180 results on '"Leung MK"'
Search Results
2. Transition Metal-Catalyzed Activation of Aliphatic C−X Bonds in Carbon−Carbon Bond Formation
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Tien-Yau Luh, Ken-Tsung Wong, and M K Leung Mk
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chemistry.chemical_classification ,Transition metal ,Chemistry ,Carbon–carbon bond ,Bond ,Polymer chemistry ,General Chemistry ,Catalysis - Published
- 2000
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3. Treating whiplash-associated disorders with intramuscular stimulation: a retrospective review of 43 patients with long-term follow-up.
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Gunn CC, Byrne D, Goldberger M, Lam A, Leung MK, McBrinn J, Nixon A, and Wong K
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Background: Trauma to the neck can cause acute pain. Chronic pain and dysfunction from such injury is called 'whiplash-associated disorder' [WAD]. The Quebec Task Force [QTF] classified WAD severity. This case study summarizes the courses of 50 WAD patients [class 2 or 3].Findings: Forty-three accepted intramuscular stimulation therapy. They had pain and abnormal physical signs [allodynia, trophedema, muscle knots, limited range of motion]. With treatment, twenty-nine achieved long-term improvement.Conclusions: The symptoms were due to abnormal function of the central nervous system. Most improved subjectively and their abnormal physical signs resolved. Such direct clinical evidence of benefit is clearly meaningful. [ABSTRACT FROM AUTHOR]
- Published
- 2001
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4. Upper lumbar radiculopathy--a seldom detected cause of back pain.
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Gunn CC, Byrne D, Chao H, Chapman L, Lam ACP, Leung MK, McBrinn J, Wong K, and Yan K
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- 2007
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5. Early diagnosis of autism spectrum disorder using structural connectivity biomarker.
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Lau WKW, Leung MK, Poon K, and Zhang R
- Abstract
Competing Interests: None declared.
- Published
- 2024
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6. Long-term effects of mobile exoneuromusculoskeleton (ENMS)-assisted self-help telerehabilitation after stroke.
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Qing W, Nam CY, Shum HM, Chan MK, Yu KP, Ng SS, Yang B, and Hu X
- Abstract
Investigation on long-term effects of robot-assisted poststroke rehabilitation is challenging because of the difficulties in administration and follow-up of individuals throughout the process. A mobile hybrid neuromuscular electrical stimulation (NMES)-robot, i.e., exoneuromusculoskeleton (ENSM) was adopted for a single-group trial to investigate the long-term effects of the robot-assisted self-help telerehabilitation on upper limb motor function after stroke. Twenty-two patients with chronic stroke were recruited to attend a 20-session telerehabilitation program assisted by the wrist/hand module of the ENMS (WH-ENMS). Participants were evaluated before, after, as well as at 3 months and 6 months after the training. The primary outcome measure was the Fugl-Meyer Assessment-Upper Extremity (FMA-UE), supplemented by secondary outcome measures of the FMA-UE of the shoulder and elbow (FMA shoulder/elbow), the FMA-UE of the wrist and hand (FMA wrist/hand), the Modified Ashworth Scale (MAS), the Action Research Arm Test (ARAT), the Wolf Motor Function Test (WMFT), the Functional Independence Measure (FIM), as well as electromyography (EMG) and kinematic measurements. Twenty participants completed the telerehabilitation program, with 19 returning for a 3-month follow-up, and 18 for a 6-month follow-up. Significantly improved clinical scores were observed after the training ( p ≤ 0.05). These improvements were maintained after 6 months in the FMA-UE, FMA shoulder/elbow, MAS at the wrist flexor, WMFT score, WMFT time, and FIM ( p ≤ 0.05). The maintained improvements in motor function were attributed to reduced muscular compensation, as indicated by EMG and kinematic parameters. The WH-ENMS-assisted self-help telerehabilitation could achieve long-lasting rehabilitative effects in chronic stroke., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The handling editor PZ declared a past co-authorship with the author XH., (Copyright © 2024 Qing, Nam, Shum, Chan, Yu, Ng, Yang and Hu.)
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- 2024
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7. Mediating roles of sleep quality and resilience in the relationships between chronotypes and mental health symptoms.
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Poon K, Ho MSH, Tai APL, Leung MK, Chan MCM, and Lau WKW
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- Adult, Humans, Female, Young Adult, Male, Mental Health, Sleep Quality, Chronotype, Sleep, Anxiety psychology, Depression psychology, Surveys and Questionnaires, Resilience, Psychological, Mental Disorders
- Abstract
Sleep and mental health are intrinsically intertwined, but not every individual with problems sleeping develops a mental health disorder. This study examined the association among chronotypes, resilience, sleep quality and mental health symptoms amongst otherwise healthy individuals. Two hundred adults (M
age = 27.75 ± 5.11, 68% female) with no previous diagnosis of mental illness were recruited and filled in a set of questionnaires measuring chronotypes, sleep quality, depression and anxiety symptoms. The findings from the path analysis showed that the morning type had a statistically significant direct effect on a range of sleep quality indices. These included better subjective sleep quality, shortened sleep latency, and fewer daytime dysfunctions, as well as a higher level of resilience. However, it did not significantly affect depression and anxiety symptoms. In addition, the morning type had statistically significant indirect effects on a higher level of resilience and fewer depression and anxiety symptoms through the mediating effect of sleep quality indices. Findings from this study support that morning type is associated with better resilience and psychological health, which is mediated through better sleep quality., (© 2024. The Author(s).)- Published
- 2024
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8. Determinants of health-related quality of life in older people with chronic musculoskeletal pain: a cross-sectional study.
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Fong HP, Choi SY, Leung MK, Lo HH, Wang B, Wong SY, and Sit RW
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- Aged, Female, Humans, Male, Cross-Sectional Studies, Health Status, Quality of Life psychology, Surveys and Questionnaires, Middle Aged, Chronic Pain diagnosis, Chronic Pain epidemiology, East Asian People, Musculoskeletal Pain diagnosis, Musculoskeletal Pain epidemiology
- Abstract
Background: This study aimed to identify the significant physical, psychological, and social determinants associated with EuroQuol-5D (EQ-5D) among Chinese older people with chronic musculoskeletal pain, and to evaluate how these determinants affected the five dimensions of EQ-5D., Method: This is a cross-sectional study. Data were collected through a cohort involving 946 community-dwelling older people aged ≥ 60 with chronic musculoskeletal pain in Hong Kong. Selected independent variables were categorized into physical, psychological, and social domains. Physical variables included age, sex, body mass index (BMI), pain severity score, number of pain regions, the most painful site, and the number of comorbidities. Psychological variables included depression level measured using the 9-question Patient Health Questionnaire (PHQ-9), and anxiety level measured using the Generalized Anxiety Disorder Assessment (GAD-7). Social variables included living, marital, and social welfare recipient's status. The dependent variables comprised the index scores and the five dimensions of the EQ-5D descriptive system. Ordinal least squares (OLS) model and logistic regression model were used for data analysis., Results: The mean age of the participants was 67.1 (SD = 5.1), with 77.6% being female. Higher pain severity scores (beta (β) coefficient =-0.044, P < 0.001), depression scores (β=-0.007, P < 0.001) and higher anxiety scores (β=-0.01, P < 0.001) were associated with lower EQ-5D index scores. Specifically, knee pain (β=-0.061, P < 0.001) was significantly associated with lower EQ-5D index scores. Participants with higher pain severity and depression scores were more likely to report problems in most EQ-5D dimensions. Participants with anxiety primarily faced challenges related to mood, and those with knee pain were more likely to have problems with mobility and daily activities., Conclusion: Among the selected determinants in our study, pain intensity, depression, anxiety, and knee pain were identified as key determinants associated with reduced HRQoL in older Chinese people with chronic musculoskeletal pain. Each of these determinants showed distinct associations with different dimensions of the EQ-5D, potentially informed resource allocation and the development of targeted interventions to improve the overall HRQoL of this specific population., (© 2024. The Author(s).)
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- 2024
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9. Examining Eye Tracking Metrics and Cognitive Function in Post-Stroke Individuals: A Comparison of Visual Searching Tasks Between Those with and without Cognitive Impairment.
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Chan MK, Wong CL, Yu KP, and Tong RK
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Introduction: After a stroke, individuals commonly experience visual problems and impaired cognitive function, which can significantly impact their daily life. In addition to visual neglect and hemianopia, stroke survivors often have difficulties with visual search tasks. Researchers are increasingly interested in using eye tracking technology to study cognitive processing and determine whether eye tracking metrics can be used to screen and assess cognitive impairment in patients with neurological disorders. As such, assessing these areas and understanding their relationship is crucial for effective stroke rehabilitation., Methods: We enrolled 60 stroke patients in this study and evaluated their eye tracking performance and cognitive function through a series of tests. Subsequently, we divided the subjects into two groups based on their scores on the HK-MoCA test, with scores below 21 out of 30 indicating cognitive impairment. We then compared the eye tracking metrics between the two groups and identified any significant differences that existed. Spearman correlation analysis was conducted to explore the relationship between clinical test scores and eye tracking metrics. Moreover, we employed a Mann-Whitney U test to compare eye tracking metrics between groups with and without cognitive impairment., Results: Our results revealed significant correlations between various eye tracking metrics and cognitive tests (p=<.001-.041). Furthermore, the group without cognitive impairment demonstrated higher saccade velocity, gaze path velocity, and shorter time to target than the group with cognitive impairment (p=<.001-.040). ROC curve analyses were performed, and the optimal cut-off values for gaze path velocity and saccade velocity were 329.665 (px/s) (sensitivity= 0.80, specificity = 0.533) and 2.150 (px/s) (sensitivity= 0.733, specificity= 0.633), respectively., Conclusions: Our findings indicate a significant correlation between eye tracking metrics and cognitive test scores. Furthermore, the group with cognitive impairment exhibited a significant difference in these metrics, and a cut-off value was identified to predict whether a client was experiencing cognitive impairment., (The Author(s). Published by S. Karger AG, Basel.)
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- 2023
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10. Exploring redox properties of a 3D Co-based framework with bis(triarylamine) terphenyl as a redox-active linker.
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Ngue CM, Zhang YY, and Leung MK
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A 3D Co-based metal-organic framework has been prepared, which contains a bis(triarylamine) with terphenyl units as a redox-active linker. Manipulation of the redox events via the electrochemical method confirmed that charge hopping is dominant within the 3D framework. Investigation of the in situ spectroelectrochemical properties within the structure leads to the formation of mono and dual radical cations obtained reversibly in two-steps due to the presence of two redox-active sites.
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- 2023
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11. The Translation of Mobile-Exoneuromusculoskeleton-Assisted Wrist-Hand Poststroke Telerehabilitation from Laboratory to Clinical Service.
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Qing W, Nam CY, Shum HM, Chan MK, Yu KP, Ng SS, Yang B, and Hu X
- Abstract
Rehabilitation robots are helpful in poststroke telerehabilitation; however, their feasibility and rehabilitation effectiveness in clinical settings have not been sufficiently investigated. A non-randomized controlled trial was conducted to investigate the feasibility of translating a telerehabilitation program assisted by a mobile wrist/hand exoneuromusculoskeleton (WH-ENMS) into routine clinical services and to compare the rehabilitative effects achieved in the hospital-service-based group ( n = 12, clinic group) with the laboratory-research-based group ( n = 12, lab group). Both groups showed significant improvements ( p ≤ 0.05) in clinical assessments of behavioral motor functions and in muscular coordination and kinematic evaluations after the training and at the 3-month follow-up, with the lab group demonstrating better motor gains than the clinic group ( p ≤ 0.05). The results indicated that the WH-ENMS-assisted tele-program was feasible and effective for upper limb rehabilitation when integrated into routine practice, and the quality of patient-operator interactions physically and remotely affected the rehabilitative outcomes.
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- 2023
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12. Conceptualizing psychological resilience through resting-state functional MRI in a mentally healthy population: a systematic review.
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Tai APL, Leung MK, Geng X, and Lau WKW
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Conceptualizations and operational definitions of psychological resilience vary across resilience neuroimaging studies. Data on the neural features of resilience among healthy individuals has been scarce. Furthermore, findings from resting-state functional magnetic resonance imaging (fMRI) studies were inconsistent across studies. This systematic review summarized resting-state fMRI findings in different modalities from various operationally defined resilience in a mentally healthy population. The PubMed and MEDLINE databases were searched. Articles that focused on resting-state fMRI in relation to resilience, and published before 2022, were targeted. Orbitofrontal cortex, anterior cingulate cortex, insula and amygdala, were reported the most from the 19 included studies. Regions in emotional network was reported the most from the included studies. The involvement of regions like amygdala and orbitofrontal cortex indicated the relationships between emotional processing and resilience. No common brain regions or neural pathways were identified across studies. The emotional network appears to be studied the most in association with resilience. Matching fMRI modalities and operational definitions of resilience across studies are essential for meta-analysis., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Tai, Leung, Geng and Lau.)
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- 2023
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13. Quantum Dot-Vitrimer Composites: An Approach for Reprocessable, Self-Healable, and Sustainable Luminescent Materials.
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Zhang YY, Liu KT, Fang MH, and Leung MK
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- Luminescence, Quantum Dots chemistry
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Quantum dots (QDs) are of great concern in many fields. However, they suffer from high toxicity and may lead to environmental pollution. We report the development of a QD-vitrimer composite with reprocessable, self-healable, and sustainable properties. Our QD-vitrimer composite reveals fine transparency and highly uniform QDs distribution without significant aggregation. The photoluminescence quantum yield (PLQY) is basically about four times higher than the commercial QD films. The QD-vitrimer composites can be recycled at least three times without any significant loss in structure and luminescence efficiency. A prototype light-emitting diode device is fabricated to demonstrate the promising potential of QD-vitrimer composites in real application. This research sheds light on developing environmentally friendly luminescent materials and opens up an avenue for designing advanced nanomaterials-vitrimer composites., (© 2023 Wiley-VCH GmbH.)
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- 2023
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14. ortho -Lithiation driven one-pot synthesis of quinazolines via [2 + 2 + 2] cascade annulation of halofluorobenzenes with nitriles.
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Hsueh JC, Szu FE, Yu YY, and Leung MK
- Abstract
A one-pot synthesis of 2,4-disubstituted quinazoline derivatives from halofluorobenzenes with nitriles was reported, via sequential nucleophilic addition and S
N Ar reaction. The advantages of the present approach are transition metal free, easy to operate, and all the starting materials are commercially available.- Published
- 2023
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15. Olfactory dysfunction: A plausible source of COVID-19-induced neuropsychiatric symptoms.
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Tai AP, Leung MK, Lau BW, Ngai SP, and Lau WK
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Olfactory dysfunction and neuropsychiatric symptoms are commonly reported by patients of coronavirus disease 2019 (COVID-19), a respiratory infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Evidence from recent research suggests linkages between altered or loss of smell and neuropsychiatric symptoms after infection with the coronavirus. Systemic inflammation and ischemic injury are believed to be the major cause of COVID-19-related CNS manifestation. Yet, some evidence suggest a neurotropic property of SARS-CoV-2. This mini-review article summarizes the neural correlates of olfaction and discusses the potential of trans -neuronal transmission of SARS-CoV-2 or its particles within the olfactory connections in the brain. The impact of the dysfunction in the olfactory network on the neuropsychiatric symptoms associated with COVID-19 will also be discussed., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Tai, Leung, Lau, Ngai and Lau.)
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- 2023
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16. Conductivity and photoconductivity in a two-dimensional zinc bis(triarylamine) coordination polymer.
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Ngue CM, Ho KF, Sainbileg B, Batsaikhan E, Hayashi M, Lee KY, Chen RS, and Leung MK
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We report the synthesis and characterization of a 2D semiconductive and photoconductive coordination polymer. [Zn(TPPB)(Cl
2 )]·H2 O (1) (TPPB = N1 , N1 , N4 , N4 -tetrakis(4-(pyridin-4-yl)phenyl)benzene-1,4-diamine) consists of a TPPB redox-active linker with bis(triarylamine) as the core. It consists of two redox sites connected with a benzene ring as a bridge. Thus, this forms an extended conjugation pathway when the TPPB ligand is coordinated with the Zn2+ metal ions. The single crystal conductivity measurement revealed conductivity of 1 to be in the range of 0.83 to 1.9 S cm-1 . Band structure analysis predicted that 1 is a semiconductor from the delocalization of electronic transport in the network. The computational calculations show the difference in charge distribution between holes and electrons, which led to spatial separation. This implies a long charge carrier lifetime as indicated by lifetime measurement. Incorporating a bis(triarylamine)-based redox-active linker could lead to a new semiconductive scaffold material with photocatalytic applications., Competing Interests: The authors declare no conflict of interest., (This journal is © The Royal Society of Chemistry.)- Published
- 2023
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17. Sustainable Synthesis of Cyclic Carbonates from Terminal Epoxides by a Highly Efficient CaI 2 /1,3-Bis[tris(hydroxymethyl)-methylamino]-propane Catalyst.
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Liu KT, Chuang JY, Jeng RJ, and Leung MK
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The nonstopping increment of atmospheric carbon dioxide (CO
2 ) concentration keeps harming the environment and human life. The traditional concept of carbon capture and storage (CCS) is no longer sufficient and has already been corrected to carbon capture, utilization, and storage (CCUS). CCUS involves significant CO2 utilization, such as cyclic carbonate formation, for its cost effectiveness, less toxicity, and abundant C1 synthon in organic synthesis. However, the high thermodynamic and kinetic stability of CO2 limits its applications. Herein, we report a mild, efficient, and practical catalyst based on abundant, nontoxic CaI2 in conjunction with biocompatible ligand 1,3-bis[tris(hydroxymethyl)-methylamino]-propane ( BTP ) for CO2 fixation under atmospheric pressure with terminal epoxides to give the cyclic carbonates. The Job plot detected the 1:1 Ca2+ / BTP binding stoichiometry. Furthermore, formation of a single crystal of the 1:1 Ca2+ / BTP complex was confirmed by single-crystal X-ray crystallography. The bis(cyclic carbonate) products exhibit potentials for components in the non-isocyanate polyurethanes (NIPUs) process. Notably, this protocol shows attractive recyclability and reusability., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)- Published
- 2021
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18. Reversible Electroactive Behavior in a Zn-Based Metal-Organic Framework via Mild Oxidation Potential.
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Ngue CM, Liu YH, Leung MK, and Lu KL
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This work describes the synthesis and characterization of a Zn-based metal-organic framework, [Zn
2 (TTPA)(SDB)2 ·(DMF)(H2 O)]n ( 1 , TTPA = tris(4-(1 H -1,2,4-triazol-1-yl)phenyl)amine, SDB = 4,4'-sulfonyldibenzoate). A newly designed strategy with a redox-active linker, TTPA, and mediated by a V-shaped carboxylic linker with Zn2+ metal ions resulted in an electroactive framework. The V-shaped carboxylic linker with Zn2+ metal ions forms linear struts interlinked by two of the side-arms of the TTPA ligands to form a square grid network. The interior of the grid is enough to accommodate the third side-arm of the TTPA ligands, acting as a confinement grid that provides steric protection when triarylamine radical cations were generated. In addition, modular packing of axially aligned TTPA ligand facilitates charge propagation. Optical switching studies confirmed that 1 is electrochemically reversible up to 48 cycles at a potential of 0.9 V vs Fc/Fc+ . Framework 1 remained robust after annealing at 180 °C for 20 h as corroborated by the PXRD. These studies confirm the importance of crystal engineering design, where electron transfer is possible in a two-ligand approach.- Published
- 2021
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19. Feasibility, Acceptability, and Efficacy of Virtual Reality Training for Older Adults and People With Disabilities: Single-Arm Pre-Post Study.
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Chau PH, Kwok YYJ, Chan MKM, Kwan KYD, Wong KL, Tang YH, Chau KLP, Lau SWM, Yiu YYY, Kwong MYF, Lai WTT, and Leung MK
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- Aged, Humans, Middle Aged, Feasibility Studies, Adult, Disabled Persons, Virtual Reality, Rehabilitation methods
- Abstract
Background: Unlike most virtual reality (VR) training programs that are targeted at homogenous populations, a set of VR games for rehabilitation purposes targeted at a heterogeneous group of users was developed. The VR games covered physical training, cognitive training (classification and reality orientation), community-living skills training, and relaxing scenery experiences. Special considerations for local older adults and people with disabilities were made in terms of hardware choice and software design., Objective: This study aimed to evaluate the feasibility, acceptance, and efficacy of VR training among users with varying abilities., Methods: A single-arm pretest-posttest evaluation study was conducted. The participants of the evaluation study were encouraged to undergo 30-minute VR training three times a week for 6 weeks. The 30-minute session consisted of 10 minutes of upper-limb motion games, 10 minutes of lower-limb motion games, and 10 minutes of cognitive games/community-living skills training/relaxing scenery experiences, as appropriate. On completion of each session, usage statistics were documented via the built-in VR software, whereas feedback on the experience of the VR games and adverse events was collected via self-reports and staff observations. Feasibility was reflected by usage statistics, and acceptance was reflected by positive feedback. In addition, health outcomes, including upper-limb dexterity, functional mobility, cognitive function, and happiness, were assessed at baseline, as well as 6 weeks and 3 months after baseline. The primary outcomes were upper-limb dexterity and acceptance of playing VR games., Results: A total of 135 participants with a mean age of 62.7 years (SD 21.5) were recruited from May 2019 to January 2020, and 124 (91.9%) completed at least one follow-up. Additionally, 76.3% (103/135) of the participants could attend at least 70% of the proposed 18 sessions, and 72.5% (1382/1906) of the sessions had a training time of at least 20 minutes. Linear mixed effect models showed statistically significant effects in terms of upper-limb dexterity (small effect) and cognitive function (moderate effect). Among the 135 participants, 88 provided positive comments. Additionally, 10.4% (14/135) reported mild discomfort, such as dizziness, and none reported severe discomfort., Conclusions: A set of VR training games for rehabilitation could be applied to users with heterogeneous abilities. Our VR games were acceptable to local older adults and those with different disabilities. Benefits in upper-limb dexterity and cognitive function were observed despite partial compliance to the training protocol. Service providers could refer to our experiences when developing VR training systems for their clients., (©Pui Hing Chau, Yan Yan Jojo Kwok, Mee Kie Maggie Chan, Ka Yu Daniel Kwan, Kam Lun Wong, Ying Ho Tang, Kan Lung Peter Chau, Sheung Wa Matthew Lau, Yan Yan Yannex Yiu, Mei Yan Fanny Kwong, Wai Ting Thomas Lai, Mun Kit Leung. Originally published in the Journal of Medical Internet Research (https://www.jmir.org), 04.05.2021.)
- Published
- 2021
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20. Hypofunctional connectivity between the posterior cingulate cortex and ventromedial prefrontal cortex in autism: Evidence from coordinate-based imaging meta-analysis.
- Author
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Lau WKW, Leung MK, and Zhang R
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- Adolescent, Autism Spectrum Disorder physiopathology, Brain Mapping, Child, Female, Humans, Image Processing, Computer-Assisted, Male, Autistic Disorder diagnostic imaging, Autistic Disorder physiopathology, Gyrus Cinguli diagnostic imaging, Gyrus Cinguli physiopathology, Magnetic Resonance Imaging methods, Neural Pathways diagnostic imaging, Neural Pathways physiopathology, Prefrontal Cortex diagnostic imaging, Prefrontal Cortex physiopathology
- Abstract
Background: Underconnectivity in the posterior cingulate cortex (PCC) may be associated with a weakened ability to interpret social signals in autism spectrum disorder (ASD) and result in cognitive inflexibility - a hallmark feature of ASD. However, previous neuroimaging studies using resting-state functional magnetic resonance imaging in ASD reported inconsistent findings on functional connectivity of the PCC. This study investigated the aberrant resting-state functional connectivity of the PCC in ASD using multilevel kernel density analysis., Methods: Online databases (MEDLINE/PubMed) were searched for PCC-based functional connectivity in ASD. Ten studies (501 subjects; 161 reported foci) met the inclusion criteria of this meta-analysis., Results: We found one consistent and strong abnormal functional connectivity of ASD during the resting state, which was the hypoconnectivity between the PCC and ventromedial prefrontal cortex (VMPFC). Importantly, the Jackknife sensitivity analysis revealed that the VMPFC cluster was stably hypoconnected with the PCC in ASD (maximum spatial overlap rate: 100%)., Conclusions: The reduced PCC-VMPFC functional coupling may provide an early insight into the effects of ASD on multiple dimensions of functioning, including higher-order cognitive and complex social functions., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2020
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21. One-Pot CuI/DBU-Catalyzed Carboxylative Cyclization toward Oxazolidinones Using Recyclable Molecular Sieves as Efficient Promoters for Fixation of CO 2 in Water Medium.
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Liu YT, Cheng CW, Lu HC, Chang TY, Chen CY, Yang HC, Yu SH, Zehra S, Liu SH, Leung MK, Lee KM, and Chen HH
- Abstract
An efficient one-pot synthesis of oxazolidinones was developed through CuI/DBU/MS joint system-catalyzed carboxylative cyclization of arylacetylene, arylaldehyde, and arylamine in water medium under a 1 atm carbon dioxide (CO
2 ) atmosphere. The 4 Å molecular sieves (MSs) were added to improve CO2 capture and facilitate carboxylation to give the products in high yields. The CuI/DBU/MS system is robust and highly effective for the reactions with different substrates, and some target products were obtained in an excellent yield of ∼96%, with no side products in the final step.- Published
- 2020
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22. Bistriazoles with a Biphenyl Core Derivative as an Electron-Favorable Bipolar Host of Efficient Blue Phosphorescent Organic Light-Emitting Diodes.
- Author
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Lee JH, Chen CH, Lin BY, Lan YH, Huang YM, Chen NJ, Huang JJ, Volyniuk D, Keruckiene R, Grazulevicius JV, Wu YR, Leung MK, and Chiu TL
- Abstract
High-quality host materials are indispensable for the construction in the emitting layer of efficient organic light-emitting diodes (OLEDs), especially in a guest and host system. The good carrier transport and energy transfer between the host and emitters are out of necessity. In this work, a wide bandgap and bipolar organic compound, 2,2'-bis(4,5-diphenyl-(1,2,4)-triazol-3-yl)biphenyl ( BTBP ), conjugating two electron-transporting triazole moieties on a hole-transporting biphenyl core, was synthesized and characterized. The wide bandgap of 4.0 eV makes the promise in efficient energy transfer between the host and various color emitters to apply as the universal host, especially for blue emitters. The close electron and hole mobilities perform the same order of 10
-5 cm2 ·V-1 ·s-1 , identified as bipolar behavior and benefited for carrier balance at low bias. Although carrier transportation belongs to bipolar behavior at a low electrical field, the electron mobility is much faster than the hole one at a high electrical field and belongs to electron-transporting behavior. Employing the BTBP as the host matrix mixed with a phosphor dopant, iridium(III)bis[4,6-di-fluorophenyl-pyridinato-N,C2 ]picolinate, a high-efficiency sky-blue phosphorescent organic light-emitting diode (OLED) was achieved with a maximum current efficiency of 65.9 cd/A, maximum power efficiency of 62.8 lm/W, and maximum external quantum efficiency of 30.2%.- Published
- 2020
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23. An Electroactive Zinc-based Metal-Organic Framework: Bifunctional Fluorescent Quenching Behavior and Direct Observation of Nitrobenzene.
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Ngue CM, Leung MK, and Lu KL
- Abstract
This work reports on the facile synthesis, characterization, and electroactivity of a zinc-based [Zn
3 (TTPA)2 (DHTP)3 ]·2DMF ( 1 , TTPA = tris(4-(1 H -1,2,4-triazol-1-yl)phenyl)amine, DHTP = dihydroxylterepthate) metal-organic framework, which has multifunctional properties due to its electroactive framework, permanent porosity, robust structure, and fluorescent nature. Topology analyses indicate that 1 contains a 3,4,4-c net. Sorption studies indicate that 1 is a suitable adsorbent for CO2 with a capacity of 10.2 wt % at 298 K; the capacity increased to 16.7 wt % at a lower temperature, 273 K. The incorporation of the redox-active TTPA ligand as an electron donor renders 1 to be an electroactive framework. The generation of radical cations from the chemical oxidation of 1 resulted in fluorescent quenching. The combination of porosity, fluorescence, and electroactivity in one entity suggests that 1 could serve as a sensing material for the detection of nitrobenzene. Exposing nitrobenzene to 1 quenches the fluorescent via host-guest interactions. The detection site of nitrobenzene in framework 1 was confirmed by single-crystal X-ray diffraction, [Zn3 (TTPA)2 (DHTP)3 ]·(H2 O)(DMF)(2NB) or 1 ⊂ NB. In addition, the inclusion of nitrobenzene into the framework 1 stabilized the disordered molecules via strong hydrogen bonding. These findings indicate that versatile MOFs with multifunctional properties can be realized via a systematic design.- Published
- 2020
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24. Impaired tumor necrosis factor-α secretion by CD4 T cells during respiratory syncytial virus bronchiolitis associated with recurrent wheeze.
- Author
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Kitcharoensakkul M, Bacharier LB, Yin-Declue H, Boomer JS, Sajol G, Leung MK, Wilson B, Schechtman KB, Atkinson JP, Green JM, and Castro M
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- Cells, Cultured, Cytokines metabolism, Female, Humans, Infant, Male, Respiratory Syncytial Virus Infections complications, Respiratory Syncytial Viruses isolation & purification, Bronchiolitis, Viral immunology, CD4-Positive T-Lymphocytes immunology, Respiratory Sounds etiology, Respiratory Syncytial Virus Infections immunology, Tumor Necrosis Factor-alpha metabolism
- Abstract
Background: Infants with severe respiratory syncytial virus (RSV) bronchiolitis have an increased risk of recurrent wheezing and asthma. We aimed to evaluate the relationships between regulatory T cell (Treg) percentage and cytokine production of in vitro-stimulated CD4+ T cells during acute bronchiolitis and the development of recurrent wheezing in the first 3 years of life., Methods: We obtained peripheral blood from 166 infants hospitalized with their first episode of RSV-confirmed bronchiolitis. Granzyme B (GZB) expression, and interleukin-10, interferon-γ, tumor necrosis factor-α (TNF-α), IL-4, and IL-5 production by in vitro anti-CD3/CD28- and anti-CD3/CD46-activated CD4+ T cells, and percentage of peripheral Treg (CD4+CD25
hi Foxp3hi ) cells were measured by flow cytometry. Wheezing was assessed every 6 months. Recurrent wheezing was defined as three or more episodes following the initial RSV bronchiolitis., Results: Sixty-seven percent (n = 111) of children had wheezing after their initial RSV infection, with 30% having recurrent wheezing. The percentage of peripheral Treg (CD4+CD25hi Foxp3hi ) cells was not significantly different between the wheezing groups. Decreased TNF-α production from anti-CD3/CD28- and anti-CD3/CD46- activated CD4+ T cells was observed in the recurrent wheezers, compared with nonwheezers (p = .048 and .03, respectively). There were no significant differences in the GZB+ CD4+ T cells and production of other inflammatory cytokines between these groups., Conclusions: We demonstrated lower TNF-α production by in vitro stimulated CD4+ T cells during severe RSV bronchiolitis in children that subsequently developed recurrent wheezing, compared with children with no subsequent wheeze. These findings support the role of CD4+ T cell immunity in the development of subsequent wheezing in these children., (© 2019 The Authors. Immunity, Inflammation and Disease published by John Wiley & Sons Ltd.)- Published
- 2020
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25. Resting-state abnormalities of posterior cingulate in autism spectrum disorder.
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Leung MK and Lau WK
- Subjects
- Autism Spectrum Disorder diagnostic imaging, Autism Spectrum Disorder physiopathology, Gyrus Cinguli physiopathology, Humans, Magnetic Resonance Imaging, Nerve Net physiopathology, Autism Spectrum Disorder pathology, Gyrus Cinguli pathology, Rest
- Abstract
The posterior cingulate cortex (PCC) plays pivotal roles in cognitive, social and emotional processing, as well as early neural development that supports complex interactions among different neural networks. Alterations in its local and long-range connectivity during resting state are often implicated in neuropathology of neurodevelopmental disorders such as autism spectrum disorder (ASD). ASD is characterized by social and communication deficits, as well as restricted and repetitive behaviors and interests. Individuals with ASD demonstrate persistent disturbances in cognitive and social-emotional functioning, and their PCC exhibits both local and long-range resting state abnormalities compared to typically developing healthy controls. In terms of regional metrics, only the dorsal part of the PCC showed local underconnectivity. As to long-range connectivity measures, the most replicated finding in ASD studies is the reduced functional coupling between the PCC and medial prefrontal cortex (MPFC), which may represent a core neuropathology of ASD unrelated to medication effects. Functional importance of these resting state abnormalities to ASD and directions of future study are discussed at the end of this chapter., (© 2020 Elsevier Inc. All rights reserved.)
- Published
- 2020
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26. Quantification of computational geometric congruence in surface-based registration for spinal intra-operative three-dimensional navigation.
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Guha D, Jakubovic R, Leung MK, Ginsberg HJ, Fehlings MG, Mainprize TG, Yee A, and Yang VXD
- Subjects
- Adult, Aged, Aged, 80 and over, Cadaver, Humans, Intraoperative Period, Middle Aged, Spinal Fusion, Spine diagnostic imaging, Tomography, Spiral Computed, Computer Simulation, Spine anatomy & histology, Spine surgery, Surgery, Computer-Assisted
- Abstract
Background Context: Computer-assisted navigation (CAN) may guide spinal instrumentation, and requires alignment of patient anatomy to imaging. Iterative closest-point (ICP) algorithms register anatomical and imaging surface datasets, which may fail in the presence of geometric symmetry (congruence), leading to failed registration or inaccurate navigation. Here we computationally quantify geometric congruence in posterior spinal exposures, and identify predictors of potential navigation inaccuracy., Methods: Midline posterior exposures were performed from C1-S1 in four human cadavers. An optically-based CAN generated surface maps of the posterior elements at each level. Maps were reconstructed to include bilateral hemilamina, or unilateral hemilamina with/without the base of the spinous process. Maps were fitted to symmetrical geometries (cylindrical/spherical/planar) using computational modelling, and the degree of model fit quantified based on the ratio of model inliers to total points. Geometric congruence was subsequently assessed clinically in 11 patients undergoing midline exposures in the cervical/thoracic/lumbar spine for posterior instrumented fusion., Results: In cadaveric testing, increased cylindrical/spherical/planar symmetry was seen in the high-cervical and subaxial cervical spine relative to the thoracolumbar spine (p<0.001). Extension of unilateral exposures to include the ipsilateral base of the spinous process decreased symmetry independent of spinal level (p<0.001). In clinical testing, increased cylindrical/spherical/planar symmetry was seen in the subaxial cervical relative to the thoracolumbar spine (p<0.001), and in the thoracic relative to the lumbar spine (p<0.001). Symmetry in unilateral exposures was decreased by 20% with inclusion of the ipsilateral base of the spinous process., Conclusions: Geometric congruence is most evident at C1 and the subaxial cervical spine, warranting greater vigilance in navigation accuracy verification. At all levels, inclusion of the base of the spinous process in unilateral registration decreases the likelihood of geometric symmetry and navigation error. This work is important to allow the extension of line-of-sight based registration techniques to minimally-invasive unilateral approaches., Competing Interests: VXDY is Chief Scientific Officer of 7D Surgical Inc., a surgical image-guidance company licensing the optical topographic imaging technology described in this study. There are no financial or other conflicts of interest arising from this role. The remaining authors have no relevant conflicts of interest to disclose.
- Published
- 2019
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27. Spectroelectrochemical studies of the redox active tris[4-(triazol-1-yl)phenyl]amine linker and redox state manipulation of Mn(ii)/Cu(ii) coordination frameworks.
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Ngue CM, Liu YH, Wen YS, Leung MK, Chiu CW, and Lu KL
- Abstract
This work describes the successful incorporation of a redox active linker, tris(4-(1H-1,2,4-triazol-1-yl)phenyl)amine (TTPA) into Mn(ii)/Cu(ii) based coordination frameworks. Solution state in situ spectroelectrochemistry of EPR and UV/Vis/NIR of the TTPA ligand were measured to gain a deeper understanding of the charge delocalization of the triphenylamine backbone. The assignments of the absorption bands for the radical cations in UV/Vis/NIR spectroelectrochemistry were supported by DFT calculations. For Mn(ii)/Cu(ii) based coordination frameworks, solid state electrochemical and in situ spectroelectrochemical methods were applied to elucidate the accessible redox states and the optical properties of the frameworks. The findings provide a basic comprehension of the interconversion of different redox states and how an electroactive framework can be potentially used in applications of electrochromic and optical devices.
- Published
- 2019
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28. Casting amorphorized SnO 2 /MoO 3 hybrid into foam-like carbon nanoflakes towards high-performance pseudocapacitive lithium storage.
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Wang H, Xie S, Yao T, Wang J, She Y, Shi JW, Shan G, Zhang Q, Han X, and Leung MK
- Abstract
We report an amorphorization-hybridization strategy to enhance lithium storage by casting atomically mixed amorphorized SnO
2 /MoO3 into porous foam-like carbon nanoflakes (denote as SnO2 /MoO3 @CNFs, or SMC in short), which are simply prepared by annealing tin(II)/molybdenum(IV) 2-ethylhexanoate within CNFs under ambient atmosphere at a low temperature (300 °C). The SnO2 /MoO3 loading amount within CNFs can be easily adjusted by controlling the Sn/Mo/C precursors. When examined as lithium ion battery (LIB) anode materials, the amorphorized SnO2 /MoO3 @CNFs with carbon content of 32 wt% (also denote as SMC-32, in which the number represents the carbon content) deliver a high reversible capacity of 1120.5 mA h/g after 200 cycles at 200 mA/g and then 651.5 mA h/g after another 300 cycles at 2000 mA/g, which is much better than that of the crystalline SnO2 /CNFs (carbon content of 34 wt%), MoO3 /CNFs (carbon content of 22.7 wt%), or SnO2 /MoO3 @CNFs (with lower carbon contents of 11 and 25 wt%). The electrochemical measurements as well as the ex situ structure characterization clearly suggest that combination of amorphorization and hybridization of SnO2 /MoO3 with CNFs synergistically contributes to the superior lithium storage performance with high pseudocapacitive contribution., (Copyright © 2019 Elsevier Inc. All rights reserved.)- Published
- 2019
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29. Resting-state abnormalities in Autism Spectrum Disorders: A meta-analysis.
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Lau WKW, Leung MK, and Lau BWM
- Subjects
- Adolescent, Adult, Child, Female, Functional Neuroimaging, Humans, Magnetic Resonance Imaging, Male, Middle Aged, Rest, Autism Spectrum Disorder diagnostic imaging, Brain diagnostic imaging, Nerve Net diagnostic imaging
- Abstract
The gold standard for clinical assessment of Autism Spectrum Disorders (ASD) relies on assessing behavior via semi-structured play-based interviews and parent interviews. Although these methods show good sensitivity and specificity in diagnosing ASD cases, behavioral assessments alone may hinder the identification of asymptomatic at-risk group. Resting-state functional magnetic resonance imaging (rs-fMRI) could be an appropriate approach to produce objective neural markers to supplement behavioral assessments due to its non-invasive and task-free nature. Previous neuroimaging studies reported inconsistent resting-state abnormalities in ASD, which may be explained by small sample sizes and phenotypic heterogeneity in ASD subjects, and/or the use of different analytical methods across studies. The current study aims to investigate the local resting-state abnormalities of ASD regardless of subject age, IQ, gender, disease severity and methodological differences, using activation likelihood estimation (ALE). MEDLINE/PubMed databases were searched for whole-brain rs-fMRI studies on ASD published until Feb 2018. Eight experiments involving 424 subjects were included in the ALE meta-analysis. We demonstrate two ASD-related resting-state findings: local underconnectivity in the dorsal posterior cingulate cortex (PCC) and in the right medial paracentral lobule. This study contributes to uncovering a consistent pattern of resting-state local abnormalities that may serve as potential neurobiological markers for ASD.
- Published
- 2019
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30. Carrier Transport and Recombination Mechanism in Blue Phosphorescent Organic Light-Emitting Diode with Hosts Consisting of Cabazole- and Triazole-Moiety.
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Cheng TY, Lee JH, Chen CH, Chen PH, Wang PS, Lin CE, Lin BY, Lan YH, Hsieh YH, Huang JJ, Lu HF, Chao I, Leung MK, Chiu TL, and Lin CF
- Abstract
In this study, we demonstrated a blue phosphorescent organic light-emitting diode (BPOLED) based on a host with two carbazole and one trizole (2CbzTAZ) moiety, 9,9'-(2-(4,5-diphenyl-4H-1,2,4-triazol-3-yl)-1,3-phenylene)bis(9H-carbazole), that exhibits bipolar transport characteristics. Compared with the devices with a carbazole host (N,N'-dicarbazolyl-3,5-benzene, (mCP)), triazole host (3-(biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole, (TAZ)), or a physical mixture of mCP:TAZ, which exhibit hole, electron, and bipolar transport characteristics, respectively, the BPOLED with the bipolar 2CbzTAZ host exhibited the lowest driving voltage (6.55 V at 10 mA/cm
2 ), the highest efficiencies (maximum current efficiency of 52.25 cd/A and external quantum efficiency of 23.89%), and the lowest efficiency roll-off, when doped with bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic) as blue phosphor. From analyses of light leakage of the emission spectra of electroluminescence, transient electroluminescence, and partially doped OLEDs, it was found that the recombination zone was well confined inside the emitting layer and the recombination rate was most efficient in a 2CbzTAZ-based OLED. For the other cases using mCP, TAZ, and mCP:TAZ as hosts, electrons and holes transported with different routes that resulted in carrier accumulation on different organic molecules and lowered the recombination rate.- Published
- 2019
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31. Simple Molecular-Engineering Approach for Enhancing Orientation and Outcoupling Efficiency of Thermally Activated Delayed Fluorescent Emitters without Red-Shifting Emission.
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Lee YT, Tseng PC, Komino T, Mamada M, Ortiz RJ, Leung MK, Chiu TL, Lin CF, Lee JH, Adachi C, Chen CT, and Chen CT
- Abstract
The inclusion of a tetraphenylbenzene (4Ph) unit in thermally activated delayed fluorescence emitters is demonstrated as a novel strategy for greatly enhancing the horizontally oriented alignment of the emitters without shifting the emission spectrum to longer wavelengths. Doping of blue-emitting 4PhOXDDMAC or greenish-blue-emitting 4PhOXDPXZ into o-DiCbzBz host layers yielded much higher degrees of horizontally oriented alignment for the emitter (up to 92%) compared to those when the 4Ph unit was excluded (69 and 75%, respectively). The enhanced alignment results in high outcoupling efficiencies of 24 and 35% in organic light-emitting diodes based on 4PhOXDDMAC and 4PhOXDPXZ, respectively, and boosts the external quantum efficiencies to values (8.8 and 29.2%, respectively) that are higher than what would be expected for randomly oriented emitters (outcoupling efficiency of 20%). These enhancements are achieved while avoiding the redshift that often occurs using the common strategy of increasing molecular length and, thereby, conjugation, to increase orientation.
- Published
- 2018
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32. Construction of Highly Efficient Carbazol-9-yl-Substituted Benzimidazole Bipolar Hosts for Blue Phosphorescent Light-Emitting Diodes: Isomer and Device Performance Relationships.
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Chang SY, Lin GT, Cheng YC, Huang JJ, Chang CL, Lin CF, Lee JH, Chiu TL, and Leung MK
- Abstract
Four isomers of carbazol-9-yl-substituted 1,2-diphenylbenzimidazole at 7, 6, 5, and 4 positions, named as 1-CbzBiz, 2-CbzBiz, 3-CbzBiz, and 4-CbzBiz, respectively, have been synthesized. Instead of having an identical molecular weight, the CbzBiz's have their glass transition temperatures ( T
g ) spanning a large range from 53 to 90 °C. Their Tg and melting point ( Tm ) basically obey the Boyer-Kauzmann rule ( Tg = g· Tm with g ≈ 0.7) on the absolute temperature scale (in kelvins). However, while 1-CbzBiz and 4-CbzBiz demonstrate a small g value of 0.66, which is significantly smaller than other common organic glass molecules, 3-CbzBiz shows an unexpectedly high g value of 0.73, implying higher intermolecular interactions in the glass. These CbzBiz's are suitable hosts for bis[2-(4,6-difluorophenyl)pyridinato- C2 , N](picolinato)iridium(III) (FIrpic) in phosphorescence organic light-emitting diodes (PhOLEDs). The optimized PhOLED of indium tin oxide/4,4'-cyclohexylidenebis[ N, N-bis(4-methylphenyl)benzenamine]/4Cbz/4-CbzBiz-FIrpic(15%)/diphenylbis(4-(pyridin-3-yl)phenyl)silane/LiF-Al shows a maximum brightness of 18 760 cd/m2 , a current efficiency of 64.1 cd/A, and the external quantum efficiency of 30.9%.- Published
- 2018
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33. Efficient Triplet-Triplet Annihilation Upconversion in an Electroluminescence Device with a Fluorescent Sensitizer and a Triplet-Diffusion Singlet-Blocking Layer.
- Author
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Chen CH, Tierce NT, Leung MK, Chiu TL, Lin CF, Bardeen CJ, and Lee JH
- Abstract
Solid-state triplet-triplet annihilation upconversion (TTAUC) blue emission in an electroluminescence device (i.e., an organic light-emitting diode (OLED)) is demonstrated. A conventional green fluorophore, tris-(8-hydroxyquinoline)aluminum (Alq
3 ), is employed as the sensitizer that generates 75% triplet under electrical pumping for the blue triplet-triplet annihilation emitter, 9,10-bis(2'-naphthyl) anthracene (ADN), with the heterojunction bilayer structure. The operation lifetime is elongated both for ADN blue (4.1x) and Alq3 green (34.8%) emission due to efficient use of excitons and separation of recombination and emission zone. To reduce the singlet quenching (SQ) of blue TTAUC signal by the Alq3 sensitizer with lower bandgap, 1-(2,5-dimethyl-4-(1-pyrenyl)phenyl)pyrene (DMPPP) is inserted between the Alq3 and ADN as a triplet-diffusion-and-singlet-blocking layer. DMPPP exhibits triplet energy close to Alq3 and higher than ADN, as well as higher singlet energy than both Alq3 and ADN. It allows triplet diffusion from Alq3 to ADN, but blocks the SQ of the blue TTAUC signal by Alq3 . 86.1% intrinsic efficiency of TTAUC is demonstrated in this trilayer (Alq3 /DMPPP/ADN) OLED., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)- Published
- 2018
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34. High Speed, High Density Intraoperative 3D Optical Topographical Imaging with Efficient Registration to MRI and CT for Craniospinal Surgical Navigation.
- Author
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Jakubovic R, Guha D, Gupta S, Lu M, Jivraj J, Standish BA, Leung MK, Mariampillai A, Lee K, Siegler P, Skowron P, Farooq H, Nguyen N, Alarcon J, Deorajh R, Ramjist J, Ford M, Howard P, Phan N, Costa LD, Heyn C, Tan G, George R, Cadotte DW, Mainprize T, Yee A, and Yang VXD
- Subjects
- Animals, Humans, Learning Curve, Neurosurgeons education, Swine, Brain diagnostic imaging, Brain surgery, Image Interpretation, Computer-Assisted methods, Imaging, Three-Dimensional instrumentation, Imaging, Three-Dimensional methods, Magnetic Resonance Imaging methods, Spinal Cord diagnostic imaging, Spinal Cord surgery, Surgery, Computer-Assisted instrumentation, Surgery, Computer-Assisted methods
- Abstract
Intraoperative image-guided surgical navigation for craniospinal procedures has significantly improved accuracy by providing an avenue for the surgeon to visualize underlying internal structures corresponding to the exposed surface anatomy. Despite the obvious benefits of surgical navigation, surgeon adoption remains relatively low due to long setup and registration times, steep learning curves, and workflow disruptions. We introduce an experimental navigation system utilizing optical topographical imaging (OTI) to acquire the 3D surface anatomy of the surgical cavity, enabling visualization of internal structures relative to exposed surface anatomy from registered preoperative images. Our OTI approach includes near instantaneous and accurate optical measurement of >250,000 surface points, computed at >52,000 points-per-second for considerably faster patient registration than commercially available benchmark systems without compromising spatial accuracy. Our experience of 171 human craniospinal surgical procedures, demonstrated significant workflow improvement (41 s vs. 258 s and 794 s, p < 0.05) relative to benchmark navigation systems without compromising surgical accuracy. Our advancements provide the cornerstone for widespread adoption of image guidance technologies for faster and safer surgeries without intraoperative CT or MRI scans. This work represents a major workflow improvement for navigated craniospinal procedures with possible extension to other image-guided applications.
- Published
- 2018
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35. A Co(ii) framework derived from a tris(4-(triazol-1-yl)phenyl)amine redox-active linker: an electrochemical and magnetic study.
- Author
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Ngue CM, Chiu CW, Lee GH, Peng SM, Leung MK, Yang CI, Liu YH, and Lu KL
- Abstract
A new 3D coordination polymer {[Co2(μ-OH2)(TTPA)(DTDN)2·DMF]·H2O}n (1, TTPA = tris(4-(1H-1,2,4-triazol-1-yl)phenyl)amine, DTDN = 6,6'-dithiodinicotinate) was synthesised and characterised. The redox properties of this framework were elucidated by solid state electrochemical and spectroelectrochemical data. This is the first investigation of the redox behaviour of TTPA in coordination polymers. Furthermore, the incorporation of a paramagnetic Co(ii) metal ion into the framework caused 1 to show spin-flop behaviour as the result of a field-induced magnetic transition. The incorporation of two flexible ligands and Co(ii) metal ions represents a feasible approach for the advancement of multifunctional materials.
- Published
- 2018
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36. Subgenual anterior cingulate-insula resting-state connectivity as a neural correlate to trait and state stress resilience.
- Author
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Shao R, Lau WKW, Leung MK, and Lee TMC
- Subjects
- Adult, Correlation of Data, Female, Humans, Magnetic Resonance Imaging, Male, Membrane Potentials physiology, Arousal physiology, Cerebral Cortex physiopathology, Character, Gyrus Cinguli physiology, Nerve Net physiology, Neural Pathways physiology, Resilience, Psychological
- Abstract
Accumulating evidence indicates important roles of the subgenual anterior cingulate cortex and rostral limbic regions such as the anterior insula, in regulating stress-related affective responses and negative affect states in general. However, research is lacking in simultaneously assessing the inter-relations between trait and state affective responses to stress, and the functional connectivity between the subgenual anterior cingulate and anterior insula. This preliminary research involved matched healthy participants with high (N = 10) and low (N = 10) self-reported trait stress resilience, and assessed their affective and subgenual anterior cingulate-anterior insula resting-state functional connectivity patterns before and after a psychosocial stress task. We found that while the low-resilience group displayed higher trait negative affect and perceived greater task-related stress, only the high-resilience group showed increase of negative affect, along with greater decrease of left subgenual anterior cingulate-right anterior insula connectivity, following stress induction. Moreover, the functional connectivity change mediated group difference in affect change following stress task. We speculate that the contingent increase of negative affect, and the associated temporary decoupling of subgenual anterior cingulate-insula circuitry, may represent a normative and adaptive stress response underpinned by adaptive and dynamic interplay between the default mode and salience networks. Such findings, if consolidated, have important implications for promoting stress resilience and reducing risk for stress-related affective disorders., (Copyright © 2018. Published by Elsevier Inc.)
- Published
- 2018
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37. Meditation-induced neuroplastic changes in amygdala activity during negative affective processing.
- Author
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Leung MK, Lau WKW, Chan CCH, Wong SSY, Fung ALC, and Lee TMC
- Subjects
- Amygdala diagnostic imaging, Female, Humans, Image Processing, Computer-Assisted, Longitudinal Studies, Magnetic Resonance Imaging, Male, Mood Disorders diagnostic imaging, Oxygen blood, Relaxation Therapy methods, Amygdala physiology, Awareness physiology, Mood Disorders rehabilitation, Negotiating methods, Neuronal Plasticity physiology
- Abstract
Recent evidence suggests that the effects of meditation practice on affective processing and resilience have the potential to induce neuroplastic changes within the amygdala. Notably, literature speculates that meditation training may reduce amygdala activity during negative affective processing. Nonetheless, studies have thus far not verified this speculation. In this longitudinal study, participants (N = 21, 9 men) were trained in awareness-based compassion meditation (ABCM) or matched relaxation training. The effects of meditation training on amygdala activity were examined during passive viewing of affective and neutral stimuli in a non-meditative state. We found that the ABCM group exhibited significantly reduced anxiety and right amygdala activity during negative emotion processing than the relaxation group. Furthermore, ABCM participants who performed more compassion practice had stronger right amygdala activity reduction during negative emotion processing. The lower right amygdala activity after ABCM training may be associated with a general reduction in reactivity and distress. As all participants performed the emotion processing task in a non-meditative state, it appears likely that the changes in right amygdala activity are carried over from the meditation practice into the non-meditative state. These findings suggest that the distress-reducing effects of meditation practice on affective processing may transfer to ordinary states, which have important implications on stress management.
- Published
- 2018
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38. Potential Mechanisms of Mindfulness in Improving Sleep and Distress.
- Author
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Lau WKW, Leung MK, Wing YK, and Lee TMC
- Abstract
The mechanisms of mindfulness-improved sleep quality are not extensively studied. Recently, attention monitoring/awareness and acceptance in mindfulness have been proposed to be the underlying mechanisms that tackle distress and related disorders. The current study tested if acceptance moderated the relationship of awareness with psychological distress and sleep quality, and verified that psychological distress mediated the relationship between mindfulness and sleep quality in a group of community-dwelling healthy adults. Three hundred and sixty-four healthy Chinese non-meditators (age 18-65, 59% female) completed a set of online self-reported questionnaires in Chinese via SurveyMonkey. Awareness and acceptance were measured by Observe and Nonreact facets in the Five Facet Mindfulness Questionnaire (FFMQ), respectively. General psychological distress levels and sleep quality were reflected in the global score of the Depression Anxiety and Stress Scales (DASS) and the Pittsburgh Sleep Quality Index (PSQI), respectively. Model 1 and model 8 in the PROCESS macro for SPSS were used to assess the moderation and moderated mediation effects. Increased level of acceptance ( Nonreact ) weakened the positive relationship between awareness ( Observe ) and poor sleep quality ( β = -0.0154, p = 0.0123), which was partially mediated through perceived psychological distress ( β = -0.0065, 95% bias-corrected bootstrap CI = -0.0128, -0.0004) in a group of community-dwelling healthy adults. Our findings suggested that awareness and acceptance could be the mechanisms of mindfulness interventions in improving sleep quality, partly via reducing psychological stress., Competing Interests: Compliance with Ethical StandardsThe authors declare that they have no conflict of interest.
- Published
- 2018
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39. Modeling of carrier transport in organic light emitting diode with random dopant effects by two-dimensional simulation.
- Author
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Kung TJ, Huang JY, Huang JJ, Tseng SH, Leung MK, Chiu TL, Lee JH, and Wu YR
- Abstract
To model the carrier transport in organic light-emitting diodes (OLEDs) with random dopant effects in the emitting layer, two-dimensional simulation was used. By including the Gaussian shape density of states and field-dependent mobility in the Poisson and drift-diffusion solver, the carrier transport, trapping in the dopant state, and radiative recombination were accurately modeled. To examine the model, the current-voltage characteristics of organic light-emitting devices were compared. The host material in the emitting layer was 2,2-bis(1-phenyl-1H-benzo[d]imidazol-2-yl)biphenyl (BImBP), which was doped with bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic) at various concentrations. By including the random doping model, the trend of mobility was altered and the radiative efficiency fitted experimental values well.
- Published
- 2017
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40. Moderating Effects of Cortisol on Neural-Cognitive Association in Cognitively Normal Elderly Subjects.
- Author
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Lau WKW, Leung MK, Law ACK, and Lee TMC
- Abstract
Cortisol homeostasis is important for healthy brain and cognitive aging. The aim of the current study is to investigate the role of serum cortisol levels in the relationship between regional brain volumes and cognitive processing speed in a group of cognitively normal elderly subjects. Forty-one healthy elderly participants were from a parallel longitudinal study. The reported data in this study reflects baseline measurements. Whole-brain anatomical scanning was performed using a 3.0 Tesla Philips Medical Systems Achieva scanner. Cognitive processing speed was assessed by the digit-symbol and symbol search tests, from the Chinese version of the Wechsler Adult Intelligence Scale-third edition (WAIS-III). Serum cortisol levels (sampled in the late morning) were measured by ELISA kits. Whole-brain regression analysis revealed that serum cortisol levels positively predicted the white matter volumes (WMV) of the right thalamus, the gray matter volumes (GMV) of the left thalamus and right cerebellar tonsil, and negatively predicted the WMV and GMV of the left middle temporal gyrus (MTG) in 41 healthy elderly participants. Furthermore, serum cortisol significantly moderated the relationship between the GMV of the left MTG and processing speed, as well as the GMV of the left thalamus and processing speed. This study provided the first piece of evidence supporting serum cortisol levels in moderating the relationship between regional brain volumes and processing speed in healthy elderly subjects. This observation enriches our understanding of the role of cortisol in brain morphology and cognitive functioning.
- Published
- 2017
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41. Effect of composites based nickel foam anode in microbial fuel cell using Acetobacter aceti and Gluconobacter roseus as a biocatalysts.
- Author
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Karthikeyan R, Krishnaraj N, Selvam A, Wong JW, Lee PK, Leung MK, and Berchmans S
- Subjects
- Acetobacter drug effects, Aniline Compounds pharmacology, Biocompatible Materials pharmacology, Chitosan pharmacology, Electric Impedance, Electrodes, Gluconobacter drug effects, Titanium pharmacology, Acetobacter metabolism, Biocatalysis drug effects, Bioelectric Energy Sources microbiology, Carbon pharmacology, Gluconobacter metabolism, Nickel pharmacology
- Abstract
This study explores the use of materials such as chitosan (chit), polyaniline (PANI) and titanium carbide (TC) as anode materials for microbial fuel cells. Nickel foam (NF) was used as the base anode substrate. Four different types of anodes (NF, NF/PANI, NF/PANI/TC, NF/PANI/TC/Chit) are thus prepared and used in batch type microbial fuel cells operated with a mixed consortium of Acetobacter aceti and Gluconobacter roseus as the biocatalysts and bad wine as a feedstock. A maximum power density of 18.8Wm(-3) (≈2.3 times higher than NF) was obtained in the case of the anode modified with a composite of PANI/TC/Chit. The MFCs running under a constant external resistance of (50Ω) yielded 14.7% coulombic efficiency with a maximum chemical oxygen demand (COD) removal of 87-93%. The overall results suggest that the catalytic materials embedded in the chitosan matrix show the best performance and have potentials for further development., (Copyright © 2016 Elsevier Ltd. All rights reserved.)
- Published
- 2016
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42. Cost-effectiveness of an influenza vaccination program offering intramuscular and intradermal vaccines versus intramuscular vaccine alone for elderly.
- Author
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Leung MK and You JH
- Subjects
- Aged, Antibodies, Viral blood, Cost-Benefit Analysis, Hong Kong epidemiology, Humans, Influenza Vaccines immunology, Influenza, Human epidemiology, Influenza, Human immunology, Influenza, Human virology, Injections, Intradermal, Injections, Intramuscular, Mortality, Outcome Assessment, Health Care, Quality-Adjusted Life Years, Vaccination, Immunization Programs economics, Influenza Vaccines administration & dosage, Influenza, Human prevention & control
- Abstract
Background: Intradermal (ID) injection is an alternative route for influenza vaccine administration in elderly with potential improvement of vaccine coverage. This study aimed to investigate the cost-effectiveness of an influenza vaccination program offering ID vaccine to elderly who had declined intramuscular (IM) vaccine from the perspective of Hong Kong public healthcare provider., Methods: A decision analytic model was used to simulate outcomes of two programs: IM vaccine alone (IM program), and IM or ID vaccine (IM/ID program) in a hypothetic cohort of elderly aged 65 years. Outcome measures included influenza-related direct medical cost, infection rate, mortality rate, quality-adjusted life years (QALYs) loss, and incremental cost per QALY saved (ICER). Model inputs were derived from literature. Sensitivity analyses evaluated the impact of uncertainty of model variables., Results: In base-case analysis, the IM/ID program was more costly (USD52.82 versus USD47.59 per individual to whom vaccine was offered) with lower influenza infection rate (8.71% versus 9.65%), mortality rate (0.021% versus 0.024%) and QALYs loss (0.00336 versus 0.00372) than the IM program. ICER of IM/ID program was USD14,528 per QALY saved. One-way sensitivity analysis found ICER of IM/ID program to exceed willingness-to-pay threshold (USD39,933) when probability of influenza infection in unvaccinated elderly decreased from 10.6% to 5.4%. In 10,000 Monte Carlo simulations of elderly populations of Hong Kong, the IM/ID program was the preferred option in 94.7% of time., Conclusions: An influenza vaccination program offering ID vaccine to elderly who had declined IM vaccine appears to be a highly cost-effective option., (Copyright © 2016 Elsevier Ltd. All rights reserved.)
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- 2016
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43. Resting-state abnormalities in amnestic mild cognitive impairment: a meta-analysis.
- Author
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Lau WK, Leung MK, Lee TM, and Law AC
- Subjects
- Amnesia complications, Amnesia diagnostic imaging, Amnesia physiopathology, Cognitive Dysfunction complications, Humans, Neuroimaging methods, Reproducibility of Results, Rest, Brain physiopathology, Brain Mapping methods, Cognitive Dysfunction diagnostic imaging, Cognitive Dysfunction physiopathology, Magnetic Resonance Imaging
- Abstract
Amnestic mild cognitive impairment (aMCI) is a prodromal stage of Alzheimer's disease (AD). As no effective drug can cure AD, early diagnosis and intervention for aMCI are urgently needed. The standard diagnostic procedure for aMCI primarily relies on subjective neuropsychological examinations that require the judgment of experienced clinicians. The development of other objective and reliable aMCI markers, such as neural markers, is therefore required. Previous neuroimaging findings revealed various abnormalities in resting-state activity in MCI patients, but the findings have been inconsistent. The current study provides an updated activation likelihood estimation meta-analysis of resting-state functional magnetic resonance imaging (fMRI) data on aMCI. The authors searched on the MEDLINE/PubMed databases for whole-brain resting-state fMRI studies on aMCI published until March 2015. We included 21 whole-brain resting-state fMRI studies that reported a total of 156 distinct foci. Significant regional resting-state differences were consistently found in aMCI patients relative to controls, including the posterior cingulate cortex, right angular gyrus, right parahippocampal gyrus, left fusiform gyrus, left supramarginal gyrus and bilateral middle temporal gyri. Our findings support that abnormalities in resting-state activities of these regions may serve as neuroimaging markers for aMCI.
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- 2016
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44. Orthogonally Substituted Benzimidazole-Carbazole Benzene As Universal Hosts for Phosphorescent Organic Light-Emitting Diodes.
- Author
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Huang JJ, Hung YH, Ting PL, Tsai YN, Gao HJ, Chiu TL, Lee JH, Chen CL, Chou PT, and Leung MK
- Abstract
The novel ambipolar hosts of o-CbzBz and o-DiCbzBz contain carbazole and benzimidazole through an ortho-connection. The orthogonal conformations cause the triplet state to be confined at the carbazole units to secure efficient energy transfer. The phosphorescent organic light-emitting diodes (PhOLEDs) show a high current efficiency, power efficiency, and low efficiency roll-off. o-DiCbzBz can be used as a host for sky-blue, green, and orange-red PhOLEDs, giving 57.5, 78.4, and 60.3 cd/A, respectively.
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- 2016
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45. Recent Development of Plasmonic Resonance-Based Photocatalysis and Photovoltaics for Solar Utilization.
- Author
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Fan W and Leung MK
- Subjects
- Catalysis, Electrochemistry, Photochemical Processes, Semiconductors, Sunlight, Nanoparticles chemistry, Solar Energy
- Abstract
Increasing utilization of solar energy is an effective strategy to tackle our energy and energy-related environmental issues. Both solar photocatalysis (PC) and solar photovoltaics (PV) have high potential to develop technologies of many practical applications. Substantial research efforts are devoted to enhancing visible light activation of the photoelectrocatalytic reactions by various modifications of nanostructured semiconductors. This review paper emphasizes the recent advancement in material modifications by means of the promising localized surface plasmonic resonance (LSPR) mechanisms. The principles of LSPR and its effects on the photonic efficiency of PV and PC are discussed here. Many research findings reveal the promise of Au and Ag plasmonic nanoparticles (NPs). Continual investigation for increasing the stability of the plasmonic NPs will be fruitful.
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- 2016
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46. Pyrrolo-[3,2-b]pyrroles for Photochromic Analysis of Halocarbons.
- Author
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Wu JY, Yu CH, Wen JJ, Chang CL, and Leung MK
- Subjects
- Photochemical Processes, Hydrocarbons, Halogenated analysis, Pyrroles chemistry
- Abstract
Dramatic photochromic-change of 2,5-bis(triphenylamine)-substituted N,N'-diphenylpyrrolo-[3,2-b]pyrrole (1) with halocarbons provides an effective route for halocarbon analysis with the naked eye. The visual detection range can reach as low as 10(-4) ∼ 10(-5) M (1-10 ppm) in CH3CN. This method can also be applied for detection of CHCl3 in water. Fabrication of a disposable paper test cartridge along with using a camera flash as the light source allows on-site halocarbon detection in seconds. Quantitative analysis for CHCl3 and CH2Cl2 have also been demonstrated.
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- 2016
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47. Can the neural-cortisol association be moderated by experience-induced changes in awareness?
- Author
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Lau WK, Leung MK, Chan CC, Wong SS, and Lee TM
- Subjects
- Adult, Brain Mapping, Female, Hippocampus, Humans, Hydrocortisone blood, Magnetic Resonance Imaging, Male, Middle Aged, Mindfulness, Prefrontal Cortex, Awareness, Brain physiology, Hydrocortisone metabolism
- Abstract
Cortisol homeostasis is important for cognitive and affective functions that depend on cortisol-sensitive brain regions including the hippocampus and prefrontal cortex. Recent studies have shown that training induces changes in the brain. We report the findings of a longitudinal study that verified the moderation effect of experience-induced changes in awareness on the neural-cortisol association in cortisol-sensitive brain regions. These findings provide the first piece of evidence that planned behavioral experience can moderate the neural-cortisol association. A range of changes in awareness was achieved in a sample of 21 Chinese participants, divided into two groups: Awareness-based compassion meditation (ABCM) (n = 10) and relaxation (n = 11). We observed that changes in awareness were significant moderators of hippocampal-cortisol changes. Furthermore, a significant negative association between changes in plasma cortisol level and the resting-state synchrony of the right hippocampal and insular-frontal-operculum regions was observed. These novel findings shed light on the inter-relationships between changes in hippocampal-cortisol levels and changes in awareness and preliminarily identify the neural underpinnings of interventions for cortisol-related abnormal functioning for further study.
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- 2015
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48. Transient monoplegia and paraesthesia after an epidural blood patch for a spinal cerebrospinal fluid leak.
- Author
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Cheung AH, Li LF, So VC, Leung MK, and Lui WM
- Subjects
- Adult, Cerebrospinal Fluid Leak complications, Cerebrospinal Fluid Leak therapy, Female, Humans, Injections, Epidural adverse effects, Intracranial Hypotension etiology, Intracranial Hypotension therapy, Blood Patch, Epidural adverse effects, Paralysis etiology, Paresthesia etiology
- Abstract
We describe the very rare complication of new onset complete paralysis and numbness of one limb after an epidural blood patch in a 36-year-old woman. Intracranial hypotension resulting from a spinal cerebrospinal fluid fistula may be treated by epidural injection of autologous blood that is, a blood patch. This is usually a safe and effective procedure. The woman's muscle strength of hip flexion, extension, ankle dorsiflexion and plantarflexion decreased from 5/5 to 0/5 following the procedure. After symptom onset, an MRI of her spine showed no compressive or ischaemic lesions amenable to urgent intervention. The cause of neurological deficit was at that time unknown and steroids were administered. Her symptoms persisted for about 2 days and gradually improved. In this paper, the management plan and the course of this rare and alarming complication is reported., (Copyright © 2015. Published by Elsevier Ltd.)
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- 2015
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49. Design, synthesis, photophysical and electrochemical properties of 2-(4,5-diphenyl-1-p-aryl-1H-imidazol-2-yl)phenol-based boron complexes.
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Mukundam V, Dhanunjayarao K, Chuang CN, Kang DY, Leung MK, Hsieh KH, and Venkatasubbaiah K
- Abstract
New hybrid organic-inorganic boron compounds using an imidazole core have been readily synthesized by a two-step procedure from commercially available simple starting materials. All boron compounds were fully characterized by multinuclear NMR spectroscopy, LC-MS, thermogravimetric analysis, cyclic voltammetry and single crystal X-ray diffraction analysis (for & ). The photoluminescence measurements of revealed distinct emission peak maxima located at 378, 379 and 387 nm, respectively. Electroluminescent devices fabricated using these boron compounds () suggest that the boron compounds are capable of transporting electrons. A maximum brightness of 6450 cd m(-2) at 12.5 V was realized when compound was used as an electron-transporting material.
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- 2015
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50. Facile synthesis of nitrogen and sulfur codoped carbon from ionic liquid as metal-free catalyst for oxygen reduction reaction.
- Author
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She Y, Lu Z, Ni M, Li L, and Leung MK
- Abstract
Developing metal-free catalysts for oxygen reduction reaction (ORR) is a great challenge in the development of fuel cells. Nitrogen and sulfur codoped carbon with remarkably high nitrogen content up to 13.00 at % was successfully fabricated by pyrolysis of homogeneous mixture of exfoliated graphitic flakes and ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Bimi][Tf2N]). The exfoliated graphite flakes served as a structure-directing substance as well as additional carbon source in the fabrication. It was demonstrated that the use of graphite flakes increased the nitrogen doping level, optimized the composition of active nitrogen configurations, and enlarged the specific surface area of the catalysts. Electrochemical characterizations revealed that the N and S codoped carbon fabricated by this method exhibited superior catalytic activities toward ORR under both acidic and alkaline conditions. Particularly in alkaline solution, the current catalyst compared favorably to the conventional 20 wt % Pt/C catalyst via four-electron transfer pathway with better ORR selectivity. The excellent catalytic activity was mainly ascribed to high nitrogen doping content, appropriate constitution of active nitrogen configurations, large specific surface area, and synergistic effect of N and S codoping.
- Published
- 2015
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