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There has been increasing interest in methods to generate synthetic lipid membranes as key constituents of artificial cells or to develop new tools for remodeling membranes in living cells. However, the biosynthesis of phospholipids involves elaborate enzymatic pathways that are challenging to reconstitute in vitro. An alternative approach is to use chemical reactions to non‐enzymatically generate natural or non‐canonical phospholipids de novo. Previous reports have shown that synthetic lipid membranes can be formed in situ using various ligation chemistries, but these methods lack biocompatibility and/or suffer from slow kinetics at physiological pH. Thus, it would be valuable to develop chemoselective strategies for synthesizing phospholipids from water‐soluble precursors that are compatible with synthetic or living cells Here, we demonstrate that amide‐forming ligations between lipid precursors bearing hydroxylamines and α‐ketoacids (KAs) or potassium acyltrifluoroborates (KATs) can be used to prepare non‐canonical phospholipids at physiological pH conditions. The generated amide‐linked phospholipids spontaneously self‐assemble into cell‐like micron‐sized vesicles similar to natural phospholipid membranes. We show that lipid synthesis using KAT ligation proceeds extremely rapidly, and the high selectivity and biocompatibility of the approach facilitates the in situ synthesis of phospholipids and associated membranes in living cells. [ABSTRACT FROM AUTHOR]

There has been increasing interest in methods to generate synthetic lipid membranes as key constituents of artificial cells or to develop new tools for remodeling membranes in living cells. However, the biosynthesis of phospholipids involves elaborate enzymatic pathways that are challenging to reconstitute in vitro. An alternative approach is to use chemical reactions to non‐enzymatically generate natural or non‐canonical phospholipids de novo. Previous reports have shown that synthetic lipid membranes can be formed in situ using various ligation chemistries, but these methods lack biocompatibility and/or suffer from slow kinetics at physiological pH. Thus, it would be valuable to develop chemoselective strategies for synthesizing phospholipids from water‐soluble precursors that are compatible with synthetic or living cells Here, we demonstrate that amide‐forming ligations between lipid precursors bearing hydroxylamines and α‐ketoacids (KAs) or potassium acyltrifluoroborates (KATs) can be used to prepare non‐canonical phospholipids at physiological pH conditions. The generated amide‐linked phospholipids spontaneously self‐assemble into cell‐like micron‐sized vesicles similar to natural phospholipid membranes. We show that lipid synthesis using KAT ligation proceeds extremely rapidly, and the high selectivity and biocompatibility of the approach facilitates the in situ synthesis of phospholipids and associated membranes in living cells. [ABSTRACT FROM AUTHOR]

Valley Hall topological insulators (VHTIs) hold great promise for enhancing the manipulation of elastic wave propagation by their intrinsic topologically protected mechanism. Different from most of VHTIs designed by the deterministic Dirac degeneracy, a more flexible design of VHTIs is proposed by the accidental Dirac degeneracy to steer elastic wave propagation. Based on the accidental Dirac degeneracy, a kind of hexagonal phononic crystal is designed to independently control the topological phase transitions at different frequency ranges. Consequently, a two-channel topological demultiplexer is designed with the function of frequency separation for flexural waves, and its effectivity is verified by numerical simulations and experimental testing. Comparing with traditional designs of demultiplexers, the VHTIs-based demultiplexer possesses a series of advantages in robust performance, easy fabrication and low energy leakage, and sheds light on developing new generation of elastic wave devices. [Display omitted] • Topological phase transitions at different frequencies are independently controlled. • Frequency dependent edge states are obtained to transmit flexural waves robustly. • A topological demultiplexer is designed to separating mixing frequency components. [ABSTRACT FROM AUTHOR]

Sphingolipids (SLs) are a unique class of nitrogen-linked lipids that are involved in membrane structure, cell signaling, and other important cellular processes. Abnormal sphingolipid metabolism is observed in several diseases including cancer, diabetes, metabolic disorders, and neurodegenerative diseases, such as Alzheimer's. However, the direct study of SLs has been hampered by their ubiquitous presence in cells and their complex metabolism. In the past few decades, efforts have been focused on creating synthetic probes and chemical tools to study SLs and decipher their roles in cellular biology. In this brief perspective, we seek to provide a concise snapshot of recently developed state-of-the-art chemical tools in SL research and the challenges that can be addressed through further development of SL probes. [ABSTRACT FROM AUTHOR]

Surgical intervention can effectively treat venous pulsatile tinnitus. To assess the effectiveness of treating of venous pulsatile tinnitus (VPT) by compression reconstruction of sigmoid sinus (SSCR) under local anesthesia. This study retrospectively reviewed 41 patients with VPT in our otolaryngology department between September 2009 and February 2019. Under local anesthesia, all patients were received SSCR. Pre- and postoperative Tinnitus Handicap Inventory (THI) degree and scores were used to evaluate the efficacy of SSCR for VPT. Of the 41 patients, 36 patients were followed up from 9 months to 8 years and 5 patients were lost to follow-up and were excluded from the data analysis. SSCR was clinically effective in 86% of patients with complete disappearance in 18 patients (50%), partial remission in 10 patients (28%), slight alleviation in 3 patients (8%), and no change in 5 patients (14%). The pre- and postoperative THI degree and scores were significantly different (p <.001 and p =.002, respectively). SSCR under local anesthesia is effective for treating patients with VPT. It is critical to perform a rigorous pre-operative clinical and radiological evaluation to reduce intra- and postoperative complications. [ABSTRACT FROM AUTHOR]

Studies the uptake and efflux of L-methionine at both the apical membrane (AP) and basolateral membrane (BL) of human intestinal epithelial model. Determination of the rate limiting step in transepithelial transport (TT); Sample analysis using liquid scintillation spectrophotometry; Uptake time course; Efflux time course; Concentration-dependent uptake.

Guided wave-based nondestructive testing and structural health monitoring methods have been developed to exhibit attractive potentials and best prospects for rapid and sensitive detection of defects or damage in engineering structures. Different modes of guided waves can provide different sensitivities of damage detection. However, the multimode and mode conversion nature of guided waves poses significant challenges to mode purification of received signals. This study aims to design a metamaterial-based smart transducer for mode purification of Lamb waves in a plate, which can filter out an undesired mode of the Lamb wave to enhance sensing and actuating signals of a dominated mode. The smart transducer consists of a periodic array of shunted piezoelectric unimorphs with staggered polarization directions and is bonded on the surface of a host plate. Numerical and experimental results show that a local resonance bandgap for an anti-symmetric Lamb wave, rather than a symmetric Lamb wave, can be obtained and tuned through the shunting inductance circuit. Within such mode bandgap, the wave control for propagating a specific mode of the Lamb wave can be further realized, i.e., the mode of the Lamb wave is purified. The design presented herein offers enhanced capabilities in controlling guided wave propagation for engineering applications and nondestructive testing techniques. [ABSTRACT FROM AUTHOR]

• The periodic characteristics of orthogonal grid stiffened panels are studied. • The influence of defects on transmission coefficients is utilized to choose excitation frequency for damage detection. • The proposed baseline-free method accurately detects multiple damage of different types. • The method is numerically and experimentally verified. Orthogonal grid stiffened panels are very useful structures widely utilized in many engineering applications. The nondestructive testing and evaluation (NDT&E) methods for these structures are still limited due to the complex vibration modes induced by stiffeners distributed in two periodic directions. A novel method based on defect modes to localize multiple damage in orthogonal grid stiffened panels is proposed in this research. Instead of utilizing defect modes in periodic structures to control vibration or wave propagation, it is proposed to analyze the influence of defects on the dynamic response properties of orthogonal grid stiffened panels. The damage-related modes can then be used to identify multiple damage. The method is successfully verified both numerically and experimentally and shows great potential for broad engineering applications. [ABSTRACT FROM AUTHOR]

While hearing loss is the greatest risk factor associated with developing tinnitus, some tinnitus patients exhibit no hearing loss on conventional pure-tone audiometry (PTA). This study was developed to assess whether tinnitus patients with normal hearing as measured via conventional PTA would exhibit differences from normal controls upon extended high-frequency (EHF) audiometric evaluation. In total, 102 tinnitus patients were separated into unilateral and bilateral tinnitus groups. Age- and sex-matched controls without tinnitus were enrolled. No significant differences were observed when comparing EHF audiometry results in the 9–14 kHz range between controls and tinnitus patients, with only left-sided tinnitus ears exhibiting higher hearing thresholds than contralateral ears at 9, 10, and 14 kHz. Relative to normal controls, the hearing thresholds in the 2–8 kHz range for tinnitus ears were significantly increased. Relative to controls, tinnitus patients with normal hearing did not exhibit any significant hearing loss in the EHF range. Unexpectedly, tinnitus patients with normal hearing exhibited significant hidden hearing loss in the conventional frequency range rather than in the EHF range. For patients with normal hearing, it appears to be unnecessary to conduct EHF examinations to detect hearing loss in the EHF range. [ABSTRACT FROM AUTHOR]

Tinnitus is common in vestibular schwannoma patients, but the postoperative tinnitus status of these patients and related factors remain unclear. To identify preoperative and operative factors associated with postoperative tinnitus status. Postoperative outcomes were retrospectively assessed in 237 vestibular schwannomas (VS) patients with preoperative tinnitus and 90 VS patients without tinnitus. When evaluating patients with preoperative tinnitus, there were significant differences in rates of improvement, no change, and worsening of tinnitus for the translabyrinthine (TL) and retrosigmoid (RS) approaches. Of patients without preoperative tinnitus, there was a significant difference in rates of not developing tinnitus and new-onset tinnitus. Similar results were observed with respect to preoperative hearing. Least-squares analyses revealed that surgical approach and preoperative hearing were independent predictors of postoperative tinnitus. Preoperative pure tone averages for TL group patients that did not develop postoperative tinnitus were 85.8 dB, whereas in patients that developed new-onset tinnitus they were significantly lower (54.9 dB). Tinnitus prognosis in VS patients is better following TL microsurgery relative to RS microsurgery and is also better in patients with worse preoperative hearing. New-onset tinnitus was more likely to occur in patients with better preoperative hearing that underwent tumor removal via a TL approach. [ABSTRACT FROM AUTHOR]

Triene 6π electrocyclization, wherein a conjugated triene undergoes a concerted stereospecific cycloisomerization to a cyclohexadiene, is a reaction of great historical and practical significance. In order to circumvent limitations imposed by the normally harsh reaction conditions, chemists have long sought to develop catalytic variants based upon the activating power of metal–alkene coordination. Herein, we demonstrate the first successful implementation of such a strategy by utilizing [(C5H5)Ru(NCMe)3]PF6 as a precatalyst for the disrotatory 6π electrocyclization of highly substituted trienes that are resistant to thermal cyclization. Mechanistic and computational studies implicate hexahapto transition‐metal coordination as responsible for lowering the energetic barrier to ring closure. This work establishes a foundation for the development of new catalysts for stereoselective electrocyclizations. [ABSTRACT FROM AUTHOR]

Triene 6π electrocyclization, wherein a conjugated triene undergoes a concerted stereospecific cycloisomerization to a cyclohexadiene, is a reaction of great historical and practical significance. In order to circumvent limitations imposed by the normally harsh reaction conditions, chemists have long sought to develop catalytic variants based upon the activating power of metal–alkene coordination. Herein, we demonstrate the first successful implementation of such a strategy by utilizing [(C5H5)Ru(NCMe)3]PF6 as a precatalyst for the disrotatory 6π electrocyclization of highly substituted trienes that are resistant to thermal cyclization. Mechanistic and computational studies implicate hexahapto transition‐metal coordination as responsible for lowering the energetic barrier to ring closure. This work establishes a foundation for the development of new catalysts for stereoselective electrocyclizations. [ABSTRACT FROM AUTHOR]

• The unified peridynamic correspondence principle is proposed on the basis of the energy compensation method. • A new peridynamic deformation gradient, shape matrix and force state are derived and redefined. • The nonlocal phase field damage constitutive model is developed in the context of peridynamics. • The linearization method of the peridynamics-based phase-field model (PD-PFM) is first presented. • The PD-PFM not only solves the zero-energy mode of the conventional peridynamic correspondence principle, but also provides the rational criterion for the breakage of the peridynamic bond. The peridynamic correspondence model is a promising and attractive candidate for the modeling of localized failure in solids, in that it can incorporate many local classical damage constitutive models through introducing a nonlocal averaged deformation gradient. However, the zero-energy mode and the limited bond breaking criterion greatly restrict the potential applications of this correspondence model. To address these two problems, a unified nonlocal peridynamics-based phase-field damage theory is proposed within the framework of thermodynamics. Firstly, the unified correspondence principle for the displacement field is developed on the basis of the energy compensation method in such a way that a new peridynamic deformation gradient, shape matrix and force state are derived and redefined. And then, the proposed principle is applied to derive the nonlocal phase-field damage constitutive model that the general nonlocal phase-field flux, phase-field flow state and phase-field internal force are defined. Moreover, we propose a mixed variational derivative method to obtain the coupled equilibrium governing equation and present the general linearization approach of the proposed peridynamics-based phase-field model (PD-PFM), where the double states for the coupled displacement and phase fields are derived in detail. It will be found that PD-PFM can not only resolve the zero-energy mode existed in the conventional peridynamic correspondence model, but also provide a rational criterion for the breakage of the peridynamic bond. Some representative numerical examples including mixed mode fracture of single-material media and interface fracture of ceramic coating systems are presented for the validation of PD-PFM. The satisfactory results show both quantitative and qualitative agreement with the available experiment. [ABSTRACT FROM AUTHOR]