Dielectronic Recombination (via N=2 --> N'=2 Core Excitations) and Radiative Recombination of Fe XX: Laboratory Measurements and Theoretical Calculations

We have measured the resonance strengths and energies for dielectronic recombination (DR) of Fe XX forming Fe XIX via N=2 --> N'=2 (Delta_N=0) core excitations. We have also calculated the DR resonance strengths and energies using AUTOSTRUCTURE, HULLAC, MCDF, and R-matrix methods, four different state-of-the-art theoretical techniques. On average the theoretical resonance strengths agree to within <~10% with experiment. However, the 1 sigma standard deviation for the ratios of the theoretical-to-experimental resonance strengths is >~30% which is significantly larger than the estimated relative experimental uncertainty of <~10%. This suggests that similar errors exist in the calculated level populations and line emission spectrum of the recombined ion. We confirm that theoretical methods based on inverse-photoionization calculations (e.g., undamped R-matrix methods) will severely overestimate the strength of the DR process unless they include the effects of radiation damping. We also find that the coupling between the DR and radiative recombination (RR) channels is small. We have used our experimental and theoretical results to produce Maxwellian-averaged rate coefficients for Delta_N=0 DR of Fe XX. For kT>~1 eV, which includes the predicted formation temperatures for Fe XX in an optically thin, low-density photoionized plasma with cosmic abundances, our experimental and theoretical results are in good agreement. We have also used our R-matrix results, topped off using AUTOSTRUCTURE for RR into J>=25 levels, to calculate the rate coefficient for RR of Fe XX. Our RR results are in good agreement with previously published calculations.Comment: To be published in ApJS. 65 pages with 4 tables and lots of figure

Dielectronic Recombination in Photoionized Gas. II. Laboratory Measurements for Fe XVIII and Fe XIX

In photoionized gases with cosmic abundances, dielectronic recombination (DR) proceeds primarily via nlj --> nl'j' core excitations (Dn=0 DR). We have measured the resonance strengths and energies for Fe XVIII to Fe XVII and Fe XIX to Fe XVIII Dn=0 DR. Using our measurements, we have calculated the Fe XVIII and Fe XIX Dn=0 DR DR rate coefficients. Significant discrepancies exist between our inferred rates and those of published calculations. These calculations overestimate the DR rates by factors of ~2 or underestimate it by factors of ~2 to orders of magnitude, but none are in good agreement with our results. Almost all published DR rates for modeling cosmic plasmas are computed using the same theoretical techniques as the above-mentioned calculations. Hence, our measurements call into question all theoretical Dn=0 DR rates used for ionization balance calculations of cosmic plasmas. At temperatures where the Fe XVIII and Fe XIX fractional abundances are predicted to peak in photoionized gases of cosmic abundances, the theoretical rates underestimate the Fe XVIII DR rate by a factor of ~2 and overestimate the Fe XIX DR rate by a factor of ~1.6. We have carried out new multiconfiguration Dirac-Fock and multiconfiguration Breit-Pauli calculations which agree with our measured resonance strengths and rate coefficients to within typically better than <~30%. We provide a fit to our inferred rate coefficients for use in plasma modeling. Using our DR measurements, we infer a factor of ~2 error in the Fe XX through Fe XXIV Dn=0 DR rates. We investigate the effects of this estimated error for the well-known thermal instability of photoionized gas. We find that errors in these rates cannot remove the instability, but they do dramatically affect the range in parameter space over which it forms.Comment: To appear in ApJS, 44 pages with 13 figures, AASTeX with postsript figure

Nitrogen K-shell photoabsorption

Reliable atomic data have been computed for the spectral modeling of the nitrogen K lines, which may lead to useful astrophysical diagnostics. Data sets comprise valence and K-vacancy level energies, wavelengths, Einstein $A$-coefficients, radiative and Auger widths and K-edge photoionization cross sections. An important issue is the lack of measurements which are usually employed to fine-tune calculations so as to attain spectroscopic accuracy. In order to estimate data quality, several atomic structure codes are used and extensive comparisons with previous theoretical data have been carried out. In the calculation of K photoabsorption with the Breit--Pauli $R$-matrix method, both radiation and Auger damping, which cause the smearing of the K edge, are taken into account. This work is part of a wider project to compute atomic data in the X-ray regime to be included in the database of the popular {\sc xstar} modeling code

Quantum chromodynamics through the geometry of M\"{o}bius structures

This paper describes a rigorous mathematical formulation providing a divergence free framework for QCD and the standard model in curved space-time. The starting point of the theory is the notion of covariance which is interpreted as (4D) conformal covariance rather than the general (diffeomorphism) covariance of general relativity. It is shown how the infinitesimal symmetry group (i.e. Lie algebra) of the theory, that is $su(2,2)$, is a linear direct sum of $su(3)$ and the algebra ${\mathfrak\kappa}\cong sl(2,{\bf C})\times u(1)$, these being the QCD algebra and the electroweak algebra. Fock space which is a graded algebra composed of Hilbert spaces of multiparticle states, where the particles can be fermions such as quarks and electrons or bosons such as gluons and photons, is described concretely. Algebra bundles whose typical fibers are the Fock spaces are defined. Scattering processes are associated with covariant linear maps between the Fock space fibers which can be generated by intertwining operators between the Fock spaces. It is shown how quark-quark scattering and gluon-gluon scattering are associated with kernels which generate such intertwining operators. The rest of the paper focusses on QCD vacuum polarization in order to compute and display the (1 loop) running coupling for QCD at different scales. Through an easy application of the technique called the spectral calculus the densities associated with the quark bubble and the gluon bubble are computed and hence the QCD vacuum polarization function is determined. It is found that the QCD running coupling has non-trivial behavior particularly at the subnuclear level. The plots of the QCD running coupling for quark separation greater than $10^{-13}$ meters are found to be consistent with the properties of asymptotic freedom in the high energy range and quark confinement in the low energy (large separation) range.Comment: With corrections and improved presentation, 44 pages, 9 figure

18F-표지 트립토판 유도체를 이용한 세로토닌 대사 PET 영상제 개발

학위논문(박사)--서울대학교 대학원 :의과대학 의학과,2019. 8. 정재민.Purpose: The serotonergic system is related to various dysfunctions in the central nervous system, such as depression, social anxiety disorder, and epilepsy. Thus, the development of a radioactive probe for imaging serotonin synthesis is important for the diagnosis of such diseases. α-[11C]Methyltryptophan ([11C]AMT) is available for the imaging of serotonin synthesis. However, the brain uptake of [11C]AMT reflects both serotonin and kynurenine metabolism. In addition, since tryptophan is rapidly cleared from the brain, α-methylation would be needed to prolong the retention time in the brain and reduce the metabolism by monoamine oxidase (MAO). In the present study, we designed and synthesized 18F- labeled [18F]trifluoromethyl-L-tryptophan ([18F]CF3-L-Trp) and [18F]trifluoromethyl-L-α-methyl tryptophan ([18F]CF3-L-AMT) which might be metabolized to serotonin only. To evaluate the feasibility of labeled tryptophan derivatives for imaging the serotonergic system, the distribution and metabolism were investigated in rat brain. Methods: Precursor of [18F]CF3-L-Trp or [18F]CF3-L-AMT was prepared by regio-selective iodination using palladium or mercury catalyst, respectively. [18F]Trifluromethyl group was introduced by copper-catalyzed coupling using methyl chlorodifluoroacetate and tetramethylenediamine at 150C for 15 min. Protecting groups were removed by 1 N HCl at 100C for 10 min. The reaction mixture was purified by HPLC and radiochemical and enantiomeric purities were measured by HPLC. Biodistribution was performed in normal BALB/c mice at 10, 60 and 120 min post injection. For the autoradiography, [18F]CF3-L-Trp and [18F]CF3-L-AMT were injected into rats by tail vein injections without anesthesia. PET studies were performed in SD rat by intravenous administration of [18F]CF3-L-Trp. Metabolite study was performed in BALB/c mice using non-radioactive CF3-L-Trp and brain, blood, and urine samples were analyzed by HPLC and LC/MS. To evaluate brain distribution of [18F]CF3-L-AMT in serotonin metabolism enhanced SD rat, lithium chloride was administered to rats 2 times per day for 5 days (85 mg/kg, i.p.). Results: Protected L-Trp and its bromo and iodo derivatives were tested for [18F]trifluoromethylation and iodo derivative showed the highest labeling efficiency. Radiochemical yield was 6±1.5% based on the isolated product and radiochemical purity was over 99%. The molar activity of [18F]CF3-L-Trp was 0.44–0.76 GBq/μmol and [18F]CF3-L-AMT was 0.94–1.44 GBq/μmol which are enough for in vivo application. Enantiomeric purity was measured by chiral HPLC and no racemic form was found. In the biodistribution, at 10 min, the brain uptakes of [18F]CF3-L-AMT and [18F]CF3-L-Trp were 2.27 ± 0.14%ID/g and 2.06 ± 0.22%ID/g, respectively and the brain uptake of [18F]CF3-L-AMT (0.73 ± 0.08%ID/g) at 60 min was significantly higher than that of [18F]CF3-L-Trp (0.43 ± 0.08%ID/g). This result indicated that α-methylation increased the retention in the brain by reducing metabolism by MAO. The bone uptake of [18F]CF3-L-AMT at 60 min (4.50 ± 0.47%ID/g) was significantly lower than that of [18F]CF3-L-Trp (9.34 ± 0.62%ID/g), suggesting the lower in vivo defluorination of [18F]CF3-L-AMT. Both of the tracers showed high uptakes in the kidney. In PET and autoradiography measurements, the uptake of raphe nucleus (dorsal and medial) was comparatively very low. Instead, pineal gland, thalamus, hypothalamus and midbrain showed particularly high uptake. [18F]CF3-L-Trp penetrated the blood-brain barrier via the L-type amino acid transporter, while [18F]CF3-D-Trp did not. In the metabolism study, CF3-serotonin peak was found in brain and blood at 60 min, and the mass value of the CF3-serotonin peak was confirmed by LC-MS. The distribution pattern of [18F]CF3-L-AMT in Li-treated SD rat brains was similar to that detected in normal SD rat brains. However, the brain uptake rate of [18F]CF3-L-AMT in Li-treated SD rats was faster than normal SD rats and the brain uptake in Li-treated SD rats lasted longer than that in normal SD rats. Conclusion: [18F]CF3-L-Trp could be successfully synthesized by [18F]trifluoromethylation, but fast washout from the brain and high in vivo defluorination showed that [18F]CF3-L-Trp was not suitable for imaging the serotonergic system. α-Methylation of tryptophan increased the retention in the brain by reducing metabolism and might decrease the in vivo defluorination. However, it is not clear that the PET imaging of [18F]CF3-L-Trp reflect serotonin metabolism due to the low uptake in raphe nucleus. A large unmetabolized form in the brain also makes it difficult to obtain the absolute serotonin synthesis rate. Nevertheless, experimental data suggest that the distribution patterns of [18F]CF3-L-AMT in normal and Li-treated SD rats were related with serotonergic activity and metabolism. Therefore, [18F]CF3-L-AMT could be used as an feasible imaging agent representing serotonergic system.목적: 세로토닌 신경계는 우울증, 사회적 불안 장애 및 간질과 같은 중추 신경계의 다양한 기능 장애와 연관이 있다. 그러므로 세로토닌의 합성을 영상화할 수 있는 방사성 프로브의 개발은 그러한 질병의 진단에 중요하다. α-[11C]메틸트립토판 ([11C]AMT)은 세로토닌 합성 영상에 이용 가능한다. 그러나 [11C]AMT 의 뇌 내 섭취는 세로토닌 대사 뿐만 아니라 키뉴레닌 대사 또한 반영할 수 있으므로 잘못된 정보를 제공할 수 있다. 또한 트립토판은 뇌에서 빠르게 제거되기 때문에 뇌에서의 머무름 시간을 연장시키고 모노 아민 산화 효소 (MAO)에 의한 대사를 감소시키기 위해 α-메틸화가 필요하다. 본 연구에서는 구리(I)를 매개로 한 [18F]트리플루오로메틸화를 이용해 인돌 고리의 2 번 위치에 18F을 표지하여 세로토닌 대사만을 반영할 수 있는 [18F]트리플루오로메틸-L-트립토판 ([18F]CF3-L-Trp)과 [18F]트리플루오로메틸-L-α-메틸트립토판 ([18F]CF3-L-AMT)을 설계하고 개발하려고 하였다. 또한 세로토닌 영상화를 위한 표지된 트립토판 유도체의 가능성을 평가하기 위하여 쥐의 뇌 내 분포와 대사를 조사하였다. 방법: [18F]CF3-L-Trp 또는 [18F]CF3-L-AMT의 전구체는 팔라듐 또는 수은 촉매를 이용한 위치 선택적 요오드화를 통해 합성하였다. [18F]트리플로오로 메틸기는 methyl chlorodifluoroacetate와 tetramethylethylenediamine를 넣고 구리 촉매 하에서 150C에서 15 분간 반응하여 도입할 수 있었고, 이 후 보호기는 1 N 염산 수용액을 넣고 100C에서 10 분간 반응하여 제거하였다. 반응 혼합물은 HPLC를 이용하여 정제하였고, 분리된 [18F]CF3-L-Trp의 방사화학적 확인 및 순도와 이성질체 확인 및 순도는 분석용 HPLC로 확인하였다. 생체 내 분포는 정상 BALB/c 마우스에서 마취 없이 [18F]CF3-L-Trp를 주사한 후 10, 60 및 120 분에 확인하였고, 자가방사기록은 SD 랫에서 주사 후 10 분째에 확인하였다. PET 영상 역시 SD 랫에서 얻었으며, 마취 없이 [18F]CF3-L-Trp를 주사한 후 5, 10, 20, 40 및 80 분에 쥐를 희생시키고 뇌를 추출하여 영상을 얻었다. 대사체 연구는 비방사성 CF3-L-Trp를 BALB/c 마우스에 투여한 후 10 분 및 60 분째에 뇌, 혈액, 및 소변에서 샘플을 얻어 HPLC와 LC/MS를 이용해 분석하였다. 세로토닌 대사가 증진된 SD 랫에서 [18F]CF3-L-AMT의 뇌 분포 및 대사를 평가하기 위해 염화 리튬을 하루 2 회 5일간 85 mg/kg을 복강주사로 SD 랫에 투여하였다. 결과: 보호된 L-Trp및 브롬화와 요오드화 유도체를 이용해 [18F]트리플루오로메틸화 반응을 수행하였고, 요오드화 유도체가 가장 높을 표지 효율을 보였다. 표지 후, 산에 불안정한 보호기를 1 N 염산 수용액을 사용하여 동시에 제거하였고, 반응 혼합물은 HPLC로 정제하였다. 방사 화학적 수율을 분리된 생성물을 기준으로 6±1.5%였으며, 방사 화학적 순도는 99% 이상이었고 [18F]CF3-L-Trp의 머무름 시간은 합성한 표준물질과 동일하였다. 몰당 비방사능은 [18F]CF3-L-Trp가 0.44–0.76 GBq/μmol이고 [18F]CF3-L-AMT가 0.94–1.46 GBq/μmol으로 친핵성 치환반응으로 합성한 18F-표지된 화합물보다는 비교적 낮지만 생체 내 적용을 하기에는 충분하였다. 거울상 이성질체 확인 및 순도는 키랄 HPLC에 의해 측정되었고 다른 이성질체는 발견되지 않았다. 10 분에 생체 분포에서 [18F]CF3-L-AMT와 [18F]CF3-L-Trp의 뇌 섭취량은 각각 2.27 ± 0.14%ID/g와 2.06 ± 0.22%ID/g 이었고 [18F]CF3-L-AMT의 뇌 섭취 (0.73 ± 0.08%ID/g)는 [18F]CF3-L-Trp (0.43 ± 0.08%ID/g)보다 60 분에서 유의하게 높았다. 이 결과는 α-메틸화가 MAO에 의한 대사를 감소시킴으로써 두뇌의 보유를 증가 시킨다는 것을 나타냈다. 60 분 (4.50 ± 0.47%ID/g)에서 [18F]CF3-L-AMT의 골 흡수는 [18F]CF3-L-Trp (9.34 ± 0.62%ID/g)의 골 흡수보다 현저히 낮았으며 두 화합물 모두 신장에서 높은 섭취를 보였다. PET 및 자가방사기록에서, 솔기핵 (지느러미 및 내측)의 섭취는 비교적 매우 낮았다. 대신 송과선, 시상, 시상 하부 및 중뇌는 특히 높은 섭취량을 보였다. [18F]CF3-L-Trp는 L형 아미노산 수송체를 통해 혈뇌장벽을 투과하였고 [18F]CF3-D-Trp는 투과하지 못하였다. 대사체 연구에서는 60 분에 뇌와 혈액에서 CF3-serotonin의 피크가 검출되었고, LC-MS를 통해 CF3-serotonin의 질량 값을 확인함으로써 뇌 및 혈액 내에서 CF3-L-Trp이 CF3-serotonin로 대사되는 것을 증명하였다. 리튬 처리 한 SD 래트 뇌에서의 [18F]CF3-L-AMT의 분포 패턴은 정상 SD 랫 뇌와 유사하였다. 그러나 리튬 처리한 SD 래트에서 [18F]CF3-L-AMT 의 뇌 흡수율은 정상 SD 랫보다 약 10 분 더 빨리 최고 농도에 도달하였고, 리튬 처리된 SD 랫트에서의 뇌 섭취는 정상 SD 랫보다 더 오래 지속되었다. 결론: 본 연구에서, 구리를 촉매로 한 [18F]트리플루오로메틸화를 이용해 성공적으로 [18F]CF3-L-Trp를 합성할 수 있었고 2 번 위치의 18F은 이 물질이 세로토닌 대사에 특이적으로 작용할 수 있도록 하였다. 하지만 뇌에서의 빠른 배출과 높은 생체 내 탈 불소화는 [18F]CF3-L-Trp가 세로토닌을 영상화하는데 적합하지 않음을 보여 주었다. 트립토판의 α-메틸화는 대사를 줄임으로써 뇌의 머무름 시간을 증가시켰으며 생체 내 탈 불소화를 감소시켰다. 하지만 낮은 솔기핵 섭취는 [18F]CF3-L-AMT의 PET 영상이 세로토닌 대사를 반영하는 지를 불분명하게 하였다. 또한 뇌에서의 [18F]CF3-L-AMT가 대사되지 않은 채 남아있음으로써 대사된 것과 대사되지 않을 것을 구분하기 어렵게 하여 절대적인 세로토닌 합성 속도 얻는 것을 어렵게 하였다. 그럼에도 불구하고 실험 결과들은 정상 및 리튬 처리된 SD 랫에서 [18F]CF3-L-AMT의 분포 패턴이 세로토닌 작용 및 대사와 관련이 있음을 시사하였다. 따라서 [18F]CF3-L-AMT는 세로토닌 대사를 영상화할 수 있는 PET 영상제로 사용될 가능성이 있으나 더 많은 검증이 필요하다.ABSTRACT - 2 LIST OF SCHEMES, FIGURES AND TABLES - 10 LIST OF ABBREVIATIONS 13 1 INTRODUCTION 16 2 MATERIALS AND METHODS - 26 2.1 General 26 2.2 [18F]Trifluoromethyl- L-tryptophan ([18F]CF3- L-Trp) 28 2.2.1 Chemistry- 28 2.2.2 General procedure for [18F]trifluoromethylation for optimization of the labeling conditions 39 2.2.3 Radiosynthesis - 40 2.2.4 Stability test - 41 2.2.5 Serum protein binding assay 41 2.2.6 Biodistribution study 42 2.2.7 [18F]CF3-L-Trp PET acquisition in rats 43 2.2.8 Autoradiography in rats - 43 2.2.9 Metabolites study 44 2.3 [18F]Trifluoromethyl-L-α-methyltryptophan ([18F]CF3-L-AMT) 46 2.3.1 Chemistry 46 2.3.2 Radiosynthesis 52 2.3.3 Stability test - 53 2.3.4 Biodistribution (in mice) 54 2.3.5 Autoradiography (in rat) 54 3 RESULTS AND DISCUSSION 57 3.1 [18F]Trifluoromethyl- L-tryptophan ([18F]CF3- L-Trp) 57 3.1.1 Chemistry 57 3.1.2 Optimization of the [18F]trifluoromethylation conditions - 62 3.1.3 Automatic radiosynthesis - 65 3.1.4 Stability test - 67 3.1.5 Serum protein binding assay 68 3.1.6 Biodistribution study 69 3.1.7 [18F]CF3-L-Trp PET acquisition in rats 71 3.1.8 Autoradiography in rats - 74 3.1.9 Metabolites study 75 3.2 [18F]Trifluoromethyl-L-α-methyltryptophan ([18F]CF3-L-AMT) 79 3.2.1 Chemistry 79 3.2.2 Radiosynthesis - 83 3.2.3 Stability test - 89 3.2.4 Biodistribution (in mice) 89 3.2.5 Autoradiography (in rat) - 91 3.2.6 Comparison of distribution and metabolism between [18F]CF3- L-Trp and [18F]CF3-L-AMT 98 4 CONCLUSION - 101 5 REFERENCES - 103 SPECTRAL ANALYSIS RESULTS 109 국문초록 141Docto

Relativistic Electron Correlation, Quantum Electrodynamics, and the Lifetime of the 1s²2s²2p²P\u3csup\u3eo\u3c/sup\u3e\u3csub\u3e3/2\u3c/sub\u3e Level in Boronlike Argon

The lifetime of the Ar13+ 1s22s22p2Po3/2 metastable level was determined at the Heidelberg Electron Beam Ion Trap to be 9.573(4)(5)ms(stat)(syst). The accuracy level of one per thousand makes this measurement sensitive to quantum electrodynamic effects like the electron anomalous magnetic moment (EAMM) and to relativistic electron-electron correlation effects like the frequency-dependent Breit interaction. Theoretical predictions, adjusted for the EAMM, cluster about a lifetime that is approximately 3σ shorter than our experimental result

Correlation and Quantum Electrodynamic Effects on the Radiative Lifetime and Relativistic Nuclear Recoil in Ar¹³⁺ and Ar¹⁴⁺ Ions

The radiative lifetime and mass isotope shift of the 1s22s22p 2P3/2 - 2P1/2 M1 transition in Ar13+ ions have been determined with high accuracies using the Heidelberg electron beam ion trap. This fundamentally relativistic transition provides unique possibilities for performing precise studies of correlation and quantum electrodynamic effects in many-electron systems. The lifetime corresponding to the transition has been measured with an accuracy of the order of one per thousand. Theoretical calculations predict a lifetime that is in significant disagreement with this high-precision experimental value. Our mass shift calculations, based on a fully relativistic formulation of the nuclear recoil operator, are in excellent agreement with the experimental results and cofirm the absolute necessity to include relativistic recoil corrections when evaluating mass shift contributions even in medium-Z ions