Hyperpolarization of 3-fluoropyridine via Signal Amplification by Reversible Exchange

Abstract. In nuclear magnetic resonance (NMR), inductive detection has been the only essential signal acquisition mechanism for decades. Recently, a fundamentally new way of detecting NMR, by observing nuclear spin-induced optical rotation (NSOR), was discovered. However, NSOR suffers from a poor signal-to-noise ratio (SNR), hindering its applications. One compelling way of improving the SNR by orders of magnitude is to use a relatively new hyperpolarization method called signal amplification by reversible exchange (SABRE). The purpose of this thesis was to see whether SABRE could enable the NSOR signal detection of fluorine and to find ways to optimize an existing continuous-flow NSOR system. This involved studying the polarization transfer process in SABRE by performing several experiments with a 3-fluoropyridine sample. The levels of obtained hyperpolarization were measured at different magnetic fields. Fluorine received the greatest levels of polarization at ultralow fields, whereas proton was hyperpolarized most effectively at milli-Tesla fields. This was attributed to the coherent polarization transfer at level anti-crossings (LACs). At magnetic field strengths where LACs are not present, the polarization transfer mechanism could not be unambiguously determined. Measured relaxation times at different magnetic fields proved to be similar for fluorine and proton. At ultralow fields, the relaxation was rather quick (~ 3 s), whereas at low and high fields, slower relaxation was observed (~ 10 s). Therefore, having a well-defined magnetic field during the sample transfer would minimize the effects of relaxation and result in better levels of polarization. Polarization build-up constants were measured at different magnetic fields. They were also quite comparable between the fluorine and the proton, while also being similar to the relaxation time constants. At ultralow fields, the polarization builds up fastest, which is a favourable result considering the continuous-flow NSOR system, as the sample is continuously pumped from the polarizing cell. Additionally, the fast build-up enables the use of faster pumping speeds to minimize the effects of relaxation during sample transfer

Wear properties of thermally sprayed tungsten-carbide coatings in paper machine environments

Thermally sprayed tungsten-carbide (WC) coatings have proven to be one of the most wear resistant coatings available and a respectable replacement for hard-chromium coatings. They are used in paper machine parts such as calender rolls. However, improved lifetime and performance are continuing considerations, as well as finding more economical alternatives. This study researched the wear phenomena of tungsten-carbide coatings in a paper machine environment. To achieve this, five different feedstock materials and coatings manufactured from these were compared by electron microscopy as well as dry abrasion-, high-speed slurry abrasion- and cavitation erosion tests. Improvements in ductility by changing the matrix material were found, while changing the particle strength had no effect on the behavior of the coatings. The findings suggest further research on altering the matrix of the feedstock could lead to overall improvements in coating quality and component lifetime

A comparison of estimates of mean annual precipitation from different proxies: a pilot study for the European Neogene

Peer reviewe

Frisbeegolfkiekon muodon vaikutus sen lentorataan

Tiivistelmä. Tässä tutkielmassa otetaan selvää, minkälaisia fysikaalisia ilmiöitä frisbeegolfkiekon lentämiseen liittyy, ja kuinka kiekon muoto vaikuttaa sen lentorataan. Ilmiöt, joihin tutkielmassa perehdytään, ovat aerodynaaminen noste, ilmanvastus ja gyroskooppinen vakaus. Lisäksi lukijalle tulee tutuksi frisbeegolfin historia sekä eri heitto- ja kiekkotyypit

Q_EC values of the Superallowed beta-Emitters 10-C, 34-Ar, 38-Ca and 46-V

The Q_EC values of the superallowed beta+ emitters 10-C, 34-Ar, 38-Ca and 46-V have been measured with a Penning-trap mass spectrometer to be 3648.12(8), 6061.83(8), 6612.12(7) and 7052.44(10) keV, respectively. All four values are substantially improved in precision over previous results.Comment: 9 pages, 7 figures, 5 table

Isomeric states close to doubly magic 132^{132}Sn studied with JYFLTRAP

The double Penning trap mass spectrometer JYFLTRAP has been employed to measure masses and excitation energies for $11/2^-$ isomers in $^{121}$Cd, $^{123}$Cd, $^{125}$Cd and $^{133}$Te, for $1/2^-$ isomers in $^{129}$In and $^{131}$In, and for $7^-$ isomers in $^{130}$Sn and $^{134}$Sb. These first direct mass measurements of the Cd and In isomers reveal deviations to the excitation energies based on results from beta-decay experiments and yield new information on neutron- and proton-hole states close to $^{132}$Sn. A new excitation energy of 144(4) keV has been determined for $^{123}$Cd$^m$. A good agreement with the precisely known excitation energies of $^{121}$Cd$^m$, $^{130}$Sn$^m$, and $^{134}$Sb$^m$ has been found.Comment: 10 pages, 6 figures, submitted to Phys. Rev.

Beta-decay branching ratios of 62Ga

Beta-decay branching ratios of 62Ga have been measured at the IGISOL facility of the Accelerator Laboratory of the University of Jyvaskyla. 62Ga is one of the heavier Tz = 0, 0+ -> 0+ beta-emitting nuclides used to determine the vector coupling constant of the weak interaction and the Vud quark-mixing matrix element. For part of the experimental studies presented here, the JYFLTRAP facility has been employed to prepare isotopically pure beams of 62Ga. The branching ratio obtained, BR= 99.893(24)%, for the super-allowed branch is in agreement with previous measurements and allows to determine the ft value and the universal Ft value for the super-allowed beta decay of 62Ga

Precision mass measurements of radioactive nuclei at JYFLTRAP

The Penning trap mass spectrometer JYFLTRAP was used to measure the atomic masses of radioactive nuclei with an uncertainty better than 10 keV. The atomic masses of the neutron-deficient nuclei around the N = Z line were measured to improve the understanding of the rp-process path and the SbSnTe cycle. Furthermore, the masses of the neutron-rich gallium (Z = 31) to palladium (Z = 46) nuclei have been measured. The physics impacts on the nuclear structure and the r-process paths are reviewed. A better understanding of the nuclear deformation is presented by studying the pairing energy around A = 100.Comment: 4 pages and 4 figures, RNB7 conf. pro

Laser Spectroscopy of Niobium Fission Fragments: First Use of Optical Pumping in an Ion Beam Cooler Buncher

A new method of optical pumping in an ion beam cooler buncher has been developed to selectively enhance ionic metastable state populations. The technique permits the study of elements previously inaccessible to laser spectroscopy and has been applied here to the study of Nb. Model independent mean-square charge radii and nuclear moments have been studied for $^{90,90 m,91,91 m,92,93,99,101,103}$Nb to cover the region of the N=50 shell closure and N≈60 sudden onset of deformation. The increase in mean-square charge radius is observed to be less than that for Y, with a substantial degree of β softness observed before and after N=60