Advancing Spatial and Temporal Resolution of MRI for Biological and Physical Applications

Increasing the spatial and temporal resolution of Magnetic Resonance Imaging (MRI) has been two major challenges in MRI for several decades. Despite substantial advances in MRI technologies, barriers to high spatiotemporal resolution remain in many applications such as diffusion MRI and visualization of ultra-fast biological and physical processes. Therefore, the goal of this PhD research project is to advance the spatial and temporal resolution of MRI to enable new biological and physical applications. To increase the spatial resolution, a novel high spatial resolution MRI technique has been developed to produce distortion-reduced diffusion images with sub-millimeter resolution. The images were analyzed by using an advanced diffusion model to probe tissue micro-structural abnormalities in the brain stem of patients with Parkinson’s disease, followed by a comparison with healthy control subjects. To advance the temporal resolution, a novel ultra-fast acquisition technique, coined Sub-millisecond Periodic Event Encoded Imaging or SPEEDI, has been developed. This technique improved the temporal resolution by 2-4 orders of magnitude from what is used clinically, making it possible to use MRI for the study of ultrafast biological and physical processes on a time scale of milliseconds or sub-milliseconds. Using this novel technique, we have successfully observed the dynamics of fast-changing current signals that mimic an action potential and characterized transient eddy currents in an MRI system. More importantly, we have applied SPEEDI to visualizing the rapid opening and closing processes of the aortic valve in human subjects with an unprecedented temporal resolution of 0.6-ms. These advances in spatiotemporal resolution of MRI are expected to open new opportunities to expand the scope of MRI applications in research and patient care

Tables, Appendix, and Figures from Theory of electric creep and electromechanical coupling with domain evolution for non-poled and fully poled ferroelectric ceramics

Electromechanical properties, Eshelby S-tensor, and figure

Theoretical Studies on Isomerization and Decomposition Reactions of 2‑Methyl-1-butanol Radicals

2-Methyl-1-butanol (2M1B) is a favorable candidate of substitute fuels characterized with high energy density and low hygroscopicity. 2M1B radicals, which are the products of H-abstraction reactions of 2M1B, and their isomerization and decomposition reactions play a cardinal impact on the distribution of combustion products. In this work, the primary isomerization and decomposition reaction channels of 2M1B radicals were investigated by using QCISD­(T)/CBS//M062x/cc-pVTZ and CBS-QB3 method, respectively. The accurate phenomenological temperature- and pressure-dependent rate constants covering temperatures of 250–2500 K and pressures from 1 × 10^–3 to 1 × 10³ bar along with high-pressure limit rate constants for these channels were computed by solving the RRKM/master equation. The calculations revealed that the isomerization reaction of RC2 → RC6 has the highest energy barrier among these reactions, while the decomposition reaction RC6 → CH₃CH₂CHCH₃ + CH₂O has the lowest energy barrier. Furthermore, the computed rate coefficients were also validated by using the previous pyrolysis experiment. The modeling results reproduce the experimental results satisfactorily. The current work not only provides reasonable kinetic data for the development of 2M1B combustion models but also lays a foundation to extend the kinetic mechanisms of alcohol with a longer chain

Variable thermal transport in black, blue, and violet phosphorene from extensive atomistic simulations with a neuroevolution potential

Phosphorus has diverse chemical bonds, and even in its two-dimensional form, there are three stable allotropes: black phosphorene (Black-P), blue phosphorene (Blue-P), and violet phosphorene (Violet-P). Due to the complexity of these structures, no efficient and accurate classical interatomic potential has been developed for them. In this paper, we develop an efficient machine-learned neuroevolution potential model for these allotropes and apply it to study thermal transport in them via extensive molecular dynamics (MD) simulations. Based on the homogeneous nonequilibrium MD method, the thermal conductivities are predicted to be 12.5±0.2 (Black-P in armchair direction), 78.4±0.4 (Black-P in zigzag direction), 128±3 (Blue-P), and 2.36±0.05 (Violet-P) Wm−1K−1. The underlying reasons for the significantly different thermal conductivity values in these allotropes are unraveled through spectral decomposition, phonon eigenmodes, and phonon participation ratio. Under external tensile strain, the thermal conductivity in black-P and violet-P are finite, while that in blue-P appears unbounded due to the linearization of the flexural phonon dispersion that increases the phonon mean free paths in the zero-frequency limit.</p

Additional file 1 of Insights into myopic choroidal neovascularization based on quantitative proteomics analysis of the aqueous humor

Supplementary Material

Meta-Analysis of Randomized Controlled Trials Comparing Latanoprost with Timolol in the Treatment of Asian Populations with Chronic Angle-Closure Glaucoma

<div><p>Background</p><p>To evaluate the efficacy and safety of latanoprost compared with timolol in the treatment of Asian patients with chronic angle-closure glaucoma (CACG).</p><p>Methods</p><p>Relevant trials were identified through systematic searches of Medline, EMBASE, PubMed, Cochrane Library, Google Scholar and several Chinese databases. The main outcome measures included absolute and relative reduction of intraocular pressure (IOP) at mean, peak and trough from baseline, ocular adverse effects and systemic adverse events.</p><p>Results</p><p>Seven randomized controlled trials with 685 patients were included. In comparison with timolol, latanoprost reduced absolute IOP in CACG patients by more than 2.3 mmHg (95%CI, 1.8∼2.9, P<0.01), 2.4 mmHg (95%CI, 1.9∼2.9, P<0.01) and 2.5 mmHg (95%CI, 1.6∼3.3, P<0.01) at mean, peak and trough, respectively. As for relative IOP, there is 9.0% (95%CI, 6.6∼11.4, P<0.01), 9.7% (95%CI, 7.6∼11.8, P<0.01), and 10.8% (95%CI, 7.4∼14.3, P<0.01) greater reduction among latanoprost users than among timolol users. The differences were statistically significant at all time points (1, 2, 4, 8, 12, and 24 weeks). More ocular adverse effects (OR = 1.49, 95% CI, 1.05∼2.10, P = 0.02) and less systemic adverse events (OR = 0.46, 95% CI, 0.25∼0.84, P = 0.01) were observed in latanoprost group in comparison with timolol group.</p><p>Conclusion</p><p>Compared with timolol, latanoprost was significantly more effective in lowering IOP of Asian patients with CACG, with higher risk of ocular adverse effects but lower risk of systemic adverse events, and might be a good substitute for CACG patients.</p></div

Comparison of Relative IOP reductions between latanoprost and timolol.

<p>Comparison of Relative IOP reductions between latanoprost and timolol.</p

Baseline Characteristics of Eligible Randomized Clinical Trial.

<p>CR indicates crossover; DB, double blind; NR, not reported; OL, open label; PG, parallel group; SB, single blind.</p><p>eve =  evening regimen, bid =  twice per day, w = week, m =  month.</p

Absolute IOP reduction from baseline at different time points.

<p> =  test for subgroup differences.</p><p>All pooling was undertaken using fixed effect model as no heterogeneity was detected by Q test.</p

Outcome Measurements of Eligible Randomized Clinical Trial.

<p>*Pooled value of IOP measured at 10 AM. and 4 PM; NR, not reported.</p