Direct Measurement of Energy Transfer in Strongly Driven Rotating Turbulence.

A short, abrupt increase in energy injection rate into steady strongly driven rotating turbulent flow is used as a probe for energy transfer in the system. The injected excessive energy is localized in time and space and its spectra differ from those of the steady turbulent flow. This allows measuring energy transfer rates, in three different domains: In real space, the injected energy propagates within the turbulent field, as a wave packet of inertial waves. In the frequency domain, energy is transferred nonlocally to the low, quasigeostrophic modes. In wave number space, energy locally cascades toward small wave numbers, in a rate that is consistent with two-dimensional (2D) turbulence models. Surprisingly however, the inverse cascade of energy is mediated by inertial waves that propagate within the flow with small, but nonvanishing frequency. Our observations differ from measurements and theoretical predictions of weakly driven turbulence. Yet, they show that in strongly driven rotating turbulence, inertial waves play an important role in energy transfer, even in the vicinity of the 2D manifold.

Protecting Quantum Information via Destructive Interference of Correlated Noise.

Decoherence and imperfect control are crucial challenges for quantum technologies. Common protection strategies rely on noise temporal autocorrelation, which is not optimal if other correlations are present. We develop and demonstrate experimentally a strategy that uses the cross-correlation of two noise sources. Utilizing destructive interference of cross-correlated noise extends the coherence time tenfold, improves control fidelity, and surpasses the state-of-the-art sensitivity for high frequency quantum sensing, significantly expanding the applicability of noise protection strategies.

Parahydrogen-Polarized Fumarate for Preclinical in Vivo Metabolic Magnetic Resonance Imaging.

We present a versatile method for the preparation of hyperpolarized [1-13C]fumarate as a contrast agent for preclinical in vivo MRI, using parahydrogen-induced polarization (PHIP). To benchmark this process, we compared a prototype PHIP polarizer to a state-of-the-art dissolution dynamic nuclear polarization (d-DNP) system. We found comparable polarization, volume, and concentration levels of the prepared solutions, while the preparation effort is significantly lower for the PHIP process, which can provide a preclinical dose every 10 min, opposed to around 90 min for d-DNP systems. With our approach, a 100 mM [1-13C]-fumarate solution of volumes up to 3 mL with 13-20% 13C-hyperpolarization after purification can be produced. The purified solution has a physiological pH, while the catalyst, the reaction side products, and the precursor material concentrations are reduced to nontoxic levels, as confirmed in a panel of cytotoxicity studies. The in vivo usage of the hyperpolarized fumarate as a perfusion agent in healthy mice and the metabolic conversion of fumarate to malate in tumor-bearing mice developing regions with necrotic cell death is demonstrated. Furthermore, we present a one-step synthesis to produce the 13C-labeled precursor for the hydrogenation reaction with high yield, starting from 13CO2 as a cost-effective source for 13C-labeled compounds.

Hyperpolarized Solution-State NMR Spectroscopy with Optically Polarized Crystals.

Nuclear spin hyperpolarization provides a promising route to overcome the challenges imposed by the limited sensitivity of nuclear magnetic resonance. Here we demonstrate that dissolution of spin-polarized pentacene-doped naphthalene crystals enables transfer of polarization to target molecules via intermolecular cross-relaxation at room temperature and moderate magnetic fields (1.45 T). This makes it possible to exploit the high spin polarization of optically polarized crystals, while mitigating the challenges of its transfer to external nuclei. With this method, we inject the highly polarized mixture into a benchtop NMR spectrometer and observe the polarization dynamics for target 1H nuclei. Although the spectra are radiation damped due to the high naphthalene magnetization, we describe a procedure to process the data to obtain more conventional NMR spectra and extract the target nuclei polarization. With the entire process occurring on a time scale of 1 min, we observe NMR signals enhanced by factors between -200 and -1730 at 1.45 T for a range of small molecules.

Towards a unified picture of polarization transfer - pulsed DNP and chemically equivalent PHIP.

Nuclear spin hyperpolarization techniques, such as dynamic nuclear polarization (DNP) and parahydrogen-induced polarization (PHIP), have revolutionized nuclear magnetic resonance and magnetic resonance imaging. In these methods, a readily available source of high spin order, either electron spins in DNP or singlet states in hydrogen for PHIP, is brought into close proximity with nuclear spin targets, enabling efficient transfer of spin order under external quantum control. Despite vast disparities in energy scales and interaction mechanisms between electron spins in DNP and nuclear singlet states in PHIP, a pseudo-spin formalism allows us to establish an intriguing equivalence. As a result, the important low-field polarization transfer regime of PHIP can be mapped onto an analogous system equivalent to pulsed-DNP. This establishes a correspondence between key polarization transfer sequences in PHIP and DNP, facilitating the transfer of sequence development concepts. This promises fresh insights and significant cross-pollination between DNP and PHIP polarization sequence developers.

Radio-Frequency Sweeps at Microtesla Fields for Parahydrogen-Induced Polarization of Biomolecules.

Magnetic resonance imaging of 13C-labeled metabolites enhanced by parahydrogen-induced polarization (PHIP) enables real-time monitoring of processes within the body. We introduce a robust, easily implementable technique for transferring parahydrogen-derived singlet order into 13C magnetization using adiabatic radio frequency sweeps at microtesla fields. We experimentally demonstrate the applicability of this technique to several molecules, including some molecules relevant for metabolic imaging, where we show significant improvements in the achievable polarization, in some cases reaching above 60% nuclear spin polarization. Furthermore, we introduce a site-selective deuteration scheme, where deuterium is included in the coupling network of a pyruvate ester to enhance the efficiency of the polarization transfer. These improvements are enabled by the fact that the transfer protocol avoids relaxation induced by strongly coupled quadrupolar nuclei.