Determination of Acrolein-Associated T 1 and T 2 Relaxation Times and Noninvasive Detection Using Nuclear Magnetic Resonance and Magnetic Resonance Spectroscopy Abstract An estimated 3.3 million people are living with a traumatic brain injury (TBI)-associated morbidity. Currently, only invasive and sacrificial methods exist to study neurochemical alterations following TBI. Nuclear magnetic resonance methods—magnetic resonance imaging (MRI) and spectroscopy (MRS)—are powerful tools which may be used noninvasively to diagnose a range of medical issues. These methods can be utilized to explore brain functionality, connectivity, and biochemistry. Unfortunately, many of the commonly studied brain metabolites (e.g., N-acetyl-aspartate, choline, creatine) remain relatively stable following mild to moderate TBI and may not be suitable for longitudinal assessment of injury severity and location. Therefore, a critical need exists to investigate alternative biomarkers of TBI, such as acrolein. Acrolein is a byproduct of lipid peroxidation and accumulates following damage to neuronal tissue. Acrolein has been shown to increase in post-mortem rat brain tissue following TBI. However, no methods exist to noninvasively quantify acrolein in vivo. Currently, we have characterized the T1 and T2 of acrolein via nuclear magnetic resonance saturation recovery and Carr–Purcell–Meiboom–Gill experiments, accordingly, to maximize the signal-to-noise ratio of acrolein obtained with MRS. In addition, we have quantified acrolein in water and whole-brain phantom using PRESS MRS and standard post-processing methods. With this potential novel biomarker for assessing TBI, we can investigate methods for predicting acute and chronic neurological dysfunction in humans and animal models. By quantifying and localizing acrolein with MRS, and investigating neurological outcomes associated with in vivo measures, patient-specific interventions could be developed to decrease TBI-associated morbidity and improve quality of life.

Evidence of the Excitation of Mn 2+ Spin-Dependent Photoluminescence in Manganese-Doped Yttrium Aluminum Garnets Abstract Mn2+ ions in yttrium positions have been studied by means of optically detected magnetic resonance (ODMR) via Mn2+ spin-dependent emission in manganese-doped yttrium aluminum garnet crystals. It was shown that the intensity of photoluminescence excited by circularly polarized light depends on the population of the spin sublevels of the Mn2+ ground state and therefore can be used to study the ODMR. EPR measurements have confirmed that Mn2+ ions in the crystals under study occupy preferentially dodecahedral positions in the YAG lattice. Observation of forbidden transitions in the ODMR spectra has proved that the observed ODMR signals belong to Mn2+. Thus the wavelength dependence of the ODMR amplitude reveals the emission band of Mn2+ ions at dodecahedral positions in YAG:Mn.

Supplemental Shimming for HR-μMAS NMR Spectroscopy Abstract Occasionally in proton high-resolution magic angle spinning nuclear magnetic resonance spectroscopy (1H HR-MAS NMR), the standard field shimming across the region-of-interest with the active shims is not sufficient in the presence of substantial magnetic susceptibility gradients. This can be ascribed to the presence of large air pocket within the sample, the proximity between sample and probehead (especially with micro-sized probes), or data acquisition at high magnetic fields. Herein, the study demonstrates a simple approach to enhance the capacity of the shim fields—by supplementing a specific passive ferro-shim—for unifying the field distributions across the sample. Qualitative field numerical analyses were carried out to illustrate the effectiveness of the applied passive shims together with the active shims.

EPR Characterization of the Light-Induced Negative Polaron in a Functionalized Dithienylthiazolo[5,4- d ]thiazole Acceptor for Organic Photovoltaics Abstract Functionalized 2,5-dithienylthiazolo[5,4-d]thiazole (DTTzTz) derivatives have attracted interest towards application as non-fullerene acceptors in solution-processed organic solar cells. Here, we present a combined high-field electron paramagnetic resonance and density functional theory study of the light-induced negative polaron on the novel acceptor 2,4-diCN-Ph-DTTzTz formed after charge transfer in bulk heterojunction blends with a donor polymer. Despite spectral overlap with the polymer cation, the g-anisotropy of the acceptor radical could be directly confirmed through detection of its unique 14N hyperfine couplings using electron–electron double resonance (ELDOR)-detected nuclear magnetic resonance (EDNMR) for spectral filtering. The spectral assignment is further underpinned by quantum-chemical calculations, which also provide detailed information about the spin density and charge distribution of the polaron in the DTTzTz acceptor.

De-noising Multi-coil Magnetic Resonance Imaging Using Patch-Based Adaptive Filtering in Wavelet Domain Abstract Magnetic resonance imaging (MRI) frequently requires transform domain de-noising methods to preserve important features in the reconstructed images such as corners, sharp structures, and edges. Wavelet transform-based image de-noising is a standard approach used in MRI to recover smooth surface and sharp edges from the given noisy MR images, thereby improving diagnostic interpretations. Parallel magnetic resonance imaging (pMRI) techniques such as SENSE have been recently developed with an aim to improve the data acquisition speed, signal-to-noise ratio (SNR), and spatial resolution of the reconstructed images. However, the SENSE reconstruction algorithm often encounters noise during data acquisition and reconstruction process which not only contaminates the quality of the reconstructed images but also leads to poor diagnostic interpretations in clinical settings. During SENSE reconstruction process, noise can appear in the reconstructed image mainly due to two reasons (1) imperfections in the receiver coils; (2) un-folding the aliased images of multiple receiver coils to obtain a single composite image. In this paper, a new adaptive patch-based filtering in wavelet domain is presented to recover sharp structures and edges without introducing any artifacts in the SENSE reconstructed images. The proposed method uses soft-thresholding function as a shrinkage process which typically involves thresholding the small wavelet coefficients to reduce the noise without affecting the important features in the SENSE reconstructed images. For the evaluation of the proposed method, several experiments are performed using simulated phantom and in vivo data sets. The SENSE reconstruction quality using the proposed method is compared with contemporary de-nosing techniques, in terms of structural similarity index (SSIM) and peak signal-to-noise ratio (PSNR). Experimental results demonstrate that the SENSE reconstruction using the proposed method when compared to the other contemporary de-nosing methods successfully removes the noise and preserves the fine details in the reconstructed MR images without introducing blurring artifacts.

Charge Transfer State in the Composite DTS(FBTTh 2 ) 2 :PC 71 BM: Dynamics of Electron–Hole Distance Distribution After Light Absorption Abstract Light-induced charge separation in an organic photovoltaic (OPV) composite DTS(FBTTh2)2:PC71BM was studied. DTS(FBTTh2)2 or DTS is a non-polymer electron donor and PC71BM is a fullerene-based electron acceptor. Electron spin echo (ESE) technique has been developed to separate the signal of interfacial charge transfer state (CTS) from that of trapped charges. Pronounced out-of-phase ESE signal was observed within first few microseconds after a laser flash exciting the composite at cryogenic temperatures. This implies correlation of unpaired electron spins of DTS+ and PC71BM– species constituting CTS. The distribution of distances between these species is derived from out-of-phase ESE envelope modulation (ESEEM). Out-of-phase ESEEM traces were numerically simulated by the model assuming both magnetic dipolar and electron–hole exchange interactions within CTS. The most probable distance between DTS+ and PC71BM– within CTS increases from 4.9 nm and 5.7 nm with delays after the laser flash increase from 200 ns to 30 µs at the lowest temperature studied 20 K. This is caused by faster recombination of CTS with shorter electron–hole distance. The electron–hole exchange interaction is about J/h = 1.15 MHz for the smallest interspin distance obtained r0 = 2.5 nm. The overall similarity of the initial electron–hole distance and CTS recombination rate for DTS:PC71BM and polymer/fullerene OPV composites studied previously points to similar photoinduced charge separation mechanisms for these systems.

On the Difficulties and Pitfalls with the Analysis of Solid-State 13 C NMR Spectra in Graphitic Materials Abstract The difficulties and pitfalls with the interpretation of solid-state 13C nuclear magnetic resonance (NMR) spectra in graphitic materials are discussed in detail here, with special emphasis on the case of 13C-enriched samples, which have been used in several recent NMR studies. The issues with the spectral simulation and the interpretation of the spectral parameters obtained by some arbitrary models reported in the recent literature are examined and alternative methods to obtain informative experimental data and to analyze them in a more appropriate way are presented.

1 H NMR study of the effect of cucurbit[7]uril on the aquation of carboplatin in biologically relevant media Abstract The aquation of carboplatin, a second-generation Pt(II)-based antitumor drug, in two biologically relevant media (PBS buffer solution and RPMI-1640 medium for cell growth) has been studied by means of 1H nuclear magnetic resonance spectroscopy. The effect of the macrocyclic cavitand cucurbit[7]uril on the carboplatin aquation rates in these two types of media has also been studied. Although, the cucurbit[7]uril does not form stable inclusion complex with carboplatin, it greatly affects the carboplatin aquation rates, presumably, through the two mechanisms: prevention of the carboplatin dimer formation and encapsulation of some components of the medium.

NMR Studies of a Nanocomposite Based on Molecular Ferroelectric Diisopropylammonium Bromide Abstract The properties of the molecular ferroelectric diisopropylammonium bromide (C6H16BrN, DIPAB) particles embedded into a nanoporous opal matrix were studied by high-resolution nuclear magnetic resonance (NMR) in the temperature range from 295 to 450 K. The 13C NMR spectra were obtained using CP-MAS technique. The results showed that structural changes in nanostructured DIPAB particles are more complex than it was previously expected. The NMR spectra of DIPAB embedded into the opal matrix revealed the coexistence of two different crystalline structures within a wide temperature range. The monoclinic ferroelectric and orthorhombic non-polar phases were seen in nanoconfined DIPAB at room temperature, meanwhile the orthorhombic phase only was found in the bulk DIPAB crystalline powder. The NMR spectra showed that the transition from the orthorhombic to the ferroelectric phase upon heating is reconstructive. The total nanocomposite transforms into the ferroelectric structure at a temperature much higher than that for the relevant transition in bulk. The size effect also leads to the increase of the temperature of the phase transition from the ferroelectric P21 phase to the P21/m paraphrase.

Isotope Effect on Diffusion in Nafion Studied by NMR Diffusometry Abstract The isotope effect H → D on diffusion in proton-exchange membrane Nafion 212 is investigated using 1H and 2H nuclear magnetic resonance (NMR) diffusometry in a static magnetic field gradient in the temperature range from 200 to 332 K for proton and from 245 to 332 K for deuteron transport. The diffusion coefficients of both isotopes have identical temperature dependence, while proton diffusion is 1.4 times faster than deuteron diffusion at the same humidity. This difference indicates a significant influence of the mass of the diffusing particle and allows us to conclude that the Grotthuss mechanism or relay diffusion of H+ or D+ ions prevails over the vehicular mechanism involving H2O molecules or H3O+ ions.