoke increased activation in mesolimbic brain areas, such as the nucleus accumbens and the amygdala. Moreover, patients show an alcohol approach bias, a tendency to more quickly approach than avoid alcohol cues. Cognitive bias modification training, which aims to retrain approach biases, has been shown to reduce alcohol craving and relapse rates. The authors investigated effects of this training on cue reactivity in alcohol-dependent patients. In a double-blind randomized design, 32 abstinent alcohol-dependent patients received either bias modification training or sham training. Both trainings consisted of six sessions of the joystick approach-avoidance task; the bias modification training entailed pushing away 90% of alcohol cues and 10% of soft drink cues, whereas this ratio was 50/50 in the sham training. Alcohol cue reactivity was measured with functional MRI before and after training. Before training, alcohol cue-evoked activation was observed in the amygdala bilaterally, as well as in the right nucleus accumbens, although here it fell short of significance. Activation in the amygdala correlated with craving and arousal ratings of alcohol stimuli; correlations in the nucleus accumbens again fell short of significance. After training, the bias modification group showed greater reductions in cue-evoked activation in the amygdala bilaterally and in behavioral arousal ratings of alcohol pictures, compared with the sham training group. Decreases in right amygdala activity correlated with decreases in craving in the bias modification but not the sham training group. These findings provide evidence that cognitive bias modification affects alcohol cue-induced mesolimbic brain activity. Reductions in neural reactivity may be a key underlying mechanism of the therapeutic effectiveness of this training.

  5. The effect of object shape and laser beam shape on lidar system resolution

    NASA Astrophysics Data System (ADS)

    Cheng, Hongchang; Wang, Jingyi; Ke, Jun

    2016-06-01

    In a LIDAR system, a pulsed laser beam is propagated to a scene, and then reflected back by objects. Ideally if the beam diameter and the pulse width are close to zero, then the reflected beam in time domain is similar to a delta function, which can accurately locate an object's position. However, in a practical system, the beam has finite size. Therefore, even if the pulse width is small, an object shape will make the reflected beam stretched along the time axis, then affect system resolution. In this paper, we assume the beam with Gaussian shape. The beam can be formulated as a delta function convolved with a shape function, such as a rectangular function, in time domain. Then the reflected beam can be defined as a system response function convolved with the shape function. We use symmetric objects to analyze the reflected beam. Corn, sphere, and cylinder objects are used to find a LIDAR system's response function. The case for large beam size is discussed. We assume the beam shape is similar to a plane wave. With this assumption, we get the simplified LIDAR system response functions for the three kinds of objects. Then we use tiny spheres to emulate an arbitrary object, and study its effect to the returned beam.

  6. Effect of Contrast Media on Megavoltage Photon Beam Dosimetry

    SciTech Connect

    Rankine, Ashley W. Lanzon, Peter J.; Spry, Nigel A.

    2008-10-01

    The purpose of this study was to quantify changes in photon beam dosimetry caused by using contrast media during computed tomography (CT) simulation and determine if the resulting changes are clinically significant. The effect of contrast on dosimetry was first examined for a single 6-MV photon beam incident on a plane phantom with a structure of varying electron densities ({rho}{sub e}) and thickness. Patient studies were then undertaken in which CT data sets were collected with and without contrast for 6 typical patients. Three patients received IV contrast (Optiray-240{sup TM}) only and 3 received IV plus oral (Gastrograffin{sup TM}) contrast. Each patient was planned using conformal multifield techniques in accordance with the department standards. Two methods were used to compare the effect of contrast on dosimetry for each patient. The phantom analysis showed that the change in dose at the isocenter for a single 10 x 10 cm{sup 2} 6-MV photon beam traversing 10 cm of a contrast-enhanced structure with {rho}{sub e} 1.22 was 7.0% (1.22 was the highest average {rho}{sub e} observed in the patient data). As a result of using contrast, increases in {rho}{sub e} were observed in structures for the 6 patients studied. Consequently, when using contrast-enhanced CT data for multifield planning, increases in dose at the isocenter and in critical structures were observed up to 2.1% and 2.5%, respectively. Planning on contrast-enhanced CT images may result in an increase in dose of up to 2.1% at the isocenter, which would generally be regarded as clinically insignificant. If, however, a critical organ is in close proximity to the planning target volume (PTV) and is planned to receive its maximum allowable dose, planning on contrast-enhanced CT images may result in that organ receiving dose beyond the recommended tolerance. In these instances, pre-contrast CT data should be used for dosimetry.

  7. Simple effective tests for beam propagation method programs

    NASA Astrophysics Data System (ADS)

    Dumitrescu, Mihail M.; Iancu, Ovidiu D.; Karam, Jean Michel

    2000-02-01

    In view of the increased need of an effective, practical and unified test set to evalute the modeling capabilities of beam propagation method (BPM) based programs, we prose an incident set of tests to be used for a standard evaluation. The proposed test have been chosen to be simple, easy to implement and enable a fairly good evaluation without the need of any experiment. Interesting aspects of the tests' results and some straightforward, practical criteria to estimate program capabilities and to tune the simulation parameters are presented. A cross-checking between 'Mode Solver' based and BPM based programs is also put into discussion. A paraxial error evaluation method is presented and the transverse mesh influence on the paraxial error is analyzed.

  8. Ion beam induced luminescence: Relevance to radiation induced bystander effects

    NASA Astrophysics Data System (ADS)

    Ahmad, S. B.; McNeill, F. E.; Byun, S. H.; Prestwich, W. V.; Seymour, C.; Mothersill, C. E.

    2012-10-01

    The aim of this work is quantify the light emitted as a result of charged particle interaction in materials which may be of relevance to radiation induced "bystander effects" studies. We have developed a system which employs single photon counting to measure the light emitted from samples irradiated under vacuum by a charged particle beam. The system uses a fast photomultiplier tube with a peak cathode response at 420 nm. It has been tested in a proof-of-principle experiment using polystyrene targets. Light output, as a result of irradiation, was measured. The luminescence yield appears to have a non-linear behavior with the incident ion fluence: it rises exponentially to an asymptotic value. The target was irradiated with beam energies varying from 1 to 2 MeV and showed saturation at or before an incident fluence rate of 3 × 1013 H+/cm2 s. The average saturation value for the photon output was found to be 40 × 106 cps. Some measurements were performed using filters to study the emission at specific wavelengths. In the case of filtered light measurements, the photon output was found to saturate at 28 × 103, 10 × 106, and 35 × 106 cps for wavelengths of 280 ± 5 nm, 320 ± 5 nm and 340 ± 5 nm respectively. The light output reaches a maximum value because of damage induced in the polymer. Our measurements indicate a "damage cross section" of the order of 10-14 cm2. The average radiant intensity was found to increase at wavelengths of 280 and 320 nm when the proton energy was increased. This was not found to occur at 340 nm. In conclusion, the light emission at specific wavelengths was found to depend upon the incident proton fluence and the proton energy. The wavelengths of the emitted light measured in this study have significance for the understanding of radiation induced bystander effects.

  9. Effects of Weak Surface Modification on Co/SiO2 Catalyst for Fischer-Tropsch Reaction

    PubMed Central

    Ning, Wensheng; Shen, Hehong; Jin, Yangfu; Yang, Xiazhen

    2015-01-01

    A weak surface modification is applied to Co/SiO2 catalyst by hydrothermal treatment at 180°C for 5 h. Aluminum is introduced to Co/SiO2 catalysts during the surface modification. The effects of surface modification on Co/SiO2 catalyst are studied by changing the operating sequences of surface modification and cobalt impregnation in the catalyst preparation. Surface modification before cobalt impregnation makes Co3O4 particle small and dispersed into the deep part of enlarged pore in SiO2, while surface modification after cobalt impregnation does not obviously change the particle size of Co3O4. The improved amplitude of catalytic activity is similar for the two kinds of catalysts, but they are benefited from different factors. The content of iso-hydrocarbons in the products is increased by the surface modifications. PMID:25938725

  10. Effects of Weak Surface Modification on Co/SiO2 Catalyst for Fischer-Tropsch Reaction.

    PubMed

    Ning, Wensheng; Shen, Hehong; Jin, Yangfu; Yang, Xiazhen

    2015-01-01

    A weak surface modification is applied to Co/SiO2 catalyst by hydrothermal treatment at 180°C for 5 h. Aluminum is introduced to Co/SiO2 catalysts during the surface modification. The effects of surface modification on Co/SiO2 catalyst are studied by changing the operating sequences of surface modification and cobalt impregnation in the catalyst preparation. Surface modification before cobalt impregnation makes Co3O4 particle small and dispersed into the deep part of enlarged pore in SiO2, while surface modification after cobalt impregnation does not obviously change the particle size of Co3O4. The improved amplitude of catalytic activity is similar for the two kinds of catalysts, but they are benefited from different factors. The content of iso-hydrocarbons in the products is increased by the surface modifications.

  11. Modification by Influenza on Health Effects of Air Pollution in Hong Kong

    PubMed Central

    Wong, Chit Ming; Yang, Lin; Thach, Thuan Quoc; Chau, Patsy Yuen Kwan; Chan, King Pan; Thomas, G. Neil; Lam, Tai Hing; Wong, Tze Wai; Hedley, Anthony J.; Peiris, J.S. Malik

    2009-01-01

    Background Both influenza viruses and air pollutants have been well documented as major hazards to human health, but few epidemiologic studies have assessed effect modification of influenza on health effects of ambient air pollutants. Objectives We aimed to assess modifying effects of influenza on health effects of ambient air pollutants. Methods We applied Poisson regression to daily numbers of hospitalizations and mortality to develop core models after adjustment for potential time-varying confounding variables. We assessed modification of influenza by adding variables for concentrations of single ambient air pollutants and proportions of influenza-positive specimens (influenza intensity) and their cross-product terms. Results We found significant effect modification of influenza (p < 0.05) for effects of ozone. When influenza intensity is assumed to increase from 0% to 10%, the excess risks per 10-μg/m3 increase in concentration of O3 increased 0.24% and 0.40% for hospitalization of respiratory disease in the all-ages group and ≥ 65 year age group, respectively; 0.46% for hospitalization of acute respiratory disease in the all-ages group; and 0.40% for hospitalization of chronic obstructive pulmonary disease in the ≥ 65 group. The estimated increases in the excess risks for mortality of respiratory disease and chronic obstructive pulmonary disease in the all-ages group were 0.59% and 1.05%, respectively. We found no significant modification of influenza on effects of other pollutants in most disease outcomes under study. Conclusions Influenza activity could be an effect modifier for the health effects of air pollutants particularly for O3 and should be considered in the studies for short-term effects of air pollutants on health. PMID:19270795

  12. Effect of electron beam irradiation on PMMA films

    SciTech Connect

    Tiwari, Pragya; Srivastava, A. K.; Khattak, B. Q.; Verma, Suveer; Upadhyay, Anuj; Sinha, A. K.; Ganguli, Tapas; Lodha, G. S.; Deb, S. K.

    2012-06-05

    Polymethyl methacrylate (PMMA) is characterized for electron beam interactions in the resist layer in lithographic applications. PMMA thin films (free standing) were prepared by solvent casting method. These films were irradiated with 30keV electron beam at different doses. Structural and chemical properties of the films were studied by means of X-ray diffraction and Fourier transform infra-red (FTIR) spectroscopy The XRD results showed that the amorphization increases with electron beam irradiation dose. FTIR spectroscopic analysis reveals that electron beam irradiation promotes the scission of carbonyl group and depletes hydrogen and converts polymeric structure into hydrogen depleted carbon network.

  13. TU-A-BRE-01: The Relative Biological Effectiveness of Proton Beams Relative to Photon Beams

    SciTech Connect

    Paganetti, H; Stewart, R; Carabe-Fernandez, A

    2014-06-15

    Proton therapy patients receive a 10% lower physical dose than the dose administered using photons, i.e. the proton relative biological effectiveness (RBE) is 1.1 in comparison to high-energy photons. The use of a generic, spatially invariant RBE within tumor targets and normal tissue structures disregards a large body of evidence indicating that proton RBE tends to increase with increasing linear energy transfer (LET). Because the doseaveraged proton LET in the distal edge of a spread out Bragg peak (SOBP) is larger than the LET in the plateau region or proximal edge of a SOBP, the use of a spatially invariant RBE is not well justified from a mechanistic point of view. On the other hand, the available clinical data on local tumor control rates and early or late side effects do not provide strong evidence against the continued use of a constant and spatially invariant clinical RBE. The only potential downside to the ongoing use of a constant RBE of 1.1 seems to be that we are missing a potential opportunity to enhance the therapeutic ratio, i.e., design proton therapy treatments in ways that exploit, rather than mitigate, spatial variations in proton RBE. Speakers in this symposium will: 1-review the laboratory and clinical evidence for and against the continued use of a spatially invariant RBE of 1.1, 2-examine some of the putative mechanisms connecting spatial variations in particle LET to estimates of the proton RBE at the molecular, cellular and tissue levels 3-assess the possible clinical significance of incorporating models for spatial variations in proton RBE into treatment planning systems. 4-discuss treatment planning and delivery techniques that will exploit the spatial variations of RBE within proton beams. Learning Objectives: To review laboratory and clinical evidence for and against the continued use of a constant RBE of 1.1 To understand major mechanisms connecting proton LET to RBE at the molecular, cellular and tissue levels. To quantify the

  14. Study of crack patterns in beam column joint due to upwards anchoring beam effect

    NASA Astrophysics Data System (ADS)

    Sabariman, Bambang; Sofianto, Mochamad Firmansyah

    2017-06-01

    Beam-column joint (BCJ) of reinforced concrete is an area of critical which must be carefully designed to absorb the seismic energy. Inability to absorb seismic energy will cause serious damage to structural failure. It will lead to shear failure, i.e. brittle and endanger users of the building if the BCJ area is not designed properly. In order to get a building structure is safe and resistant to disasters, mainly due to the earthquake, the structure must be designed in accordance to the rules of standard construction (eligible detailing). In general, the anchorages (detailing) reinforcement beams to the column is pointing downwards, however, what if the steel anchoring beams are pointing upwards. Different anchoring will result in the behavior of different structures, such as fracturing pattern. This study observes two anchoring model, by making two test specimens of BCJ. One set of reinforcement beams anchored BCJ upward and downward respectively, which are applied with monotonic static load. The study investigated the pattern of cracks and ductility of the beam displacement on BCJ. The results showed that the downward anchoring in the fracturing pattern out of the area BCJ was anchoring upward pattern rift goes deep into the area BCJ, thus anchoring above makes BCJ unsafe. Downward anchoring are more ductile than the upward anchoring, however the deflection of all BJC specimens was higher than the boundaries maximum deflection prediction (Δprediction = 10.45 mm < eksp Δexp-min = 13.15 mm), which can be assumed that all BCJ specimens were ductile, but it still in ductile limited due to displacement ductility μΔ<3,5.

  15. Effective doses from cone beam CT investigation of the jaws

    PubMed Central

    Davies, J; Johnson, B; Drage, NA

    2012-01-01

    Objectives The purpose of the study was to calculate the effective dose delivered to the patient undergoing cone beam (CB) CT of the jaws and maxillofacial complex using the i-CAT Next Generation CBCT scanner (Imaging Sciences International, Hatfield, PA). Methods A RANDO® phantom (The Phantom Laboratory, Salem, NY) containing thermoluminence dosemeters were scanned 10 times for each of the 6 imaging protocols. Effective doses for each protocol were calculated using the 1990 and approved 2007 International Commission on Radiological Protection (ICRP) recommended tissue weighting factors (E1990, E2007). Results The effective dose for E1990 and E2007, respectively, were: full field of view (FOV) of the head, 47 μSv and 78 μSv; 13 cm scan of the jaws, 44 μSv and 77 μSv; 6 cm standard mandible, 35 μSv and 58 μSv; 6 cm high resolution mandible, 69 μSv and 113 μSv; 6 cm standard maxilla, 18 μSv and 32 μSv; and 6 cm high resolution maxilla, 35 μSv and 60 μSv. Conclusions Using the new generation of CBCT scanner, the effective dose is lower than the original generation machine for a similar FOV using the ICRP 2007 tissue weighting factors. PMID:22184626

  16. EFFECT OF SOLENOID FIELD ERRORS ON ELECTRON BEAM TEMPERATURES IN THE RHIC ELECTRON COOLER.

    SciTech Connect

    MONTAG,C.KEWISCH,J.

    2003-05-12

    As part of a future upgrade to the Relativistic Heavy Ion Collider (RHIC), electron cooling is foreseen to decrease ion beam emittances. Within the electron cooling section, the ''hot'' ion beam is immersed in a ''cold'' electron beam. The cooling effect is further enhanced by a solenoid field in the cooling section, which forces the electrons to spiral around the field lines with a (Larmor) radius of 10 micrometers, reducing the effective transverse temperature by orders of magnitude. Studies of the effect of solenoid field errors on electron beam temperatures are reported.

  17. Acute effects of air pollution on pediatric asthma exacerbation: evidence of association and effect modification.

    PubMed

    Samoli, E; Nastos, P T; Paliatsos, A G; Katsouyanni, K; Priftis, K N

    2011-04-01

    We investigated the short-term effects of particulate matter with aerodynamic diameter <10 μg/m(3) (PM(10)), sulfur dioxide (SO(2)), nitrogen dioxide (NO(2)) and ozone (O(3)) on pediatric asthma emergency admissions in Athens, Greece over the period 2001-2004. We explored effect modification patterns by season, sex, age and by the presence of desert dust transported mainly from the Sahara area. We used daily time-series data provided by the children's hospitals and the fixed monitoring stations. The associations were investigated using Poisson regression models controlling for seasonality, weather, influenza episodes, day of the week and holiday effects. A 10 μg/m(3) increase in PM(10) was associated with a 2.54% increase (95% confidence interval (CI): 0.06%, 5.08%) in the number of pediatric asthma hospital admissions, while the same increase in SO(2) was associated with a 5.98% (95% CI: 0.88%, 11.33%) increase. O(3) was associated with a statistically significant increase in asthma admissions among older children in the summer. Our findings provide limited evidence of an association between NO(2) exposure and asthma exacerbation. Statistically significant PM(10) effects were higher during winter and during desert dust days, while SO(2) effects occurred mainly during spring. Our study confirms previously reported PM(10) effects on emergency hospital admissions for pediatric asthma and further provides evidence of stronger effects during desert dust days. We additionally report severe effects of SO(2), even at today's low concentration levels. Copyright © 2011 Elsevier Inc. All rights reserved.

  18. Generation of highly confined optical bottle beams by exploiting the photonic nanojet effect

    NASA Astrophysics Data System (ADS)

    Kim, Myun-Sik; Scharf, Toralf; Mühlig, Stefan; Rockstuhl, Carsten; Herzig, Hans Peter

    2012-03-01

    We report on the generation of photonic nanojets, which resemble optical bottle beams. They are realized by manipulating the illumination of dielectric microspheres. As illumination we use the outer region of deliberately truncated Bessel-Gauss beam or a focused Gaussian beam with intentionally induced spherical aberrations. For the Bessel-Gauss beam possessing a single side lobe only, the nanojet spot resembles an optical bottle beam with a strong confinement due to the nanojet effect. When multiple side lobes of the aberrated focal spot are used, a chain of 3D optical bottle beams appears. We show the 3D intensity distributions close to the spot and discuss the main characteristics of such optical bottle beams.

  19. Developing a Sealing Material: Effect of Epoxy Modification on Specific Physical and Mechanical Properties

    PubMed Central

    Schoberleitner, Christoph; Archodoulaki, Vasiliki-Maria; Koch, Thomas; Lüftl, Sigrid; Werderitsch, Markus; Kuschnig, Gerhard

    2013-01-01

    To develop a matched sealing material for socket rehabilitation of grey cast iron pipes, an epoxy resin is modified by the addition of different components to improve the flexibility. Three different modifications are made by adding ethylene-propylene diene monomer (EPDM) rubber powder, reactive liquid polymer (ATBN) and epoxidized modifier. In this paper the effect of the modification method as well as the influence of absorption of water on the mechanical and physical properties are analyzed in terms of: tensile strength, modulus of elasticity, adhesion performance, pressure resistance, glass transition temperature and water content. A comparison with neat epoxy shows for all materials that the modulus of elasticity and strength decrease. Unlike other tested modification methods, the modification with rubber powder did not enhance the flexibility. All materials absorb water and a plasticization effect arises with further changes of mechanical and physical properties. The application of the sealant on the grey cast iron leads to a reduction of the strain at break (in comparison to the common tensile test of the pure materials) and has to be evaluated. The main requirement of pressure resistance up to 1 MPa was tested on two chosen materials. Both materials fulfill this requirement. PMID:28788404

  20. Developing a Sealing Material: Effect of Epoxy Modification on Specific Physical and Mechanical Properties.

    PubMed

    Schoberleitner, Christoph; Archodoulaki, Vasiliki-Maria; Koch, Thomas; Lüftl, Sigrid; Werderitsch, Markus; Kuschnig, Gerhard

    2013-11-27

    To develop a matched sealing material for socket rehabilitation of grey cast iron pipes, an epoxy resin is modified by the addition of different components to improve the flexibility. Three different modifications are made by adding ethylene-propylene diene monomer (EPDM) rubber powder, reactive liquid polymer (ATBN) and epoxidized modifier. In this paper the effect of the modification method as well as the influence of absorption of water on the mechanical and physical properties are analyzed in terms of: tensile strength, modulus of elasticity, adhesion performance, pressure resistance, glass transition temperature and water content. A comparison with neat epoxy shows for all materials that the modulus of elasticity and strength decrease. Unlike other tested modification methods, the modification with rubber powder did not enhance the flexibility. All materials absorb water and a plasticization effect arises with further changes of mechanical and physical properties. The application of the sealant on the grey cast iron leads to a reduction of the strain at break (in comparison to the common tensile test of the pure materials) and has to be evaluated. The main requirement of pressure resistance up to 1 MPa was tested on two chosen materials. Both materials fulfill this requirement.

  1. Separate and combined effects of methylphenidate and behavior modification on boys with attention deficit-hyperactivity disorder in the classroom.

    PubMed

    Pelham, W E; Carlson, C; Sams, S E; Vallano, G; Dixon, M J; Hoza, B

    1993-06-01

    This study evaluated the separate and combined effects of behavior modification and 2 doses of methylphenidate (MPH; 0.3 and 0.6 mg/kg) compared with baseline (no behavior modification and a placebo) on the classroom behavior and academic performance of 31 ADHD (attention deficit-hyperactivity disorder) boys attending a summer treatment program. Results revealed significant effects of both interventions, with the mean effect size of medication being more than twice as great as that of behavior modification. Relatively small incremental value was gained by the higher dose of medication or the addition of behavior modification, compared with the effects of the low dose of MPH. In contrast, the addition of either dose of MPH resulted in improvement beyond the effects of behavior modification alone. These group effects reflected those obtained in analyses of individual differences. Furthermore, comparisons of individual responsiveness showed that boys who responded to one treatment also responded to the other.

  2. Temperature dependence of electron-beam induced effects in amorphous apatite

    SciTech Connect

    Bae, In-Tae; Zhang, Yanwen; Weber, William J.; Ishimaru, Manabu; Hirotsu, Yoshihiko; Higuchi, Mikio

    2008-06-07

    Irradiation effects on pre-amorphized Sr2Nd8(SiO4)6O2 have been investigated under 200 and 300 keV electron-beam irradiation at 130 and 480 K using in situ transmission electron microscopy. At 480 K, recrystallization occurred from the amorphous/crystalline interface under both 200 and 300 keV e-beam irradiation. At 130 K, the 200 keV e-beam irradiation induced recrystallization only; however, 300 keV e-beam irradiation induced both recrystallization and an electron hammering effect in the amorphous material that resulted in radial expansion perpendicular to the incident electron-beam direction and shrinkage parallel to the electron-beam direction. Ionization-induced processes and knock-on displacement damage are suggested to be the mechanisms for the recrystallization and the electron hammering effect, respectively.

  3. The lensing effect of trapped particles in a dual-beam optical trap.

    PubMed

    Grosser, Steffen; Fritsch, Anatol W; Kiessling, Tobias R; Stange, Roland; Käs, Josef A

    2015-02-23

    In dual-beam optical traps, two counterpropagating, divergent laser beams emitted from opposing laser fibers trap and manipulate dielectric particles. We investigate the lensing effect that trapped particles have on the beams. Our approach makes use of the intrinsic coupling of a beam to the opposing fiber after having passed the trapped particle. We present measurements of this coupling signal for PDMS particles, as well as a model for its dependence on size and refractive index of the trapped particle. As a more complex sample, the coupling of inhomogeneous biological cells is measured and discussed. We show that the lensing effect is well captured by the simple ray optics approximation. The measurements reveal intricate details, such as the thermal lens effect of the beam propagation in a dual-beam trap. For a particle of known size, the model further allows to infer its refractive index simply from the coupling signal.

  4. The effects of the RHIC E-lenses magnetic structure layout on the proton beam trajectory

    SciTech Connect

    Gu, X.; Pikin, A.; Luo, Y.; Okamura, M.; Fischer, W.; Gupta, R.; Hock, J.; Raparia, D.

    2011-03-28

    We are designing two electron lenses (E-lens) to compensate for the large beam-beam tune spread from proton-proton interactions at IP6 and IP8 in the Relativistic Heavy Ion Collider (RHIC). They will be installed in RHIC IR10. First, the layout of these two E-lenses is introduced. Then the effects of e-lenses on proton beam are discussed. For example, the transverse fields of the e-lens bending solenoids and the fringe field of the main solenoids will shift the proton beam. For the effects of the e-lens on proton beam trajectory, we calculate the transverse kicks that the proton beam receives in the electron lens via Opera at first. Then, after incorporating the simplified E-lens lattice in the RHIC lattice, we obtain the closed orbit effect with the Simtrack Code.

  5. 77 FR 59241 - Notice of Effective Date of Modifications to Certain Textile and Apparel Rules of Origin of the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-26

    ... of Effective Date of Modifications to Certain Textile and Apparel Rules of Origin of the Dominican... Representative. ACTION: Notice of Effective Date of Modifications to Certain Textile and Apparel Rules of Origin...''). SUMMARY: Public Law 112-163 modified the rules of origin for certain textile and apparel goods of...

  6. Modification of the genetic effect of gamma irradiation by electric current

    SciTech Connect

    Grigor'eva, N.N.; Shakbazov, V.G.

    1985-09-01

    The authors study the effect of direct current of varying strength and polarity on the genetic damage due to gamma irradiation of Vicia faba seedlings. The modificational effect of direct current observed earlier is confirmed here. The extent and nature of this effect depends on the strength and polarity of the current as well as interval between irradiation and exposure to the electric field. Conditions having no effect on the irradiated seedlings, those protecting the cells from damage and enhancing the irradiation effect, are identified.

  7. Effects of cognitive bias modification on social anxiety: A meta-analysis.

    PubMed

    Liu, Haining; Li, Xianwen; Han, Buxin; Liu, Xiaoqian

    2017-01-01

    Cognitive bias modification (CBM), a set of techniques for modifying bias in information processing-is considered a novel intervention for social anxiety disorder (SAD), which has drawn considerable interest from researchers. However, the effects of CBM on SAD are not consistent. Some studies have demonstrated significant positive effects compared to control groups, while others have found no such effects. We conducted a meta-analysis aimed at quantitatively assessing the effects of CBM on SAD at post-test. Through a systematic literature search by two independent raters, 34 articles (36 randomized studies) including 2,550 participants were identified. A multilevel modeling approach was employed to assess the effects of CBM on SAD, and to explore the potentially crucial procedures and sample characteristics that enhance the effectiveness of benign training. In general, there were small but significant effects of CBM on the primary symptoms of SAD (g = 0.17), cognitive bias (CB) toward threat (g = 0.32), and reactivity in stressful situations (g = 0.25), but non-significant effects on secondary symptoms. However, the interpretation modification program was more effective than was attentional bias modification in reducing SAD primary symptoms and negative CB. Laboratory training procedures produced larger primary symptom reductions compared to Internet-based training, whereas the percentage of contingency and feedback about training performance boosted cognitive effects only. Finally, the following groups were more likely to benefit from CBM: younger participants (primary symptoms and cognitive effects), women (primary symptom effects), and samples with stronger CB (stressor effects). The quality of the randomized controlled trials was less than desirable, as there was some indication of publication bias in our study. Current findings broadly supported cognitive theories of SAD that consider a bidirectional or mutually reinforcing relationship between symptoms and

  8. Effects of cognitive bias modification on social anxiety: A meta-analysis

    PubMed Central

    Liu, Haining; Li, Xianwen; Han, Buxin; Liu, Xiaoqian

    2017-01-01

    Background Cognitive bias modification (CBM), a set of techniques for modifying bias in information processing—is considered a novel intervention for social anxiety disorder (SAD), which has drawn considerable interest from researchers. However, the effects of CBM on SAD are not consistent. Some studies have demonstrated significant positive effects compared to control groups, while others have found no such effects. Aims We conducted a meta-analysis aimed at quantitatively assessing the effects of CBM on SAD at post-test. Method Through a systematic literature search by two independent raters, 34 articles (36 randomized studies) including 2,550 participants were identified. A multilevel modeling approach was employed to assess the effects of CBM on SAD, and to explore the potentially crucial procedures and sample characteristics that enhance the effectiveness of benign training. Results In general, there were small but significant effects of CBM on the primary symptoms of SAD (g = 0.17), cognitive bias (CB) toward threat (g = 0.32), and reactivity in stressful situations (g = 0.25), but non-significant effects on secondary symptoms. However, the interpretation modification program was more effective than was attentional bias modification in reducing SAD primary symptoms and negative CB. Laboratory training procedures produced larger primary symptom reductions compared to Internet-based training, whereas the percentage of contingency and feedback about training performance boosted cognitive effects only. Finally, the following groups were more likely to benefit from CBM: younger participants (primary symptoms and cognitive effects), women (primary symptom effects), and samples with stronger CB (stressor effects). The quality of the randomized controlled trials was less than desirable, as there was some indication of publication bias in our study. Conclusions Current findings broadly supported cognitive theories of SAD that consider a bidirectional or mutually

  9. Alumina reinforced zirconia implants: effects of cyclic loading and abutment modification on fracture resistance.

    PubMed

    Spies, Benedikt Christopher; Sauter, Carmen; Wolkewitz, Martin; Kohal, Ralf-Joachim

    2015-03-01

    The aim of the study was to evaluate the thermomechanical behavior of alumina-toughened zirconia (ATZ) oral implants in the artificial mouth and the fracture resistance (fracture load and bending moment) in a subsequent static fracture load test. The effects of abutment modification and different cyclic loadings were evaluated. A total of 48 implants were used. 24 implants were left as machined (Group A), and 24 implants were shape modified at the abutment (Group B). Groups were divided into three subgroups composed of 8 samples each (A1/B1: no cyclic loading; A2/B2: 1.2 million cycles; A3/B3: 5 million cycles). Subsequently, all implants were statically loaded to the point of fracture. The implants showed the following survival rates after the artificial mouth: A2 and B2 100%; A3 and B3 87.5%. The following average fracture resistance values were found (fracture load [N]/bending moment [Nmm]): A1 (583/2907), B1 (516/2825), A2 (618/2737), B2 (550/3150), A3 (802/3784) and B3 (722/3809). After 5 million loading cycles a significant increase in fracture load and bending moment was found. Modification of the abutment significantly decreased the fracture load of implants without foregoing dynamic loading. However, the shape modification altered the lever arm. For that reason, a smaller load resulted in the same bending moment. Therefore, abutment modification had no significant influence on the fracture resistance of ATZ. Neither thermomechanical cycling in an aqueous environment nor modification of the abutment had a negative effect on the fracture resistance of ATZ. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  10. Effects of Selenylation Modification on Antioxidative Activities of Schisandra chinensis Polysaccharide.

    PubMed

    Yue, Chanjuan; Chen, Jin; Hou, Ranran; Liu, Jie; Li, Xiuping; Gao, Zhenzhen; Liu, Cui; Wang, Deyun; Lu, Yu; Li, Hongquan; Hu, Yuanliang

    2015-01-01

    The selenylation modification of Schisandra chinensis polysaccharide (SCP) was conducted by the HNO3-Na2SeO3 method respectively under nine conditions according to L9(34) orthogonal design. Nine selenizing SCPs, sSCP1-sSCP9, were obtained, and their antioxidant activities were compared. In vitro test, the free radical-scavenging rates of nine sSCPs were determined for DPPH., .OH and ABTS+. sSCP1 presented the most significant effect, and could inhibit the nonenzymatic protein glycation. In vivo test, 14-day-old chickens were injected respectively with sSCP1 and SCP, the serum contents of CAT, SOD and MDA were determined. The result showed that as compared with the SCP group, the SOD and CAT activities were significantly or numerically raised and MDA content was significantly or numerically lowered in the sSCP1 group. These results indicate that selenylation modification can significantly enhance the antioxidant and antiglycative activity of SCP in vitro or in vivo. sSCP1 possesses the best efficacy and its modification conditions can be as optimal modification conditions that were 200 mg of Na2SeO3 for 500 mg of SCP, reaction temperature of 50°C and reaction time of 6 h.

  11. Effects of Selenylation Modification on Antioxidative Activities of Schisandra chinensis Polysaccharide

    PubMed Central

    Yue, Chanjuan; Chen, Jin; Hou, Ranran; Liu, Jie; Li, Xiuping; Gao, Zhenzhen; Liu, Cui; Wang, Deyun; Lu, Yu; Li, Hongquan; Hu, Yuanliang

    2015-01-01

    The selenylation modification of Schisandra chinensis polysaccharide (SCP) was conducted by the HNO3–Na2SeO3 method respectively under nine conditions according to L9(34) orthogonal design. Nine selenizing SCPs, sSCP1–sSCP9, were obtained, and their antioxidant activities were compared. In vitro test, the free radical-scavenging rates of nine sSCPs were determined for DPPH., .OH and ABTS+. sSCP1 presented the most significant effect, and could inhibit the nonenzymatic protein glycation. In vivo test, 14-day-old chickens were injected respectively with sSCP1 and SCP, the serum contents of CAT, SOD and MDA were determined. The result showed that as compared with the SCP group, the SOD and CAT activities were significantly or numerically raised and MDA content was significantly or numerically lowered in the sSCP1 group. These results indicate that selenylation modification can significantly enhance the antioxidant and antiglycative activity of SCP in vitro or in vivo. sSCP1 possesses the best efficacy and its modification conditions can be as optimal modification conditions that were 200 mg of Na2SeO3 for 500 mg of SCP, reaction temperature of 50°C and reaction time of 6 h. PMID:26230941

  12. Collinearity alignment of probe beams in a laser-based Faraday effect diagnostica)

    NASA Astrophysics Data System (ADS)

    Lin, L.; Ding, W. X.; Brower, D. L.

    2012-10-01

    Two counter-rotating circularly polarized beams are used in a laser-based polarimetry diagnostic providing a phase measurement of the Faraday effect. Collinearity of these beams is a key issue that affects measurement accuracy. Spatial offset from even small misalignment induces systematic error due to density gradient and path length difference. Here, we report an alignment technique using a rotating dielectric wedge, which is capable of reducing spatial offset of two probe beams below 0.1 mm for beams with 40 mm diameter. With optimized alignment, 0.05° Faraday effect fluctuations associated with global tearing modes are resolved with an uncertainty below 0.01°.

  13. Green's functions of the forced vibration of Timoshenko beams with damping effect

    NASA Astrophysics Data System (ADS)

    Li, X. Y.; Zhao, X.; Li, Y. H.

    2014-03-01

    This paper is concerned with the dynamic solutions for forced vibrations of Timoshenko beams in a systematical manner. Damping effects on the vibrations of the beam are taken into consideration by introducing two characteristic parameters. Laplace transform method is applied in the present study and corresponding Green's functions are presented explicitly for beams with various boundaries. The present solutions can be readily reduced to those for others classical beam models by setting corresponding parameters to zero or infinite. Numerical calculations are performed to validate the present solutions and the effects of various important physical parameters are investigated.

  14. The Effects of Towfish Motion on Sidescan Sonar Images: Extension to a Multiple-Beam Device

    DTIC Science & Technology

    1994-02-01

    Towfish Motion on Sidescan Sonar Images: Extension to a Multiple -Beam Device Acceso NTIS CRA&I S.D. Anstee u; ,-, o* , J.* ttiicatorn By "By...THE EFFECTS OF TOWFISH MOTION ON SIDESCAN SONAR IMAGES: EXTENSION TO A MULTIPLE -BEAM DEVICE S, S.D. ANSTEE 6 2 9 Nm MRL-TN-660 FEBRUARY 1994 Al DTIC...previously used to estimate the geometrical effects oftowjish motion on single-beam sidescan sonar images is modified to simulate a multiple -beam

  15. Effective dose from cone beam CT examinations in dentistry.

    PubMed

    Roberts, J A; Drage, N A; Davies, J; Thomas, D W

    2009-01-01

    Cone beam CT (CBCT) is becoming an increasingly utilized imaging modality for dental examinations in the UK. Previous studies have presented little information on patient dose for the range of fields of view (FOVs) that can be utilized. The purpose of the study was therefore to calculate the effective dose delivered to the patient during a selection of CBCT examinations performed in dentistry. In particular, the i-CAT CBCT scanner was investigated for several imaging protocols commonly used in clinical practice. A Rando phantom containing thermoluminescent dosemeters was scanned. Using both the 1990 and recently approved 2007 International Commission on Radiological Protection recommended tissue weighting factors, effective doses were calculated. The doses (E(1990), E(2007)) were: full FOV head (92.8 microSv, 206.2 microSv); 13 cm scan of the jaws (39.5 microSv, 133.9 microSv); 6 cm high-resolution mandible (47.2 microSv, 188.5 microSv); 6 cm high-resolution maxilla (18.5 microSv, 93.3 microSv); 6 cm standard mandible (23.9 microSv, 96.2 microSv); and 6 cm standard maxilla (9.7 microSv, 58.9 microSv). The doses from CBCT are low compared with conventional CT but significantly higher than conventional dental radiography techniques.

  16. Intermediate energy neutron beams from the MURR.

    PubMed

    Brugger, R M; Herleth, W H

    1990-01-01

    Several reactors in the United States are potential candidates to deliver beams of intermediate energy neutrons for NCT. At this time, moderators, as compared to filters, appear to be the more effective means of tailoring the flux of these reactors. The objective is to sufficiently reduce the flux of fast neutrons while producing enough intermediate energy neutrons for treatments. At the University of Missouri Research Reactor (MURR), the code MCNP has recently been used to calculate doses in a phantom. First, "ideal" beams of 1, 35, and 1000 eV neutrons were analyzed to determine doses and advantage depths in the phantom. Second, a high quality beam that had been designed to fit in the thermal column of the MURR, was reanalyzed. MCNP calculations of the dose in phantom in this beam confirmed previous calculations and showed that this beam would be a nearly ideal one with neutrons of the desired energy and also a high neutron current. However, installation of this beam will require a significant modification of the thermal column of the MURR. Therefore, a second beam that is less difficult to build and install, but of lower neutron current, has been designed to fit in MURR port F. This beam is designed using inexpensive A1, S, and Pb. The doses calculated in the phantom placed in this beam show that it will be satisfactory for sample tests, animal tests, and possible initial patient trials. Producing this beam will require only modest modifications of the existing tube.

  17. Carbon nanotubes toxicology and effects on metabolism and immunological modification in vitro and in vivo

    NASA Astrophysics Data System (ADS)

    Chiaretti, M.; Mazzanti, G.; Bosco, S.; Bellucci, S.; Cucina, A.; LeFoche, F.; Carru, G. A.; Mastrangelo, S.; Di Sotto, A.; Masciangelo, R.; Chiaretti, A. M.; Balasubramanian, C.; DeBellis, G.; Micciulla, F.; Porta, N.; Deriu, G.; Tiberia, A.

    2008-11-01

    The aim of this research is focused on the biological effects of multi wall carbon nanotubes (MWCNTs) on three different human cell types, laboratory animals in vivo, and immunological effects. Large numbers of researchers are directly involved in the handling of nanostructured materials such as MWCNTs and nanoparticles. It is important to assess the potential health risks related to their daily exposure to carbon nanotubes. The administration of sterilized nanosamples has been performed on laboratory animals, in both acute and chronic administration, and the pathological effects on the parenchymal tissues have been investigated. We studied the serum immunological modifications after intraperitoneal administration of the MWCNTs. We did not observe any antigenic reaction; the screening of ANA, anti-ENA, anti-cardiolipin, C-ANCA and P-ANCA was negative. No quantitative modification of immunoglobulins was observed, hence no modification of humoral immunity was documented. We also studied the effects of MWCNTs on the proliferation of three different cell types. MCF-7 showed a significant inhibition of proliferation for all conditions studied, whereas hSMCs demonstrated a reduction of cell growth only for the highest MWCNTs concentrations after 72 h. Also, no growth modification was observed in the Caco-2 cell line. We observed that a low quantity of MWCNTs does not provoke any inflammatory reaction. However, for future medical applications, it is important to realize prosthesis based on MWCNTs, through studying the corresponding implantation effects. Moreover, it has to be emphasized that this investigation does not address, at the moment, the carcinogenicity of MWCNTs, which requires a detailed follow-up investigation on the specific topic. In view of the subsequent and more extensive use of MWCNTs, especially in applications where carbon nanotubes are injected into the human body for drug delivery, as a contrast agent carrying entities for MRI, or as the basic

  18. The effect of polarization in passive coherent beam combining of fiber lasers

    NASA Astrophysics Data System (ADS)

    Chiang, Hung-Sheng; Leger, James R.; Huszar, Emese; Nilsson, Johan; Sahu, Jayanta

    2014-03-01

    A Yb-doped, dual-core, double-clad, polarization-maintaining fiber is used to demonstrate passive coherent beam combining. A homemade Dammann grating is employed as a passive beam-combining optical element. Self-phasing is observed in this laser system, where we attribute the self-phasing behavior to the Kramers-Kronig effect. We experimentally demonstrate the importance of polarization on coherent beam combining efficiency as well as on Kramers-Kronig induced self-phasing.

  19. Effect of bentonite modification on hardness and mechanical properties of natural rubber nanocomposites

    SciTech Connect

    Santiago, Denise Ester O.; Pajarito, Bryan B.; Mangaccat, Winna Faye F.; Tigue, Maelyn Rose M.; Tipton, Monica T.

    2016-05-18

    The effect of sodium activation, ion-exchange with tertiary amine salt, surface treatment with non-ionic surfactant, and wet grinding of bentonite on hardness and mechanical properties of natural rubber nanocomposites (NRN) was studied using full factorial design of experiment. Results of X-ray diffraction (XRD) show increase in basal spacing d of bentonite due to modification, while attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) confirm the organic modification of bentonite. Analysis of variance (ANOVA) shows that the main effect of surface treatment increases the hardness and decreases the tensile modulus of the NRN. The surface treatment and wet grinding of bentonite decrease the tensile stresses at 100, 200 and 300% strain of NRN. Sodium activation and ion-exchange negatively affect the compressive properties, while surface treatment significantly improves the compressive properties of NRN.

  20. Effect of bentonite modification on hardness and mechanical properties of natural rubber nanocomposites

    NASA Astrophysics Data System (ADS)

    Santiago, Denise Ester O.; Pajarito, Bryan B.; Mangaccat, Winna Faye F.; Tigue, Maelyn Rose M.; Tipton, Monica T.

    2016-05-01

    The effect of sodium activation, ion-exchange with tertiary amine salt, surface treatment with non-ionic surfactant, and wet grinding of bentonite on hardness and mechanical properties of natural rubber nanocomposites (NRN) was studied using full factorial design of experiment. Results of X-ray diffraction (XRD) show increase in basal spacing d of bentonite due to modification, while attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) confirm the organic modification of bentonite. Analysis of variance (ANOVA) shows that the main effect of surface treatment increases the hardness and decreases the tensile modulus of the NRN. The surface treatment and wet grinding of bentonite decrease the tensile stresses at 100, 200 and 300% strain of NRN. Sodium activation and ion-exchange negatively affect the compressive properties, while surface treatment significantly improves the compressive properties of NRN.

  1. Evaluation of thermal effects on the beam quality of disk laser with unstable resonator

    NASA Astrophysics Data System (ADS)

    Shayganmanesh, Mahdi; Beirami, Reza

    2017-01-01

    In this paper thermal effects of the disk active medium and associated effects on the beam quality of laser are investigated. Using Collins integral and iterative method, transverse mode of an unstable resonator including a Yb:YAG active medium in disk geometry is calculated. After that the beam quality of the laser is calculated based on the generalized beam characterization method. Thermal lensing of the disk is calculated based on the OPD (Optical Path Difference) concept. Five factors influencing the OPD including temperature gradient, disk thermal expansion, photo-elastic effect, electronic lens and disk deformation are considered in our calculations. The calculations show that the effect of disk deformation factor on the quality of laser beam in the resonator is strong. However the total effect of all the thermal factors on the internal beam quality is fewer. Also it is shown that thermal effects degrade the output power, beam profile and beam quality of the output laser beam severely. As well the magnitude of each of affecting factors is evaluated distinctly.

  2. Chemical modification of the bifunctional human serum pseudocholinesterase. Effect on the pseudocholinesterase and aryl acylamidase activities.

    PubMed

    Boopathy, R; Balasubramanian, A S

    1985-09-02

    The effect of chemical modification on the pseudocholinesterase and aryl acylamidase activities of purified human serum pseudocholinesterase was examined in the absence and presence of butyrylcholine iodide, the substrate of pseudocholinesterase. Modification by 2-hydroxy-5-nitrobenzyl bromide, N-bromosuccinimide, diethylpyrocarbonate and trinitrobenzenesulfonic acid caused a parallel inactivation of both pseudocholinesterase and aryl acylamidase activities that could be prevented by butyrylcholine iodide. With phenylglyoxal and 2,4-pentanedione as modifiers there was a selective activation of pseudocholinesterase alone with no effect on aryl acylamidase. This activation could be prevented by butyrylcholine iodide. N-Ethylmaleimide and p-hydroxy-mercuribenzoate when used for modification did not have any effect on the enzyme activities. The results suggested essential tryptophan, lysine and histidine residues at a common catalytic site for pseudocholinesterase and aryl acylamidase and an arginine residue (or residues) exclusively for pseudocholinesterase. The use of N-acetylimidazole, tetranitromethane and acetic anhydride as modifiers indicated a biphasic change in both pseudocholinesterase and aryl acylamidase activities. At low concentrations of the modifiers a stimulation in activities and at high concentrations an inactivation was observed. Butyrylcholine iodide or propionylcholine chloride selectively protected the inactivation phase without affecting the activation phase. Protection by the substrates at the inactivation phase resulted in not only a reversal of the enzyme inactivation but also an activation. Spectral studies and hydroxylamine treatment showed that tyrosine residues were modified during the activation phase. The results suggested that the modified tyrosine residues responsible for the activation were not involved in the active site of pseudocholinesterase or aryl acylamidase and that they were more amenable for modification in comparison to

  3. Effects of energy spectrum on dose distribution calculations for high energy electron beams.

    PubMed

    Toutaoui, Abdelkader; Khelassi-Toutaoui, Nadia; Brahimi, Zakia; Chami, Ahmed Chafik

    2009-01-01

    In an early work we have demonstrated the possibility of using Monte Carlo generated pencil beams for 3D electron beam dose calculations. However, in this model the electron beam was considered as monoenergetic and the effects of the energy spectrum were taken into account by correction factors, derived from measuring central-axis depth dose curves. In the present model, the electron beam is considered as polyenergetic and the pencil beam distribution of a clinical electron beam, of a given nominal energy, is represented as a linear combination of Monte Carlo monoenergetic pencil beams. The coefficients of the linear combination describe the energy spectrum of the clinical electron beam, and are chosen to provide the best-fit between the calculated and measured central axis depth dose, in water. The energy spectrum is determined by the constrained least square method. The angular distribution of the clinical electron beam is determined by in-air penumbra measurements. The predictions of this algorithm agree very well with the measurements in the region near the surface, and the discrepancies between the measured and calculated dose distributions, behind 3D heterogeneities, are reduced to less than 10%. We have demonstrated a new algorithm for 3D electron beam dose calculations, which takes into account the energy spectra. Results indicate that the use of this algorithm leads to a better modeling of dose distributions downstream, from complex heterogeneities.

  4. Effects of energy spectrum on dose distribution calculations for high energy electron beams

    PubMed Central

    Toutaoui, Abdelkader; Khelassi-Toutaoui, Nadia; Brahimi, Zakia; Chami, Ahmed Chafik

    2009-01-01

    In an early work we have demonstrated the possibility of using Monte Carlo generated pencil beams for 3D electron beam dose calculations. However, in this model the electron beam was considered as monoenergetic and the effects of the energy spectrum were taken into account by correction factors, derived from measuring central-axis depth dose curves. In the present model, the electron beam is considered as polyenergetic and the pencil beam distribution of a clinical electron beam, of a given nominal energy, is represented as a linear combination of Monte Carlo monoenergetic pencil beams. The coefficients of the linear combination describe the energy spectrum of the clinical electron beam, and are chosen to provide the best-fit between the calculated and measured central axis depth dose, in water. The energy spectrum is determined by the constrained least square method. The angular distribution of the clinical electron beam is determined by in-air penumbra measurements. The predictions of this algorithm agree very well with the measurements in the region near the surface, and the discrepancies between the measured and calculated dose distributions, behind 3D heterogeneities, are reduced to less than 10%. We have demonstrated a new algorithm for 3D electron beam dose calculations, which takes into account the energy spectra. Results indicate that the use of this algorithm leads to a better modeling of dose distributions downstream, from complex heterogeneities. PMID:20126560

  5. A study of spatial phenomena in semiconductor lasers: Beam filamentation and optical feedback effects

    NASA Astrophysics Data System (ADS)

    Marciante, John Robert

    1997-10-01

    In an effort to improve the performance of high-power semiconductor lasers to meet the demands of applications, this thesis contains work studying the issues which limit their performance: beam filamentation and spatial feedback effects. Through computer simulations, we investigate the role of three nonlinear mechanisms which can lead to filamentation, and determine the stability boundaries of the material parameters for which the device will not exhibit filamentary tendencies. We use an analytic theory to verify these findings, and to predict the spatio- temporal nature of the filaments through an analytic expression for the gain, in which contributions of the various mechanisms can clearly be seen. We experimentally verify the spatio-temporal characteristics of the filaments, discover effects of the stripe width and transitions to chaos, and discuss how to compare the relative severity of filamentation among different devices. We propose a new method of controlling filamentation using below-bandgap semiconductor nonlinearities. With simulations, we determine under what conditions this imposed nonlinearity can counteract the carrier-induced self-focusing inside the active region. We fabricate a prototype device using new epitaxial layers containing the below-bandgap nonlinearities, and compare the performance of these new devices to a control set. In studying the spatial effects of optical feedback, we use Fresnel diffraction theory to derive an expression for the field that is reflected back into the laser. This result is applied to our computer model and used to explore the effects of feedback on narrow-stripe, broad- area, and tapered-stripe semiconductor lasers. Re- examining feedback in narrow-stripe devices through experiments and analytic theory, we investigate the coupling effects between the narrow waveguide and the feedback field, and the changes in the operating characteristics of the laser due to this coupling. We experimentally examine the beam

  6. Effects of MHD instabilities on neutral beam current drive

    SciTech Connect

    Podestà, M.; Gorelenkova, M.; Darrow, D. S.; Fredrickson, E. D.; Gerhardt, S. P.; White, R. B.

    2015-04-17

    One of the primary tools foreseen for heating, current drive (CD) and q-profile control in future fusion reactors such as ITER and a Fusion Nuclear Science Facility is the neutral beam injection (NBI). However, fast ions from NBI may also provide the drive for energetic particle-driven instabilities (e.g. Alfvénic modes (AEs)), which in turn redistribute fast ions in both space and energy, thus hampering the control capabilities and overall efficiency of NB-driven current. Based on experiments on the NSTX tokamak (M. Ono et al 2000 Nucl. Fusion 40 557), the effects of AEs and other low-frequency magneto-hydrodynamic instabilities on NB-CD efficiency are investigated. When looking at the new fast ion transport model, which accounts for particle transport in phase space as required for resonant AE perturbations, is utilized to obtain consistent simulations of NB-CD through the tokamak transport code TRANSP. It is found that instabilities do indeed reduce the NB-driven current density over most of the plasma radius by up to ~50%. Moreover, the details of the current profile evolution are sensitive to the specific model used to mimic the interaction between NB ions and instabilities. Finally, implications for fast ion transport modeling in integrated tokamak simulations are briefly discussed.

  7. Effective dose span of ten different cone beam CT devices.

    PubMed

    Rottke, D; Patzelt, S; Poxleitner, P; Schulze, D

    2013-01-01

    Evaluation and reduction of dose are important issues. Since cone beam CT (CBCT) has been established now not just in dentistry, the number of acquired examinations continues to rise. Unfortunately, it is very difficult to compare the doses of available devices on the market owing to different exposition parameters, volumes and geometries. The aim of this study was to evaluate the spans of effective doses (EDs) of ten different CBCT devices. 48 thermoluminescent dosemeters were placed in 24 sites in a RANDO(®) head phantom. Protocols with lowest exposition parameters and protocols with highest exposition parameters were performed for each of the ten devices. The ED was calculated from the measured energy doses according to the International Commission on Radiological Protection 2007 recommendations for each protocol and device, and the statistical values were evaluated afterwards. The calculation of the ED resulted in values between 17.2 µSv and 396 µSv for the ten devices. The mean values for protocols with lowest and highest exposition parameters were 31.6 µSv and 209 µSv, respectively. It was not the aim of this study to evaluate the image quality depending on different exposition parameters but to define the spans of EDs in which different CBCT devices work. There is a wide span of ED for different CBCT devices depending on the selected exposition parameters, required spatial resolution and many other factors.

  8. Effective dose span of ten different cone beam CT devices

    PubMed Central

    Rottke, D; Patzelt, S; Poxleitner, P; Schulze, D

    2013-01-01

    Objectives: Evaluation and reduction of dose are important issues. Since cone beam CT (CBCT) has been established now not just in dentistry, the number of acquired examinations continues to rise. Unfortunately, it is very difficult to compare the doses of available devices on the market owing to different exposition parameters, volumes and geometries. The aim of this study was to evaluate the spans of effective doses (EDs) of ten different CBCT devices. Methods: 48 thermoluminescent dosemeters were placed in 24 sites in a RANDO® head phantom. Protocols with lowest exposition parameters and protocols with highest exposition parameters were performed for each of the ten devices. The ED was calculated from the measured energy doses according to the International Commission on Radiological Protection 2007 recommendations for each protocol and device, and the statistical values were evaluated afterwards. Results: The calculation of the ED resulted in values between 17.2 µSv and 396 µSv for the ten devices. The mean values for protocols with lowest and highest exposition parameters were 31.6 µSv and 209 µSv, respectively. Conclusions: It was not the aim of this study to evaluate the image quality depending on different exposition parameters but to define the spans of EDs in which different CBCT devices work. There is a wide span of ED for different CBCT devices depending on the selected exposition parameters, required spatial resolution and many other factors. PMID:23584925

  9. Effect of plasma rotation on sawtooth stabilization by beam ions

    SciTech Connect

    N. N. Gorelenkov; M. F. F. Nave; R. Budny; C. Z. Cheng; G. Y. Fu; J. Hastie; J. Manickam; W. Park

    2000-06-23

    The sawtooth period in JET ELM-free H-Mode plasmas is increasing with Neutral Beam Injection (NBI) power. For injected power PNBI 12MW no large sawtooth crash is observed during the ELM-free period. However, as the edge stability is improved and external kink modes and ELMs are delayed, a possible sawtooth crash at a high plasma beta becomes a concern. In JET DT experiments, delaying sawteeth was found to be crucial in the quest for high fusion power. Fast particles are known to provide stabilizing effect on sawteeth, however, sawtooth stabilization by NBI ions is not clearly understood, since NBI ions are usually not ''fast'' enough to stabilize the m/n = 1/1 internal kink mode which is believed to cause the crash. In order to understand the observed sawteeth stabilization in tokamak experiments with NBI heating, the internal kink m/n = 1/1 mode stability of JET plasmas was modeled using the NOVA-K code, which is also benchmarked with the nonperturbative version of NOVA and the M3D code. Comparison of m/n = 1/1 mode stabilization by NBI ions in JET and TFTR and application of the nonlinear stabilization criteria is given.

  10. Effects of MHD instabilities on neutral beam current drive

    DOE PAGES

    Podestà, M.; Gorelenkova, M.; Darrow, D. S.; ...

    2015-04-17

    One of the primary tools foreseen for heating, current drive (CD) and q-profile control in future fusion reactors such as ITER and a Fusion Nuclear Science Facility is the neutral beam injection (NBI). However, fast ions from NBI may also provide the drive for energetic particle-driven instabilities (e.g. Alfvénic modes (AEs)), which in turn redistribute fast ions in both space and energy, thus hampering the control capabilities and overall efficiency of NB-driven current. Based on experiments on the NSTX tokamak (M. Ono et al 2000 Nucl. Fusion 40 557), the effects of AEs and other low-frequency magneto-hydrodynamic instabilities on NB-CDmore » efficiency are investigated. When looking at the new fast ion transport model, which accounts for particle transport in phase space as required for resonant AE perturbations, is utilized to obtain consistent simulations of NB-CD through the tokamak transport code TRANSP. It is found that instabilities do indeed reduce the NB-driven current density over most of the plasma radius by up to ~50%. Moreover, the details of the current profile evolution are sensitive to the specific model used to mimic the interaction between NB ions and instabilities. Finally, implications for fast ion transport modeling in integrated tokamak simulations are briefly discussed.« less

  11. The effect of beam directivity on the inspection of anisotropic materials using ultrasonic arrays

    NASA Astrophysics Data System (ADS)

    Lane, C. J. L.; Wilcox, P. D.

    2012-05-01

    The beam directivity from an ultrasonic transducer in isotropic materials is well documented. However, beam directivities in elastically anisotropic materials and their effect on ultrasonic NDE inspection has been investigated far less extensively. In this paper, analytical and numerical finite element models are developed to predict the beam directivity in a single crystal nickel-based superalloy. This material is highly anisotropic and is used widely in the gas-turbine industry. The developed models are used to investigate the effect of the crystallographic orientation on the beam directivity. In turn, the effect of beam directivity on defect detection sensitivity and characterization capability using an ultrasonic array is demonstrated. It is shown that the effect is particularly important for the accurate sizing of small defects.

  12. Transgenerational effects of proton beam irradiation on Caenorhabditis elegans germline apoptosis.

    PubMed

    Min, Hyemin; Sung, Minhee; Son, Miseol; Kawasaki, Ichiro; Shim, Yhong-Hee

    2017-08-26

    When treating cancer using radiation therapy, it is critical to increase patient survival rates and to reduce side effects. In this respect, proton beam radiation treatment performs better than other radiation treatments because of its high target specificity. However, complications still remain after proton beam radiation treatment. Among them, the risk to progeny after irradiation of their parents is a major concern. In this study, we analyzed the transgenerational effects of proton beam irradiation using the model organism Caenorhabditis. elegans. We found that germline apoptosis increased after proton beam irradiation and its effects were sustained transgenerationally. Moreover, we identified that a germline-specific histone methyltransferase component, SET-2, has a critical role in transmitting the transgenerational effect on germline apoptosis to the next generation after proton beam irradiation. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Effect of ultrarelativistic laser beam filamentation on third harmonic spectrum

    NASA Astrophysics Data System (ADS)

    Gupta, Ruchika; Sharma, Prerana; Chauhan, Prashant K.; Rafat, M.; Sharma, R. P.

    2009-04-01

    This paper investigates the generation of plasma wave and third harmonic generation in a hot collision less plasma by an intense laser beam. On the account of the V→×B→ force, a plasma wave at 2ω0 (here ω0 is the pump laser frequency) is generated. The solution of the pump laser beam has been obtained within the nonparaxial ray approximation. Filamentary structures of the laser beam are observed due to relativistic nonlinearity. By expanding the eikonal and the other relevant quantities up to the fourth power of r it is observed that the focusing of the laser beams become fast in the nonparaxial region. Interaction of the plasma wave with the incident laser beam generates the third harmonics. The mechanism of the plasma wave, third harmonic generation, and the parameters, which govern the third harmonic yield and hence the spectrum of third harmonics, have been studied in detail. Correlation of the third harmonic spectrum with the filamentation has been pointed out. Therefore, the broadening of the third harmonic spectra can be used as a diagnostic tool to study the presence of the filamentation of laser beams in laser plasma experiments.

  14. Effect of ultrarelativistic laser beam filamentation on third harmonic spectrum

    SciTech Connect

    Gupta, Ruchika; Rafat, M.; Sharma, Prerana; Chauhan, Prashant K.; Sharma, R. P.

    2009-04-15

    This paper investigates the generation of plasma wave and third harmonic generation in a hot collision less plasma by an intense laser beam. On the account of the V-vectorxB-vector force, a plasma wave at 2{omega}{sub 0} (here {omega}{sub 0} is the pump laser frequency) is generated. The solution of the pump laser beam has been obtained within the nonparaxial ray approximation. Filamentary structures of the laser beam are observed due to relativistic nonlinearity. By expanding the eikonal and the other relevant quantities up to the fourth power of r it is observed that the focusing of the laser beams become fast in the nonparaxial region. Interaction of the plasma wave with the incident laser beam generates the third harmonics. The mechanism of the plasma wave, third harmonic generation, and the parameters, which govern the third harmonic yield and hence the spectrum of third harmonics, have been studied in detail. Correlation of the third harmonic spectrum with the filamentation has been pointed out. Therefore, the broadening of the third harmonic spectra can be used as a diagnostic tool to study the presence of the filamentation of laser beams in laser plasma experiments.

  15. Modification of the bulk properties of the porous poly(lactide-co-glycolide) scaffold by irradiation with a cyclotron ion beam with high energy for its application in tissue engineering.

    PubMed

    Woo, Jung Hoon; Kim, Do Yeon; Jo, Seong Yeun; Kang, Hyunki; Noh, Insup

    2009-08-01

    Understanding the bulk properties of a prefabricated scaffold for handling and degradation during cell culture may be advantageous to its application in tissue engineering. Modification of the bulk properties of the porous poly(lactide-co-glycolide) (PLGA) scaffold was performed by irradiation with a high energy cyclotron proton ion beam. The porous PLGA scaffolds were fabricated in advance by the gas-foaming method by employing ammonium bicarbonate particles as porogens. Irradiation with ion beams was performed with 40 MeV for 3, 6 and 9 min on the scaffolds at a distance of 30 cm from the beam exit to the scaffold surface. The bulk area of the ion beam-treated PLGA scaffold apparently demonstrated no color changes when observed with a digital camera. The chemical structures of the untreated samples seemed to be kept well when analyzed by both Fourier transformed infrared but a subtle change was observed in its x-ray photoelectron spectroscopy. The results of in vitro tissue culture with smooth muscle cells for up to 4 weeks also demonstrated no significant difference in terms of its handling stability during cell culture and cellular behavior between the untreated PLGA scaffolds and the ion beam-treated ones. However, significant changes were observed in its molecular weight as measured by gel permeation chromatography, indicating a significant reduction of its molecular weights. These results of in vitro tests and GPC measurements indicated that while bulk modification of the scaffold was processed, its handling was stable during in vitro cell culture for up to 4 weeks.

  16. Application of nonlocal models to nano beams. Part I: Axial length scale effect.

    PubMed

    Kim, Jun-Sik

    2014-10-01

    Applicability of nonlocal models to nano-beams is discussed in terms of physical implications via the similarity between a nonlocal Euler-Bernoulli (EB) beam theory and a classical Rankine-Timoshenko (RT) beam theory. The nonlocal EB beam model, Eringen's model, is briefly reviewed and the classical RT beam theory is recast by the primary variables of the EB model. A careful comparison of these two models reveals that the scale parameter used to the Eringen's model has a strike resemblance to the shear flexibility in the RT model. This implies that the nonlocal model employed in literature consider the axial length scale effect only. In addition, the paradox for a cantilevered nano-beam subjected to tip shear force is clearly explained by finding appropriate displacement prescribed boundary conditions.

  17. Boundary effects in finite size plasmonic crystals: focusing and routing of plasmonic beams for optical communications.

    PubMed

    Benetou, M I; Bouillard, J-S; Segovia, P; Dickson, W; Thomsen, B C; Bayvel, P; Zayats, A V

    2015-11-06

    Plasmonic crystals, which consist of periodic arrangements of surface features at a metal-dielectric interface, allow the manipulation of optical information in the form of surface plasmon polaritons. Here we investigate the excitation and propagation of plasmonic beams in and around finite size plasmonic crystals at telecom wavelengths, highlighting the effects of the crystal boundary shape and illumination conditions. Significant differences in broad plasmonic beam generation by crystals of different shapes are demonstrated, while for narrow beams, the propagation from a crystal onto the smooth metal film is less sensitive to the crystal boundary shape. We show that by controlling the boundary shape, the size and the excitation beam parameters, directional control of propagating plasmonic modes and their behaviour such as angular beam splitting, focusing power and beam width can be efficiently achieved. This provides a promising route for robust and alignment-independent integration of plasmonic crystals with optical communication components.

  18. Effect of the electron lenses on the RHIC proton beam closed orbit

    SciTech Connect

    Gu, X.; Luo, Y.; Pikin, A.; Okamura, M.; Fischer, W.; Montag, C.; Gupta, R.; Hock, J.; Jain, A.; Raparia, D.

    2011-02-01

    We are designing two electron lenses (E-lens) to compensate for the large beam-beam tune spread from proton-proton interactions at IP6 and IP8 in the Relativistic Heavy Ion Collider (RHIC). They will be installed at RHIC IR10. The transverse fields of the E-lenses bending solenoids and the fringe field of the main solenoids will shift the proton beam. We calculate the transverse kicks that the proton beam receives in the electron lens via Opera. Then, after incorporating the simplified E-lens lattice in the RHIC lattice, we obtain the closed orbit effect with the Simtrack Code.

  19. Effect of Geometric Azimuthal Asymmetries of PPM Stack on Electron Beam Characteristics

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.; Heinen, Vernon (Technical Monitor)

    2000-01-01

    A three-dimensional (3D) beam optics model has been developed using the electromagnetic particle-in-cell (PIC) code MAFIA. The model includes an electron beam with initial transverse velocity distribution focused by a periodic permanent magnet (PPM) stack. All components of the model are simulated in three dimensions allowing several azimuthally asymmetric traveling wave tube (TWT) characteristics to be investigated for the first time. These include C-magnets, shunts, and magnet misalignment and their effects on electron beam behavior. The development of the model is presented and 3D TWT electron beam characteristics are compared in the absence of and under the influence of the azimuthally asymmetric characteristics described.

  20. Polarization of a probe laser beam due to nonlinear QED effects

    NASA Astrophysics Data System (ADS)

    Shakeri, Soroush; Kalantari, Seyed Zafarollah; Xue, She-Sheng

    2017-01-01

    Nonlinear QED interactions induce different polarization properties on a given probe beam. We consider the polarization effects caused by the photon-photon interaction in laser experiments, when a laser beam propagates through a constant magnetic field or collides with another laser beam. We solve the quantum Boltzmann equation within the framework of the Euler-Heisenberg Lagrangian for both time-dependent and constant background field to explore the time evolution of the Stokes parameters Q, U, and V describing polarization. Assuming an initially linearly polarized probe laser beam, we also calculate the induced ellipticity and rotation of the polarization plane.

  1. Electron Cloud Effects in Intense, Ion Beam Linacs Theory and Experimental Planning for HIF

    NASA Astrophysics Data System (ADS)

    Molvik, A. W.; Cohen, R. H.; Lund, S. M.; Bieniosek, F. M.; Lee, E. P.

    2002-05-01

    Heavy-ion accelerators for HIF will operate at high aperture-fill factors with high beam current and long pulses. This will lead to beam ions impacting walls: liberating gas molecules and secondary electrons. Theory and particle-in-cell simulations suggest that electrons, from ionization of residual and desorbed gas and secondary electrons from vacuum walls, will be radially trapped in the approximately 4 kV ion beam potential. Diagnostics are being developed tto measure the energy and flux of electrons and gas evolved from walls, and the net charge and gas density within magnetic quadrupoles, as well as their effect on the ion beam.

  2. Effect of Geometric Azimuthal Asymmetrics of PPM Stack on Electron Beam Characteristics

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.

    2000-01-01

    A three-dimensional (3D) beam optics model has been developed using the electromagnetic particle-in-cell (PIC) code MAFIA. The model includes an electron beam with initial transverse velocity distribution focused by a periodic permanent magnet (PPM) stack. All components of the model are simulated in three dimensions allowing several azimuthally asymmetric traveling wave tube (TWT) characteristics to be investigated for the first time. These include C-magnets, shunts and magnet misalignment and their effects on electron beam behavior. The development of the model is presented and 3D TWT electron beam characteristics are compared in the absence of and under the influence of the azimuthally asymmetric characteristics described.

  3. Surface modification by molecular ions

    SciTech Connect

    Hanley, L.; Schultz, D. G.; Ada, E. T.

    1999-06-10

    There are several advantages in using molecular ions for surface modification. The modification can be confined to the uppermost layer of the surface, the molecular character of the ion can be imparted to the surface, and sputter yields are often higher. These effects are demonstrated by the use of mass selected ion beams incident on well characterized surfaces. Energy transfer is examined by detecting the masses and energies of ions scattered off surfaces and performing molecular dynamics simulations. Surface modification is followed by chemical analysis with x-ray photoelectron spectroscopy and surface mass spectrometry. TRIDYN monte carlo simulations are used to support some of the modification experiments. Energy transfer is examined for Si(CD{sub 3}){sub 3}{sup +} scattered off clean and hexanethiolate covered Au(111). Adsorbate desorption cross sections and substrate damage depths for NH{sub 3}/CO/Ni(111) are compared for 10-1000 eV isobaric atomic and polyatomic ions, Xe{sup +} and SF{sub 5}{sup +}. The surface chemical modification of polystyrene thin films by 10-100 eV SF{sub 5}{sup +} and C{sub 3}F{sub 5}{sup +} ions is also examined.

  4. The Effect of Substrate Temperature on Surface Modification of Polystyrene by using Nitrogen Plasma

    NASA Astrophysics Data System (ADS)

    Novi, A. F.; Santjojo, D. J. D. H.; Masruroh

    2017-05-01

    Studies on the effect of substrate temperature on the modification process of a thin layer of polystyrene samples deposited on glass by using spin coating technique have been conducted. The polystyrene thin film surface was modified by using nitrogen plasma generated in a vacuum reactor by a capacitive plasma generator with a frequency of 40 kHz. The substrate temperature was set by variation of 60, 70 and 80 °C during the modification process to determine the effect of substrate temperature on the level of roughness and hydrophobicity of the film. Observations were conducted by using optical microscopy, optical micro-profiler, and measuring the contact angle of liquid. The results showed a decrease in roughness due to modification at a temperature of 60 °C and 70 °C. On the other hand, the treatment at a temperature of 80 °C resulted in an increase of roughness. By measuring the contact angle, it was proven that hydrophobicity is not only influenced by the surface roughness of thin layers.

  5. Maternal Behavior Modifications during Pretense and Their Long-Term Effects on Toddlers’ Understanding of Pretense

    PubMed Central

    Nakamichi, Naoko

    2015-01-01

    Recent studies indicate the need to investigate the sources of toddlers’ understanding of another person's pretense. The present study is a cultural and longitudinal extension of the work of Lillard and Witherington (2004), who claimed that mothers modify their behaviors during pretense and that the some of these behavior modifications help their toddlers understand maternal pretense. Experiment 1 investigated whether mothers would change their behaviors during pretense with a sample of 31 Japanese mother–infant pairs. Experiment 2, with a subsample of 20 mother–child pairs who had participated in Experiment 1, examined whether the maternal behavior modifications at 18 months predicted their toddlers’ understanding of pretense at 24 months. The results of Experiment 1 indicated that Japanese mothers smiled more frequently, gazed at their toddlers longer, used sound effects more frequently, and engaged in more frequent snack-related actions in a “pretense condition” than in a “real condition.” In addition, some of these behaviors were significantly related to their toddlers’ apparent understanding of pretense. Experiment 2 showed that both the frequency of maternal smiles and the number of sound effects in the pretense condition at 18 months predicted toddlers’ understanding of the pretense enacted by a strange adult at 24 months. This research indicates the impact of maternal behavior modifications during pretense on the development of symbolic thought in the 2nd year of life. PMID:26430391

  6. Feedback in classroom behavior modification: effects on the target and her classmates.

    PubMed

    Drabman, R S; Lahey, B B

    1974-01-01

    A behavior modification program that employed feedback with no additional contingencies was initiated and withdrawn in an ABAB design on a target child within a classroom. The disruptive behavior of the target child as well as that of her peers was monitored. Additionally, the sociometric status of the target child was recorded. Finally, the positive and negative comments made to the target by her teacher and her peers were related to initiation and withdrawal of the feedback contingency. Results indicate that (1) feedback alone may be an effective behavior modification procedure, (2) the disruptive behavior of the target's classmates changed, even though they were not directly treated, (3) sociometric status of the target was altered by behavioral contingencies, (4) positive comments by classmates to the target increased, and (5) negative comments from the teacher to the target child decreased.

  7. Effect of avidin-like proteins and biotin modification on mesenchymal stem cell adhesion

    PubMed Central

    Schmidt, Ray C.; Healy, Kevin E.

    2013-01-01

    The avidin-biotin system is a highly specific reaction that has been used in a wide range of biomedical applications, including surface modification and cell patterning. We systematically examined a number of avidin derivatives as the basis for a simple and cost effective tissue culture polystyrene substrate surface modification for human stem cell culture. Non-specific adhesion between human mesenchymal stem cells and various avidin derivatives, media conditions, and subsequent biotinylation reactions was quantified. We observed significant non-specific cell adhesion to avidin and strepthavidin, indicating that previous observations using this system may be artifactual. Seeding of cells in serum free media, blocking with bovine-serum albumin, and the use of the avidin derivative Neutravidin were all necessary for elimination of background adhesion. Neutravidin conjugated with biotinylated bsp-RGD(15) peptide provided the most robust cell adhesion, as well as the greatest increase in cell adhesion over background levels. PMID:23452388

  8. The Effect of Single-Session Interpretation Modification on Attention Bias in Socially Anxious Individuals

    PubMed Central

    Amir, Nader; Bomyea, Jessica; Beard, Courtney

    2009-01-01

    Research suggests that individuals with social anxiety interpret ambiguous social information negatively (e.g., Amir, Foa, & Coles, 1998) and that much negative interpretation bias may share a common mechanism with other information processing biases (e.g., Mathews, Mackintosh, & Fulcher, 1997). In the current study, we examined effectiveness of an interpretation modification program in changing attention biases in socially anxious individuals. Participants were randomly assigned to either an Interpretation Modification Program (IMP) that guided them to make benign interpretations of ambiguous social scenarios or an Interpretation Control Condition (ICC) that did not guide participants' interpretation in either direction. Results revealed that individuals in the IMP group demonstrated greater ability to disengage attention from threat stimuli after completing the program, while individuals in the ICC did not. These results are consistent with the hypothesis that information processing biases in anxious individuals may share a common mechanism that may contribute to the maintenance of anxiety. PMID:19926442

  9. Does attention redirection contribute to the effectiveness of attention bias modification on social anxiety?

    PubMed

    Yao, Nisha; Yu, Hongyu; Qian, Mingyi; Li, Songwei

    2015-12-01

    Attention bias modification (ABM) is designed to modify threat-related attention bias and thus alleviate anxiety. The current research examined whether consistently directing attention towards targeted goals per se contributes to ABM efficacy. We randomly assigned 68 non-clinical college students with elevated social anxiety to non-valence-specific attend-to-geometrics (AGC), attention modification (AMC), or attention control (ACC) conditions. We assessed subjective, behavioral, and physiological reactivity to a speech task and self-reported social anxiety symptoms. After training, participants in the AMC exhibited an attention avoidance from threat, and those in the AGC responded more rapidly toward targeted geometrics. There was a significant pre- to post-reduction in subjective speech distress across groups, but behavioral and physiological reactivity to speech, as well as self-report social anxiety symptoms, remained unchanged. These results lead to questions concerning effectiveness of ABM training for reducing social anxiety. Further examination of the current ABM protocol is required.

  10. Evaluation of some scale effects in the response and failure of composite beams

    NASA Technical Reports Server (NTRS)

    Jackson, Karen E.; Morton, John

    1991-01-01

    The feasibility of using scale model testing for predicting full-scale behavior of composite beams loaded in tension and flexure was investigated. Classical laws of similitude were applied to fabricate and test replica model beams to identify scaling effects in the load response, strength, and mode of failure. Experiments were conducted using graphite-epoxy composite beams having different laminate stacking sequences and a range of scaled sizes. Results indicated that the elastic response of scaled composite beams was independent of specimen size. However, a significant scale effect in strength was observed. In addition, a transition in failure mode was observed among scaled beams of certain laminate stacking sequences. Weibull statistical and fracture mechanics based models were applied to predict the strength scale effect since standard failure criteria cannot account for the influence of absolute specimen size in failure.

  11. Effects of tooth profile modification on dynamic responses of a high speed gear-rotor-bearing system

    NASA Astrophysics Data System (ADS)

    Hu, Zehua; Tang, Jinyuan; Zhong, Jue; Chen, Siyu; Yan, Haiyan

    2016-08-01

    A finite element node dynamic model of a high speed gear-rotor-bearing system considering the time-varying mesh stiffness, backlash, gyroscopic effect and transmission error excitation is developed. Different tooth profile modifications are introduced into the gear pair and corresponding time-varying mesh stiffness curves are obtained. Effects of the tooth profile modification on mesh stiffness are analyzed, and the natural frequencies and mode shapes of the gear-rotor-bearing transmission system are given. The dynamic responses with respect to a wide input speed region including dynamic factor, vibration amplitude near the bearing and dynamic transmission error are obtained by introducing the time-varying mesh stiffness in different tooth profile modification cases into the gear-rotor-bearing dynamic system. Effects of the tooth profile modification on the dynamic responses are studied in detail. The numerical simulation results show that both the short profile modification and the long profile modification can affect the mutation of the mesh stiffness when the number of engaging tooth pairs changes. A short profile modification with an appropriate modification amount can improve the dynamic property of the system in certain work condition.

  12. Structual Effects of Cytidine 2^' Ribose Modifications as Determined by Irmpd Action Spectroscopy

    NASA Astrophysics Data System (ADS)

    Hamlow, Lucas; He, Chenchen; Fan, Lin; Wu, Ranran; Yang, Bo; Rodgers, M. T.; Berden, Giel; Oomens, J.

    2015-06-01

    Modified nucleosides, both naturally occurring and synthetic play an important role in understanding and manipulating RNA and DNA. Naturally occurring modified nucleosides are commonly found in functionally important regions of RNA and also affect antibiotic resistance or sensitivity. Synthetic modifications of nucleosides such as fluorinated and arabinosyl nucleosides have found uses as anti-virals and chemotherapy agents. Understanding the effect that modifications have on structure and glycosidic bond stability may lend insight into the functions of these modified nucleosides. Modifications such as the naturally occurring 2^'-O-methylation and the synthetic 2^'-fluorination are believed to help stabilize the nucleoside through the glycosidic bond stability and intramolecular hydrogen bonding. Changing the sugar from ribose to arabinose alters the stereochemistry at the 2^' position and thus shifts the 3D orientation of the 2^'-hydroxyl group, which also affects intramolecular hydrogen bonding and glycosidic bond stability. The structures of 2^'-deoxy-2^'-fluorocytidine, 2^'-O-methylcytidine and cytosine arabinoside are examined in the current work by measuring the infrared spectra in the IR fingerprint region using infrared multiple photon dissociation (IRMPD) action spectroscopy. The structures accessed in the experiments were determined via comparison of the measured IRMPD action spectra to the theoretical linear IR spectra determined by density functional theory and molecular modeling for the stable low-energy structures. Although glycosidic bond stability cannot be quantitatively determined from this data, complementary TCID studies will establish the effect of these modifications. Comparison of these modified nucleosides with their RNA and DNA analogues will help elucidate differences in their intrinsic chemistry.

  13. Surface Properties of Fluorosilicone Copolymers and Their Surface Modification Effects on PVC Film.

    PubMed

    Kim; Lee; Doh

    1998-09-15

    The fluorosilicone copolymers were synthesized using a fluorine-containing monomer and silicone-containing monomers by free-radical random copolymerization, and their surface properties and surface modification ability were investigated. The fluorine-containing monomer used was perfluoroalkyl ethyl acrylate (FA), and the silicone-containing monomers used were 3-[tris(trimethylsilyloxy)silyl]propyl methacrylate (SiMA), vinyltrimethoxy silane (VTMS), and vinyltriethoxy silane (VTES). The surface free energies of the fluorosilicone copolymers prepared were estimated from the contact angle data measured by sessile-drop method. And, the surface free energies of poly(vinyl chloride) (PVC) films modified by the fluorosilicone copolymers were also analyzed using the contact angle data. The fluorosilicone copolymers exhibit the surface free energies of about 8-23 dyn/cm dependent on the molecular weight of the fluorosilicone copolymers. The surface free energies of the fluorosilicone copolymers decrease with increasing molecular weight in the range of 2,000-10,000 (Mw). Among the fluorosilicone copolymers prepared in this study, PFA-r-PSiMA was found to be the most effective as a surface modification agent for PVC film. The inherent surface free energy of PFA-r-PSiMA was estimated to be about 9.0 dyn/cm. The desirable molecular weight of PFA-r-PSiMA seems to be more than 4,000 (Mw). However, it is expected that the fluorosilicone copolymers having the molecular weight of much higher than 10,000 (Mw) may not be suitable as surface modification additives because their compatibility with other polymers will decrease with the molecular weight. The optimum concentration of PFA-r-PSiMA added to PVC film is about 1.0 wt.%. PFA-r-PSiMA is expectedto be an effective additive for surface modification of PVC films. Copyright 1998 Academic Press.

  14. The Modification of Polymer Surfaces and the Fabrication of Submicron- Scale Functionalized Structures by Deep-UV and Electron Beam Lithography

    DTIC Science & Technology

    1993-06-10

    to the polymer via photogenerated or electron beam generated, highly reactive nitrene intermediates derived from the PFPA. Using this technique we...electron beam generated, highly reactive nitrene intermediates derived from the PFPA. Using this technique we demonstrate that well- defined surface...PFPAs in hydrocarbon solvents efficiently produce CH insertion products via highly reactive nitrene intermediates.13-1 Taking advantage of the

  15. The impact of cold spells on mortality and effect modification by cold spell characteristics

    PubMed Central

    Wang, Lijun; Liu, Tao; Hu, Mengjue; Zeng, Weilin; Zhang, Yonghui; Rutherford, Shannon; Lin, Hualiang; Xiao, Jianpeng; Yin, Peng; Liu, Jiangmei; Chu, Cordia; Tong, Shilu; Ma, Wenjun; Zhou, Maigeng

    2016-01-01

    In China, the health impact of cold weather has received little attention, which limits our understanding of the health impacts of climate change. We collected daily mortality and meteorological data in 66 communities across China from 2006 to 2011. Within each community, we estimated the effect of cold spell exposure on mortality using a Distributed Lag Nonlinear Model (DLNM). We also examined the modification effect of cold spell characteristics (intensity, duration, and timing) and individual-specific factors (causes of death, age, gender and education). Meta-analysis method was finally used to estimate the overall effects. The overall cumulative excess risk (CER) of non-accidental mortality during cold spell days was 28.2% (95% CI: 21.4%, 35.3%) compared with non-cold spell days. There was a significant increase in mortality when the cold spell duration and intensity increased or occurred earlier in the season. Cold spell effects and effect modification by cold spell characteristics were more pronounced in south China. The elderly, people with low education level and those with respiratory diseases were generally more vulnerable to cold spells. Cold spells statistically significantly increase mortality risk in China, with greater effects in southern China. This effect is modified by cold spell characteristics and individual-level factors. PMID:27922084

  16. The impact of cold spells on mortality and effect modification by cold spell characteristics

    NASA Astrophysics Data System (ADS)

    Wang, Lijun; Liu, Tao; Hu, Mengjue; Zeng, Weilin; Zhang, Yonghui; Rutherford, Shannon; Lin, Hualiang; Xiao, Jianpeng; Yin, Peng; Liu, Jiangmei; Chu, Cordia; Tong, Shilu; Ma, Wenjun; Zhou, Maigeng

    2016-12-01

    In China, the health impact of cold weather has received little attention, which limits our understanding of the health impacts of climate change. We collected daily mortality and meteorological data in 66 communities across China from 2006 to 2011. Within each community, we estimated the effect of cold spell exposure on mortality using a Distributed Lag Nonlinear Model (DLNM). We also examined the modification effect of cold spell characteristics (intensity, duration, and timing) and individual-specific factors (causes of death, age, gender and education). Meta-analysis method was finally used to estimate the overall effects. The overall cumulative excess risk (CER) of non-accidental mortality during cold spell days was 28.2% (95% CI: 21.4%, 35.3%) compared with non-cold spell days. There was a significant increase in mortality when the cold spell duration and intensity increased or occurred earlier in the season. Cold spell effects and effect modification by cold spell characteristics were more pronounced in south China. The elderly, people with low education level and those with respiratory diseases were generally more vulnerable to cold spells. Cold spells statistically significantly increase mortality risk in China, with greater effects in southern China. This effect is modified by cold spell characteristics and individual-level factors.

  17. The impact of cold spells on mortality and effect modification by cold spell characteristics.

    PubMed

    Wang, Lijun; Liu, Tao; Hu, Mengjue; Zeng, Weilin; Zhang, Yonghui; Rutherford, Shannon; Lin, Hualiang; Xiao, Jianpeng; Yin, Peng; Liu, Jiangmei; Chu, Cordia; Tong, Shilu; Ma, Wenjun; Zhou, Maigeng

    2016-12-06

    In China, the health impact of cold weather has received little attention, which limits our understanding of the health impacts of climate change. We collected daily mortality and meteorological data in 66 communities across China from 2006 to 2011. Within each community, we estimated the effect of cold spell exposure on mortality using a Distributed Lag Nonlinear Model (DLNM). We also examined the modification effect of cold spell characteristics (intensity, duration, and timing) and individual-specific factors (causes of death, age, gender and education). Meta-analysis method was finally used to estimate the overall effects. The overall cumulative excess risk (CER) of non-accidental mortality during cold spell days was 28.2% (95% CI: 21.4%, 35.3%) compared with non-cold spell days. There was a significant increase in mortality when the cold spell duration and intensity increased or occurred earlier in the season. Cold spell effects and effect modification by cold spell characteristics were more pronounced in south China. The elderly, people with low education level and those with respiratory diseases were generally more vulnerable to cold spells. Cold spells statistically significantly increase mortality risk in China, with greater effects in southern China. This effect is modified by cold spell characteristics and individual-level factors.

  18. Effect of Scanning Beam for Superficial Dose in Proton Therapy.

    PubMed

    Moskvin, Vadim P; Estabrook, Neil C; Cheng, Chee-Wai; Das, Indra J; Johnstone, Peter A S

    2015-10-01

    Proton beam delivery technology is under development to minimize the scanning spot size for uniform dose to target, but it is also known that the superficial dose could be as high as the dose at Bragg peak for narrow and small proton beams. The objective of this study is to explore the characteristics of dose distribution at shallow depths using Monte Carlo simulation with the FLUKA code for uniform scanning (US) and discrete spot scanning (DSS) proton beams. The results show that the superficial dose for DSS is relatively high compared to US. Additionally, DSS delivers a highly heterogeneous dose to the irradiated surface for comparable doses at Bragg peak. Our simulation shows that the superficial dose can become as high as the Bragg peak when the diameter of the proton beam is reduced. This may compromise the advantage of proton beam therapy for sparing normal tissue, making skin dose a limiting factor for the clinical use of DSS. Finally, the clinical advantage of DSS may not be essential for treating uniform dose across a large target, as in craniospinal irradiation (CSI).

  19. One- and two-photon absorption in solution: The effects of a passive auxiliary beam

    SciTech Connect

    Ford, J. S.; Andrews, D. L.

    2014-07-21

    The efficiencies of one- and two-photon absorption by chromophores in solution may be significantly modified by a sufficiently intense beam of off-resonant light. A molecular analysis based on quantum electrodynamics (QED) fully accounts for this phenomenon of laser-modified absorption. A time-dependent perturbation-theory treatment describes the process in terms of stimulated forward Rayleigh-scattering of the auxiliary beam occurring simultaneously with the absorption interaction(s). Our formulation accommodates media modifications to the basic character of light-matter interactions, taking into account the refractive and dispersive properties of a solution-phase environment. This introduces the bulk refractive index of the solvent directly into the QED framework. The measurable electronic response of molecules freely rotating in solution is defined by an average of all orientations. We explicitly derive fixed-orientation and rotationally averaged calculations for the Fermi-rule rate of laser-modified one- and two-photon absorption. For a given beam polarization geometry, the solution-phase molecular response is expressible as a set of natural invariant scalars. These results reveal details of the dependence on the beam polarisations and on the rotationally averaged molecular response: we illustrate the breadth of variation available via geometric manipulation of beam polarization, and raise new possibilities for quantum weak measurements of laser states.

  20. One- and two-photon absorption in solution: the effects of a passive auxiliary beam.

    PubMed

    Ford, J S; Andrews, D L

    2014-07-21

    The efficiencies of one- and two-photon absorption by chromophores in solution may be significantly modified by a sufficiently intense beam of off-resonant light. A molecular analysis based on quantum electrodynamics (QED) fully accounts for this phenomenon of laser-modified absorption. A time-dependent perturbation-theory treatment describes the process in terms of stimulated forward Rayleigh-scattering of the auxiliary beam occurring simultaneously with the absorption interaction(s). Our formulation accommodates media modifications to the basic character of light-matter interactions, taking into account the refractive and dispersive properties of a solution-phase environment. This introduces the bulk refractive index of the solvent directly into the QED framework. The measurable electronic response of molecules freely rotating in solution is defined by an average of all orientations. We explicitly derive fixed-orientation and rotationally averaged calculations for the Fermi-rule rate of laser-modified one- and two-photon absorption. For a given beam polarization geometry, the solution-phase molecular response is expressible as a set of natural invariant scalars. These results reveal details of the dependence on the beam polarisations and on the rotationally averaged molecular response: we illustrate the breadth of variation available via geometric manipulation of beam polarization, and raise new possibilities for quantum weak measurements of laser states.

  1. One- and two-photon absorption in solution: The effects of a passive auxiliary beam

    NASA Astrophysics Data System (ADS)

    Ford, J. S.; Andrews, D. L.

    2014-07-01

    The efficiencies of one- and two-photon absorption by chromophores in solution may be significantly modified by a sufficiently intense beam of off-resonant light. A molecular analysis based on quantum electrodynamics (QED) fully accounts for this phenomenon of laser-modified absorption. A time-dependent perturbation-theory treatment describes the process in terms of stimulated forward Rayleigh-scattering of the auxiliary beam occurring simultaneously with the absorption interaction(s). Our formulation accommodates media modifications to the basic character of light-matter interactions, taking into account the refractive and dispersive properties of a solution-phase environment. This introduces the bulk refractive index of the solvent directly into the QED framework. The measurable electronic response of molecules freely rotating in solution is defined by an average of all orientations. We explicitly derive fixed-orientation and rotationally averaged calculations for the Fermi-rule rate of laser-modified one- and two-photon absorption. For a given beam polarization geometry, the solution-phase molecular response is expressible as a set of natural invariant scalars. These results reveal details of the dependence on the beam polarisations and on the rotationally averaged molecular response: we illustrate the breadth of variation available via geometric manipulation of beam polarization, and raise new possibilities for quantum weak measurements of laser states.

  2. Effect of meson cloud on the jet nuclear modification factor in pA collisions

    NASA Astrophysics Data System (ADS)

    Zakharov, B. G.

    2017-02-01

    We study the effect of the nucleon meson cloud on centrality dependence of the jet nuclear modification factor R pA . We find that the meson-baryon Fock components may lead to a noticeable deviation of R pA from unity. Our results for R pA show the same tendency as that observed by ATLAS in p + Pb collisions at √s = 5.02 TeV. The meson cloud suppresses the central jet events and enhances the peripheral jet events. But quantitatively the effect is somewhat smaller than in the data.

  3. Relative biological effectiveness (RBE) and out-of-field cell survival responses to passive scattering and pencil beam scanning proton beam deliveries.

    PubMed

    Butterworth, Karl T; McGarry, Conor K; Clasie, Ben; Carabe-Fernandez, Alejandro; Schuemann, Jan; Depauw, Nicolas; Tang, Shikui; McMahon, Stephen J; Schettino, Giuseppe; O'Sullivan, Joe M; Lu, Hsaio-Ming; Kooy, Hanne; Paganetti, Harald; Hounsell, Alan R; Held, Kathryn D; Prise, Kevin M

    2012-10-21

    The relative biological effectiveness (RBE) of passive scattered (PS) and pencil beam scanned (PBS) proton beam delivery techniques for uniform beam configurations was determined by clonogenic survival. The radiobiological impact of modulated beam configurations on cell survival occurring in- or out-of-field for both delivery techniques was determined with intercellular communication intact or physically inhibited. Cell survival responses were compared to those observed using a 6 MV photon beam produced with a linear accelerator. DU-145 cells showed no significant difference in survival response to proton beams delivered by PS and PBS or 6 MV photons taking into account a RBE of 1.1 for protons at the centre of the spread out Bragg peak. Significant out-of-field effects similar to those observed for 6 MV photons were observed for both PS and PBS proton deliveries with cell survival decreasing to 50-60% survival for scattered doses of 0.05 and 0.03 Gy for passive scattered and pencil beam scanned beams respectively. The observed out-of-field responses were shown to be dependent on intercellular communication between the in- and out-of-field cell populations. These data demonstrate, for the first time, a similar RBE between passive and actively scanned proton beams and confirm that out-of-field effects may be important determinants of cell survival following exposure to modulated photon and proton fields.

  4. Relative biological effectiveness (RBE) and out-of-field cell survival responses to passive scattering and pencil beam scanning proton beam deliveries

    NASA Astrophysics Data System (ADS)

    Butterworth, Karl T.; McGarry, Conor K.; Clasie, Ben; Carabe-Fernandez, Alejandro; Schuemann, Jan; Depauw, Nicolas; Tang, Shikui; McMahon, Stephen J.; Schettino, Giuseppe; O'Sullivan, Joe M.; Lu, Hsaio-Ming; Kooy, Hanne; Paganetti, Harald; Hounsell, Alan R.; Held, Kathryn D.; Prise, Kevin M.

    2012-10-01

    The relative biological effectiveness (RBE) of passive scattered (PS) and pencil beam scanned (PBS) proton beam delivery techniques for uniform beam configurations was determined by clonogenic survival. The radiobiological impact of modulated beam configurations on cell survival occurring in- or out-of-field for both delivery techniques was determined with intercellular communication intact or physically inhibited. Cell survival responses were compared to those observed using a 6 MV photon beam produced with a linear accelerator. DU-145 cells showed no significant difference in survival response to proton beams delivered by PS and PBS or 6 MV photons taking into account a RBE of 1.1 for protons at the centre of the spread out Bragg peak. Significant out-of-field effects similar to those observed for 6 MV photons were observed for both PS and PBS proton deliveries with cell survival decreasing to 50-60% survival for scattered doses of 0.05 and 0.03 Gy for passive scattered and pencil beam scanned beams respectively. The observed out-of-field responses were shown to be dependent on intercellular communication between the in- and out-of-field cell populations. These data demonstrate, for the first time, a similar RBE between passive and actively scanned proton beams and confirm that out-of-field effects may be important determinants of cell survival following exposure to modulated photon and proton fields

  5. A laboratory experiment to examine the effect of auroral beams on spacecraft charging in the ionosphere

    SciTech Connect

    Siddiqui, M. U.; Gayetsky, L. E.; Mella, M. R.; Lynch, K. A.; Lessard, M. R.

    2011-09-15

    A 2.54 cm diameter conducting electrically isolated Copper sphere is suspended in a low density (10{sup 4} cm{sup -3}), low temperature (T{sub e} = 0.5 eV) Argon plasma, which mimics a spacecraft in an ionospheric plasma. An electron beam with current density of approximately 10{sup -10} A/cm{sup 2} and beam spot of 10.2 cm diameter, which mimics an auroral electron beam, is fired at the sphere while varying the beam energy from 100 eV to 2 keV. The plasma potential in the sheath around the sphere is measured using an emissive probe as the electron beam energy is varied. To observe the effects of the electron beam, the experimental sheath potential profiles are compared to a model of the plasma potential around a spherically symmetric charge distribution in the absence of electron beams. Comparison between the experimental data and the model shows that the sphere is less negative than the model predicts by up to half a volt for beam energies that produce high secondary electron emission from the surface of the sphere. It is shown that this secondary emission can account for changes in potential of spacecraft in the ionosphere as they pass through auroral beams and thus helps to improve interpretations of ionospheric thermal ion distributions.

  6. Dose-Response Effect of Charged Carbon Beam on Normal Rat Retina Assessed by Electroretinography

    SciTech Connect

    Mizota, Atsushi; Tanaka, Minoru; Kubota, Mariko; Negishi, Hisanari; Watanabe, Emiko; Tsuji, Hiroshi; Miyahara, Nobuyuki; Furusawa, Yoshiya

    2010-12-01

    Purpose: To compare the effects of carbon beam irradiation with those of proton beam irradiation on the physiology of the retina of rats. Methods and Materials: Eight-week-old Wister rats were used. The right eyes were irradiated with carbon beam (1, 2, 4, 8, and 16 Gy) or proton beam (4, 8, 16, and 24 Gy) with the rats under general anesthesia. Electroretinograms were recorded 1, 3, 6, and 12 months after the irradiation, and the amplitudes of the a and b waves were compared with those of control rats. Results: The amplitude of b waves was reduced more than that of a waves at lower irradiation doses with both types of irradiation. With carbon ion irradiation, the amplitudes of the b wave were significantly reduced after radiation doses of 8 and 16 Gy at 6 months and by radiation doses of 4, 8, and 16 Gy at 12 months. With proton beam irradiation, the b-wave amplitudes were significantly reduced after 16 and 24 Gy at 6 months and with doses of 8 Gy or greater at 12 months. For the maximum b-wave amplitude, a significant difference was observed in rats irradiated with carbon beams of 4 Gy or more and with proton beams of 8 Gy or more at 12 months after irradiation. Conclusions: These results indicate that carbon beam irradiation is about two times more damaging than proton beam irradiation on the rat retina at the same dose.

  7. Viscous Effects in the Elastodynamics of Thick Beams

    NASA Technical Reports Server (NTRS)

    Johnson, A. R.; Tessler, A.

    1997-01-01

    A viscoelastic higher-order thick beam finite element formulation is extended to include elastodynamic deformations. The material constitutive law is a special differential form of the Maxwell solid. In the constitutive model, the elastic strains and the conjugate viscous strains are coupled through a system of first- order ordinary differential equations. The total time-dependent stress is the superposition of its elastic and viscous components. The elastodynamic equations of motion are derived from the virtual work principle. Computational examples are carried out for a thick orthotropic cantilevered beam. A quasi-static relaxation problem is employed as a validation test for the elastodynamic algorithm. The elastodynamic code is demonstrated by analyzing the damped vibrations of the beam which is deformed and then released to freely vibrate.

  8. [Effect of platelet CD42a modification by mPEG-SPA with different molecular masses].

    PubMed

    Zhang, Yin-ze; Xiong, Wen; Li, Zhen; Shao, Chao-peng; Li, Tian-jun; Zhao, Feng; Yang, Bao-cheng

    2007-03-01

    To observe the effect platelet antigen modification by mPEG-SPA with different molecular masses. Platelet CD42a was modified by 5 kD and 20 kD mPEG-SPA, respectively, and the fluorescence intensity of CD42a was detect by flow cytometry and the three-dimensional structure of CD42a simulated to analyze the distribution of lysine in CD42a molecule. After platelet CD42a modification by 5 kD and 20 kD mPEG-SPA, the fluorescence intensity of CD42a decreased sharply by 85.54% and 88.65%, respectively, and multiple lysine regions were identified on the surface of CD42a molecule. Both 5 kD and 20 kD mPEG-SPA allow useful modification of platelet CD42a, but 20 kD mPEG-SPA is more advantageous than 5 kD mPEG-SPA.

  9. Effect of lysine modification on the stability and cellular binding of human amyloidogenic light chains.

    PubMed

    Davern, S; Murphy, C L; O'Neill, H; Wall, J S; Weiss, D T; Solomon, A

    2011-01-01

    AL amyloidosis is characterized by the pathologic deposition as fibrils of monoclonal light chains (i.e., Bence Jones proteins [BJPs]) in particular organs and tissues. This phenomenon has been attributed to the presence in amyloidogenic proteins of particular amino acids that cause these molecules to become unstable, as well as post-translational modifications and, in regard to the latter, we have investigated the effect of biotinylation of lysyl residues on cell binding. We utilized an experimental system designed to test if BJPs obtained from patients with AL amyloidosis or, as a control, multiple myeloma (MM), bound human fibroblasts and renal epithelial cells. As documented by fluorescence microscopy and ELISA, the amyloidogenic BJPs, as compared with MM components, bound preferentially and this reactivity increased significantly after chemical modification of their lysyl residues with sulfo-NHS-biotin. Further, based on tryptophan fluorescence and circular dichroism data, it was apparent that their conformation was altered, which we hypothesize exposed a binding site not accessible on the native protein. The results of our studies indicate that post-translational structural modifications of pathologic light chains can enhance their capacity for cellular interaction and thus may contribute to the pathogenesis of AL amyloidosis and multiple myeloma.

  10. Effect of surface modifications on the thermal and moisture behavior of wool fabric

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Zhao, Yuan; Li, Wenbin; Wang, Hao

    2015-07-01

    Thermal and moisture behavior is crucial in determining the comfort of clothing. Surface modification of fibers brings new functions and properties to fibrous materials, but the comfort of the as-made clothing changes accordingly due to different thermal and moisture behaviors. In this study, physical and chemical modifications have been conducted to wool fabric to investigate their effects on the thermal and moisture behaviors of clothing. Surface wettability, wicking properties, thermal and moisture resistance together with surface temperature and humidity of the microclimate have been tested. It has been found that the wettability of wool fabric is greatly improved and wicking properties are granted to the fabric. Higher thermal and moisture resistance have been noticed for the treated wool fabric. The treated fabric shows longer moisture liberation process and the surface temperature and humidity varies in a different way compared with untreated fabric. Understanding the thermal and moisture behaviors of fabric after surface modification would benefit the further development of surface functionalizing technology and design of next to skin clothing.

  11. The effect of hypusine modification on the intracellular localization of eIF5A

    SciTech Connect

    Lee, Seung Bum; Park, Jong Hwan; Kaevel, Joern; Sramkova, Monika; Weigert, Roberto; Park, Myung Hee

    2009-06-12

    Eukaryotic translation initiation factor 5A (eIF5A) is a highly conserved protein essential for eukaryotic cell proliferation and is the only protein containing hypusine, [N{sup {epsilon}}-(4-amino-2-hydroxybutyl)lysine]. eIF5A is activated by the post-translational synthesis of hypusine. eIF5A also undergoes an acetylation at specific Lys residue(s). In this study, we have investigated the effect of hypusine modification and acetylation on the subcellular localization of eIF5A. Immunocytochemical analyses showed differences in the distribution of non-hypusinated eIF5A precursor and the hypusine-containing mature eIF5A. While the precursor is found in both cytoplasm and nucleus, the hypusinated eIF5A is primarily localized in cytoplasm. eIF5A mutant proteins, defective in hypusine modification (K50A, K50R) were localized in a similar manner to the eIF5A precursor, whereas hypusine-modified mutant proteins (K47A, K47R, K68A) were localized mainly in the cytoplasm. These findings provide strong evidence that the hypusine modification of eIF5A dictates its localization in the cytoplasmic compartment where it is required for protein synthesis.

  12. Effect of Lysine Modification on the Stability and Cellular Binding of Human Amyloidogenic Light Chains

    SciTech Connect

    O'Neill, Hugh Michael; Davern, Sandra M.; Murphy, Charles L.; Wall, Jonathan; Deborah, Weiss T.; Solomon, Alan

    2011-01-01

    AL amyloidosis is characterized by the pathologic deposition as fibrils of monoclonal light chains (i.e., Bence Jones proteins [BJPs]) in particular organs and tissues. This phenomenon has been attributed to the presence in amyloidogenic proteins of particular amino acids that cause these molecules to become unstable, as well as post-translational modifications and, in regard to the latter, we have investigated the effect of biotinylation of lysyl residues on cell binding. We utilized an experimental system designed to test if BJPs obtained from patients with AL amyloidosis or, as a control, multiple myeloma (MM), bound human fibroblasts and renal epithelial cells. As documented by fluorescent microscopy and ELISA, the amyloidogenic BJPs, as compared with MM components, bound preferentially and this reactivity increased significantly after chemical modification of their lysyl residues with sulfo-NHS-biotin. Further, based on tryptophan fluorescence and circular dichorism data, it was apparent that their conformation was altered, which we hypothesize exposed a binding site not accessible on the native protein. The results of our studies indicate that post-translational structural modifications of pathologic light chains can enhance their capacity for cellular interaction and thus may contribute to the pathogenesis of AL amyloidosis and multiple myeloma.

  13. Asymmetry and non-random orientation of the inflight effective beam pattern in the WMAP data

    SciTech Connect

    Chiang, Lung-Yih

    2014-04-20

    Tentative evidence for statistical anisotropy in the Wilkinson Microwave Anisotropy Probe data was alleged to be due to 'insufficient handling of beam asymmetries'. In this paper, we investigate this issue and develop a method to estimate the shape of the inflight effective beam, particularly the asymmetry and azimuthal orientation. We divide the whole map into square patches and exploit the information in the Fourier space. For patches containing bright extragalactic point sources, we can directly estimate their shapes, from which the inflight effective beam can be estimated. For those without, we estimate the pattern from iso-power contours in two-dimensional Fourier space. We show that the inflight effective beam convolving the signal is indeed non-symmetric for most of the sky, and it is not randomly oriented. Around the ecliptic poles, however, the asymmetry is smaller due to the averaging effect from different orientations of the beam from the scan strategy. The orientations of the effective beam with significant asymmetry are parallel to the lines of ecliptic longitude. In the foreground-cleaned Internal Linear Combination map, however, the systematics caused by beam effect is significantly lessened.

  14. SIMULATION OF RF BREAKDOWN EFFECTS ON NLC BEAM

    SciTech Connect

    Dolgashev, V

    2004-08-24

    The linacs of the Next Linear Collider / Global Linear Collider will contain several thousand traveling wave X-band accelerator structures operating at an input power of about 60 MW. At this input power, prototypes of NLC/GLC structures have breakdown rates lower than one breakdown in ten hours. RF breakdowns disrupt flow of energy inside the structure and create arcs with electron and ion currents. Electromagnetic fields of these currents interact with the NLC beam. The authors simulated the deflection of the NLC beam caused by breakdown currents using the particle-in-cell code MAGIC. In this paper they present modeling considerations and simulation results.

  15. Effect of 4-Hydroxy-2-Nonenal Modification on Alpha-Synuclein Aggregation

    SciTech Connect

    Qin, Z.; Hu, D.; Han, S.; Reaney, S.H.; Monte, D.A.Di; Fink, A.L.

    2007-07-12

    Several observations have implicated oxidative stress and aggregation of the presynaptic protein alpha-synuclein in the pathogenesis of PD. alpha-Synuclein has been shown to have affinity for unsaturated fatty acids and membranes enriched in PUFAs, which are especially sensitive to oxidation under conditions of oxidative stress. One of the most important products of lipid oxidation is 4-hydroxynonenal (HNE), which has been implicated in the pathogenesis of Parkinson's disease. Consequently we investigated the effects of the interaction of HNE with alpha-synuclein. Incubation of HNE with alpha-synuclein at pH 7.4, 37oC resulted in covalent modification of the protein, with up to six HNE molecules incorporated as Michael addition products. FTIR and CD spectra indicated that HNE modification of alpha-synuclein resulted in a major conformational change involving increased beta-sheet. HNE modification of alpha-synuclein led to inhibition of fibrillation in an HNE-concentration-dependent manner. This inhibition of fibrillation was shown to be due to the formation of soluble oligomers based on SEC HPLC and AFM data. Small-angle X-ray scattering analysis indicated that the HNE-induced oligomers are compact and tightly packed. Treatment with guanidinium chloride (GuHCl) demonstrated that the HNE-induced oligomers were very stable with an extremely slow rate of dissociation. Addition of 5 uM HNE-modified oligomers to primary mesencephalic cultures caused marked neurotoxicity, since the integrity of dopaminergic and GABAergic neurons was reduced by 95% and 85%, respectively. Our observations indicate that HNE-modification of alpha-synuclein prevents fibrillation but may result in toxic oligomers which could therefore contribute to the demise of neurons subjected to oxidative damage.

  16. Thermal lensing analysis of TGG and its effect on beam quality.

    PubMed

    Jalali, Amir A; Rybarsyk, James; Rogers, Evan

    2013-06-03

    An analysis is presented of a TGG crystal rod under high power laser operation. A semianalytical thermal analysis is investigated to obtain the temperature profile and thermal lensing effect in a TGG crystal upon incidence of a high power laser light. By solving the heat transfer equation for the TGG crystal and taking the Gaussian beam transverse intensity profile as the heat source, the optical path difference due to induced thermal effects was obtained. Moreover, a detailed model for the dependence of thermal lensing and beam degradation which takes into account up to the fifth-order spherical aberration is presented. Based on this model, it is shown that up to a critical value of the beam power the degradation of the beam is not significant. The experimental results on thermal lensing and degradation on beam quality of a high power laser passing through a TGG crystal rod are in agreement with the main results from our model.

  17. Evidence for anomalous optical transition radiation linear polarization effects in beam-profile monitors

    NASA Astrophysics Data System (ADS)

    Lumpkin, A. H.; Johnson, A. S.; Ruan, J.; Thurman-Keup, R. M.; Yao, C.-Y.; Evtushenko, P.

    2013-10-01

    Investigations of the effects of optical transition radiation (OTR) polarization components on beam profiles are presented. The transverse profiles are examined using the OTR perpendicular and parallel polarization components with respect to the dimension of interest. We observed ˜15% projected profile size reductions with the perpendicularly polarized components on a 65-μm beam image size case at 14 MeV, a 150-μm beam image size at 4.5 GeV, and a 1100-μm beam image size at 7 GeV. These effects are all several times larger than expected (and anomalous in this sense) when compared to the standard OTR point-spread function calculations. We propose the time-averaged induced-current distribution which generates the OTR represents the actual beam size more faithfully with the perpendicular polarization component and recommend its routine use and subsequent deconvolution.

  18. Effect of spatial coherence on laser beam self-focusing from orbit to the ground in the atmosphere.

    PubMed

    Deng, Hanling; Ji, Xiaoling; Li, Xiaoqing; Zhang, Hao; Wang, Xianqu; Zhang, Yuqiu

    2016-06-27

    The effect of spatial coherence on laser beam self-focusing in the atmosphere to assist delivering powerful laser beams from orbit to the ground is studied. It is found that a fully coherent beam is more strongly compressed on the ground than a partially (spatial) coherent beam (PCB), even so, for a PCB the compressed spot size on the ground may be reduced below the diffraction limit due to self-focusing effect, and a PCB has higher threshold critical power than a fully coherent beam. Furthermore, an effective design rule for maximal compression without beam splitting of the transported PCB from orbit to the ground is presented.

  19. Unusual spin Hall effect of a light beam in chiral metamaterials

    SciTech Connect

    Wang Hailei; Zhang Xiangdong

    2011-05-15

    We present a solution to the problem of reflection and refraction of a polarized Gaussian beam at the interface between the transparent medium and the chiral metamaterials. Some unusual spin Hall effects of reflected and transmitted light have been found. It is shown that the spin-dependent displacements of the reflected beam centroid can not only reach several tens of wavelengths at certain incident angles; the reversed effect for the transmitted beams can also be realized by tuning the chiral parameters. These findings provide an alternative pathway for controlling the spin Hall effects of light and thereby open up the possibility for developing new nanophotonic devices.

  20. Effects of high source flow and high pumping speed on gas source molecular beam epitaxy / chemical beam epitaxy

    NASA Astrophysics Data System (ADS)

    McCollum, M. J.; Jackson, S. L.; Szafranek, I.; Stillman, G. E.

    1990-10-01

    We report the growth of GaAs by molecular beam epitaxy (MBE), gas source molecular beam epitaxy (GSMBE), and chemical beam epitaxy (CBE) in an epitaxial III-V reactor which features high pumping speed. The system is comprised of a modified Perkin-Elmer 430P molecular beam epitaxy system and a custom gas source panel from Emcore. The growth chamber is pumped with a 7000 1/s (He) diffusion pump (Varian VHS-10 with Monsanto Santovac 5 oil). The gas source panel includes pressure based flow controllers (MKS 1150) allowing triethylaluminum (TEA), triethylgallium (TEG), and trimethylindium (TMI) to be supplied without the use of hydrogen. All source lines, including arsine and phosphine, are maintained below atmospheric pressure. The high pumping speed allows total system flow rates as high as 100 SCCM and V/III ratios as high as 100. The purity of GaAs grown by MBE in this system increases with pumping speed. GaAs layers grown by GSMBE with arsine flows of 10 and 20 SCCM have electron concentrations of 1 × 10 15 cm -3 (μ 77=48,000 cm 2/V·) and 2 × 10 14 cm -3 (μ 77=78,000 cm 2/V·s) respectively. El ectron concentration varies with hydride injector temperature such that the minimum in electron concentration occurs for less than complete cracking. The effect of V/III ratio and the use of a metal eutectic bubbler on residual carrier concentration in GaAs grown by CBE is presented. Intentional Si and Be doping of CBE grown GaAs is demonstrated at a high growth rate of 5.4 μm/h.

  1. How can we enhance cognitive bias modification techniques? The effects of prospective cognition.

    PubMed

    Lee, Jong-Sun; Mathews, Andrew; Shergill, Sukhi; Chan, Daniel Ka Yiu; Majeed, Nadia; Yiend, Jenny

    2015-12-01

    Cognitive bias modification for interpretation, a computerized program which manipulates biased interpretations, has shown therapeutic promise, including evidence that negatively biased interpretations can be reduced, leading to corresponding improvements in symptoms. Cognitive bias modification for cognitive errors (CBM-errors) is a second generation CBM-I procedure which manipulates seven types of cognitive error and is especially relevant to depressive cognition. The aim of this study was to investigate whether the effects of the CBM-errors manipulation would be enhanced by adding a component facilitating prospective cognition to help embed and extend newly acquired interpretations. A sample of 80 volunteers completed a single session experiment. With a pretraining-posttraining design, we compared the effects of enhanced CBM-errors (targeting cognitive errors plus prospective cognition) with standard CBM-errors (targeting cognitive errors without prospective cognition), on interpretations of new material and mood. Significant differences between enhanced and standard CBM-errors revealed that enhanced positive training was more effective at decreasing negative interpretations compared to the standard procedure. Extending the current investigation to a sample dysphoria or depression is needed for an appropriate next step. The findings serve as 'a proof of principle' for the potential of prospective cognition to enhance the effects of CBM-errors and other similar CBM procedures. Further work to enhance the effectiveness of CBM procedures is needed. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Accurate model of electron beam profiles with emittance effects for pierce guns

    NASA Astrophysics Data System (ADS)

    Zeng, Peng; Wang, Guangqiang; Wang, Jianguo; Wang, Dongyang; Li, Shuang

    2016-09-01

    Accurate prediction of electron beam profile is one of the key objectives of electron optics, and the basis for design of the practical electron gun. In this paper, an improved model describing electron beam in Pierce gun with both space charge effects and emittance effects is proposed. The theory developed by Cutler and Hines is still applied for the accelerating region of the Pierce gun, while the motion equations of the electron beams in the anode aperture and drift tunnel are improved by modifying electron optics theory with emittance. As a result, a more universal and accurate formula of the focal length of the lens for the electron beam with both effects is derived for the anode aperture with finite dimension, and a modified universal spread curve considering beam emittance is introduced in drift tunnel region. Based on these improved motion equations of the electron beam, beam profiles with space charge effects and emittance effects can be theoretically predicted, which are subsequently approved to agree well with the experimentally measured ones. The developed model here is helpful to design more applicable Pierce guns at high frequencies.

  3. Effect of transients on the beam in the Superconducting Supercollider Coupled-Cavity Linac

    SciTech Connect

    Young, L.M.; Nath, S.

    1992-10-01

    Each module of the Superconducting Super Collider (SSC) Coupled-Cavity Linac (CCL) consists of eight tanks (10 accelerating cells each) coupled with bridge couplers. The radio frequency (rf) power drive is in the center of the module at the bridge coupler between the fourth and fifth tanks. In this simulation of the beam dynamics, the rf power is turned on 10 {mu}s before the beam is turned on. This time lapse allows the fields to build up and stabilize before they are required by the beam. When the beam is turned on, the beam loading causes the fields to change. This transient state of the fields together with their effect on the beam is presented. A model has been developed to calculate field distribution throughout the module as a function of time. Beam dynamics simulations were run with the results of this model at several times during the beam pulse. An estimate of the effect of the transients is given by the results of these simulations.

  4. Effect of transients on the beam in the Superconducting Supercollider Coupled-Cavity Linac

    SciTech Connect

    Young, L.M.; Nath, S.

    1992-01-01

    Each module of the Superconducting Super Collider (SSC) Coupled-Cavity Linac (CCL) consists of eight tanks (10 accelerating cells each) coupled with bridge couplers. The radio frequency (rf) power drive is in the center of the module at the bridge coupler between the fourth and fifth tanks. In this simulation of the beam dynamics, the rf power is turned on 10 {mu}s before the beam is turned on. This time lapse allows the fields to build up and stabilize before they are required by the beam. When the beam is turned on, the beam loading causes the fields to change. This transient state of the fields together with their effect on the beam is presented. A model has been developed to calculate field distribution throughout the module as a function of time. Beam dynamics simulations were run with the results of this model at several times during the beam pulse. An estimate of the effect of the transients is given by the results of these simulations.

  5. The effect of material heterogeneity in curved composite beams for use in aircraft structures

    NASA Technical Reports Server (NTRS)

    Otoole, Brendan J.; Santare, Michael H.

    1992-01-01

    A design tool is presented for predicting the effect of material heterogeneity on the performance of curved composite beams for use in aircraft fuselage structures. Material heterogeneity can be induced during processes such as sheet forming and stretch forming of thermoplastic composites. This heterogeneity can be introduced in the form of fiber realignment and spreading during the manufacturing process causing a gradient in material properties in both the radial and tangential directions. The analysis procedure uses a separate two-dimensional elasticity solution for the stresses in the flanges and web sections of the beam. The separate solutions are coupled by requiring the forces and displacements match at the section boundaries. Analysis is performed for curved beams loaded in pure bending and uniform pressure. The beams can be of any general cross-section such as a hat, T-, I-, or J-beam. Preliminary results show that geometry of the beam dictates the effect of heterogeneity on performance. Heterogeneity plays a much larger role in beams with a small average radius to depth ratio, R/t, where R is the average radius of the beam and t is the difference between the inside and outside radius. Results of the analysis are in the form of stresses and displacements, and they are compared to both mechanics of materials and numerical solutions obtained using finite element analysis.

  6. The effects of x-ray beam hardening on detective quantum efficiency and radiation dose.

    PubMed

    Wong, Molly Donovan; Wu, Xizeng; Liu, Hong

    2011-01-01

    The goal of this preliminary study was to investigate the effects of x-ray beam hardening on the detective quantum efficiency (DQE) and the radiation dose of an inline x-ray imaging system. The ability to decrease the risk of harmful radiation to the patient without compromising the detection capability would more effectively balance the tradeoff between image quality and radiation dose, and therefore benefit the fields of diagnostic x-ray imaging, especially mammography. The DQE and the average glandular dose were both calculated under the same experimental conditions for a range of beam hardening levels, corresponding to no added beam hardening and two thicknesses each of Rhodium (Rh) and Molybdenum (Mo) filters. The dose calculation results demonstrate a reduction of 15% to 24% for the range of beam hardening levels. The comparison of all quantities comprising the DQE exhibit very close correlation between the results obtained without added beam hardening to the results corresponding to the range of beam hardening levels. For the specific experimental conditions utilized in this preliminary study, the results are an indication that the use of beam hardening holds the potential to reduce the radiation dose without decreasing the performance of the system. Future studies will seek to apply this method in a clinical environment and perform a comprehensive image quality evaluation, in an effort to further evaluate the potential of beam hardening to balance the tradeoff between dose and image quality.

  7. Quantum coherent tractor beam effect for atoms trapped near a nanowaveguide.

    PubMed

    Sadgrove, Mark; Wimberger, Sandro; Nic Chormaic, Síle

    2016-07-21

    We propose several schemes to realize a tractor beam effect for ultracold atoms in the vicinity of a few-mode nanowaveguide. Atoms trapped near the waveguide are transported in a direction opposite to the guided mode propagation direction. We analyse three specific examples for ultracold (23)Na atoms trapped near a specific nanowaveguide (i.e. an optical nanofibre): (i) a conveyor belt-type tractor beam effect, (ii) an accelerator tractor beam effect, and (iii) a quantum coherent tractor beam effect, all of which can effectively pull atoms along the nanofibre toward the light source. This technique provides a new tool for controlling the motion of particles near nanowaveguides with potential applications in the study of particle transport and binding as well as atom interferometry.

  8. Quantum coherent tractor beam effect for atoms trapped near a nanowaveguide

    PubMed Central

    Sadgrove, Mark; Wimberger, Sandro; Nic Chormaic, Síle

    2016-01-01

    We propose several schemes to realize a tractor beam effect for ultracold atoms in the vicinity of a few-mode nanowaveguide. Atoms trapped near the waveguide are transported in a direction opposite to the guided mode propagation direction. We analyse three specific examples for ultracold 23Na atoms trapped near a specific nanowaveguide (i.e. an optical nanofibre): (i) a conveyor belt-type tractor beam effect, (ii) an accelerator tractor beam effect, and (iii) a quantum coherent tractor beam effect, all of which can effectively pull atoms along the nanofibre toward the light source. This technique provides a new tool for controlling the motion of particles near nanowaveguides with potential applications in the study of particle transport and binding as well as atom interferometry. PMID:27440516

  9. Quantum coherent tractor beam effect for atoms trapped near a nanowaveguide

    NASA Astrophysics Data System (ADS)

    Sadgrove, Mark; Wimberger, Sandro; Nic Chormaic, Síle

    2016-07-01

    We propose several schemes to realize a tractor beam effect for ultracold atoms in the vicinity of a few-mode nanowaveguide. Atoms trapped near the waveguide are transported in a direction opposite to the guided mode propagation direction. We analyse three specific examples for ultracold 23Na atoms trapped near a specific nanowaveguide (i.e. an optical nanofibre): (i) a conveyor belt-type tractor beam effect, (ii) an accelerator tractor beam effect, and (iii) a quantum coherent tractor beam effect, all of which can effectively pull atoms along the nanofibre toward the light source. This technique provides a new tool for controlling the motion of particles near nanowaveguides with potential applications in the study of particle transport and binding as well as atom interferometry.

  10. Effects of Electron Beam Loading on an Operating Piezoelectric Transformer

    DTIC Science & Technology

    2013-06-01

    The setup of the optical diagnostic that was used to measure the internal stress and electric field within the PT is shown in Figure 5. A helium ... neon (HeNe) laser with a wavelength of 632.8 nm was used as the light source. A linear polarizer was used to ensure that the beam was linearly

  11. Side effects of the Yuzpe regimen of emergency contraception and two modifications.

    PubMed

    Shochet, Tara; Blanchard, Kelly; King, Helen; Henchcliffe, Bridget; Hunt, Janice; McCaig, Chris; Weaver, Kate; Stirling, Alex; Glasier, Anna; Webb, Anne; Ellertson, Charlotte

    2004-04-01

    We investigated side effects after the standard Yuzpe regimen or two modifications: substituting norethindrone as the progestin or eliminating the second dose. We also examined the impact of taking either dose with food. Nearly two thirds of women reported at least one side effect, the majority of which were mild or moderate. Women in our study experienced more side effects after the second dose than after the first. Taking the first dose within 1 h of a meal or snack was associated with increased nausea and vomiting; taking the second dose within 1 h of a meal or snack was associated with decreased nausea and vomiting. A targeted approach to prophylactic antiemetic use could reduce the number of women given these drugs, and the number who experience unnecessary side effects. The impact of counseling on side effects should be further evaluated.

  12. CONTROL OF LASER RADIATION PARAMETERS: Gerchberg—Saxton algorithm: experimental realisation and modification for the problem of formation of multimode laser beams

    NASA Astrophysics Data System (ADS)

    Il'ina, I. V.; Cherezova, T. Yu; Kudryashov, A. V.

    2009-06-01

    An original method is proposed to calculate the formation of specified far-field intensity distributions by a bimorph mirror in the case of initial transverse-multimode beams. The method is based on the Gerchberg—Saxton algorithm with replacement of the phase function in the plane of the control element by a function that takes into account both the intensity and phase distributions of each mode. The numerical results on the formation of a beam with the third-order super-Gaussian intensity distribution from beams composed of two or four lowest transverse modes are discussed. The experimental results on using the conventional Gerchberg—Saxton algorithm to form a desired intensity distribution from single-mode laser beams using a liquid-crystal modulator are presented.

  13. Position-dependent performance of copper phthalocyanine based field-effect transistors by gold nanoparticles modification.

    PubMed

    Luo, Xiao; Li, Yao; Lv, Wenli; Zhao, Feiyu; Sun, Lei; Peng, Yingquan; Wen, Zhanwei; Zhong, Junkang; Zhang, Jianping

    2015-01-21

    A facile fabrication and characteristics of copper phthalocyanine (CuPc)-based organic field-effect transistor (OFET) using the gold nanoparticles (Au NPs) modification is reported, thereby achieving highly improved performance. The effect of Au NPs located at three different positions, that is, at the SiO2/CuPc interface (device B), embedding in the middle of CuPc layer (device C), and on the top of CuPc layer (device D), is investigated, and the results show that device D has the best performance. Compared with the device without Au NPs (reference device A), device D displays an improvement of field-effect mobility (μ(sat)) from 1.65 × 10(-3) to 5.51 × 10(-3) cm(2) V(-1) s(-1), and threshold voltage decreases from -23.24 to -16.12 V. Therefore, a strategy for the performance improvement of the CuPc-based OFET with large field-effect mobility and saturation drain current is developed, on the basis of the concept of nanoscale Au modification. The model of an additional electron transport channel formation by FET operation at the Au NPs/CuPc interface is therefore proposed to explain the observed performance improvement. Optimum CuPc thickness is confirmed to be about 50 nm in the present study. The device-to-device uniformity and time stability are discussed for future application.

  14. Effect of arginine modification on kidney brush-border-membrane transport activity.

    PubMed

    Strevey, J; Brunette, M G; Béliveau, R

    1984-11-01

    The effect of phenylglyoxylation on brush-border-membrane functions was studied with membrane vesicles from rat kidney cortex. Na+-gradient-dependent uptake of phosphate, glucose and alanine was inhibited by 65, 88 and 70% by pre-incubation of vesicles with 50 mM-phenylglyoxal for 2 min. The inhibition showed a dependency for alkaline pH. Borate co-operativity in butanedione inactivation was used to prove that inhibition was caused by arginine modification. Intravesicular volumes, alkaline phosphatase, aminopeptidase M and Na+-H+ exchange were not affected by phenylglyoxal treatment. Inhibition of phosphate uptake was studied in more detail and showed that the chemical modification introduced by phenylglyoxal inhibited the overshoot of phosphate uptake caused by the Na+ gradient, and decreased the apparent maximal velocity of the phosphate-transport system in its interaction with Na+. Phosphate uptake measured in the absence of Na+ was not affected by phenylglyoxal. Shunting of the transmembrane electrical potential with K+ and valinomycin had no effect on phenylglyoxal inhibition, proving that the alteration of transmembrane electrical potential could not be responsible for this effect. Phenylglyoxal had no ionophoric effect on the Na+ gradients studied (1-100 mM). Na+ efflux was also unaffected by phenylglyoxal treatment. Na+, harmaline and amiloride were ineffective in protecting against phenylglyoxal inhibition, suggesting that the site modified was not an Na+-binding site. These results indicate the involvement of highly reactive arginine residues in phosphate, glucose and alanine uptake.

  15. Effect of arginine modification on kidney brush-border-membrane transport activity.

    PubMed Central

    Strevey, J; Brunette, M G; Béliveau, R

    1984-01-01

    The effect of phenylglyoxylation on brush-border-membrane functions was studied with membrane vesicles from rat kidney cortex. Na+-gradient-dependent uptake of phosphate, glucose and alanine was inhibited by 65, 88 and 70% by pre-incubation of vesicles with 50 mM-phenylglyoxal for 2 min. The inhibition showed a dependency for alkaline pH. Borate co-operativity in butanedione inactivation was used to prove that inhibition was caused by arginine modification. Intravesicular volumes, alkaline phosphatase, aminopeptidase M and Na+-H+ exchange were not affected by phenylglyoxal treatment. Inhibition of phosphate uptake was studied in more detail and showed that the chemical modification introduced by phenylglyoxal inhibited the overshoot of phosphate uptake caused by the Na+ gradient, and decreased the apparent maximal velocity of the phosphate-transport system in its interaction with Na+. Phosphate uptake measured in the absence of Na+ was not affected by phenylglyoxal. Shunting of the transmembrane electrical potential with K+ and valinomycin had no effect on phenylglyoxal inhibition, proving that the alteration of transmembrane electrical potential could not be responsible for this effect. Phenylglyoxal had no ionophoric effect on the Na+ gradients studied (1-100 mM). Na+ efflux was also unaffected by phenylglyoxal treatment. Na+, harmaline and amiloride were ineffective in protecting against phenylglyoxal inhibition, suggesting that the site modified was not an Na+-binding site. These results indicate the involvement of highly reactive arginine residues in phosphate, glucose and alanine uptake. PMID:6508741

  16. Soil modification by invasive plants: Effects on native and invasive species of mixed-grass prairies

    USGS Publications Warehouse

    Jordan, N.R.; Larson, D.L.; Huerd, S.C.

    2008-01-01

    Invasive plants are capable of modifying attributes of soil to facilitate further invasion by conspecifics and other invasive species. We assessed this capability in three important plant invaders of grasslands in the Great Plains region of North America: leafy spurge (Euphorbia esula), smooth brome (Bromus inermis) and crested wheatgrass (Agropyron cristatum). In a glasshouse, these three invasives or a group of native species were grown separately through three cycles of growth and soil conditioning in both steam-pasteurized and non-pasteurized soils, after which we assessed seedling growth in these soils. Two of the three invasive species, Bromus and Agropyron, exhibited significant self-facilitation via soil modification. Bromus and Agropyron also had significant facilitative effects on other invasives via soil modification, while Euphorbia had significant antagonistic effects on the other invasives. Both Agropyron and Euphorbia consistently suppressed growth of two of three native forbs, while three native grasses were generally less affected. Almost all intra- and interspecific effects of invasive soil conditioning were dependent upon presence of soil biota from field sites where these species were successful invaders. Overall, these results suggest that that invasive modification of soil microbiota can facilitate plant invasion directly or via 'cross-facilitation' of other invasive species, and moreover has potential to impede restoration of native communities after removal of an invasive species. However, certain native species that are relatively insensitive to altered soil biota (as we observed in the case of the forb Linum lewisii and the native grasses), may be valuable as 'nurse'species in restoration efforts. ?? 2007 Springer Science+Business Media B.V.

  17. Meta-analysis of the effects of lifestyle modifications on coronary and carotid atherosclerotic burden.

    PubMed

    Jhamnani, Sunny; Patel, Dhavalkumar; Heimlich, Layla; King, Fred; Walitt, Brian; Lindsay, Joseph

    2015-01-15

    Lifestyle modifications are the crux of atherosclerotic disease management. The goal of this study was to determine the effectiveness of diet and exercise in decreasing coronary and carotid atherosclerotic burden. Randomized controlled trials examining the effects of intensive lifestyle measures on atherosclerotic progression in coronary and carotid arteries as measured by baseline and follow-up quantitative coronary angiogram and ultrasonographic carotid intimal-medial thickness (CIMT), respectively, were included. Studies were excluded if the intervention additionally included a medication. MEDLINE, EMBASE, CINAHL, Cochrane Controlled Trials Registers, reports, and abstracts from major cardiology meetings were searched by 2 researchers independently and verified by the primary investigator. Standardized mean difference (SMD) with 95% confidence intervals (CIs) was calculated using random-effects model. Publication bias and heterogeneity were assessed. Fourteen trials were included. Seven used quantitative coronary angiogram, and 7 used CIMT; 1,343 lesions in 340 patients in the coronary group and 919 patients in the carotid group were analyzed. Overall, lifestyle modifications were associated with a decrease in coronary atherosclerotic burden in percent stenosis by -0.34 (95% CI -0.48 to -0.21) SMD, with no significant publication bias and heterogeneity (p = 0.21, I(2) = 28.25). Similarly, in the carotids, there was a decrease in the CIMT, in millimeter, by -0.21 (95% CI -0.36 to -0.05) SMD and by -0.13 (95% CI -0.25 to -0.02) SMD, before and after accounting for publication bias and heterogeneity (p = 0.13, I(2) = 39.91; p = 0.54, I(2) = 0), respectively. In conclusion, these results suggest that intensive lifestyle modifications are associated with a decrease in coronary and carotid atherosclerotic burden.

  18. A screen of chemical modifications identifies position-specific modification by UNA to most potently reduce siRNA off-target effects

    PubMed Central

    Bramsen, Jesper B.; Pakula, Malgorzata M.; Hansen, Thomas B.; Bus, Claus; Langkjær, Niels; Odadzic, Dalibor; Smicius, Romualdas; Wengel, Suzy L.; Chattopadhyaya, Jyoti; Engels, Joachim W.; Herdewijn, Piet; Wengel, Jesper; Kjems, Jørgen

    2010-01-01

    Small interfering RNAs (siRNAs) are now established as the preferred tool to inhibit gene function in mammalian cells yet trigger unintended gene silencing due to their inherent miRNA-like behavior. Such off-target effects are primarily mediated by the sequence-specific interaction between the siRNA seed regions (position 2–8 of either siRNA strand counting from the 5′-end) and complementary sequences in the 3′UTR of (off-) targets. It was previously shown that chemical modification of siRNAs can reduce off-targeting but only very few modifications have been tested leaving more to be identified. Here we developed a luciferase reporter-based assay suitable to monitor siRNA off-targeting in a high throughput manner using stable cell lines. We investigated the impact of chemically modifying single nucleotide positions within the siRNA seed on siRNA function and off-targeting using 10 different types of chemical modifications, three different target sequences and three siRNA concentrations. We found several differently modified siRNAs to exercise reduced off-targeting yet incorporation of the strongly destabilizing unlocked nucleic acid (UNA) modification into position 7 of the siRNA most potently reduced off-targeting for all tested sequences. Notably, such position-specific destabilization of siRNA–target interactions did not significantly reduce siRNA potency and is therefore well suited for future siRNA designs especially for applications in vivo where siRNA concentrations, expectedly, will be low. PMID:20453030

  19. Estimating the effects of transcription factors binding and histone modifications on gene expression levels in human cells

    PubMed Central

    Zhang, Lu-Qiang; Li, Qian-Zhong

    2017-01-01

    Transcription factors and histone modifications are vital for the regulation of gene expression. Hence, to estimate the effects of transcription factors binding and histone modifications on gene expression, we construct a statistical model for the genome-wide 15 transcription factors binding data, 10 histone modifications profiles and DNase-I hypersensitivity data in three mammalian. Remarkably, our results show POLR2A and H3K36me3 can highly and consistently predict gene expression in three cell lines. And H3K4me3, H3K27me3 and H3K9ac are more reliable predictors than other histone modifications in human embryonic stem cells. Moreover, genome-wide statistical redundancies exist within and between transcription factors and histone modifications, and these phenomena may be caused by the regulation mechanism. In further study, we find that even though transcription factors and histone modifications offer similar effects on expression levels of genome-wide genes, the effects of transcription factors and histone modifications on predictive abilities are different for genes in independent biological processes. PMID:28454114

  20. Effects on the photon beam from an electromagnetic array used for patient localization and tumor tracking.

    PubMed

    Zou, Wei; Betancourt, Ricardo; Yin, Lingshu; Metz, James; Avery, Stephen; Kassaee, Alireza

    2013-05-06

    One of the main components in a Calypso 4D localization and tracking system is an electromagnetic array placed above patients that is used for target monitoring during radiation treatment. The beam attenuation and beam spoiling properties of the Calypso electromagnetic array at various beam angles were investigated. Measurements were performed on a Varian Clinac iX linear accelerator with 6 MV and 15 MV photon beams. The narrow beam attenuation properties were measured under a field size of 1 cm × 1 cm, with a photon diode placed in a cylindrical graphite buildup cap. The broad beam attenuation properties were measured under a field size of 10 cm × 10 cm, with a 0.6 cc cylindrical Farmer chamber placed in a polystyrene buildup cap. Beam spoiling properties of the array were studied by measuring depth-dose change from the array under a field size of 10 cm × 10 cm in a water-equivalent plastic phantom with an embedded Markus parallel plate chamber. Change in depth doses were measured with the array placed at distances of 2, 5, and 10 cm from the phantom surface. Narrow beam attenuation and broad beam attenuation from the array were found to be less than 2%-3% for both 6 MV and 15 MV beams at angles less than 40°, and were more pronounced at more oblique angles. Spoiling effects are appreciable at beam buildup region, but are insignificant at depths beyond dmax. Dose measurements in a QA phantom using patient IMRT and VMAT treatment plans were shown to have less than 2.5% dose difference with the Calypso array. The results indicate that the dose difference due to the placement of Calypso array is clinically insignificant.

  1. Glycation of antibodies: Modification, methods and potential effects on biological functions.

    PubMed

    Wei, Bingchuan; Berning, Kelsey; Quan, Cynthia; Zhang, Yonghua Taylor

    2017-03-08

    Glycation is an important protein modification that could potentially affect bioactivity and molecular stability, and glycation of therapeutic proteins such as monoclonal antibodies should be well characterized. Glycated protein could undergo further degradation into advance glycation end (AGE) products. Here, we review the root cause of glycation during the manufacturing, storage and in vivo circulation of therapeutic antibodies, and the current analytical methods used to detect and characterize glycation and AGEs, including boronate affinity chromatography, charge-based methods, liquid chromatography-mass spectrometry and colorimetric assay. The biological effects of therapeutic protein glycation and AGEs, which ranged from no affect to loss of activity, are also discussed.

  2. Effect of low dose electron beam irradiation on the alteration layer formed during nuclear glass leaching

    NASA Astrophysics Data System (ADS)

    Mougnaud, S.; Tribet, M.; Renault, J.-P.; Jollivet, P.; Panczer, G.; Charpentier, T.; Jégou, C.

    2016-12-01

    This investigation concerns borosilicate glass leaching mechanisms and the evolution of alteration layer under electron beam irradiation. A simple glass doped with rare earth elements was selected in order to access mechanistic and structural information and better evaluate the effects of irradiation. It was fully leached in initially pure water at 90 °C and at high glass surface area to solution volume ratio (S/V = 20 000 m-1) in static conditions. Under these conditions, the system quickly reaches the residual alteration rate regime. A small particle size fraction (2-5 μm) was sampled in order to obtain a fairly homogeneous altered material enabling the use of bulk characterization methods. External irradiations with 10 MeV electrons up to a dose of 10 MGy were performed either before or after leaching, to investigate respectively the effect of initial glass irradiation on its alteration behavior and the irradiation stability of the alteration layer. Glass dissolution rate was analyzed by regular leachate samplings and the alteration layer structure was characterized by Raman, luminescence (continuous or time-resolved), and 29Si MAS NMR and EPR spectroscopy. It was shown that the small initial glass evolutions under irradiation did not induce any modification of the leaching kinetic nor of the structure of the alteration layer. The alteration process seemed to "smooth over" the created defects. Otherwise, the alteration layer and initial glass appeared to have different behaviors under irradiation. No Eu3+ reduction was detected in the alteration layer after irradiation and the defect creation efficiency was much lower than for initial glass. This can possibly be explained by the protective role of pore water contained in the altered material (∼20%). Moreover, a slight depolymerization of the silicon network of the altered glass under irradiation with electrons was evidenced, whereas in the initial glass it typically repolymerizes.

  3. Investigation of Weakly Relativistic Ponderomotive Effects on Self-Focusing During Interaction of High Power Elliptical Laser Beam with Plasma

    NASA Astrophysics Data System (ADS)

    Walia, Keshav; Tripathi, Deepak; Tyagi, Yachna

    2017-08-01

    This paper presents an investigation of weakly relativistic ponderomotive effects on self-focusing during interaction of high power elliptical laser beam with plasma. The nonlinear differential equations for the beam width parameters of elliptical laser beam have set up by using Wentzal-Krammers-Brillouin (WKB) and paraxial approximations. These equations have been solved numerically by using fourth order Runge-Kutta method to study the variation of these beam width parameters against normalized distance of propagation. Effects of variation in laser beam intensity, plasma density and electron temperature on the beam width parameters are also analyzed.

  4. Cooperative effect of ultraviolet and near-infrared beams in laser-induced condensation

    SciTech Connect

    Matthews, M.; Henin, S.; Pomel, F.; Kasparian, J.; Wolf, J.-P.; Théberge, F.; Daigle, J.-F.; Lassonde, P.; Kieffer, J.-C.

    2013-12-23

    We demonstrate the cooperative effect of near infrared (NIR) and ultraviolet (UV) beams on laser-induced condensation. Launching a UV laser after a NIR pulse yields up to a 5-fold increase in the production of nanoparticles (25–300 nm) as compared to a single NIR beam. This cooperative effect exceeds the sum of those from the individual beams and occurs for delays up to 1 μs. We attribute it to the UV photolysis of ozone created by the NIR pulses. The resulting OH radicals oxidize NO{sub 2} and volatile organic compounds, producing condensable species.

  5. Interferometric Measurement for Improved Understanding of Boundary Effects in Micromachined Beams

    SciTech Connect

    Bitsie, Fernando; Jensen, Brian D.; de Boer, Maarten

    1999-07-15

    Micromachined beams are commonly used to measure material properties in MEMS. Such measurements are complicated by the fact that boundary effects at the ends of the beams have a significant effect on the properties being measured. In an effort to improve the accuracy and resolution of such measurements, we are conducting a study of support post compliance in cantilever and fixed-fixed beams. Three different support post designs have been analyzed by finite element modeling. The results are then compared to measurements made on actual devices using interferometry. Using this technique, the accuracy of measurements of Young's modulus has been improved. Continuing work will also improve the measurement of residual stress.

  6. Compensation of Beam Line Polarizing Effects at UE112 of BESSY II

    SciTech Connect

    Bahrdt, J.; Follath, R.; Frentrup, W.; Gaupp, A.; Scheer, M.

    2010-06-23

    Reflections in synchrotron radiation beam lines tend to change the state of polarization of the radiation. This effect is more pronounced for steep angle of incidence, i.e. at low photon energy (say below 100 eV) beam lines. The APPLE II undulator UE112 at BESSY has all four magnetic rows shiftable and thus generates any state of polarization. To provide any intended polarization state at the sample we perform polarization measurements based on simple and fast linear polarization analysis that together with calculations of the undulator radiation predicts undulator settings that cancel beam line polarization effects.

  7. Thermal effects in high power cavities for photoneutralization of D{sup −} beams in future neutral beam injectors

    SciTech Connect

    Fiorucci, Donatella; Feng, Jiatai; Pichot, Mikhaël; Chaibi, Walid

    2015-04-08

    Photoneutralization may represent a key issue in the neutral beam injectors for future fusion reactors. In fact, photodetachment based neutralization combined with an energy recovery system increase the injector overall efficiency up to 60%. This is the SIPHORE injector concept in which photoneutralization is realized in a refolded cavity [1]. However, about 1 W of the several megaWatts intracavity power is absorbed by the mirrors coatings and gives rise to important thermoelastic distortions. This is expected to change the optical behavior of the mirrors and reduce the enhancement factor of the cavity. In this paper, we estimate these effects and we propose a thermal system to compensate it.

  8. Effects of coherence on anisotropic electromagnetic Gaussian-Schell model beams on propagation.

    PubMed

    Wang, Hua; Wang, Xiangzhao; Zeng, Aijun; Yang, Kun

    2007-08-01

    An analytical formula for the cross-spectral density matrix of the electric field of anisotropic electromagnetic Gaussian-Schell model beams propagating in free space is derived by using a tensor method. The effects of coherence on those beams are studied. It is shown that two anisotropic stochastic electromagnetic beams that propagate from the source plane z=0 into the half-space z>0 may have different beam shapes (i.e., spectral density) and states of polarization in the half-space, even though they have the same beam shape and states of polarization in the source plane. This fact is due to a difference in the coherence properties of the field in the source plane.

  9. Potential-Well Distortion, Microwave Instability, and Their Effects with Colliding Beams at KEKB

    SciTech Connect

    Cai, Yunhai; Flanagan, J.; Fukuma, H.; Funakoshi, Y.; Ieiri, T.; Ohmi, K.; Oide, K.; Suetsugu, Y.; Rorie, Jamal; /Hawaii U.

    2009-04-01

    Microwave instability in the Low Energy Ring of KEKB was studied using a broadband impedance model. The model gave excellent descriptions of longitudinal dynamics for both positive and negative momentum compactions. Moreover, it predicted that the threshold of microwave instability was a factor of two lower than the machine nominal operating bunch current. The prediction was confirmed by a measurement using the Belle detector. Furthermore, we integrated the longitudinal wakefield into the beam-beam simulation and applied it to study the combined effects in KEKB. As a result, the beam-beam simulation became truly three-dimensional with emittance growth in all three dimensions simultaneously as the beam currents increase. In addition, an observed mystery of asymmetry in the horizontal scan could also be explained by our simulations.

  10. Monitoring electron-beam irradiation effects on graphenes by temporal Auger electron spectroscopy.

    PubMed

    Xu, Mingsheng; Fujita, Daisuke; Hanagata, Nobutaka

    2010-07-02

    Because of its unique electronic transport properties, graphene has attracted an enormous amount of interest recently. By using standard Auger electron spectroscopy and Raman spectroscopy, we have studied electron-beam irradiation effects on graphene damage. We have shown that irradiation with an electron-beam can selectively remove graphene layers and induce chemical reactions, as well as possible structural transformations. We have also demonstrated the dependence of damage in graphene on electron-beam dose. Our work provides ideas on how to optimize the experimental conditions for graphene characterization and device fabrication. The results throw light on how energy transfer from the electron beam to graphene layers leads to the removal of carbon atoms from graphene layers and on the possibility of using electron-beam irradiation to locally induce chemical reactions in a controlled manner.

  11. Effect of induced charge at boundaries on transverse dynamics of a space-charge-dominated beam

    SciTech Connect

    Celata, C.M.; Haber, I.; Laslett, L.J.; Smith, L.; Tiefenback, M.G.

    1985-05-01

    A particle simulation code has been used to study the effect of transverse beam dynamics of charge induced on focusing electrodes. A linear transport system was assumed. The initial particle distribution was taken to be that of a uniform elliptical beam with a Gaussian velocity distribution. For misaligned, highly space-charge-dominated beams (betatron phase advance per lattice period less than or equal to 10/sup 0/), a large oscillation of the rms emittance occurred in a beat pattern. Linearized Vlasov analysis shows the oscillation to be a sextupole oscillation, driven by the beam coherent betatron motion. Emittance growth accompanied the oscillation. Preliminary experimental results from the Single Beam Transport Experiment (SBTE) are consistent with the code results. Addition of a dodecapole nonlinearity to the computational focusing field greatly reduces the oscillation amplitude.

  12. [Effects in eyes, caused by laser rays emitted by laser-beam projectors].

    PubMed

    Mal'kova, N Iu; Ushkova, I N; Romanenko, E I

    2014-01-01

    Health assessment of laser radiation emitted by laser-beam projectors used for laser shows in concert and theatrical events was carried out. The effects of various laser radiation wavelengths and regimes on functional state of eye retina were studied.

  13. The effects of x-ray beam hardening on detective quantum efficiency and radiation dose

    PubMed Central

    Wong, Molly Donovan; Wu, Xizeng; Liu, Hong

    2011-01-01

    The goal of this preliminary study was to investigate the effects of x-ray beam hardening on the detective quantum efficiency (DQE) and the radiation dose of an inline x-ray imaging system. The DQE and the average glandular dose were both calculated under the same experimental conditions for a range of beam hardening levels, corresponding to no added beam hardening and two thicknesses each of Rhodium (Rh) and Molybdenum (Mo) filters. The dose calculation results demonstrate a reduction of 15% to 24% for the range of beam hardening levels. The comparison of all quantities comprising the DQE exhibit very close correlation between the results obtained without added beam hardening to the results corresponding to the range of beam hardening levels. For the specific experimental conditions utilized in this preliminary study, the results are an indication that the use of beam hardening holds the potential to reduce the radiation dose without decreasing the performance of the system. Future studies will seek to apply this method in a clinical environment and perform a comprehensive image quality evaluation, in an effort to further evaluate the potential of beam hardening to balance the tradeoff between dose and image quality. PMID:25214383

  14. Quantification of Treatment Effect Modification on Both an Additive and Multiplicative Scale.

    PubMed

    Girerd, Nicolas; Rabilloud, Muriel; Pibarot, Philippe; Mathieu, Patrick; Roy, Pascal

    2016-01-01

    In both observational and randomized studies, associations with overall survival are by and large assessed on a multiplicative scale using the Cox model. However, clinicians and clinical researchers have an ardent interest in assessing absolute benefit associated with treatments. In older patients, some studies have reported lower relative treatment effect, which might translate into similar or even greater absolute treatment effect given their high baseline hazard for clinical events. The effect of treatment and the effect modification of treatment were respectively assessed using a multiplicative and an additive hazard model in an analysis adjusted for propensity score in the context of coronary surgery. The multiplicative model yielded a lower relative hazard reduction with bilateral internal thoracic artery grafting in older patients (Hazard ratio for interaction/year = 1.03, 95%CI: 1.00 to 1.06, p = 0.05) whereas the additive model reported a similar absolute hazard reduction with increasing age (Delta for interaction/year = 0.10, 95%CI: -0.27 to 0.46, p = 0.61). The number needed to treat derived from the propensity score-adjusted multiplicative model was remarkably similar at the end of the follow-up in patients aged < = 60 and in patients >70. The present example demonstrates that a lower treatment effect in older patients on a relative scale can conversely translate into a similar treatment effect on an additive scale due to large baseline hazard differences. Importantly, absolute risk reduction, either crude or adjusted, can be calculated from multiplicative survival models. We advocate for a wider use of the absolute scale, especially using additive hazard models, to assess treatment effect and treatment effect modification.

  15. The Effects of Landscape Modifications on the Long-Term Persistence of Animal Populations

    PubMed Central

    Nabe-Nielsen, Jacob; Sibly, Richard M.; Forchhammer, Mads C.; Forbes, Valery E.; Topping, Christopher J.

    2010-01-01

    Background The effects of landscape modifications on the long-term persistence of wild animal populations is of crucial importance to wildlife managers and conservation biologists, but obtaining experimental evidence using real landscapes is usually impossible. To circumvent this problem we used individual-based models (IBMs) of interacting animals in experimental modifications of a real Danish landscape. The models incorporate as much as possible of the behaviour and ecology of four species with contrasting life-history characteristics: skylark (Alauda arvensis), vole (Microtus agrestis), a ground beetle (Bembidion lampros) and a linyphiid spider (Erigone atra). This allows us to quantify the population implications of experimental modifications of landscape configuration and composition. Methodology/Principal Findings Starting with a real agricultural landscape, we progressively reduced landscape complexity by (i) homogenizing habitat patch shapes, (ii) randomizing the locations of the patches, and (iii) randomizing the size of the patches. The first two steps increased landscape fragmentation. We assessed the effects of these manipulations on the long-term persistence of animal populations by measuring equilibrium population sizes and time to recovery after disturbance. Patch rearrangement and the presence of corridors had a large effect on the population dynamics of species whose local success depends on the surrounding terrain. Landscape modifications that reduced population sizes increased recovery times in the short-dispersing species, making small populations vulnerable to increasing disturbance. The species that were most strongly affected by large disturbances fluctuated little in population sizes in years when no perturbations took place. Significance Traditional approaches to the management and conservation of populations use either classical methods of population analysis, which fail to adequately account for the spatial configurations of landscapes

  16. Effect of ion compensation of the beam space charge on gyrotron operation

    SciTech Connect

    Fokin, A. P.; Glyavin, M. Yu.; Nusinovich, G. S.

    2015-04-15

    In gyrotrons, the coherent radiation of electromagnetic waves takes place when the cyclotron resonance condition between the wave frequency and the electron cyclotron frequency or its harmonic holds. The voltage depression caused by the beam space charge field changes the relativistic cyclotron frequency and, hence, can play an important role in the beam-wave interaction process. In long pulse and continuous-wave regimes, the beam space charge field can be partially compensated by the ions, which appear due to the beam impact ionization of neutral molecules of residual gases in the interaction space. In the present paper, the role of this ion compensation of the beam space charge on the interaction efficiency is analyzed. We also analyze the effect of the electron velocity spread on the limiting currents and discuss some effects restricting the ion-to-beam electron density ratio in the saturation stage. It is shown that the effect of the ion compensation on the voltage depression caused by the beam space charge field can cause significant changes in the efficiency of gyrotron operation and, in some cases, even result in the break of oscillations.

  17. THE EFFECT OF NONLINEAR LANDAU DAMPING ON ULTRARELATIVISTIC BEAM PLASMA INSTABILITIES

    SciTech Connect

    Chang, Philip; Lamberts, Astrid; Broderick, Avery E.; Shalaby, Mohamad; Pfrommer, Christoph; Puchwein, Ewald

    2014-12-20

    Very high energy gamma-rays from extragalactic sources produce pairs from the extragalactic background light, yielding an electron-positron pair beam. This pair beam is unstable to various plasma instabilities, especially the ''oblique'' instability, which can be the dominant cooling mechanism for the beam. However, recently, it has been claimed that nonlinear Landau damping renders it physically irrelevant by reducing the effective damping rate to a low level. Here we show with numerical calculations that the effective damping rate is 8 × 10{sup –4} the growth rate of the linear instability, which is sufficient for the ''oblique'' instability to be the dominant cooling mechanism of these pair beams. In particular, we show that previous estimates of this rate ignored the exponential cutoff in the scattering amplitude at large wave numbers and assumed that the damping of scattered waves entirely depends on collisions, ignoring collisionless processes. We find that the total wave energy eventually grows to approximate equipartition with the beam by increasingly depositing energy into long-wavelength modes. As we have not included the effect of nonlinear wave-wave interactions on these long-wavelength modes, this scenario represents the ''worst case'' scenario for the oblique instability. As it continues to drain energy from the beam at a faster rate than other processes, we conclude that the ''oblique'' instability is sufficiently strong to make it the physically dominant cooling mechanism for high-energy pair beams in the intergalactic medium.

  18. BEAM-BEAM SIMULATIONS FOR DOUBLE-GAUSSIAN BEAMS.

    SciTech Connect

    MONTAG, C.; MALITSKY, N.; BEN-ZVI, I.; LITVINENKO, V.

    2005-05-16

    Electron cooling together with intra-beam scattering results in a transverse distribution that can best be described by a sum of two gaussians, one for the high-density core and one for the tails of the distribution. Simulation studies are being performed to understand the beam-beam interaction of these double-gaussian beams. Here we report the effect of low-frequency random tune modulations on diffusion in double-gaussian beams and compare the effects to those in beam-beam interactions with regular gaussian beams and identical tune shift parameters.

  19. The Effects of Fiber Surface Modification and Thermal Aging on Composite Toughness and Its Measurement

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.; Madhukar, Madhu; Papadopolous, Demetrios S.; Inghram, Linda; Mccorkle, Linda

    1995-01-01

    A detailed experimental study was conducted to establish the structure-property relationships between elevated temperature aging and fiber-matrix bonding, Mode 2 interlaminar fracture toughness, and failure modes of carbon fiber/PMR-15 composites. The fiber-matrix adhesion was varied by using carbon fibers with different surface treatments. Short beam shear tests were used to quantify the interfacial shear strength afforded by the use of the different fiber surface treatments. The results of the short beam shear tests showed that, for times up to 1000 hr, the aging process caused no changes in the bulk of the three composite materials that would degrade the shear properties of the material. Comparisons between the interlaminar shear strengths (ILSS) measured by the short beam shear tests and the GIIC test results, as measured by the ENF test, indicated that the differences in the surface treatments significantly affected the fracture properties while the effect of the aging process was probably limited to changes at the starter crack tip. The fracture properties changed due to a shift in the fracture from an interfacial failure to a failure within the matrix when the fiber was changed from AU-4 to AS-4 or AS-4G. There appears to be an effect of the fiber/matrix bonding on the thermo-oxidative stability of the composites that were tested. The low bonding afforded by the AU 1 fiber resulted in weight losses about twice those experienced by the AS 1 reinforced composites, the ones with the best TOS.

  20. The Effects of Fiber Surface Modification and Thermal Aging on Composite Toughness And its Measurement

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.; Madhukar, Madhu; Papadopoulos, Demetrios; Inghram, Linda; McCorkle, Linda

    1997-01-01

    A detailed experimental study was conducted to establish the structure-property relationships between elevated temperature aging and (I) fiber-matrix bonding, (2) Mode II interlaminar fracture toughness, and (3) failure modes of carbon fiber/PMR-15 composites. The fiber-matrix adhesion was varied by using carbon fibers with different surface treatments. Short beam shear tests were used to quantify the interfacial shear strength afforded by the use of the different fiber surface treatments. The results of the short beam shear tests definitely showed that, for aging times up to 1000 hr, the aging process caused no observable changes in the bulk of the three composite materials that---would degrade the shear properties of the material. Comparisons between the interlaminar shear strength (ILSS) measured by the short beam shear tests and the GII c test results, as measured by the ENF test, indicated that the differences in the surface treatments significantly affected the fracture properties while the effect of the aging process was probably limited to changes at the starter crack tip. The fracture properties changed due to a shift in the fracture from an interfacial failure to a failure within the matrix when the fiber was changed from AU-4 to AS-4 or AS-4G. There appears to be an effect of the fiber/matrix bonding on the thermo-oxidative stability of the composites that were tested. The low bonding afforded by the AU-4 fiber resulted in weight losses about twice those experienced by the AS-4 reinforced composites, the ones with the best TOS.