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Abstract: This article presents a case of severe CPR-related injuries leading to diagnosis of vascular Ehlers-Danlos syndrome. The subject is a 36-year-old female with a past medical history of a 10-mm aneurysm of the right internal carotid artery discovered on imaging 3 years prior to death. Major autopsy findings included subarachnoid hemorrhage in the base of the brain, bilateral hemothoraces, hemopericardium, laceration of the interatrial septum, laceration of the left pulmonary artery, and changes secondary to chronic alveolar hemorrhage in the lungs. The autopsy findings and subsequent unremarkable toxicology studies led to the suspicion of an underlying and clinically undiagnosed connective tissue disorder. Broad genetic exome testing revealed a mutation consistent with vascular Ehlers-Danlos syndrome. An overview of this disease, its diagnosis, and differential are further described herein, along with recommendations for forensic pathologists., Competing Interests: The authors report no conflict of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

The inherently low signal-to-noise ratio of NMR and MRI is now being addressed by hyperpolarization methods. For example, iridium-based catalysts that reversibly bind both parahydrogen and ligands in solution can hyperpolarize protons (SABRE) or heteronuclei (X-SABRE) on a wide variety of ligands, using a complex interplay of spin dynamics and chemical exchange processes, with common signal enhancements between 10 3 and 10 4 . This does not approach obvious theoretical limits, and further enhancement would be valuable in many applications (such as imaging mM concentration species in vivo). Most SABRE/X-SABRE implementations require far lower fields (μT-mT) than standard magnetic resonance (>1T), and this gives an additional degree of freedom: the ability to fully modulate fields in three dimensions. However, this has been underexplored because the standard simplifying theoretical assumptions in magnetic resonance need to be revisited. Here, we take a different approach, an evolutionary strategy algorithm for numerical optimization, multi-axis computer-aided heteronuclear transfer enhancement for SABRE (MACHETE-SABRE). We find nonintuitive but highly efficient multiaxial pulse sequences which experimentally can produce a sevenfold improvement in polarization over continuous excitation. This approach optimizes polarization differently than traditional methods, thus gaining extra efficiency., Competing Interests: Competing interests statement:The authors declare no competing interest.

Hyperpolarized [1- 13 C]pyruvate is a revolutionary molecular probe enabling ultrafast metabolic MRI scans in 1 min. This technology is now under evaluation in over 30 clinical trials, which employ dissolution Dynamic Nuclear Polarization (d-DNP) to prepare a batch of the contrast agent; however, d-DNP technology is slow and expensive. The emerging SABRE-SHEATH hyperpolarization technique enables fast (under 1 min) and robust production of hyperpolarized [1- 13 C]pyruvate via simultaneous chemical exchange of parahydrogen and pyruvate on IrIMes hexacoordinate complexes. Here, we study the application of microtesla pulses to investigate their effect on C-13 polarization efficiency, compared to that of conventional SABRE-SHEATH employing a static field (∼0.4 μT), to provide the matching conditions of polarization transfer from parahydrogen-derived hydrides to the 13 C-1 nucleus. Our results demonstrate that using square-microtesla pulses with optimized parameters can produce 13 C-1 polarization levels of up to 14.8% (when detected, averaging over all resonances), corresponding to signal enhancement by over 122,000-fold at the clinically relevant field of 1.4 T. We anticipate that our results can be directly translated to other structurally similar biomolecules such as [1- 13 C]α-ketoglutarate and [1- 13 C]α-ketoisocaproate. Moreover, other more advanced pulse shapes can potentially further boost heteronuclear polarization attainable via pulsed SABRE-SHEATH.

Nitric oxide (NO) is an important signaling molecule involved in a wide range of biological processes. Development of non-invasive, real-time detection of NO is greatly desired yet remains challenging. Here we report the design and development of novel 15 N- and 13 C-labeled NO-sensing probes for hyperpolarized nuclear magnetic resonance (HP-NMR) studies. These probes undergo selective and rapid reaction with NO to generate in situ AZO-products that can be monitored with distinguishable NMR signals as a read-out. This study also allows for a direct comparison of the 15 N and 13 C nuclei performances in hyperpolarized reaction-based probes. The simple and general SABRE-SHEATH hyperpolarization method works on the 15 N- and 13 C-NO-sensing probes. Measured long spin-lattice relaxation (T 1 ) values, especially for 15 N-NO probes, will allow for real-time reaction-based imaging of NO., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Abstract: Autoerotic death is defined as an accidental death that occurs when some type of apparatus is used to enhance sexual stimulation and causes an unintended death. We present the case of an atypical autoerotic death of a 23-year-old man found deceased in a bathroom. An electrical cord with a standard wall plug on one end and exposed wires twisted into loops on the other end was on the floor near his body. Minute black burns were present on each nipple. The outlet was protected by a ground fault circuit interrupter that was demonstrated to be in working order. An electrical consultant concluded that the cause of death could not be electrocution. Ground fault circuit interrupters work by detecting differences in current within a circuit. If a ground fault occurs, the circuit is broken to prevent a fatal electrocution. In the present case, the ground fault circuit interrupter did not shut off because the decedent had wired himself in parallel with the circuit. This, with the other scene findings, indicated this to be a case of atypical autoerotic death. Autoerotic deaths by means other than asphyxiation are rare. This case serves to illustrate the circumstances of an atypical autoerotic death by means of electrocution., Competing Interests: The authors report no conflict of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Signal Amplification By Reversible Exchange (SABRE) and the heteronuclear variant, X-SABRE, increase the sensitivity of magnetic resonance techniques using order derived from reversible binding of para-hydrogen. One current limitation of SABRE is suboptimal polarization transfer over the lifetime of the complex. Here, we demonstrate a multiaxial low-field pulse sequence which allows optimal polarization build-up during a low-field "evolution" pulse, followed by a high-field "mixing" pulse which permits proton decoupling along an orthogonal axis. This preserves the singlet character of the hydrides while allowing exchange to replenish the ligands on the iridium catalyst. This strategy leads to a 2.5-fold improvement over continuous field SABRE SHEATH experimentally which was confirmed with numerical simulation., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Pump-probe microscopy of melanin in tumors has been proposed to improve diagnosis of malignant melanoma, based on the hypothesis that aggressive cancers disaggregate melanin structure. However, measured signals of melanin are complex superpositions of multiple nonlinear processes, which makes interpretation challenging. Polarization control during measurement and data fitting are used to decompose signals of melanin into their underlying molecular mechanisms. We then identify the molecular mechanisms that are most susceptible to melanin disaggregation and derive false-coloring schemes to highlight these processes in biological tissue. We demonstrate that false-colored images of a small set of melanoma tumors correlate with clinical concern. More generally, our systematic approach of decomposing pump-probe signals can be applied to a multitude of different samples.

SABRE (Signal Amplification by Reversible Exchange) methods provide a simple, fast, and cost-effective method to hyperpolarize a wide variety of molecules in solution, and have been demonstrated with protons and, more recently, with heteronuclei (X-SABRE). Here, we present several oscillating pulse sequences that use magnetic fields far away from the resonance condition of continuous excitation and can commonly triple the polarization. An analysis with average Hamiltonian theory indicates that the oscillating pulse, in effect, adjusts the J-couplings between hydrides and target nuclei and that a much weaker coupling produces maximum polarization. This theoretical treatment, combined with simulations and experiment, shows substantial magnetization improvements relative to traditional X-SABRE methods. It also shows that, in contrast to most pulse sequence applications, waveforms with reduced time symmetry in the toggling frame make magnetization generation more robust to experimental imperfections.

Hyperpolarization methods in magnetic resonance overcome sensitivity limitations, especially for low-γ nuclei such as 13 C and 15 N. Signal Amplification By Reversible Exchange (SABRE) and extended SABRE (X-SABRE) are efficient and low-cost methods for generating large polarizations on a variety of nuclei, but they most commonly use low magnetic fields (μT-mT). High field approaches, where hyperpolarization is generated directly in the spectrometer, are potentially much more convenient but have been limited to selectively hyperpolarize single targets. Here we introduce a new pulse sequence-based approach that affords broadband excitation of SABRE hyperpolarization at high magnetic fields without having to tailor pulse sequence parameters to specific targets. This permits simultaneous hyperpolarization of multiple targets for the first time at high field and offers a direct approach to integration of high-field SABRE hyperpolarization into routine NMR applications, such as NMR-based metabonomics and biomolecular NMR.

Signal amplification by reversible exchange (SABRE) creates "hyperpolarization" (large spin magnetization) using a transition metal catalyst and parahydrogen, addressing the sensitivity limitations of magnetic resonance. SABRE and its heteronuclear variant X-SABRE are simple, fast, and general, but to date have not produced polarization levels as large as more established methods. We show here that the commonly used theoretical framework for these applications, which focuses on avoided crossings (also called level anticrossings or LACs), steer current SABRE and X-SABRE experiments away from optimal solutions. Accurate simulations show astonishingly rich and unexpected dynamics in SABRE/X-SABRE, which we explain with a combination of perturbation theory and average Hamiltonian approaches. This theoretical picture predicts simple pulse sequences with field values far from LACs (both instantaneously and on average) using different terms in the effective Hamiltonian to strategically control evolution and improve polarization transfer. Substantial signal enhancements under such highly nonintuitive conditions are verified experimentally.

Azide moieties, unique linear species containing three nitrogen atoms, represent an attractive class of molecular tag for hyperpolarized magnetic resonance imaging (HP-MRI). Here we demonstrate ( 15 N) 3 -azide-containing molecules exhibit long-lasting hyperpolarization lifetimes up to 9.8 min at 1 T with remarkably high polarization levels up to 11.6% in water, thus establishing ( 15 N) 3 -azide as a powerful spin storage for hyperpolarization. A single ( 15 N)-labeled azide has also been examined as an effective alternative tag with long-lived hyperpolarization. A variety of biologically important molecules are studied in this work, including choline, glucose, amino acid, and drug derivatives, demonstrating great potential of 15 N-labeled azides as universal hyperpolarized tags for nuclear magnetic resonance imaging applications., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Background: Exposure to household air pollution through the burning of biomass fuels is a global health concern and can lead to negative health outcomes such as asthma and lung disease., Objectives: The goal of this four-year study was to determine whether an intervention to reduce household air pollution (HAP) which included health education and a new well-ventilated cooking location would reduce exposure to HAP, lower carbon monoxide (CO) levels and improve the health of women and children in Port Sudan, Sudan., Methods: In 2016, 115 women of low socioeconomic status and their children were invited to participate in the study at two women's centers. One hundred and eleven women consented to participate and were divided into study and control groups on the basis of home ownership. Women who owned their homes learned about the adverse effects of HAP and a well-ventilated outside cooking location ( rakoobah ) was provided. Control women did not receive HAP education or a rakoobah . Questionnaires were used to assess the effect of education and a new well-ventilated cooking location for a group of Sudanese women who cook with biomass fuels. CO-oximetry was performed. Each year from 2017-2019, the questionnaires and CO-oximetry were repeated., Results: Sixty-five women and 33 children were assigned to the study group and 46 women and 19 children were assigned to the control group in 2016. Women were enrolled in 2016 with CO levels of 17.8% and 17.4%, respectively. One year later some of the study group women had lower CO levels and others higher, while the CO levels of the controls were stable. An intensive HAP education program was started for the study group women. By 2019, the last study year, the CO levels of both the study and control group women had dropped to normal levels of 2.9% and 3.1%, respectively. Control group women may have benefited from the HAP education and modeled behavior of those in the study group., Conclusions: The health impact of the change in cooking location was unclear, yet both groups reported fewer health care visits in 2019. Education and an outside cooking location resulted in lower CO levels of Sudanese women and children., Participant Consent: Obtained., Ethics Approval: The study was approved by the Penn State Milton S. Hershey Medical Center Institutional Review Board and the Ethics Committee of the Red Sea University Faculty of Medicine located in Port Sudan, Sudan., Competing Interests: The authors declare no competing financial interests., (© Pure Earth 2021.)

Pump-probe microscopy is an emerging nonlinear imaging technique based on high repetition rate lasers and fast intensity modulation. Here, we present new methods for pump-probe microscopy that keep the beam intensity constant and instead modulate the inter-pulse time delay or the relative polarization. These techniques can improve image quality for samples that have poor heat dissipation or long-lived radiative states and can selectively address nonlinear interactions in the sample. We experimentally demonstrate this approach and point out the advantages over conventional intensity modulation.

Mandates for mask use in public during the recent coronavirus disease 2019 (COVID-19) pandemic, worsened by global shortage of commercial supplies, have led to widespread use of homemade masks and mask alternatives. It is assumed that wearing such masks reduces the likelihood for an infected person to spread the disease, but many of these mask designs have not been tested in practice. We have demonstrated a simple optical measurement method to evaluate the efficacy of masks to reduce the transmission of respiratory droplets during regular speech. In proof-of-principle studies, we compared a variety of commonly available mask types and observed that some mask types approach the performance of standard surgical masks, while some mask alternatives, such as neck gaiters or bandanas, offer very little protection. Our measurement setup is inexpensive and can be built and operated by nonexperts, allowing for rapid evaluation of mask performance during speech, sneezing, or coughing., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution License 4.0 (CC BY).)

Here we report on chelating ligands for Signal Amplification By Reversible Exchange (SABRE) catalysts that permit hyperpolarisation on otherwise sterically hindered substrates. We demonstrate 1 H enhancements of ∼100-fold over 8.5 T thermal for 2-substituted pyridines, and smaller, yet significant enhancements for provitamin B 6 and caffeine. We also show 15 N-enhancements of ∼1000-fold and 19 F-enhancements of 30-fold.

Many important applications in biochemistry, materials science, and catalysis sit squarely at the interface between quantum and statistical mechanics: Coherent evolution is interrupted by discrete events, such as binding of a substrate or isomerization. Theoretical models for such dynamics usually truncate the incorporation of these events to the linear response limit, thus requiring small step sizes. Here, we completely reassess the foundations of chemical exchange models and redesign a master equation treatment for exchange accurate to infinite order in perturbation theory. The net result is an astonishingly simple correction to the traditional picture, which vastly improves convergence with no increased computational cost. We demonstrate that this approach accurately and efficiently extracts physical parameters from complex experimental data, such as coherent hyperpolarization dynamics in magnetic resonance, and is applicable to a wide range of other systems., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).)

We present a new imaging method for pump-probe microscopy that explores non-collinear excitation. This method (crossed-beam pump-probe microscopy, or CBPM) can significantly improve the axial resolution when imaging through low-NA lenses, providing an alternative way for depth-resolved, large field-of-view imaging. We performed a proof-of-concept demonstration, characterized CBPM's resolution using different imaging lenses, and measured an enhanced axial resolution for certain types of low-NA lenses.

15 N 2 -Diazirines represent an attractive class of imaging tags for hyperpolarized magnetic resonance imaging (HP-MRI), offering desirable biocompatibility, ease of incorporation into a variety of molecules, and ability to deliver long-lasting polarization. We have recently established hyperpolarization of 15 N 2 -diazirines in organic solvents using SABRE-Shield Enables Alignment Transfer to Heteronuclei (SABRE-SHEATH). Yet, the current challenge of SABRE-SHEATH in water, specifically poor polarization efficiency, presents a barrier in examining the practical use of 15 N 2 -diazirines for HP-MRI. Herein, we show that efficient polarization of diverse 15 N 2 -diazirine-labeled molecules in water can be readily achieved by dissolution dynamic nuclear polarization (d-DNP), a hyperpolarization technique used in clinical practice. Hyperpolarization by d-DNP also demonstrates greater enhancement for long-lasting 15 N signals, in comparison with SABRE-SHEATH. Various biologically important molecules are studied in this work, including amino acid, sugar, and drug compounds, demonstrating the great potential of 15 N 2 -diazirines as molecular tags in broad biomedical and clinical applications.

Herein, we demonstrate "direct" 13 C hyperpolarization of 13 C-acetate via signal amplification by reversible exchange (SABRE). The standard SABRE homogeneous catalyst [Ir-IMes; [IrCl(COD)(IMes)], (IMes=1,3-bis(2,4,6-trimethylphenyl), imidazole-2-ylidene; COD=cyclooctadiene)] was first activated in the presence of an auxiliary substrate (pyridine) in alcohol. Following addition of sodium 1- 13 C-acetate, parahydrogen bubbling within a microtesla magnetic field (i.e. under conditions of SABRE in shield enables alignment transfer to heteronuclei, SABRE-SHEATH) resulted in positive enhancements of up to ≈100-fold in the 13 C NMR signal compared to thermal equilibrium at 9.4 T. The present results are consistent with a mechanism of "direct" transfer of spin order from parahydrogen to 13 C spins of acetate weakly bound to the catalyst, under conditions of fast exchange with respect to the 13 C acetate resonance, but we find that relaxation dynamics at microtesla fields alter the optimal matching from the traditional SABRE-SHEATH picture. Further development of this approach could lead to new ways to rapidly, cheaply, and simply hyperpolarize a broad range of substrates (e.g. metabolites with carboxyl groups) for various applications, including biomedical NMR and MRI of cellular and in vivo metabolism., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The spatial heterogeneity of carrier dynamics in mixed halide perovskite CH 3 NH 3 PbI 3-x Cl x thin films with a range of different chloride additions is mapped using femtosecond transient absorption microscopy (TAM). The comparison of TAM images of fibrous and granular polycrystalline CH 3 NH 3 PbI 3-x Cl x films indicates that the impact of chloride addition on the local heterogeneity of carrier dynamics is highly dependent on the film preparation method and the resulting morphology. In addition to signals of pristine CH 3 NH 3 PbI 3 , CH 3 NH 3 PbI 3-x Cl x films with a fibrous structure show long-lived excited state absorption (ESA) signals in localized, microscopic regions. The ESA signal exhibits transient absorption with a rise time of about 5 ps after the excitation pulse, indicating that these distinct micrograins have preferential carrier trapping properties. The chemical composition of these micrograins does not differ detectably from their surroundings. In contrast, in CH 3 NH 3 PbI 3-x Cl x films with a granular structure, Cl addition does not seem to affect the charge carrier dynamics. These results provide insight into the localized effects of halide mixing and on the resulting photophysical properties of mixed halide perovskite materials on the micrometer length scale.

Melatonin (MEL) is a neurohormone in humans produced in a number of locations. Starting with the amino acid tryptophan, MEL is produced through a number of enzymatic steps that includes serotonin as an intermediate compound. The primary production of MEL is in the pineal gland located in the brain. It is directly associated with the the suprachiasmatic nucleus (SCN) located in the hypothalamus. In young and adult humans, the blood levels of MEL are typically in the picogram levels and produced in a cyclic schedule highly regulated by light detected in the retina by intrinsically photosensitive retinal ganglion cells (ipRGCs), resulting in production primarily during periods of darkness. During periods of light, MEL levels are typically very low or undetectable. Basal levels of MEL in infants have been observed to be either undetectable or also in the picogram levels, although some medical treatment has involved administration of exogenous MEL resulting in peak levels in the nanogram range. MEL is considered to be well tolerated and there have been limited reports of toxicity. In this case, an infant was found unresponsive and cause of death was ruled as Undetermined. Melatonin was detected in the peripheral blood at a concentration of 1,400ng/mL., (Copyright © 2019. Published by Elsevier B.V.)

Signal Amplification By Reversible Exchange, or SABRE, uses the singlet-order of parahydrogen to generate hyperpolarized signals on target nuclei, bypassing the limitations of traditional magnetic resonance. Experiments performed directly in the magnet provide a route to generate large magnetizations continuously without having to field-cycle the sample. For heteronuclear SABRE, these high-field methods have been restricted to the few SABRE complexes that exhibit efficient exchange with symmetric ligand environments as co-ligands induce chemical shift differences between the parahydrogen-derived hydrides, destroying the hyperpolarized spin order. Through careful consideration of the underlying spin physics, we introduce 1 H decoupled LIGHT-SABRE pulse sequence variants which bypasses this limitation, drastically expanding the scope of heteronuclear SABRE at high field., (Copyright © 2019 Elsevier Inc. All rights reserved.)

A one-pot metal-free conversion of unprotected amino acids to terminal diazirines has been developed using phenyliodonium diacetate (PIDA) and ammonia. This PIDA-mediated transformation occurs via three consecutive reactions and involves an iodonitrene intermediate. This method is tolerant to most functional groups found on the lateral chain of amino acids, it is operationally simple, and it can be scaled up to provide multigram quantities of diazirine. Interestingly, we also demonstrated that this transformation could be applied to dipeptides without racemization. Furthermore, 14 N 2 and 15 N 2 isotopomers can be obtained, emphasizing a key trans-imination step when using 15 NH 3 . In addition, we report the first experimental observation of 14 N/ 15 N isotopomers directly creating an asymmetric carbon. Finally, the 15 N 2 -diazirine from l-tyrosine was hyperpolarized by a parahydrogen-based method (SABRE-SHEATH), demonstrating the products' utility as hyperpolarized molecular tag.

Diazirine moieties are chemically stable and have been incorporated into biomolecules without impediment of biological activity. The 15 N 2 labeled diazirines are appealing motifs for hyperpolarization supporting relaxation protected states with long-lived lifetimes. The (-CH 15 N 2 ) diazirine groups investigated here are analogues to methyl groups, which provides the opportunity to transfer polarization stored on a relaxation protected (-CH 15 N 2 ) moiety to 1 H, thus combining the advantages of long lifetimes of 15 N polarization with superior sensitivity of 1 H detection. Despite the proximity of 1 H to 15 N nuclei in the diazirine moiety, 15 N T 1 times of up to (4.6±0.4) min and singlet lifetimes T s of up to (17.5±3.8) min are observed. Furthermore, we found terminal diazirines to support hyperpolarized 1 H 2 singlet states in CH 2 groups of chiral molecules. The singlet lifetime of 1 H singlets is up to (9.2±1.8) min, thus exceeding 1 H T 1 relaxation time (at 8.45 T) by a factor of ≈100., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We report on an extension of the quasi-resonance (QUASR) pulse sequence used for signal amplification by reversible exchange (SABRE), showing that we may target distantly J -coupled 19 F-spins. Polarization transfer from the parahydrogen-derived hydrides to the 19 F nucleus is accomplished via weak five-bond J -couplings using a shaped QUASR radio frequency pulse at a 0.05 T magnetic field. The net result is the direct generation of hyperpolarized 19 F z -magnetization, derived from the parahydrogen singlet order. An accumulation of 19 F polarization on the free ligand is achieved with subsequent repetition of this pulse sequence. The hyperpolarized 19 F signal exhibits clear dependence on the pulse length, irradiation frequency, and delay time in a manner similar to that reported for 15 N QUASR-SABRE. Moreover, the hyperpolarized 19 F signals of 3- 19 F- 14 N-pyridine and 3- 19 F- 15 N-pyridine isotopologues are similar, suggesting that (i) polarization transfer via QUASR-SABRE is irrespective of the nitrogen isotopologue and (ii) the presence or absence of the spin-1/2 15 N nucleus has no impact on the efficiency of QUASR-SABRE polarization transfer. Although optimization of polarization transfer efficiency to 19 F ( P 19 F ≈ 0.1%) was not the goal of this study, we show that high-field SABRE can be efficient and broadly applicable for direct hyperpolarization of 19 F spins.

Signal Amplification By Reversible Exchange (SABRE) and its heteronuclear variant SABRE in SHield Enables Alignment Transfer to Heteronuclei create large nuclear magnetization in target ligands, exploiting level crossings in an iridium catalyst that transiently binds both the ligands and parahydrogen. This requires a specific, small magnetic field to match Zeeman splittings to scalar couplings. Here, we explore a different strategy, direct creation of heteronuclear singlet states in the target ligands, which produces enhanced signals at other field strengths, including zero field. We also show that pulsed methods (including pulsed field nulling) coherently and selectively pump such singlets, affording a significant enhancement on the resulting hyperpolarization.

The NMR hyperpolarization of uniformly 15 N-labeled [ 15 N 3 ]metronidazole is demonstrated by using SABRE-SHEATH. In this antibiotic, the 15 NO 2 group is hyperpolarized through spin relays created by 15 N spins in [ 15 N 3 ]metronidazole, and the polarization is transferred from parahydrogen-derived hydrides over six chemical bonds. In less than a minute of parahydrogen bubbling at approximately 0.4 μT, a high level of nuclear spin polarization (P 15N ) of around 16 % is achieved on all three 15 N sites. This product of 15 N polarization and concentration of 15 N spins is around six-fold better than any previous value determined for 15 N SABRE-derived hyperpolarization. At 1.4 T, the hyperpolarized state persists for tens of minutes (relaxation time, T 1 ≈10 min). A novel synthesis of uniformly 15 N-enriched metronidazole is reported with a yield of 15 %. This approach can potentially be used for synthesis of a wide variety of in vivo metabolic probes with potential uses ranging from hypoxia sensing to theranostic imaging., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Here, we demonstrate the use of pump-probe microscopy for high-resolution studies of vermilion degradation. Vermilion (mostly α-HgS), an important red pigment used in historical paintings, blackens over time, and metallic Hg and β-HgS have been implicated as possible degradation products. Conventional analysis techniques have trouble differentiating α- and β-HgS with sufficiently high spatial resolution. However, pump-probe microscopy can differentiate metallic mercury, α- and β-HgS, and map each distribution on the microscopic scale. We studied artificial degradation of α-HgS; femtosecond-pulsed laser irradiation induces an irreversible phase shift of α- to β-HgS, in which the initial presence of β-HgS grains can increase the rate of conversion in their vicinity. Continuous ultraviolet exposure instead generates both liquid Hg and β-HgS, with a conversion rate that increases with elevated temperatures. Last, we reveal the presence of β-HgS as a natural degradation product in discolored vermilion layers in a 14th century Italian painting.

Purpose: We analyze melanin structure and biochemical composition in conjunctival melanocytic lesions using pump-probe microscopy to assess the potential for this method to assist in melanoma diagnosis., Methods: Pump-probe microscopy interrogates transient excited-state photodynamic properties of absorbing molecules, which yields highly specific molecular information with subcellular spatial resolution. This method is applied to analyze melanin in 39 unstained, thin biopsy specimens of melanocytic conjunctival lesions. Quantitative features of the biochemical composition and structure of melanin in histopathologic specimens are assessed using a geometric representation of principal component analysis (PCA) and principles of mathematical morphology. Diagnostic power is determined using a feature selection algorithm combined with cross validation., Results: Conjunctival melanomas show higher biochemical heterogeneity and different overall biochemical composition than primary acquired melanosis of the conjunctiva (PAM) without severe atypia. The molecular signatures of PAMs with severe atypia more closely resemble melanomas than other types of PAMs. Pigment organization in the tissue becomes more disorganized as diagnosis of the lesions worsen, but nevi are more inconsistent biochemically and structurally than other lesions. Relatively high sensitivity (SE) and specificity (SP) is achieved for differentiating between various melanocytic lesions, particularly PAMs without severe atypia and melanomas (SE = 89%; SP = 87%)., Conclusions: Pump-probe microscopy is a powerful tool that can identify quantitative, phenotypic differences between various types of conjunctival melanocytic lesions., Translational Relevance: This study further validates the use of pump-probe microscopy as a potential diagnostic aid for histopathologic evaluation of conjunctival melanocytic lesions.

More people die from melanoma after a stage I diagnosis than after a stage IV diagnosis, because the tools available to clinicians do not readily identify which early-stage cancers will be aggressive. Near-infrared pump-probe microscopy detects fundamental differences in melanin structure between benign human moles and melanoma and also correlates with metastatic potential. However, the biological mechanisms of these changes have been difficult to quantify, as many different mechanisms can contribute to the pump-probe signal. We use model systems (sepia, squid, and synthetic eumelanin), cellular uptake studies, and a range of pump and probe wavelengths to demonstrate that the clinically observed effects come from alterations of the aggregated mode from "thick oligomer stacks" to "thin oligomer stacks" (due to changes in monomer composition) and (predominantly) deaggregation of the assembled melanin structure. This provides the opportunity to use pump-probe microscopy for the detection and study of melanin-associated diseases.

Signal amplification by reversible exchange (SABRE) is an efficient method to hyperpolarize spin-1/2 nuclei and affords signals that are orders of magnitude larger than those obtained by thermal spin polarization. Direct polarization transfer to heteronuclei such as 13 C or 15 N has been optimized at static microTesla fields or using coherence transfer at high field, and relies on steady state exchange with the polarization transfer catalyst dictated by chemical kinetics. Here we demonstrate that pulsing the excitation field induces complex coherent polarization transfer dynamics, but in fact pulsing with a roughly 1% duty cycle on resonance produces more magnetization than constantly being on resonance. We develop a Monte Carlo simulation approach to unravel the coherent polarization dynamics, show that existing SABRE approaches are quite inefficient in use of para-hydrogen order, and present improved sequences for efficient hyperpolarization.

In this work, we investigate the relationship between the complex hierarchical assembly structure of eumelanin, its characteristic broad absorption band, and the highly unusual nonlinear dynamics revealed by pump-probe or transient absorption microscopy. Melanin-like nanoparticles (MelNPs), generated by spontaneous oxidation of dopamine, were created with uniform but adjustable size distributions, and kinetically controlled oxidation was probed with a wide range of characterization methods. This lets us explore the broad absorption bands of eumelanin models at different assembly levels, such as small subunit fractions (single monomeric and oligomeric units and small oligomer stacks), stacked oligomer fractions (protomolecules), and large-scale aggregates of protomolecules (parental particles). Both the absorption and pump-probe dynamics are very sensitive to these structural differences or to the size of intact particles (a surprising result for an organic polymer). We show that the geometric packing order of protomolecules in long-range aggregation is key secondary interactions to extend the absorption band of eumelanin to the low energy spectrum and produce drastic changes in the transient absorption spectrum.

In this paper, we analyze fundamental photoexcitation processes and charge carrier kinetics in Cu 2 BaSnS 4- x Se x (CBTSSe), a recently introduced alternative to Cu(In,Ga)(S,Se) 2 and Cu 2 ZnSnS 4- x Se x (CZTSSe) photovoltaic/photoelectrochemical absorbers, using advanced laser spectroscopy and microscopy techniques. The broadband pump-probe diffuse reflectance spectroscopy technique facilitates monitoring the ultrafast processes in opaque CBTSSe films deposited on Mo-coated glass substrates, similar to the configuration found in functional devices. We spectrally resolve a sharp ground-state bleaching (GSB) peak for CBTSSe films, formed around the band edge transition, which is spectrally narrower than the GSB and stimulated emission in corresponding CZTSSe films. The presence of sharp electronic transitions is further deduced from the ensemble pump-probe spectroscopy and steady-state UV-vis diffuse reflectance spectra. Furthermore, using pump-probe diffuse reflectance scanning microscopy, we monitor the charge carrier formation and excited state pattern within the film grains at few hundred nanometer resolution and localize the kinetics of photogenerated carriers in each grain. The unique sensitivity of pump-probe microscopy and sharp electronic transitions allow for detection of small S/Se stoichiometry variations, Δ x ≤ 0.3, in CBTSSe grains-i.e., features that are largely unresolved for ensemble spectroscopy or luminescence measurements. By noting the sharp band edge transition, we show that the band tailing issue (prevalent for CZTSSe) is largely resolved for CBTSSe; however, other issues may remain, such as deep defects and fast carriers relaxations, which may still impact the photocurrent and open circuit voltage of the CBTSSe devices/films examined.

Analysis of red organic pigments in artworks (and in forensics applications) is challenging, because conventional nondestructive mapping techniques provide little contrast, and most chemical analyses with high specificity require sample removal. Here we demonstrate a new optical approach, pump-probe microscopy, for the analysis of red organic pigments. We investigate Carmine naccarat, Lac dye, purpurin, alizarin, madder lake, and eosin Y and show that their intrinsic photophysical properties produce distinctive pump-probe spectra. We utilize this contrast for high-resolution, three-dimensional imaging without the need for physical sample removal. Lastly, we highlight the potential of pump-probe microscopy as an analytical tool for forensics of other types of organic colorants by investigating a series of automotive paints.

Here we present the feasibility of NMR signal amplification by reversible exchange (SABRE) using radio frequency irradiation at low magnetic field (0.05 T) in the regime where the chemical shifts of free and catalyst-bound species are similar. In SABRE, the 15 N-containing substrate and parahydrogen perform simultaneous chemical exchange on an iridium hexacoordinate complex. A shaped spin-lock induced crossing (SLIC) radio frequency pulse sequence followed by a delay is applied at quasi-resonance (QUASR) conditions of 15 N spins of a 15 N-enriched substrate. As a result of this pulse sequence application, 15 N z-magnetization is created from the spin order of parahydrogen-derived hyperpolarized hydrides. The repetition of the pulse sequence block consisting of a shaped radio frequency pulse and the delay leads to the buildup of 15 N magnetization. The modulation of this effect by the irradiation frequency, pulse duration and amplitude, delay duration, and number of pumping cycles was demonstrated. Pyridine- 15 N, acetonitrile- 15 N, and metronidazole- 15 N 2 - 13 C 2 substrates were studied representing three classes of compounds (five- and six-membered heterocycles and nitrile), showing the wide applicability of the technique. Metronidazole- 15 N 2 - 13 C 2 is an FDA-approved antibiotic that can be injected in large quantities, promising noninvasive and accurate hypoxia sensing. The 15 N hyperpolarization levels attained with QUASR-SABRE on metronidazole- 15 N 2 - 13 C 2 were more than 2-fold greater than those with SABRE-SHEATH (SABRE in shield enables alignment transfer to heteronuclei), demonstrating that QUASR-SABRE can deliver significantly more efficient means of SABRE hyperpolarization.

Hyperpolarized magnetic resonance (HP-MR) is a powerful, sensitive, and noninvasive approach to visualize molecular structure, function, and dynamics in vitro and in vivo. Current applications of HP-MR mostly rely on hyperpolarization of target compounds in dedicated hyperpolarizers because biomolecules can typically not be hyperpolarized directly in vivo. The injected hyperpolarized probes often undergo multiple metabolic pathways in living systems, and it remains challenging to localize and identify specific targets with high chemical selectivity. To address these current limitations in HP-MR, we report a novel hyperpolarization tagging strategy that integrates bioorthogonal chemistry and hyperpolarization to achieve the specific hyperpolarization of targets. This strategy is demonstrated by studies of hyperpolarized 15 N 4 -1,2,4,5-tetrazines, which undergo rapid and selective cycloaddition with cyclooctyne to provide hyperpolarized 15 N 2 -containing cycloaddition products and hyperpolarized 15 N 2 gas. This work not only suggests great potential of 15 N 4 -1,2,4,5-tetrazines as molecular tags in HP-MR imaging (HP-MRI) but also supports the production of hyperpolarized para - 15 N 2 gas, a biologically and medically innocuous gas with great potential for HP-MRI. This bioorthogonal reaction-based hyperpolarization tagging strategy enables a new class of in vitro and in vivo applications.

A systematic experimental study is reported on the polarization transfer to distant spins, which do not directly bind to the polarization transfer complexes employed in Signal Amplification By Reversible Exchange (SABRE) experiments. Both, long-range transfer to protons and long-range transfer to heteronuclei i.e. 13 C and 15 N are examined. Selective destruction of hyperpolarization on 1 H, 13 C, and 15 N sites is employed, followed by their re-hyperpolarization from neighboring spins within the molecules of interest (pyridine for 1 H studies and metronidazole- 15 N 2 - 13 C 2 for 13 C and 15 N studies). We conclude that long-range sites can be efficiently hyperpolarized when a network of spin-½ nuclei enables relayed polarization transfer ( i.e . via short-range interactions between sites). In case of proton SABRE in the milli-Tesla regime, a relay network consisting of protons only is sufficient. However, in case 13 C and 15 N are targeted (i.e. via SABRE in SHield Enables Alignment Transfer to Heteronuclei or SABRE-SHEATH experiment), the presence of a heteronuclear network ( e.g . consisting of 15 N) enables a relay mechanism that is significantly more efficient than the direct transfer of spin order from para -H 2 -derived hydrides.

The published online version contains mistake. Warren S. Warren was not included in the author group section. Corrected author group section is shown above.

Diazirines are an attractive class of potential molecular tags for magnetic resonance imaging owing to their biocompatibility and ease of incorporation into a large variety of molecules. As recently reported, 15 N 2 -diazirine can be hyperpolarized by the SABRE-SHEATH method, sustaining both singlet and magnetization states, thus offering a path to long-lived polarization storage. Herein, we show the generality of this approach by illustrating that the diazirine tag alone is sufficient for achieving excellent signal enhancements with long-lasting polarization. Our investigations reveal the critical role of Lewis basic additives, including water, on achieving SABRE-promoted hyperpolarization. The application of this strategy to a 15 N 2 -diazirine-containing choline derivative demonstrates the potential of 15 N 2 -diazirines as molecular imaging tags for biomedical applications., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Fluorine-19 has high NMR detection sensitivity-similar to that of protons-owing to its large gyromagnetic ratio and high natural abundance (100 %). Unlike protons, however, fluorine-19 ( 19 F) has a negligible occurrence in biological objects, as well as a more sensitive chemical shift. As a result, in vivo 19 F NMR spectroscopy and MR imaging offer advantages of negligible background signal and sensitive reporting of the local molecular environment. Here we report on NMR hyperpolarization of 19 F nuclei using reversible exchange reactions with parahydrogen gas as the source of nuclear spin order. NMR signals of 3-fluoropyridine were enhanced by ≈100 fold, corresponding to 0.3 % 19 F nuclear spin polarization (at 9.4 T), using about 50 % parahydrogen. While future optimization efforts will likely significantly increase the hyperpolarization levels, we already demonstrate the utility of 19 F hyperpolarization for high-resolution hyperpolarized 19 F imaging and hyperpolarized 19 F pH sensing., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Microscopic variations in melanin composition can be mapped through linear and nonlinear optical responses. Though instrumentation to measure linear attenuation is simple and inexpensive, the nonlinear response provides more degrees of freedom with which to spectroscopically resolve pigments. The objective of this study is to assess differences in imaging melanin contrast by comparing hyperspectral (linear) versus pump-probe (nonlinear) microscopy of unstained histology sections of pigmented lesions. The images and analysis we have presented here show that pump-probe uncovers a greater variation in pigment composition, compared with hyperspectral microscopy, and that the two methods yield complimentary biochemical information.

Parahydrogen is an inexpensive and readily available source of hyperpolarization used to enhance magnetic resonance signals by up to four orders of magnitude above thermal signals obtained at ∼10 T. A significant challenge for applications is fast signal decay after hyperpolarization. Here we use parahydrogen-based polarization transfer catalysis at microtesla fields (first introduced as SABRE-SHEATH) to hyperpolarize 13 C 2 spin pairs and find decay time constants of 12 s for magnetization at 0.3 mT, which are extended to 2 min at that same field, when long-lived singlet states are hyperpolarized instead. Enhancements over thermal at 8.5 T are between 30 and 170 fold (0.02 to 0.12% polarization). We control the spin dynamics of polarization transfer by choice of microtesla field, allowing for deliberate hyperpolarization of either magnetization or long-lived singlet states. Density functional theory calculations and experimental evidence identify two energetically close mechanisms for polarization transfer: First, a model that involves direct binding of the 13 C 2 pair to the polarization transfer catalyst and, second, a model transferring polarization through auxiliary protons in substrates.

Nuclear spin hyperpolarization techniques are revolutionizing the field of 13 C molecular MRI. While dissolution dynamic nuclear polarization (d-DNP) is currently the leading technique, it is generally slow (requiring ≈1 h) and costly (≈$USD10 6 ). As a consequence of carbon's central place in biochemistry, tremendous progress using 13 C d-DNP bioimaging has been demonstrated to date including a number of clinical trials. Despite numerous attempts to develop alternatives to d-DNP, the competing methods have faced significant translational challenges. Efficient hyperpolarization of 15 N, 31 P, and other heteronuclei using signal amplification by reversible exchange (SABRE) has been reported in 2015, but extension of this technique to 13 C has proven to be challenging. Here, we present efficient hyperpolarization of 13 C nuclei using micro-Tesla SABRE. Up to ca. 6700-fold enhancement of nuclear spin polarization at 8.45 T is achieved within seconds, corresponding to P 13C ≈4.4 % using 50 % parahydrogen (P 13C >14 % would be feasible using more potent ≈100 % parahydrogen). Importantly, the 13 C polarization achieved via SABRE strongly depends not only upon spin-lattice relaxation, but also upon the presence of 15 N (I=1/2) versus quadrupolar 14 N (I=1) spins in the site binding the hexacoordinate Ir atom of the catalytic complex. We show that different 13 C nuclei in the test molecular frameworks-pyridine and acetonitrile-can be hyperpolarized, including 13 C sites up to five chemical bonds away from the exchangeable hydrides. The presented approach is highly scalable and can be applied to a rapidly growing number of biomolecules amendable to micro-Tesla SABRE., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Signal amplification by reversible exchange (SABRE) is an inexpensive, fast, and even continuous hyperpolarization technique that uses para-hydrogen as hyperpolarization source. However, current SABRE faces a number of stumbling blocks for translation to biochemical and clinical settings. Difficulties include inefficient polarization in water, relatively short-lived 1 H-polarization, and relatively limited substrate scope. Here we use a water-soluble polarization transfer catalyst to hyperpolarize nitrogen-15 in a variety of molecules with SABRE-SHEATH (SABRE in shield enables alignment transfer to heteronuclei). This strategy works in pure H 2 O or D 2 O solutions, on substrates that could not be hyperpolarized in traditional 1 H-SABRE experiments, and we record 15 N T 1 relaxation times of up to 2 min.

Objectives: Melanomas of the female genital tract present a unique clinical challenge. Not only are these lesions in an anatomically sensitive area, but also they tend to be multifocal and have high recurrence rates. Furthermore, several benign melanocytic proliferations resemble early-stage melanoma clinically and/or histopathologically. Thus, there is a significant need for additional tools that can help correctly diagnose and stage these lesions. Here, we quantitatively and nondestructively analyze the chemical composition of melanin in excised pigmented lesions of the female genital tract using pump-probe microscopy, a high-resolution optical imaging technique that is sensitive to many biochemical properties of melanin., Materials and Methods: Thirty-one thin (~5 μm) tissue sections previously excised from female genital tract melanocytic lesions were imaged with pump-probe microscopy and analyzed., Results: We find significant quantitative differences in melanin type and structure between melanoma and nonmalignant melanocytic proliferations. Our analysis also suggests a link between the molecular signatures of melanins and lesion-specific genetic mutations. Finally, significant differences are found between metastatic and nonmetastatic melanomas. The limitations of this work include the fact that molecular information is restricted to melanin pigment and the sample size is relatively small., Conclusions: Pump-probe microscopy provides unique information regarding the biochemical composition of genital tract melanocytic lesions, which can be used to improve the diagnosis and staging of vulvar melanomas.

Signal Amplification by Reversible Exchange (SABRE) is a fast and convenient NMR hyperpolarization method that uses cheap and readily available para -hydrogen as a hyperpolarization source. SABRE can hyperpolarize protons and heteronuclei. Here we focus on the heteronuclear variant introduced as SABRE-SHEATH (SABRE in SHield Enables Alignment Transfer to Heteronuclei) and nitrogen-15 targets in particular. We show that 15 N-SABRE works more efficiently and on a wider range of substrates than 1 H-SABRE, greatly generalizing the SABRE approach. In addition, we show that nitrogen-15 offers significantly extended T 1 times of up to 12 minutes. Long T 1 times enable higher hyperpolarization levels but also hold the promise of hyperpolarized molecular imaging for several tens of minutes. Detailed characterization and optimization are presented, leading to nitrogen-15 polarization levels in excess of 10% on several compounds.

We integrate spectroscopic optical coherence tomography (SOCT) with stimulated Raman scattering (SRS) to enable simultaneously multiplexed spatial and spectral imaging with sensitivity to many endogenous biochemical species that play an important role in biology and medicine. The combined approach, termed SRS-SOCT, overcomes the limitations of each individual method. Ultimately, SRS-SOCT has the potential to achieve fast, volumetric, and highly sensitive label-free molecular imaging. We demonstrate the approach by imaging excised human adipose tissue and detecting the lipids' Raman signatures in the high-wavenumber region.