Publications by authors named "Tong Shi"

77 Publications

Gate-Defined Quantum Confinement in CVD 2D WS.

Adv Mater 2021 Aug 26:e2103907. Epub 2021 Aug 26.

Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore.

Temperature-dependent transport measurements are performed on the same set of chemical vapor deposition (CVD)-grown WS single- and bilayer devices before and after atomic layer deposition (ALD) of HfO . This isolates the influence of HfO deposition on low-temperature carrier transport and shows that carrier mobility is not charge impurity limited as commonly thought, but due to another important but commonly overlooked factor: interface roughness. This finding is corroborated by circular dichroic photoluminescence spectroscopy, X-ray photoemission spectroscopy, cross-sectional scanning transmission electron microscopy, carrier-transport modeling, and density functional modeling. Finally, electrostatic gate-defined quantum confinement is demonstrated using a scalable approach of large-area CVD-grown bilayer WS and ALD-grown HfO . The high dielectric constant and low leakage current enabled by HfO allows an estimated quantum dot size as small as 58 nm. The ability to lithographically define increasingly smaller devices is especially important for transition metal dichalcogenides due to their large effective masses, and should pave the way toward their use in quantum information processing applications.
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http://dx.doi.org/10.1002/adma.202103907DOI Listing
August 2021

Silver, silicon co-substituted hydroxyapatite modulates bacteria-cell competition for enhanced osteogenic function.

Biomed Mater 2021 Aug 31;16(5). Epub 2021 Aug 31.

Department of Mechanical Engineering, National University of Singapore, Singapore, Singapore.

Combating bacteria while promoting tissue regeneration is an aim of highest priority for employing biomaterials in orthopedics that often embroiled with pre-operative contamination. Through simulating a surgical site infection environment and an infected implant site, we showcase the ability of a functionally modified hydroxyapatite, Ag,Si-HA that permits preferential adhesion of human bone marrow derived mesenchymal stem cells (BMSCs) over co-cultured bacterial pathogen,, by displaying immediate suppression and killing of the bacteria present with minimum cytotoxicity for 28 d. And, at the same time, Ag,Si-HA stimulates BMSCs towards osteogenic differentiation despite being within the contaminated milieu. These findings provide well-defined requirements for incorporating antibacterial properties to biomaterials in managing pre-operative contamination. In addition, it highlights the dual positive attributes of Ag,Si-HA as an effective antibacterial biomaterial and at the same time, promotes bone tissue regeneration.
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http://dx.doi.org/10.1088/1748-605X/ac1c62DOI Listing
August 2021

Impacts of compacting methods on the delivery of erythromycin and vancomycin from calcium polyphosphate hydrogel matrices.

J Biomed Mater Res B Appl Biomater 2021 Jul 24. Epub 2021 Jul 24.

Department of Biomedical Engineering, Wayne State University, Detroit, Michigan, USA.

Designing hydrogels for controlled drug delivery remains a big challenge. We developed a calcium polyphosphate hydrogel (CPP) as matrix for delivery of vancomycin (VCM) and erythromycin (EM) by unique ionic binding and physical wrapping. In this continuing study, we investigated if gel discs prepared by mechanical compaction (at 3000 psi pressure, C-discs) is superior to that of discs prepared by regular manual compaction (M-discs) for the release of VCM and EM (10 wt.%). Data demonstrated a significant reduction of burst release of VCM and EM in C-discs (1.8% and 5%, respectively) as compared to that from M-discs within 72 hr (55% and 60%, respectively, p < 0.05). In addition, C-discs significantly extended the VCM release (1500 hr) and EM (800 hr) as compared to M-discs (160 and 96 hr, respectively, p < 0.05). The VCM released from C-discs retained its bactericidal activity much longer (1500 hr) than that from M-discs (700 hr, p < 0.05). Raman Spectroscopy indicated an ionic bond of both VCM and EM with fully hydrated polyphosphate chains of CPP hydrogel matrix for both M-discs and C-discs. Micro CT showed that C-discs had much denser microstructures and less number/depth of microcracks as a result of high pressure. We propose that CPP hydrogel represents an excellent tool for the controllable and sustained delivery of VCM and EM. Extensive experiments are currently underway to evaluate the potential impacts of the modification of compaction techniques, other antibiotics, gel concentrations on the drug release, degradation behavior and infection control both in vitro and in vivo.
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http://dx.doi.org/10.1002/jbm.b.34917DOI Listing
July 2021

Effect of glutamic acid on the preparation and characterization of Pickering emulsions stabilized by zein.

Food Chem 2022 Jan 15;366:130598. Epub 2021 Jul 15.

School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, China. Electronic address:

In this study, glutamic acid and zein were utilized to prepare colloidal nanoparticles as stabilizers for Pickering emulsions. The effect of the ratio of glutamic acid to zein on the stability, zeta potential, particle size, morphology, and structure of colloidal nanoparticles was studied. The results showed that zein and glutamic acid combined in the form of noncovalent bonds, which changed the characteristics of the zein. In addition, colloidal particles aggregation was induced by glutamic acid, which altered the distribution of droplets in the emulsion, and increased the adsorption of proteins on the surface of the oil droplets, as reflected by the analysis of the size, microstructure, rheological behaviours, and driving force of the Pickering emulsion. Hydrophobic interactions and electrostatic interactions were the main driving forces for the formation of colloidal particles, which was determined by driving force analysis and the change of the zeta potential.
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http://dx.doi.org/10.1016/j.foodchem.2021.130598DOI Listing
January 2022

Editing flagellin derivatives for exploration of potent radioprotective agents.

Eur J Pharmacol 2021 Sep 18;907:174259. Epub 2021 Jun 18.

State Key Laboratory of Radiation Medicine and Protection, School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiological Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou, 215123, Jiangsu, China. Electronic address:

Exploration of medical radiation countermeasures (MRCs) has great implications in protection of mammals from radiation damages. While flagellin has been recently reported to show radioprotective effects, the relationships between flagellin structure and radioprotective activity are rarely explored. Herein, we deliberately edited the amino acid sequence of flagellin in its binding domain with toll-like receptor 5 (TLR5) for exploration of potent flagellin derivatives (Fds). An in vitro screening paradigm was developed to examine the radioprotective effects of six engineered Fds. Notably, mutation of 103 threonine on flagellin into asparagine resulted in a potent MRC candidate (Fd-T103N) displaying 1.28-fold increment of interactions with TLR5. Fd-T103N was able to further activate NF-κB pathway, induce immune protective cytokine (e.g. G-CSF) release, and significantly ameliorate γ-irradiation induced cell death. The protection effects of Fd-T103N were further validated in mice exposed to 10 Gy γ-irradiations. Compared to parent flagellin, Fd-T103N treatment showed higher G-CSF release in mouse blood, lower intestine damages, and 13% increments of mouse survival rates. In short, the established predictive paradigm could greatly reduce the labor-, time- and animal-costs in exploration of MRC candidates. Fd-T103N is a promising candidate of investigational new drug for radioprotection.
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http://dx.doi.org/10.1016/j.ejphar.2021.174259DOI Listing
September 2021

Climate Change and Temperature-related Mortality: Implications for Health-related Climate Policy.

Biomed Environ Sci 2021 May;34(5):379-386

Department of Environmental Health, Boston University School of Public Health, Boston MA02215, USA.

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http://dx.doi.org/10.3967/bes2021.050DOI Listing
May 2021

Recent developments in maintaining gel properties of surimi products under reduced salt conditions and use of additives.

Crit Rev Food Sci Nutr 2021 May 28:1-16. Epub 2021 May 28.

School of Food and Biological Engineering, Jiangsu University, Zhenjiang, China.

Salt is a necessary condition to produce a surimi product that is based on the gelation of salt-soluble myofibrillar proteins. Recently, there has been a growing concern among consumers to consume healthy foods due to the threat of several chronic diseases caused by an unhealthy diet. Methods of reducing salt content out of concern for health issues caused by excessive sodium intake may affect the gel properties of surimi, as can many health-oriented food additives. Several studies have investigated different strategies to improve the health characteristics of surimi products without decreasing gel properties. This review reports recent developments in this area and how the gel properties were successfully maintained under reduced-salt conditions and the use of additives. This review of recent studies presents a great deal of progress made in the health benefits of surimi and can be used as a reference for further development in the surimi product processing industry.
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http://dx.doi.org/10.1080/10408398.2021.1931024DOI Listing
May 2021

Associations of sleep duration and fruit and vegetable intake with the risk of metabolic syndrome in Chinese adults.

Medicine (Baltimore) 2021 Mar;100(10):e24600

School of Health Sciences.

Abstract: To understand the adverse association of short sleep duration and insufficient fruit and vegetable intake (FVI) with and their combined effect on metabolic syndrome (MetS) in Chinese adults.This cross-sectional study analyzed 7052 adults aged 18∼64 years old in 2009, with fasting blood samples collected. Participants were divided into short/normal/long sleep duration groups and sufficient/insufficient FVI groups in accordance with self-reported information. Metabolic syndrome was defined by National Cholesterol Education Program's Adult Treatment Panel III criteria.The prevalence of MetS among the study subjects was 21.74%. Participants were classified into short (<7 h/d), normal (7∼9 h/d), and long (>9 h/d) groups according to their daily sleep duration. Participants with less than 500 g of FVI per day was considered as insufficient FVI. After adjusting for confounders, the negative effect of short sleep duration on MetS was statistically significant, with an OR of 1.29 (95%CI = 1.06∼1.56); and high fasting glucose levels were significantly associated with insufficient FVI. Compared with subjects with normal sleep duration and sufficient FVI, participants with short sleep time and insufficient FVI had the highest risk of MetS (OR = 1.37, 95% CI: 1.04-1.66).This study revealed that insufficient FVI and short sleep duration were significantly associated with an increased risk of MetS among Chinese adults. Increasing FVI and normal sleep duration during Chinese adults could be significant targets for reducing the prevalence of MetS.
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http://dx.doi.org/10.1097/MD.0000000000024600DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7969326PMC
March 2021

Ameliorative effects of L-arginine? On heat-induced phase separation of Aristichthys nobilis myosin are associated with the absence of ordered secondary structures of myosin.

Food Res Int 2021 03 18;141:110154. Epub 2021 Jan 18.

School of Food and Biological Engineering, Jiangsu University, Zhenjiang, Jiangsu Province 212013, China; Bio-resources Key Laboratory of Shaanxi Province, School of Biological Science and Engineering, Sha'anxi University of Technology, Hanzhong, Shaanxi Province 723001, China. Electronic address:

This investigation aimed to study the potential mechanism of L-arginine (L-Arg) on the heat-induced phase separation phenomenon of myosin from the perspective of conformational changes of myosin. L-Arg ameliorated the phase separation of myosin after a two-step heating procedure via suppression of heat-induced aggregation of myosin. The effect of L-Arg on the heating of myosin at high temperatures (75-85 °C) was more pronounced than that in the setting stage (35-45 °C), suggesting that the ameliorative effects of L-Arg on the heat-induced phase separation of myosin are mainly attributed to the inhibition of rod-rod cross-linking between denatured myosin molecules. Additionally, L-Arg without pH modification exhibited an increased ability to suppress the gelation of myosin compared with pH modification, indicating that both pH effects and the particular structure of L-Arg play noticeable roles in the suppression of myosin gelation. Far-UV circular dichroism, intrinsic fluorescence spectroscopy and differential scanning calorimetry demonstrated that L-Arg induced the absence of ordered secondary structures of myosin molecules, especially β-sheets, and thus generated a looser protein structure, which may represent the dominant suppression mechanisms of L-Arg on the heat-induced aggregation of myosin. This work provided support for the use of L-Arg as a food additive, and the results of this study will be attractive to the meat and beverage products.
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http://dx.doi.org/10.1016/j.foodres.2021.110154DOI Listing
March 2021

Properties of erythromycin-loaded polymeric dicalcium phosphate dehydrate bone graft substitute.

J Orthop Res 2020 Dec 31. Epub 2020 Dec 31.

Department of Biomedical Engineering, Wayne State University, Detroit, Michigan, USA.

A self-setting, injectable polymeric dicalcium phosphate dehydrate bone graft substitute that is mechanically strong and has excellent cohesion was developed. We assessed the performance of erythromycin-loaded polymeric dicalcium phosphate dehydrate cement. Its properties include drug release, growth inhibition against Staphylococcus aureus and biocompatibility with osteoblastic MC3T3 cells. The impact of erythromycin loading on cement injectability, setting time, and mechanical strength were also evaluated. A sustained, low burst release of erythromycin was observed. Eluents collected from erythromycin-loaded cement showed a considerable zone of inhibition for up to 28 days. Direct contact of erythromycin-loaded cement discs with agar plate showed a similarly sizable zone of inhibition for up to 22 days. Degraded ceramic residues had strong zones of inhibition as well. While the erythromycin-loaded cement was injectable, a notable delay of the setting time was observed (49.2 ± 6.8 min) as compared with control (drug-free cement, 12.2 ± 2.6 min). A slight increase in compressive strength (60.83 ± 6.28 MPa) was observed in erythromycin-loaded cement as compared with control (59.41 ± 6.48 MPa). Erythromycin-loaded cement was biocompatible although reduced cell growth was observed in the presence of the cement eluent. We propose that the bactericidal efficacy of erythromycin-loaded cement was caused by the combined effects of erythromycin released and exposed on the contact surface of degrading ceramics. Our data may elucidate the future application of polymeric dicalcium phosphate dehydrate bone graft substitute for the treatment of orthopedic infections and opportunities to use other antibiotics and applications considering its comparable handling and mechanical strength to poly (methyl methacrylate) cements.
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http://dx.doi.org/10.1002/jor.24979DOI Listing
December 2020

The influence of various additives on coagulation process at different dosing point: From a perspective of structure properties.

J Environ Sci (China) 2021 Mar 28;101:168-176. Epub 2020 Aug 28.

Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100086, China. Electronic address:

Structure properties of flocs (size, fractal dimension (D), etc.) have a high impact on coagulation efficiency. In this work, the influences of three different additives (ferric salt (Fe), phosphate (P), and citric acid (CA)) on coagulation process/efficiency were investigated. Results showed that a small amount of extra Fe can facilitate the growth of Al flocs by providing more 'active sites'. Although zeta potential and D showed a limited change, the average floc size increased apparently and the increment was more obvious when Fe was added after the formation of the flocs. In contrast, P addition during the rapid mixing period will decrease the final average floc size, while the influence is less significant when P was added after the growth of the flocs. In terms of CA, a more striking negative effect on the growth ability of the flocs was observed compared to P. The strong complexing/coordination interactions between CA and aluminum hydroxide is the main reason behind the influence. CA also significantly decreased the D value of the flocs compared to P, and D showed a comparatively higher decrease when P or CA was added during the rapid mixing stage compared to the addition after the flocs formation. These results indicated that the addition of CA or P during the rapid mixing stage 'inactivated' or occupied more 'active sites' on the preliminarily formed Al NPs during the hydrolysis process, and therefore presented stronger impact on the morphology/size of the formed flocs.
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http://dx.doi.org/10.1016/j.jes.2020.08.016DOI Listing
March 2021

Repeated low-dose exposures to sarin disrupted the homeostasis of phospholipid and sphingolipid metabolism in guinea pig hippocampus.

Toxicol Lett 2021 Mar 27;338:32-39. Epub 2020 Nov 27.

State Key Laboratory of NBC Protection for Civilian, Beijing, 102205, PR China. Electronic address:

Repeated low-level exposure to sarin results to hippocampus dysfunction. Metabonomics involves a holistic analysis of a set of metabolites in an organism in the search for a relationship between these metabolites and physiological or pathological changes. The objective of the present study was to evaluate the effects of repeated exposure to low-level sarin on the metabonomics in hippocampus of a guinea pig model. Guinea pigs were divided randomly into control and sarin treated groups (n = 14). Guinea pigs in the control group received saline; while the sarin-treated group received 0.4×LD (16.8 μg/kg) sarin. Daily injections (a total of 14 days) were administered sc between the shoulder blades in a volume of 1.0 ml/kg body weight. At the end of the final injection, 6 animals in each group were chosen for Morris water maze test. The rest guinea pigs (n = 8 for each group) were sacrificed by decapitation, and hippocampus were dissected for analysis. Compared with the control-group, the escape latency in sarin-group was significantly (p < 0.05) longer while the crossing times were significantly decreased in the Morris water task (p < 0.05). Sarin inhibited activities of acetylcholinesterase (AChE) and neuropathy target esterase (NTE) in hippocampus. The AChE activity of hippocampus from sarin-treated groups is equivalent to 59.9 ± 6.4 %, and the NTE activity of hippocampus from sarin-groups is equivalent to 78.1 ± 8.3 % of that from control-group. Metabolites were identified and validated. A total of 14 variables were selected as potential biomarkers. Phospholipids [phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidic acid (PA), phosphatidylglycerol (PG), phosphatidylinositol (PI), Lysophosphatidylethanolamine (LysoPE or LPE)] and sphingolipids (SPs) [sphinganine (SA), phytosphingosine (PSO) and sphinganine-1-phosphate (SA1P)] were clearly modified. In conclusion, repeated low-dose exposures to sarin disrupted the homeostasis of phospholipid and sphingolipid metabolism in guinea pig hippocampus and may lead to a neuronal-specific function disorders. Identified metabolites such as SA1P need to be studied more deeply on their biological function that against sarin lesions. In future research, we should pay more attention to characterize the physiological roles of lipid metabolism enzymes as well as their involvement in pathologies induced by repeated low-level sarin exposure.
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http://dx.doi.org/10.1016/j.toxlet.2020.11.020DOI Listing
March 2021

Dry Rolling/Sliding Wear of Bainitic Rail Steels under Different Contact Stresses and Slip Ratios.

Materials (Basel) 2020 Oct 20;13(20). Epub 2020 Oct 20.

Metals and Chemistry Research Institute, China Academy of Railway Sciences, Beijing 100081, China.

This study aims to deeply understand the effect of contact stress and slip ratio on wear performances of bainitic rail steels. The results showed that the wear loss increased as the contact stress and slip ratio increased. Based on the surface damage morphology and microstructural analyses, it revealed that the rolling contact fatigue wear mechanism played a significant role under the low slip ratio, but the dominant wear mechanism transferred to the abrasive wear at the high slip ratio. Meanwhile, the bainitic steel specifically presented worse wear resistance under the abrasive wear mode. Compared with the influence of a slip ratio, the increase in contact stress led to severer plastic flows and contributed to the propagation of cracks. In addition, the contact stress and slip ratio had the opposite effect on the friction coefficient, that is, the friction coefficient of bainitic steels behaved the inverse proportion with the contact stress, but positive proportion with the slip ratio. At last, the increase in slip ratio had more significant effect on the reduction of retained austenite (RA) than the enlargement of contact stress due to the fact that the RA would probably be removed before the martensitic transformation occurred under the abrasive wear mechanism.
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http://dx.doi.org/10.3390/ma13204678DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7594084PMC
October 2020

Construction of Microunits by Adipose-Derived Mesenchymal Stem Cells Laden with Porous Microcryogels for Repairing an Acute Achilles Tendon Rupture in a Rat Model.

Int J Nanomedicine 2020 29;15:7155-7171. Epub 2020 Sep 29.

Department of Orthopedic Surgery, Key Laboratory of Musculoskeletal Trauma &war Injuries PLA, Beijing Key Laboratory of Regenerative Medicine in Orthopedics, Chinese PLA General Hospital, Beijing 100853, People's Republic of China.

Objective: Tissue engineering approaches seem to be an attractive therapy for tendon rupture. Novel injectable porous gelatin microcryogels (GMs) can promote cell attachment and proliferation, thus facilitating the repair potential for target tissue regeneration. The research objectives of this study were to assess the efficacy of tissue-like microunits constructed by multiple GMs laden with adipose-derived mesenchymal stem cells (ASCs) in accelerated tendon regeneration in a rat model.

Methods: Through a series of experiments, such as isolation and identification of ASCs, scanning electron microscopy, mercury intrusion porosimetry (MIP), laser scanning confocal microscopy and the CCK-8 test, the biocompatibility of GMs was evaluated. In an in vivo study, 64 rat right transected Achilles tendons were randomly divided into four groups: the ASCs+GMs group (microunits aggregated by multiple ASC-laden GMs injected into the gap), the ASCs group ( injected into the gap), the GMs group (GMs injected into the gap) and the blank defect group (non-treated). At 2 and 4 weeks postoperatively, the healing tissue was harvested to evaluate the gross observation and scoring, biomechanical testing, histological staining and quantitative scoring. Gait analysis was performed over time. The 64 rats were randomly assigned into 4 groups: (1) micro-unit group (ASCs+GMs) containing ASC (10)-loaded 120 GMs in 60 μL DMEM; (2) cell control group (ASCs) containing 10 ASCs in 60 μL DMEM; (3) GM control group (GMs) containing 120 blank GMs in 60 μL DMEM; (4) blank defect group (Defect) containing 60 μL DMEM, which were injected into the defect sites. All animals were sacrificed at 2 and 4 weeks postsurgery (Table 1).

Results: In an in vitro study, GMs (from 126 μm to 348 μm) showed good porosities and a three-dimensional void structure with a good interpore connectivity of the micropores and exhibited excellent biocompatibility with ASCs. As the culture time elapsed, the extracellular matrix (ECM) secreted by ASCs encased the GMs, bound multiple microspheres together, and then formed active tendon tissue-engineering microunits. In animal experiments, the ASCs+GMs group and the ASCs group showed stimulatory effects on Achilles tendon healing. Moreover, the ASCs+GMs group was the best at improving the macroscopic appearance, histological morphology, Achilles functional index (AFI), and biomechanical properties of repair tissue without causing adverse immune reactions.

Conclusion: Porous GMs were conducive to promoting cell proliferation and facilitating ECM secretion. The ASCs-GMs matrices showed an obvious therapeutic efficiency for Achilles tendon rupture in rats.
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http://dx.doi.org/10.2147/IJN.S238399DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7535144PMC
November 2020

Use of l-arginine-assisted ultrasonic treatment to change the molecular and interfacial characteristics of fish myosin and enhance the physical stability of the emulsion.

Food Chem 2021 Apr 7;342:128314. Epub 2020 Oct 7.

School of Food and Biological Engineering, Jiangsu University, Zhenjiang, Jiangsu Province 212013, China; Bio-resources Key Laboratory of Shaanxi Province, School of Biological Science and Engineering, Sha'anxi University of Technology, Hanzhong 723001, China. Electronic address:

The effects of l-arginine (Arg)-assisted ultrasonic treatment on the molecular and interfacial characteristics of myosin and emulsifying properties of the emulsion were evaluated to ascertain the underlying mechanism in improving the emulsion stability. Ultrasonication induced the exposure of residues of native myosin, which was increased by the addition of Arg (40 mM). Furthermore, in terms of emulsions containing Arg, the higher the ultrasonication intensity was, the greater the increase in adsorbed protein (from 15.43 ± 0.28% to 50.49 ± 1.65%) and π value, and the decrease in droplet sizes (from 4098 nm to 2324 nm) (P < 0.05). Moreover, the increase in the ordered structures of interfacial myosin induced by Arg and ultrasonication favoured the formation of a protein gelation network. In summary, Arg-assisted ultrasonic treatment improved the stability of the emulsion by inducing the exposure of native myosin and facilitating the formation of ordered structures of interfacial myosin.
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http://dx.doi.org/10.1016/j.foodchem.2020.128314DOI Listing
April 2021

Quantum Transport in Two-Dimensional WS with High-Efficiency Carrier Injection through Indium Alloy Contacts.

ACS Nano 2020 Oct 15;14(10):13700-13708. Epub 2020 Sep 15.

Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, 138634 Singapore.

Two-dimensional transition metal dichalcogenides (TMDCs) have properties attractive for optoelectronic and quantum applications. A crucial element for devices is the metal-semiconductor interface. However, high contact resistances have hindered progress. Quantum transport studies are scant as low-quality contacts are intractable at cryogenic temperatures. Here, temperature-dependent transfer length measurements are performed on chemical vapor deposition grown single-layer and bilayer WS devices with indium alloy contacts. The devices exhibit low contact resistances and Schottky barrier heights (∼10 kΩ μm at 3 K and 1.7 meV). Efficient carrier injection enables high carrier mobilities (∼190 cm V s) and observation of resonant tunnelling. Density functional theory calculations provide insights into quantum transport and properties of the WS-indium interface. Our results reveal significant advances toward high-performance WS devices using indium alloy contacts.
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http://dx.doi.org/10.1021/acsnano.0c05915DOI Listing
October 2020

Anisotropic Collective Charge Excitations in Quasimetallic 2D Transition-Metal Dichalcogenides.

Adv Sci (Weinh) 2020 May 16;7(10):1902726. Epub 2020 Apr 16.

Department of Physics Faculty of Science National University of Singapore S12 Science Drive 3 Singapore 117551 Singapore.

The quasimetallic 1T' phase 2D transition-metal dichalcogenides (TMDs) consist of 1D zigzag metal chains stacked periodically along a single axis. This gives rise to its prominent physical properties which promises the onset of novel physical phenomena and applications. Here, the in-plane electronic correlations are explored, and new mid-infrared plasmon excitations in 1T' phase monolayer WSe and MoS are observed using optical spectroscopies. Based on an extensive first-principles study which analyzes the charge dynamics across multiple axes of the atomic-layered systems, the collective charge excitations are found to disperse only along the direction perpendicular to the chains. Further analysis reveals that the interchain long-range coupling is responsible for the coherent 1D charge dynamics and the spin-orbit coupling affects the plasmon frequency. Detailed investigation of these charge collective modes in 2D-chained systems offers opportunities for novel device applications and has implications for the underlying mechanism that governs superconductivity in 2D TMD systems.
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http://dx.doi.org/10.1002/advs.201902726DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7237846PMC
May 2020

Phosphate limitation increases coenzyme Q production in industrial HY01.

Synth Syst Biotechnol 2019 Dec 30;4(4):212-219. Epub 2019 Nov 30.

State Key Laboratory of Bioreactor Engineering (SKLBE), And School of Biotechnology, East China University of Science and Technology (ECUST), No. 130 Meilong Road, Shanghai, 200237, China.

Coenzyme Q (CoQ) is an important component of the respiratory chain in humans and some bacteria. As a high-value-added nutraceutical antioxidant, CoQ has excellent capacity to prevent cardiovascular disease. The content of CoQ in the industrial HY01 is hundreds of folds higher than normal physiological levels. In this study, we found that overexpression or optimization of the synthetic pathway failed CoQ overproduction in the HY01 strain. Moreover, under phosphate- limited conditions (decreased phosphate or in the absence of inorganic phosphate addition), CoQ production increased significantly by 12% to220 mg/L, biomass decreased by 12%, and the CoQ productivity of unit cells increased by 27%. In subsequent fed-batch fermentation, CoQ production reached 272 mg/L in the shake-flask fermentation and 1.95 g/L in a 100-L bioreactor under phosphate limitation. Furthermore, to understand the mechanism associated with CoQ overproduction under phosphate- limited conditions, the comparatve transcriptome analysis was performed. These results indicated that phosphate limitation combined with glucose fed-batch fermentation represented an effective strategy for CoQ production in the HY01. Phosphate limitation induced a pleiotropic effect on cell metabolism, and that improved CoQ biosynthesis efficiency was possibly related to the disturbance of energy metabolism and redox potential.
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http://dx.doi.org/10.1016/j.synbio.2019.11.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6909082PMC
December 2019

A CRISPR-Cas12a-derived biosensing platform for the highly sensitive detection of diverse small molecules.

Nat Commun 2019 08 14;10(1):3672. Epub 2019 Aug 14.

The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800 Kgs, Lyngby, Denmark.

Besides genome editing, CRISPR-Cas12a has recently been used for DNA detection applications with attomolar sensitivity but, to our knowledge, it has not been used for the detection of small molecules. Bacterial allosteric transcription factors (aTFs) have evolved to sense and respond sensitively to a variety of small molecules to benefit bacterial survival. By combining the single-stranded DNA cleavage ability of CRISPR-Cas12a and the competitive binding activities of aTFs for small molecules and double-stranded DNA, here we develop a simple, supersensitive, fast and high-throughput platform for the detection of small molecules, designated CaT-SMelor (CRISPR-Cas12a- and aTF-mediated small molecule detector). CaT-SMelor is successfully evaluated by detecting nanomolar levels of various small molecules, including uric acid and p-hydroxybenzoic acid among their structurally similar analogues. We also demonstrate that our CaT-SMelor directly measured the uric acid concentration in clinical human blood samples, indicating a great potential of CaT-SMelor in the detection of small molecules.
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http://dx.doi.org/10.1038/s41467-019-11648-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6694116PMC
August 2019

Effects of l-arginine and l-histidine on heat-induced aggregation of fish myosin: Bighead carp (Aristichthys nobilis).

Food Chem 2019 Oct 13;295:320-326. Epub 2019 May 13.

School of Food and Biological Engineering, Jiangsu University, Zhenjiang, Jiangsu Province 212013, China. Electronic address:

This research focused on the effects of l-arginine (l-Arg) and l-histidine (l-His) on the heat-induced aggregation of fish myosin. l-Arg/l-His increased the pH of the myosin solution from 6.82 to 8.74 and 7.24, respectively, and decreased the turbidity, aggregate size, shear modulus, and breaking force. The incorporation of l-Arg/l-His decreased the surface hydrophobicity during setting, but increased it during the two-step heating. The heat-induced aggregation of myosin was suppressed by both amino acids, with the inhibitory effect being greater for l-Arg than l-His. On one hand, the change in the pH played a critical role in suppressing the heat-induced aggregation of myosin. On the other hand, the characteristics of l-Arg/l-His themselves, such as net charges and particular R-groups, were another main contributor to aggregation suppression. Particularly, l-Arg/l-His could interact with exposed aromatic residues of myosin, and the interactions may dominate and overwhelm the burial of aromatic residues during two-step heating.
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http://dx.doi.org/10.1016/j.foodchem.2019.05.095DOI Listing
October 2019

Comparing the release of erythromycin and vancomycin from calcium polyphosphate hydrogel using different drug loading methods.

J Biomed Mater Res B Appl Biomater 2020 02 9;108(2):475-483. Epub 2019 May 9.

Department of Biomedical Engineering, Wayne State University, Detroit, Michigan.

Calcium polyphosphate (CPP) hydrogel is used to load erythromycin (EM) and vancomycin (VCM) by means of two loading methods: they are either added directly to the formed CPP hydrogel (Gel Mixture method) or mixed with CPP powders, followed by the formation of CPP-antibiotic hydrogel (Powder Mixture method). The release of loaded antibiotics from CPP hydrogel is measured up to 48 hr. Compared to Powder Mixture method, Gel Mixture method significantly reduced the burst release of embedded antibiotics. A significant change in CPP hydrogel Raman characteristic peaks is observed only in Gel Mixture method, indicating a close interaction between embedded antibiotics with CPP hydrogel matrix. In contrast, a similarity between characteristic peaks of CPP hydrogel and Powder Mixture method shows that antibiotic incorporation does not interfere with CPP gel formation, resulting in no ionic interaction between antibiotic and polyphosphate chains. Rheometer analysis further confirms that the hydrophobic nature of EM impacts the viscoelastic properties of CPP hydrogel, whereas the hydrophilic VCM exhibits a higher loading efficiency. The potential application of CPP hydrogel as a ceramic matrix for sustained drug release warrants further investigation.
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http://dx.doi.org/10.1002/jbm.b.34404DOI Listing
February 2020

Employing a Bifunctional Molybdate Precursor To Grow the Highly Crystalline MoS for High-Performance Field-Effect Transistors.

ACS Appl Mater Interfaces 2019 Apr 5;11(15):14239-14248. Epub 2019 Apr 5.

Institute of Materials Research and Engineering, Agency for Science Technology and Research , 2 Fusionopolis Way, #08-03 Innovis , 138634 , Singapore.

Growth of the large-sized and high-quality MoS single crystals for high-performance low-power electronic applications is an important step to pursue. Despite the significant improvement made in minimizing extrinsic MoS contact resistance based on interfacial engineering of the devices, the electron mobility of field-effect transistors (FETs) made of a synthetic monolayer MoS is yet far below the expected theoretical values, implying that the MoS crystal quality needs to be further improved. Here, we demonstrate the high-performance two-terminal MoS FETs with room-temperature electron mobility up to ∼90 cm V s based on the sulfurization growth of the bifunctional precursor, sodium molybdate dihydrate. This unique transition-metal precursor, serving as both the crystalline Mo source and seed promotor (sodium), could facilitate the lateral growth of the highly crystalline monolayer MoS crystals (edge length up to ∼260 μm). Substrate surface treatment with oxygen plasma prior to the deposition of the Mo precursor is fundamental to increase the wettability between the Mo source and the substrate, promoting the thinning and coalescence of the source clusters during the growth of large-sized MoS single crystals. The control of growth temperature is also an essential step to grow a strictly monolayer MoS crystal. A proof-of-concept for thermoelectric device integration utilizing monolayer MoS sheds light on its potential in low-voltage and self-powered electronics.
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http://dx.doi.org/10.1021/acsami.9b01444DOI Listing
April 2019

Facile Preparation of Stereoblock PLA From Ring-Opening Polymerization of -Lactide by a Synergetic Binary Catalytic System Containing Ureas and Alkoxides.

Front Chem 2018 9;6:547. Epub 2018 Nov 9.

Key Laboratory of Biobased Polymer Materials, Shandong Provincial Education Department, College of Polymer Science and Engineering, Qingdao University of Science and Technology, Qingdao, China.

Ring-opening polymerization (ROP) of cyclic esters/lactones by efficient catalysts is a powerful method for synthesis of biodegradable and biocompatible polyesters with well-defined structures. To develop catalytic systems that are fast, selective and controlled is a persistent effort of chemists. In this contribution, we report a binary urea/alkoxide catalytic system that could catalyze ROP of -LA in a fast (over 90% conversion within 1-2 min), stereoselective ( up to 0.93) and controlled manner, indicated by narrow MW distributions, linear relationship between the monomer conversions and s, end-group fidelity, and chain extension experiments. Remarkably, the catalytic system described here is simple, easily prepared, and structurally tunable and thus has versatile catalytic performances.
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http://dx.doi.org/10.3389/fchem.2018.00547DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6240762PMC
November 2018

Amorphous Porous Organic Polymers Based on Schiff-Base Chemistry for Highly Efficient Iodine Capture.

Chem Asian J 2018 Jun 5. Epub 2018 Jun 5.

Key Laboratory of Biobased Polymer Materials, Shandong Provincial Education Department, School of Polymer Science and Engineering, Qingdao University of Science and Technology (QUST), Qingdao, 266042, P. R. China.

Porous organic polymers (POPs) have been considered as prominent adsorbents for volatile iodine. So far, both crystalline and amorphous POPs have accomplished excellent iodine capture capability. Considering the difficulty and challenges in preparing perfect crystalline POPs, more explorations into developing versatile amorphous POPs are needed. Herein, amorphous POPs based on the Schiff-base reaction were designed and synthesized for volatile iodine removal. Four amorphous POPs products named as NDB-H, NDB-S, ADB-HS, and ADB-S obtained under different solvothermal conditions were investigated in terms of their morphologies, porosity, and their iodine enrichment performance in detail. It is noteworthy that excellent efficiency for removing iodine vapor was acquired for NDB-S (≈425 wt %), ADB-HS (≈345 wt %), and ADB-S (≈342 wt %). Remarkably, NDB-H exhibited an iodine capture capacity up to ≈443 wt %. Excellent reusability was obtained as well. Amorphous NDB-H has accomplished an extremely high iodine capture performance, illustrating the great chance to exploit versatile amorphous POPs for iodine enrichment and removal based on Schiff-base chemistry.
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http://dx.doi.org/10.1002/asia.201800698DOI Listing
June 2018

Modification of Vapor Phase Concentrations in MoS Growth Using a NiO Foam Barrier.

ACS Nano 2018 02 22;12(2):1339-1349. Epub 2018 Jan 22.

Institute of Materials Research and Engineering, Agency for Science Technology and Research , 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634.

Single-layer molybdenum disulfide (MoS) has attracted significant attention due to its electronic and physical properties, with much effort invested toward obtaining large-area high-quality monolayer MoS films. In this work, we demonstrate a reactive-barrier-based approach to achieve growth of highly homogeneous single-layer MoS on sapphire by the use of a nickel oxide foam barrier during chemical vapor deposition. Due to the reactivity of the NiO barrier with MoO, the concentration of precursors reaching the substrate and thus nucleation density is effectively reduced, allowing grain sizes of up to 170 μm and continuous monolayers on the centimeter length scale being obtained. The quality of the monolayer is further revealed by angle-resolved photoemission spectroscopy measurement by observation of a very well resolved electronic band structure and spin-orbit splitting of the bands at room temperature with only two major domain orientations, indicating the successful growth of a highly crystalline and well-oriented MoS monolayer.
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http://dx.doi.org/10.1021/acsnano.7b07682DOI Listing
February 2018

Toll-like receptor 5 agonist CBLB502 induces radioprotective effects in vitro.

Acta Biochim Biophys Sin (Shanghai) 2017 Jun;49(6):487-495

State Key Laboratory of NBC Protection for Civilian, Beijing 102205, China.

CBLB502 derived from Salmonella flagellin is a novel agonist of Toll-like receptor 5 (TLR5). It has been shown that CBLB502 can exert high radioprotective efficacy on mice and primates from both GI and hematopoietic syndromes during whole-body irradiation with low toxicity and immunogenicity. However, no effective system has been used to investigate the protective effect of CBLB502 against irradiation and the related mechanism in vitro. In this study, we investigated the radioprotective properties of CBLB502 in HEK293-N-T cells constitutively expressing human TLR5 and NF-κB-dependent luciferase. HEK293-N-T cells were treated with different doses of CBLB502 prior to 60Co-γ ray irradiation. After irradiation, cell viability was real-time measured for 4 days by using the real-time cell analysis system. We found that CBLB502 was capable of efficiently maintaining the survival rate of irradiated HEK293-N-T cells. Then apoptotic cell death and cell cycle were detected by flow cytometry. The results showed that CBLB502 pre-treatment could reduce the apoptosis and promote the recovery of irradiated HEK293-N-T cells from G2-phase arrest in a dose-dependent manner. Our data indicated that CBLB502 has a direct radioprotective effect in vitro via anti-apoptosis and promotes cell cycle recovery. The method developed here could be an effective in vitro system to screen other TLR5-target radioprotectants like CBLB502.
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http://dx.doi.org/10.1093/abbs/gmx034DOI Listing
June 2017

Thermally Stable Mesoporous Perovskite Solar Cells Incorporating Low-Temperature Processed Graphene/Polymer Electron Transporting Layer.

ACS Appl Mater Interfaces 2016 Nov 24;8(43):29496-29503. Epub 2016 Oct 24.

Department of Chemistry and Centre for Advanced 2D Materials, National University of Singapore , 3 Science Drive 3, Singapore 119260.

In the short time since its discovery, perovskite solar cells (PSCs) have attained high power conversion efficiency but their lack of thermal stability remains a barrier to commercialization. Among the experimentally accessible parameter spaces for optimizing performance, identifying an electron transport layer (ETL) that forms a thermally stable interface with perovskite and which is solution-processable at low-temperature will certainly be advantageous. Herein, we developed a mesoporous graphene/polymer composite with these advantages when used as ETL in CHNHPbI PSCs, and a high efficiency of 13.8% under AM 1.5G solar illumination could be obtained. Due to the high heat transmission coefficient and low isoelectric point of mesoporous graphene-based ETL, the PSC device enjoys good chemical and thermal stability. Our work demonstrates that the mesoporous graphene-based scaffold is a promising ETL candidate for high performance and thermally stable PSCs.
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http://dx.doi.org/10.1021/acsami.6b10278DOI Listing
November 2016

Uniformly-dispersed nanohydroxapatite-reinforced poly(ε-caprolactone) composite films for tendon tissue engineering application.

Mater Sci Eng C Mater Biol Appl 2017 Jan 18;70(Pt 2):1149-1155. Epub 2016 Mar 18.

Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117 576, Singapore. Electronic address:

Regeneration of injuries at tendon-to-bone interface (TBI) remains a challenging issue due to the complex tissue composition involving both soft tendon tissues and relatively hard bone tissues. Tissue engineering using polymeric/ceramic composites has been of great interest to generate scaffolds for tissue's healing at TBI. Herein, we presented a novel method to blend polymers and bioceramics for tendon tissue engineering application. A homogeneous composite comprising of nanohydroxyapatite (nHA) particles in poly(ε-caprolactone) (PCL) matrix was obtained using a combination of solvent and mechanical blending process. X-ray diffraction analysis showed that the as-fabricated PCL/nHA composite film retained phase-pure apatite and semi-crystalline properties of PCL. Infrared spectroscopy spectra confirmed that the PCL/nHA composite film exhibited the characteristics functional groups of PCL and nHA, without alteration to the chemical properties of the composite. The incorporation of nHA resulted in PCL/nHA composite film with improved mechanical properties such as Young's Modulus and ultimate tensile stress, which were comparable to that of the native human rotator tendon. Seeding with human tenocytes, cells attached on the PCL/nHA composite film, and after 14days of culturing, these cells could acquire elongated morphology without induced cytotoxicity. PCL/nHA composite film could also result in increased cell metabolism with prolonged culturing, which was comparable to that of the PCL group and higher than that of the nHA group. All these results demonstrated that the developed technique of combining solvent and mechanical blending could be applied to fabricate composite films with potential for tendon tissue engineering applications.
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http://dx.doi.org/10.1016/j.msec.2016.03.051DOI Listing
January 2017

Purification and characterisation of a salt-stable protease from the halophilic archaeon Halogranum rubrum.

J Sci Food Agric 2017 Mar 9;97(5):1412-1419. Epub 2016 Aug 9.

School of Food and Biological Engineering, Jiangsu University, Zhenjiang, 212013, China.

Background: Because proteases play an important role in the fermentation of fish sauce, the purification and characterisation of an extracellular protease from the halophilic archaeon Halogranum rubrum was investigated.

Results: The molecular mass of the protease was estimated to be approximately 47 kDa based on sodium dodecyl sulfate-polyacrylamide gel electropheresis (SDS-PAGE) and native-PAGE analysis. The optimum conditions for catalytic activity were pH 8.0 and 50°C. The protease showed alkaline stability (pH 7.0-10.0). The protease also exhibited novel catalytic ability over a broad range of salinity (NaCl 0-3 mol L ). Calcium ion enhanced the proteolytic activity of the enzyme. The K and V values of the purified protease for casein were calculated to be 4.89 mg mL and 1111.11 U mL , respectively. The protease was strongly inhibited by ethylenediamine tetraacetic acid (EDTA) and phenylmethanesulfonyl fluoride (PMSF). Meanwhile, the protease was stable in the presence of Triton X-100, isopropanol, ethanol or dithio-bis-nitrobenzoic (DTNB), but was inhibited by sodium dodecyl sulfate (SDS), dimethyl sulfoxide (DMSO) or methanol. MALDI -TOF/TOF MS analysis revealed that the protease shared some functional traits with protease produced by Halogranum salarium. Furthermore, it exhibited high hydrolytic activity on silver carp myosin protein.

Conclusion: The protease is an alkaline and salt-tolerant enzyme that hydrolyses silver carp myosin with high efficiency. These excellent characteristics make this protease an attractive candidate for industrial use in low-salt fish sauce fermentation. © 2016 Society of Chemical Industry.
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http://dx.doi.org/10.1002/jsfa.7879DOI Listing
March 2017

Microdialysis combined with liquid chromatography-tandem mass spectrometry for the determination of nimodipine in the guinea pig hippocampus.

J Chromatogr B Analyt Technol Biomed Life Sci 2016 Apr 2;1017-1018:226-232. Epub 2016 Mar 2.

Department of Pharmacy, Navy General Hospital, Beijing 100048, PR China. Electronic address:

Nimodipine is a dihydropyridine calcium-channel blocker that has been recently shown to be effective on the function of central nervous system. It has been reported that treatment against deficits of learning and memory in animals and human by maintain the calcium homeostasis in hippocampus with nimodipine may be promising therapeutic strategies. A rapid and sensitive liquid chromatography-tandem mass spectrometric method was developed to determination the nimodipine in hippocampus using microdialysis technique. The separation was accomplished on an Agilent Zorbax SB-C18 column (100mm×2.1mm ID, 3.5μm) with the mobile phase composed of methanol-water (80:20, v/v) containing 0.2% formic acid at a flow rate of 0.2ml/min. Multiple reaction monitoring of the precursor-product ion transitions 419→343 for nimodipine and 361→315 nitrendipine (IS) was used for quantitation. The method was sensitive with a lower limit of quantitation (LLOQ) of 0.2ng/ml for nimodipine, with good linearity in the range of 0.2-20ng/ml. All the validation data, such as accuracy, precision, intra- and inter-day repeatability and stability were within the required limits. The method was successfully applied to p harmacokinetic study of the nimodipine in the guinea pig hippocampus.
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http://dx.doi.org/10.1016/j.jchromb.2016.02.042DOI Listing
April 2016
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