Pathway to cryogen free production of hyperpolarized krypton-83 and xenon-129

yperpolarized (hp) 129Xe and hp 83Kr for magnetic resonance imaging (MRI) are typically obtained through spin-exchange optical pumping (SEOP) in gas mixtures with dilute concentrations of the respective noble gas. The usage of dilute noble gases mixtures requires cryogenic gas separation after SEOP, a step that makes clinical and preclinical applications of hp 129Xe MRI cumbersome. For hp 83Kr MRI, cryogenic concentration is not practical due to depolarization that is caused by quadrupolar relaxation in the condensed phase. In this work, the concept of stopped flow SEOP with concentrated noble gas mixtures at low pressures was explored using a laser with 23.3 W of output power and 0.25 nm linewidth. For 129Xe SEOP without cryogenic separation, the highest obtained MR signal intensity from the hp xenon-nitrogen gas mixture was equivalent to that arising from 15.561.9% spin polarized 129Xe in pure xenon gas. The production rate of the hp gas mixture, measured at 298 K, was 1.8 cm3/min. For hp 83Kr, the equivalent of 4.460.5% spin polarization in pure krypton at a production rate of 2 cm3/min was produced. The general dependency of spin polarization upon gas pressure obtained in stopped flow SEOP is reported for various noble gas concentrations. Aspects of SEOP specific to the two noble gas isotopes are discussed and compared with current theoretical opinions. A non-linear pressure broadening of the Rb D1 transition was observed and taken into account for the qualitative description of the SEOP process

Cryogenics free production of hyperpolarized 129Xe and 83Kr for biomedical MRI applications

As an alternative to cryogenic gas handling, hyperpolarized (hp) gas mixtures were extracted directly from the spin exchange optical pumping (SEOP) process through expansion followed by compression to ambient pressure for biomedical MRI applications. The omission of cryogenic gas separation generally requires the usage of high xenon or krypton concentrations at low SEOP gas pressures to generate hp 129Xe or hp 83Kr with sufficient MR signal intensity for imaging applications. Two different extraction schemes for the hp gasses were explored with focus on the preservation of the nuclear spin polarization. It was found that an extraction scheme based on an inflatable, pressure controlled balloon is sufficient for hp 129Xe handling, while 83Kr can efficiently be extracted through a single cycle piston pump. The extraction methods were tested for ex vivo MRI applications with excised rat lungs. Precise mixing of the hp gases with oxygen, which may be of interest for potential in vivo applications, was accomplished during the extraction process using a piston pump. The 83Kr bulk gas phase T1 relaxation in the mixtures containing more than approximately 1% O2 was found to be slower than that of 129Xe in corresponding mixtures. The experimental setup also facilitated 129Xe T1 relaxation measurements as a function of O2 concentration within excised lungs

Bell inequalities for entangled kaons and their unitary time evolution

We investigate Bell inequalities for neutral kaon systems from Phi resonance decay to test local realism versus quantum mechanics. We emphasize the unitary time evolution of the states, that means we also include all decay product states, in contrast to other authors. Only this guarantees the use of the complete Hilbert space. We develop a general formalism for Bell inequalities including both arbitrary "quasi spin" states and different times; finally we analyze Wigner-type inequalities. They contain an additional term, a correction function h, as compared to the spin 1/2 or photon case, which changes considerably the possibility of quantum mechanics to violate the Bell inequality. Examples for special "quasi spin" states are given, especially those which are sensitive to the CP parameters epsilon and epsilon'.Comment: REVTeX, 22 page

The Finite Size SU(3) Perk-Schultz Model with Deformation Parameter q=exp(i 2 pi/3)

From extensive numeric diagonalizations of the SU(3) Perk-Schultz Hamiltonian with a special value of the anisotropy and different boundary conditions, we have observed simple regularities for a significant part of its eigenspectrum. In particular the ground state energy and nearby excitations belong to this part of the spectrum. Our simple formulae describing these regularities remind, apart from some selection rules, the eigenspectrum of the free fermion model. Based on the numerical observations we formulate several conjectures. Using explicit solutions of the associated nested Bethe-ansatz equations, guessed from an analysis of the functional equations of the model, we provide evidence for a part of them.Comment: 19 pages, no figure

Pulmonary MRI contrast using Surface Quadrupolar Relaxation (SQUARE) of hyperpolarized 83Kr

Hyperpolarized 83Kr has previously been demonstrated to enable MRI contrast that is sensitive to the chemical composition of the surface in a porous model system. Methodological advances have lead to a substantial increase in the 83Kr hyperpolarization and the resulting signal intensity. Using the improved methodology for spin exchange optical pumping of isotopically enriched 83Kr, internal anatomical details of ex vivo rodent lung were resolved with hyperpolarized 83Kr MRI after krypton inhalation. Different 83Kr relaxation times were found between the main bronchi and the parenchymal regions in ex vivo rat lungs. The T1 weighted hyperpolarized 83Kr MRI provided a first demonstration of surface quadrupolar relaxation (SQUARE) pulmonary MRI contrast

Decoherence of entangled kaons and its connection to entanglement measures

We study the time evolution of the entangled kaon system by considering the Liouville - von Neumann equation with an additional term which allows for decoherence. We choose as generators of decoherence the projectors to the 2-particle eigenstates of the Hamiltonian. Then we compare this model with the data of the CPLEAR experiment and find in this way an upper bound on the strength $\lambda$ of the decoherence. We also relate $\lambda$ to an effective decoherence parameter $\zeta$ considered previously in literature. Finally we discuss our model in the light of different measures of entanglement, i.e. the von Neumann entropy $S$, the entanglement of formation $E$ and the concurrence $C$, and we relate the decoherence parameter $\zeta$ to the loss of entanglement: $1 - E$.Comment: comments and references added, 18 pages, 1 figur

Measurements of the Generalized Electric and Magnetic Polarizabilities of the Proton at Low Q2 Using the VCS Reaction

The mean square polarizability radii of the proton have been measured for the first time in a virtual Compton scattering experiment performed at the MIT-Bates out-of-plane scattering facility. Response functions and polarizabilities obtained from a dispersion analysis of the data at Q2=0.06 GeV2/c2 are in agreement with O(p3) heavy baryon chiral perturbation theory. The data support the dominance of mesonic effects in the polarizabilities, and the increase of beta with increasing Q2 is evidence for the cancellation of long-range diamagnetism by short-range paramagnetism from the pion cloud

Molecular hydrogen and catalytic combustion in the production of hyperpolarized 83Kr and 129Xe MRI contrast agents

Hyperpolarized (hp) 83Kr is a promising MRI contrast agent for the diagnosis of pulmonary diseases affecting the surface of the respiratory zone. However, the distinct physical properties of 83Kr that enable unique MRI contrast also complicate the production of hp 83Kr. This work presents a radically new approach in the generation of hp 83Kr that can likewise be utilized for the production of hp 129Xe. Molecular nitrogen, typically used as buffer gas in spin exchange optical pumping (SEOP), was replaced by molecular hydrogen without penalty for the achievable hyperpolarization. In this particular study, the highest obtained nuclear spin polarizations were P = 29 % for 83Kr and P = 63 % for 129Xe. The results were reproduced over many SEOP cycles despite the laser induced on-resonance formation of rubidium hydride (RbH). Following SEOP, the H2 was reactively removed via catalytic combustion without measurable losses in hyperpolarized spin state of either 83Kr or 129Xe. Highly spin polarized 83Kr can now be purified for the first time to provide high signal intensity for the advancement of in vivo hp 83Kr MRI. More generally, a chemical reaction appears as a viable alternative to the cryogenic separation process, the primary purification method of hp 129Xe for the past 2 . decades. The inherent simplicity of the combustion process will facilitate hp 129Xe production and should allow for on-demand continuous flow of purified and highly spin polarized 129Xe

Investigation of the conjectured nucleon deformation at low momentum transfer

We report new precise H$(e,e^\prime p)\pi^0$ measurements at the $\Delta(1232)$ resonance at $Q^2= 0.127$ (GeV/c)$^2$ using the MIT/Bates out-of-plane scattering (OOPS) facility. The data reported here are particularly sensitive to the transverse electric amplitude ($E2$) of the $\gamma^* N\to\Delta$ transition. Analyzed together with previous data yield precise quadrupole to dipole amplitude ratios $EMR = (-2.3 \pm 0.3_{stat+sys} \pm 0.6_{model})$ and $CMR = (-6.1 \pm 0.2_{stat+sys}\pm 0.5_{model})$ and for $M^{3/2}_{1+} = (41.4 \pm 0.3_{stat+sys}\pm 0.4_{model})(10^{-3}/m_{\pi^+})$. They give credence to the conjecture of deformation in hadronic systems favoring, at low $Q^2$, the dominance of mesonic effects.Comment: 4 pages, 1figur