Acquiring gait parameters from usual walking is important to predict clinical outcomes including life expectancy, risk of fall, and neurocognitive performance in older people. We developed a novel gait analysis tool that is small, less-intrusive and is based on two-dimensional light detection and ranging (2D-LiDAR) technology. Using an object-tracking algorithm, we conducted a validation study of the spatiotemporal tracking of ankle locations of young, healthy participants (n = 4) by comparing our tool and a stereo camera with the motion capture system as a gold standard modality. We also assessed parameters including step length, step width, cadence, and gait speed. The 2D-LiDAR system showed a much better accuracy than that of a stereo camera system, where mean absolute errors were 46.2 ± 17.8 mm and 116.3 ± 69.6 mm, respectively. Gait parameters from the 2D-LiDAR system were in good agreement with those from the motion capture system (r = 0.955 for step length, r = 0.911 for cadence). Simultaneous tracking of multiple targets by the 2D-LiDAR system was also demonstrated. The novel system might be useful in space and resource constrained clinical practice for older adults.
We studied surface and electronic structures of barium stannate (BaSnO3) thin-film by low energy electron diffraction (LEED), and angle-resolved photoemission spectroscopy (ARPES) techniques. BaSnO3/Ba0.96La0.04SnO3/SrTiO3 (10 nm/100 nm/0.5 mm) samples were grown using pulsed-laser deposition (PLD) method and were ex-situ transferred from PLD chamber to ultra-high vacuum (UHV) chambers for annealing, LEED and ARPES studies. UHV annealing starting from 300 • C up to 550 • C, followed by LEED and ARPES measurements show 1×1 surfaces with non-dispersive energy-momentum bands. The 1×1 surface reconstructs into a √ 2× √ 2R45 • one at the annealing temperature of 700 • C where the ARPES data shows clear dispersive bands with valence band maximum located around 3.3 eV below Fermi level. While the √ 2× √ 2R45 • surface reconstruction is stable under further UHV annealing, it is reversed to 1×1 surface by annealing the sample in 400 mTorr oxygen at 600 • C. Another UHV annealing at 600 • C followed by LEED and ARPES measurements, suggests that LEED √ 2× √ 2R45 • surface reconstruction and ARPES dispersive bands are reproduced. Our results provide a better picture of electronic structure of BaSnO3 surface and are suggestive of role of oxygen vacancies in the reversible √ 2× √ 2R45 • surface reconstruction.
A concise (9-step) synthesis of the tropoloisoquinoline alkaloid pareitropone has been achieved starting from 2-bromoisovanillin. The key step features oxidative cyclization of a readily available phenolic nitronate for the convenient construction of the fused tropone ring. This work underscores the synthetic utility of intramolecular oxidative coupling reactions of phenolic nitronates.Pareitropone (1), isolated from the roots of Cissampelos pareira (Menispermaceae), was reported to display the most potent cytotoxicity (against P388 cells) among a small family of naturally occurring tropoloisoquinolines. 1 These alkaloids are structurally similar to the mitotic inhibitor colchicine. Although deceptively simple, they pose considerable synthetic challenges. Among a small number of total syntheses documented in the literature, 2-4 there has been only one synthesis of 1 by Feldman, which features an elegant application of alkynyliodonium chemistry. 5 Prompted by the scarcity and promising bioactivity of 1, we report herein its concise synthesis. 6 Extension of the [4 + 3] oxyallyl cycloaddition approach would require furan 2, which differs from a previously utilized cycloaddition substrate in the substitution pattern, for the regioselective installation of the tropone (Scheme 1). 4c Instead of developing a new route to 2, we decided to pursue an alternate approach based on oxidative cyclization of phenolic nitronates, which had been developed by Kende. 7 Kende's elegant method for preparing fused tropones features radical anion coupling of 4 and subsequent norcaradiene rearrangement of the presumed intermediate 3a. This approach could provide an efficient and scalable route to the target alkaloid under mild conditions. Our synthesis began with O-methylation of 5 8 (97%) to give known 2-bromoveratraldehyde (7). The Suzuki coupling of 7 with 8 9 gave the biaryl adduct 9 in quantitative yield (Scheme 2). 10 The isoquinoline ring was next installed by the Pomeranz-Fritsch method. 2b,4c,11 Thus, reductive amination of 9 with aminoacetaldehyde dimethylacetal and subsequent tosylation of 10 delivered the ring-closure substrate 11 in good yield. Cyclization of 11 by the action of 2,4-dinitrobenzenesulfonic acid gave the desired isoquinoline 12 in 68% yield, whereas the use of 6 M HCl produced the corresponding desilylated phenol. The next task was the introduction of the requisite nitromethyl group onto the isoquinoline ring, which proved to be challenging. After considerable experimentation, an attractive solution was found in a slight modification of Yadav's procedure. 12 Addition of nitromethane to 12 took place in the presence of 3-butyn-2-one to yield the Reissert-type adduct 13 in 88% yield. Desilylation of 13 furnished the phenol 14 to set the stage for the Kende cyclization.The Kende annulation for the preparation of a fused tropone was first implemented in model studies (15 → 16 → 17 in Scheme 3). 13,14 Similarly, exposure of a solution of 14 in 1 M aqueous KOH to an excess amount of K 3 Fe(CN) 6 result...
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