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All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Special features of single-particle proton spectra of nickel, zinc, and germanium isotopes in the vicinity of the proton drip line

The single-particle proton spectra of the neutron-deficient isotopes {sup 50,52}Ni, {sup 56,58,60,62}Zn, and {sup 60,62,64}Ge were calculated on the basis of the dispersive optical model whose parameters were extrapolated from the region of stable isotopes. The resulting parameter values lead to agreement between the total number of protons in bound states and the charge number Z of the respective nucleus. The results of the calculations are indicative of a weakly magic character of the {sup 58}Zn nucleus, which has a traditional magic number of N = 28 and a nearly magic number of Z = 30, and the {sup 64}Ge nucleus, for which N = Z = 32.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

Nuclear Data Sheets for A = 54

The 2005 evaluation for A=54 (2006Hu08) has been updated. Detailed experimental nuclear structure data and decay data for all nuclei with mass chain A=54 are presented in this current evaluation. The new data and information are given in following datasets: {sup 54}Ca: {sup 9}Be({sup 76}Ge, X) and Be({sup 55}Sc, p), ({sup 56}Ti, 2p) {sup 54}Sc: {sup 54}Ca β{sup −} decay and {sup 54}Sc IT decay {sup 54}Ti: {sup 54}Sc β{sup −} decay {sup 54}Cr: {sup 54}Mn ε decay, {sup 56}Fe(μ, nupng), and {sup 238}U({sup 64}Ni, Xγ) {sup 54}Mn: {sup 51}V({sup 20}Ne, Xγ), {sup 55}Mn(p, pn), and {sup 56}Fe(μ, nu2ng) {sup 54}Fe: {sup 58}Ni α decay, {sup 9}Be({sup 55}Co, Xγ), {sup 54}Fe(e, e'), {sup 54}Fe(p, p'), and Coulomb Excitation {sup 54}Co: {sup 54}Ni ε decay, {sup 55}Cu εp decay, {sup 28}Si({sup 32}S, αpnγ), {sup 54}Fe(p,n), and {sup 54}Fe({sup 3}He, t) {sup 54}Ni: {sup 54}Ni IT decay, {sup 55}Zn εp decay, {sup 9}Be({sup 55}Ni, Xγ), and {sup 24}Mg({sup 32}S, Xγ) {sup 54}Zn: Ni({sup 58}Ni, X)

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

The ({sup 18}O, {sup 16}O) reaction as a probe for nuclear spectroscopy

The response of nuclei to the ({sup 18}O, {sup 16}O) two-neutron transfer reaction at 84 MeV incident energy has been systematically studied at the Catania INFN-LNS laboratory. The experiments were performed using several solid targets from light ({sup 9}Be, {sup 11}B, {sup 12,13}C, {sup 16}O, {sup 28}Si) to heavy ones ({sup 58,64}Ni, {sup 120}Sn, {sup 208}Pb). The {sup 16}O ejectiles were detected at forward angles by the MAGNEX magnetic spectrometer. Exploiting the large momentum acceptance (−10%, +14%) and solid angle (50 msr) of the spectrometer, energy spectra were obtained with a relevant yield up to about 20 MeV excitation energy. The application of the powerful trajectory reconstruction technique did allow to get energy spectra with energy resolution of about 150 keV and angular distributions with angular resolution better than 0.3°. A common feature observed with light nuclei is the appearance of unknown resonant structures at high excitation energy. The strong population of these latter together with the measured width can reveal the excitation of a collective mode connected with the transfer of a pair.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Isotope anomalies in the FE-group elements in meteorites and connections to nucleosynthesis in AGB stars

We study the effects of neutron captures in AGB stars on “Fe-group” elements, with an emphasis on Cr, Fe, and Ni. These elements show anomalies in {sup 54}Cr, {sup 58}Fe, and {sup 64}Ni in solar system materials, which are commonly attributed to supernovae (SNe). However, as large fractions of the interstellar medium (ISM) were reprocessed in AGB stars, these elements were reprocessed, too. We calculate the effects of such reprocessing on Cr, Fe, and Ni through 1.5 M{sub ⊙} and 3 M{sub ⊙} AGB models, adopting solar and 1/3 solar metallicities. All cases produce excesses of {sup 54}Cr, {sup 58}Fe, and {sup 64}Ni, while the other isotopes are little altered; hence, the observations may be explained by AGB processing. The results are robust and not dependent on the detailed initial isotopic composition. Consequences for other “Fe group” elements are then explored. They include {sup 50}Ti excesses and some production of {sup 46,47,49}Ti. In many circumstellar condensates, Ti quantitatively reflects these effects of AGB neutron captures. Scatter in the data results from small variations (granularity) in the isotopic composition of the local ISM. For Si, the main effects are instead due to variations in the local ISM from different SN sources. The problem of Ca is discussed, particularly with regard to {sup 48}Ca. The measured data are usually represented assuming terrestrial values for {sup 42}Ca/{sup 44}Ca. Materials processed in AGB stars or sources with variable initial {sup 42}Ca/{sup 44}Ca ratios can give apparent {sup 48}Ca excesses/deficiencies, attributed to SNe. The broader issue of galactic chemical evolution is also discussed in view of the isotopic granularity in the ISM.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Universal Surface Engineering of Transition Metals for Superior Electrocatalytic Hydrogen Evolution in Neutral Water

The development of low-cost hybrid water splitting-biosynthetic systems that mimic natural photosynthesis to achieve solar-to-chemical conversion is of great promise for future energy demands. However, it is often limited by the kinetically sluggish hydrogen evolution reaction (HER) on the surface of nonprecious transition metal catalysts in neutral media. It is thus highly desirable to rationally tailor the reaction interface to boost the neutral HER catalytic kinetics. Herein, we report a general surface nitrogen modification of diverse transition metals (e.g., iron, cobalt, nickel, copper, and nickel-cobalt alloy), accomplished by a facile low-temperature ammonium carbonate treatment, for significantly improved hydrogen generation from neutral water. Various physicochemical characterization techniques including synchrotron X-ray absorption spectroscopy (XAS) and theory modeling demonstrate that the surface nitrogen modification does not change the chemical composition of the underlying transition metals. Notably, the resulting nitrogen-modified nickel framework (N-Ni) exhibits an extremely low overpotential of 64 mV at 10 mA cm -2 , which is, to our knowledge, the best among those nonprecious electrocatalysts reported for hydrogen evolution at pH 7. Our combined experimental results and density functional theory (DFT) calculations reveal that the surface electron-rich nitrogen simultaneously facilitates the initial adsorption of water via the electron-deficient H atom and the subsequent dissociation of the electron-rich HO-H bond via H transfer to N on the nickel surface, beneficial to the overall hydrogen evolution process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Iron and nickel isotope compositions of presolar silicon carbide grains from supernovae

Here we report the carbon, silicon, iron, and nickel isotope compositions of twenty-five presolar SiC grains of mostly supernova (SN) origin. The iron and nickel isotope compositions were measured with the new Chicago Instrument for Laser Ionization, CHILI, which allows the analysis of all iron and nickel isotopes without the isobaric interferences that plagued previous measurements with the NanoSIMS. Despite terrestrial iron and nickel contamination, significant isotopic anomalies in 54 Fe/ 56 Fe, 57 Fe/ 56 Fe, 60 Ni/ 58 Ni, 61 Ni/ 58 Ni, 62 Ni/ 58 Ni, and 64 Ni/ 58 Ni were detected in nine SN grains (of type X). Combined multi-isotope data of three grains with the largest nickel isotope anomalies (>100% or <-100% in at least one isotope ratio, when expressed as deviation from the solar value) are compared with the predictions of two SN models, one with and one without hydrogen ingestion in the He shell prior to SN explosion. One grain's carbon-silicon-iron-nickel isotope composition is consistent with the prediction of the model without hydrogen ingestion, whereas the other two grains' isotope anomalies could not be reproduced using either SN models. The discrepancies between the measured isotope compositions and model predictions may indicate element fractionation in the SN ejecta prior to or during grain condensation, and reiterate the need for three-dimensional SN models.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

SU-E-I-62: Assessing Radiation Dose Reduction and CT Image Optimization Through the Measurement and Analysis of the Detector Quantum Efficiency (DQE) of CT Images Using Different Beam Hardening Filters

Purpose: Reducing patient dose while maintaining (or even improving) image quality is one of the foremost goals in CT imaging. To this end, we consider the feasibility of optimizing CT scan protocols in conjunction with the application of different beam-hardening filtrations and assess this augmentation through noise-power spectrum (NPS) and detector quantum efficiency (DQE) analysis. Methods: American College of Radiology (ACR) and Catphan phantoms (The Phantom Laboratory) were scanned with a 64 slice CT scanner when additional filtration of thickness and composition (e.g., copper, nickel, tantalum, titanium, and tungsten) had been applied. A MATLAB-based code was employed to calculate the image of noise NPS. The Catphan Image Owl software suite was then used to compute the modulated transfer function (MTF) responses of the scanner. The DQE for each additional filter, including the inherent filtration, was then computed from these values. Finally, CT dose index (CTDIvol) values were obtained for each applied filtration through the use of a 100 mm pencil ionization chamber and CT dose phantom. Results: NPS, MTF, and DQE values were computed for each applied filtration and compared to the reference case of inherent beam-hardening filtration only. Results showed that the NPS values were reduced between 5 and 12% compared to inherent filtration case. Additionally, CTDIvol values were reduced between 15 and 27% depending on the composition of filtration applied. However, no noticeable changes in image contrast-to-noise ratios were noted. Conclusion: The reduction in the quanta noise section of the NPS profile found in this phantom-based study is encouraging. The reduction in both noise and dose through the application of beam-hardening filters is reflected in our phantom image quality. However, further investigation is needed to ascertain the applicability of this approach to reducing patient dose while maintaining diagnostically acceptable image qualities in a clinical setting.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

High-precision B(E2) measurements of semi-magic 58,60,62,64Ni by Coulomb excitation

High-precision reduced electric-quadrupole transition probabilities B(E2) have been measured from single-step Coulomb excitation of semi-magic 58,60,62,64 Ni (Z = 28) beams at 1.8 MeV per nucleon on a natural carbon target. The energy loss of the nickel beams through the carbon target were directly measured with a zero-degree Bragg detector and the absolute B(E2) values were normalized by Rutherford scattering. The B(E2) values disagree with recent lifetime studies that employed the Doppler-shift attenuation method. The present high-precision B(E2) values reveal an asymmetry about 62 Ni, midshell between N = 28 and 40, with larger values towards 56 Ni (Z = N = 28). The experimental B(E2) values are compared with shell-model calculations in the full pf model space and the results indicate a soft 56 Ni core.

Allmond, James M↗
DOE OSTI2016

Evolution of the N = 40 neutron subshell in 20 ≤ Z ≤ 30 nuclei within the dispersive optical model

The evolution of single-particle neutron spectra in the N = 40 isotones {sup 60}Ca, {sup 62}Ti, {sup 64}Cr, {sup 66}Fe, {sup 68}Ni, and {sup 70}Zn is calculated on the basis of the mean-field model featuring a dispersive optical potential. The results of these calculations agree with the idea that the degree of collectivity becomes higher in the {sup 64}Сr nucleus and that the coupling of single-particle motion to this collectivity becomes stronger, as well as with available experimental data, which are indicative of the closure of the N = 40 subshell in {sup 68}Ni and of the trend toward this closure in {sup 60}Ca.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Shock wave formation from head-on collision of two subsonic vortex rings

Vortex ring collisions have attracted intense interest in both water and air studies (Baird in Proc R Soc Lond Ser Math Phys Sci 409:59–65, 1987, Poudel et al. in Phys Fluids 33:096105, 2021, Lim and Nickels in Nature 357:225, 1992, New et al. in Exp Fluids 57:109, 2016, Suzuki et al. in Geophys Res Lett 34, 2007, Yan et al. in J Fluids Eng 140:054502, 2018, New et al. in J Fluid Mech 899, 2020, Cheng et al. in Phys Fluids 31:067107, 2019, Hernández and Reyes in 29:103604, 2017, Mishra et al. in Phys Rev Fluids, 2021, Zednikova et al. in Chem Eng Technol 42:843–850, 2019, Kwon et al. in Nature 600:64–69, 2021). These toroidal structures spin around a central axis and travel in the original direction of impulse while spinning around the core until inertial forces become predominant causing the vortex flow to spontaneously decay to turbulence (Vortex Rings, https://projects.iq.harvard.edu/smrlab/vortex-rings). Previous studies have shown the collision of subsonic vortex rings resulting in reconnected vortex rings, but the production of a shock wave from the collision has not been demonstrated visibly (Lim and Nickels in Nature 357:225, 1992, Cheng et al. in Phys Fluids 31:067107, 2019). Here we present the formation of a shock wave due to the collision of explosively formed subsonic vortex rings. As the vortex rings travel at Mach 0.66 toward the collision point, they begin to trap high pressure air between them. Upon collision, high pressure air was imploded and released radially away from the axis of the collision, generating a visible shock wave traveling through and away from the colliding vortices at Mach 1.22. Our results demonstrate a pressure gradient with high pressure release creating a shock wave. We anticipate our study to be a starting point for more explosively formed vortex collisions. For example, explosives with different velocities of detonation could be tested to produce vortex rings of varying velocities.

42 ENGINEERING↗
DOE OSTI1988

Nuclear Safety [Vol. 29, No. 1, January-March 1988]

Nuclear Safety is a review journal that covers significant developments in the field of nuclear safety. Its scope includes the analysis and control of hazards associated with nuclear energy, operations involving fissionable materials, and the products of nuclear fission and their effects on the environment. Primary emphasis is on safety in reactor design, construction, and operation; however, the safety aspects of the entire fuel cycle, including fuel fabrication, spent-fuel processing, nuclear waste disposal, handling of radioisotopes, and environmental effects of these operations, are also treated. Table of Contents for this issue follows. THE CHERNOBYL ACCIDENT: 1 Core History and Nuclide Inventory of the Chernobyl Core at the Time of Accident by Gerald Kirchner and Cornelius C. Noack; GENERAL SAFETY CONSIDERATIONS: 6 Nonprescriptive Nuclear Safety Regulation: The Example of Loss of Offsite Power by M. W. Golay, V. P. Manno, and C. Vlahoplus, Jr., 20 Nuclear Power Safety Goals in Light of the Chernobyl Accident by C. Whipple and C. Starr; ACCIDENT ANALYSIS: 29 Containment Loads from Severe Accidents—U.S. Program by W. Kerr and M. K. Dey; PLANT SAFETY FEATURES: 36 Safety Characteristics of Modern High-Temperature Reactors: Focus on German Designs by W. Kröger, H. Nickel, and R. Schulten; ENVIRONMENTAL EFFECTS: 49 Radiation Hormesis and Nuclear Safety by C. C. Congdon; OPERATING EXPERIENCES: 58 Evaluation of Nonradiological Water Chemistry at Power Reactors by Harvey Zibulsky, James J. Kottan, Walter J. Pasciak, Mary Ann Castrogivanni, and Sujit Banerjee, 64 Reactor Shutdown Experience Compiled by J. W. Cletcher, 67 Operating U.S. Power Reactors Compiled by E. G. Silver; RECENT DEVELOPMENTS: 85 General Administrative Activities Compiled by E. G. Silver, 94 Reports, Standards, and Safety Guides by D. S. Queener, 100 Status of Power-Reactor Projects Undergoing Licensing Review Compiled by E. G. Silver, 103 Proposed Rule Changes as of Sept. 30, 1987; ANNOUNCEMENTS: 5 Northwestern University Short Course on Radiation Safety, 28 International Approach to Nuclear Safety (After Three-Mile Island and Chernobyl), 57 RPI Short Course on Modern Developments in Boiling Heat Transfer and Two-Phase Flow, 107 20th DOE/NRC Nuclear Air Cleaning Conference, 110 Third International Topical Meeting on Nuclear Power Plant Thermal Hydraulics and Operations, 108 The Authors, 111 Indexes to Nuclear Safety, Volume 28.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI1988

Nuclear Safety [Vol. 29, No. 1, January-March 1988]

Nuclear Safety is a review journal that covers significant developments in the field of nuclear safety. Its scope includes the analysis and control of hazards associated with nuclear energy, operations involving fissionable materials, and the products of nuclear fission and their effects on the environment. Primary emphasis is on safety in reactor design, construction, and operation; however, the safety aspects of the entire fuel cycle, including fuel fabrication, spent-fuel processing, nuclear waste disposal, handling of radioisotopes, and environmental effects of these operations, are also treated. Table of Contents for this issue follows. THE CHERNOBYL ACCIDENT: 1 Core History and Nuclide Inventory of the Chernobyl Core at the Time of Accident by Gerald Kirchner and Cornelius C. Noack; GENERAL SAFETY CONSIDERATIONS: 6 Nonprescriptive Nuclear Safety Regulation: The Example of Loss of Offsite Power by M. W. Golay, V. P. Manno, and C. Vlahoplus, Jr., 20 Nuclear Power Safety Goals in Light of the Chernobyl Accident by C. Whipple and C. Starr; ACCIDENT ANALYSIS: 29 Containment Loads from Severe Accidents—U.S. Program by W. Kerr and M. K. Dey; PLANT SAFETY FEATURES: 36 Safety Characteristics of Modern High-Temperature Reactors: Focus on German Designs by W. Kröger, H. Nickel, and R. Schulten; ENVIRONMENTAL EFFECTS: 49 Radiation Hormesis and Nuclear Safety by C. C. Congdon; OPERATING EXPERIENCES: 58 Evaluation of Nonradiological Water Chemistry at Power Reactors by Harvey Zibulsky, James J. Kottan, Walter J. Pasciak, Mary Ann Castrogivanni, and Sujit Banerjee, 64 Reactor Shutdown Experience Compiled by J. W. Cletcher, 67 Operating U.S. Power Reactors Compiled by E. G. Silver; RECENT DEVELOPMENTS: 85 General Administrative Activities Compiled by E. G. Silver, 94 Reports, Standards, and Safety Guides by D. S. Queener, 100 Status of Power-Reactor Projects Undergoing Licensing Review Compiled by E. G. Silver, 103 Proposed Rule Changes as of Sept. 30, 1987; ANNOUNCEMENTS: 5 Northwestern University Short Course on Radiation Safety, 28 International Approach to Nuclear Safety (After Three-Mile Island and Chernobyl), 57 RPI Short Course on Modern Developments in Boiling Heat Transfer and Two-Phase Flow, 107 20th DOE/NRC Nuclear Air Cleaning Conference, 110 Third International Topical Meeting on Nuclear Power Plant Thermal Hydraulics and Operations, 108 The Authors, 111 Indexes to Nuclear Safety, Volume 28.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Magnetic, Magnetocaloric Properties, and Phenomenological Model in Amorphous Ni{sub 80−x}Fe{sub x}(SiB){sub 20} Alloys with (x = 0, 2.4, 8, and 16)

Amorphous Ni{sub 80−x}Fe{sub x}(SiB){sub 20} ribbons with different Fe concentrations (0 ≤ x ≤ 16) were fabricated by melt spinning technique, and their magnetic and magnetocaloric properties were investigated and a phenomenological model was also applied. The Curie temperature (T{sub C}), magnetic moment of transition metal and maximum magnetic entropy change (− ΔS{sub M}) increase with increasing Fe content. At a magnetic field change of 2 T, the (− ΔS{sub M}) and relative cooling power (RCP) show the highest values of 0.53 J/kg K and 85 J kg{sup −1} respectively for Fe{sub 16}Ni{sub 64}(SiB){sub 20} alloys. In addition, a satisfactory agreement between the experimental and Hamad’s phenomenological model is reported.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Electrochemical reduction of ammonia-captured CO 2 to CO over a nickel single-atom catalyst

Carbon reactive capture and conversion offers a sustainable route to valuable chemicals and fuels while aiding Green House Gas (GHG) reduction. Direct electrochemical conversion of capture solutions like bicarbonate avoids the energy demands of conventional CO 2 regeneration. Ammonium bicarbonate (NH 4 HCO 3 ) is particularly attractive due to its low decomposition temperature and ability to supply in situ CO 2 from dilute sources without requiring purified CO 2 . Meanwhile, single-atom catalysts (SACs) with nitrogen-coordinated metal sites further enhance CO 2 reduction efficiency using Earth-abundant materials. In this study, we demonstrate a nickel single-atom catalyst (Ni-SAC)-based electrolyzer that utilizes NH 4 HCO 3 as the CO 2 source, achieving significantly improved CO production performance compared to the conventional silver cathodes used in the CO 2 reduction reaction (CO 2 RR) to produce CO. The Ni-SAC cathode exhibited a Faradaic efficiency of 60.1% for CO production at −200 mA cm −2 , while the silver cathode achieved a Faradaic efficiency of only 2%, likely due to ammonium-induced poisoning. Furthermore, the integration of a customized microporous layer onto the electrode significantly increased the Faradaic efficiency from 64% to 83% at −100 mA cm −2 , emphasizing the crucial role of electrode structure optimization in enhancing CO selectivity. These findings demonstrate a sustainable and economically viable strategy for green CO production directly from CO 2 capture solutions.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2014

SU-E-I-57: Evaluation and Optimization of Effective-Dose Using Different Beam-Hardening Filters in Clinical Pediatric Shunt CT Protocol

Purpose: Study image optimization and radiation dose reduction in pediatric shunt CT scanning protocol through the use of different beam-hardening filters Methods: A 64-slice CT scanner at OU Childrens Hospital has been used to evaluate CT image contrast-to-noise ratio (CNR) and measure effective-doses based on the concept of CT dose index (CTDIvol) using the pediatric head shunt scanning protocol. The routine axial pediatric head shunt scanning protocol that has been optimized for the intrinsic x-ray tube filter has been used to evaluate CNR by acquiring images using the ACR approved CT-phantom and radiation dose CTphantom, which was used to measure CTDIvol. These results were set as reference points to study and evaluate the effects of adding different filtering materials (i.e. Tungsten, Tantalum, Titanium, Nickel and Copper filters) to the existing filter on image quality and radiation dose. To ensure optimal image quality, the scanner routine air calibration was run for each added filter. The image CNR was evaluated for different kVps and wide range of mAs values using above mentioned beam-hardening filters. These scanning protocols were run under axial as well as under helical techniques. The CTDIvol and the effective-dose were measured and calculated for all scanning protocols and added filtration, including the intrinsic x-ray tube filter. Results: Beam-hardening filter shapes energy spectrum, which reduces the dose by 27%. No noticeable changes in image low contrast detectability Conclusion: Effective-dose is very much dependent on the CTDIVol, which is further very much dependent on beam-hardening filters. Substantial reduction in effective-dose is realized using beam-hardening filters as compare to the intrinsic filter. This phantom study showed that significant radiation dose reduction could be achieved in CT pediatric shunt scanning protocols without compromising in diagnostic value of image quality.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Cutting-Balloon Angioplasty Versus Balloon Angioplasty as Treatment for Short Atherosclerotic Lesions in the Superficial Femoral Artery: Randomized Controlled Trial

Purpose: To evaluate the treatments of a short-segment atherosclerotic stenosis in the superficial femoral arteries with the cutting balloon angioplasty (CBA) versus conventional balloon angioplasty [percutaneous transluminal angioplasty (PTA)] in a randomized controlled trial. Material and Methods: The study group comprised 60 patients (33 men, 27 women; average age 64 years) with a short ({<=}5 cm) focal SFA de novo atherosclerotic stenosis associated with a history of intermittent claudication or rest pain. The primary end point of this study was the rate of binary restenosis in the treated segment 12 months after the intervention. All patients were evenly randomized to either the PTA or CBA treatment arms. Follow-up angiograms and ankle-brachial index (ABI) measurements were performed after 12 months. The evaluation of the restenosis rates and factors influencing its occurrence were calculated by logistic regression analysis. Results: In the intention-to-treat analysis, restenosis rates after 2-month follow-up were 9 of 30 (30 %) in the PTA group and 4 of 30 (13 %) in the CBA group (p = 0.117). In the actual treatment analysis, after exclusion of patients who required nitinol stent placement for a suboptimal result after angioplasty alone (5 patients in the PTA group and none in the CBA group), restenosis rates were 9 of 25 (36 %) and 4 of 30 (13 %), respectively (p = 0.049). In the intention-to-treat analysis there were also significant differences in ABI values between the PTA and CBA groups at 0.77 {+-} 0.11 versus 0.82 {+-} 0.12, respectively (p = 0.039), at 12 months. Conclusion: Based on the presented results of the trial, CBA seems to be a safer and more effective than PTA for treatment of short atherosclerotic lesions in the superior femoral artery.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

SUMO-fusion, purification, and characterization of a (+)-zizaene synthase from Chrysopogon zizanioides

An uncharacterized plant cDNA coding for a polypeptide presumably having sesquiterpene synthase activity, was expressed in soluble and active form. Two expression strategies were evaluated in Escherichia coli. The enzyme was fused to a highly soluble SUMO domain, in addition to being produced in an unfused form by a cold-shock expression system. Yields up to ∼325 mg/L{sup −1} were achieved in batch cultivations. The 6x-His-tagged enzyme was purified employing an Ni{sup 2+}-IMAC-based procedure. Identity of the protein was established by Western Blot analysis as well as peptide mass fingerprinting. A molecular mass of 64 kDa and an isoelectric point of pI 4.95 were determined by 2D gel electrophoresis. Cleavage of the fusion domain was possible by digestion with specific SUMO protease. The synthase was active in Mg{sup 2+} containing buffer and catalyzed the production of (+)-zizaene (syn. khusimene), a precursor of khusimol, from farnesyl diphosphate. Product identity was confirmed by GC–MS and comparison of retention indices. Enzyme kinetics were determined by measuring initial reaction rates for the product, using varying substrate concentrations. By assuming a Michaelis–Menten model, kinetic parameters of K{sub M} = 1.111 μM (±0.113), v{sub max} = 0.3245 μM min{sup −1} (±0.0035), k{sub cat} = 2.95 min{sup −1}, as well as a catalytic efficiency k{sub cat}/K{sub M} = 4.43 × 10{sup 4} M{sup −1} s{sup −1} were calculated. Fusion to a SUMO moiety can substantially increase soluble expression levels of certain hard to express terpene synthases in E. coli. The kinetic data determined for the recombinant synthase are comparable to other described plant sesquiterpene synthases and in the typical range of enzymes belonging to the secondary metabolism. This leaves potential for optimizing catalytic parameters through methods like directed evolution. - Highlights: • Uncharacterized (+)-zizaene synthase from C. zizanoides was cloned and expressed. • Fusion to SUMO and cold-shock induction enhanced soluble yields in E. coli. • Ni{sup 2+}-IMAC purification of the SUMO-fused and unfused enzyme. • (+)-Zizaene identified as main cyclization product by GC–MS. • Enzyme kinetic parameters comparable to related sesquiterpene synthases.

60 APPLIED LIFE SCIENCES↗