41 results on '"Ng BC"'
Search Results
2. The effect of crystal orientation on crack nucleation and arrest in a near-gamma TiAl alloy
- Author
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Ng, Bc, Thomas Bieler, and Crimp, Ma
3. Imaging Dislocations in Duplex Tial Using Electron Channeling Contrast.
- Author
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Bailey, GW, Jerome, WG, McKernan, S, Mansfield, JF, Price, RL, Ng, BC, Bieler, TR, and Crimp, MA
- Published
- 1999
- Full Text
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4. Imaging Dislocations in Duplex Tial Using Electron Channeling Contrast
- Author
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Ng, BC, Bieler, TR, and Crimp, MA
- Abstract
Electron channeling contrast imaging (ECCI), performed using a scanning electron microscope, has been used to observe dislocations in bulk TiAl with a duplex microstructure. The ECCI technique is based on the dependence of the back-scattered electron (BSE) yield (of the incident beam orientation) on the crystal lattice and defect orientation near the specimen surface. This allows nearsurface defects to be imaged in bulk specimens [1, 2]. ECCI was carried out in a Camscan 44FE FEG-SEM operated at 25 kV using a beam divergence of ∽8 mrad and a beam current of ∽ 2nA. Specimens were observed at a working distance of approximately 11 mm. To record the BSE signal, the microscope was fitted with an annular (four quadrant) silicon diode detector array attached to the final lens pole-piece, resulting in a solid angle collection of approximately ∽0.6 π str. Images were recorded as 32 frame averages using ∽1.1 frames/sec.
- Published
- 1999
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5. Acceptance of disability in stroke: A qualitative metasynthesis.
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Lim MJ, Tan J, Neo AY, Ng BC, and Asano M
- Abstract
Disability acceptance has been conceptualized as an internalization of oneself as a person experiencing disability and associated with better coping and motivation for rehabilitation. This is particularly pertinent to individuals experiencing stroke because many are initially not fully aware of their stroke-related impairments, which affects the acceptance process. This qualitative metasynthesis aimed to synthesize qualitative findings regarding disability acceptance in stroke and identify barriers and facilitators associated with it. Eighteen studies published from 2003 to 2022, conducted in Asia, Europe, and Australasia, were included in our review. A thematic synthesis was carried out through line-by-line coding and identification of descriptive and analytical themes. Three analytical themes emerged from the analysis: "understanding impairments," "flexibility and active engagement," and "disability acceptance as a non-linear process." Healthcare professionals may facilitate this process by guiding individuals experiencing stroke to recognize that they can manage their limitations and still lead meaningful lives., Competing Interests: Declaration of conflicting interestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
- Published
- 2024
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6. Modification of Liquid Separation Membranes Using Multidimensional Nanomaterials: Revealing the Roles of Dimension Based on Classical Titanium Dioxide.
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Goh PS, Samavati Z, Ismail AF, Ng BC, Abdullah MS, and Hilal N
- Abstract
Membrane technology has become increasingly popular and important for separation processes in industries, as well as for desalination and wastewater treatment. Over the last decade, the merger of nanotechnology and membrane technology in the development of nanocomposite membranes has emerged as a rapidly expanding research area. The key motivation driving the development of nanocomposite membranes is the pursuit of high-performance liquid separation membranes that can address the bottlenecks of conventionally used polymeric membranes. Nanostructured materials in the form of zero to three-dimensions exhibit unique dimension-dependent morphology and topology that have triggered considerable attention in various fields. While the surface hydrophilicity, antibacterial, and photocatalytic properties of TiO
2 are particularly attractive for liquid separation membranes, the geometry-dependent properties of the nanocomposite membrane can be further fine-tuned by selecting the nanostructures with the right dimension. This review aims to provide an overview and comments on the state-of-the-art modifications of liquid separation membrane using TiO2 as a classical example of multidimensional nanomaterials. The performances of TiO2 -incorporated nanocomposite membranes are discussed with attention placed on the special features rendered by their structures and dimensions. The innovations and breakthroughs made in the synthesis and modifications of structure-controlled TiO2 and its composites have enabled fascinating and advantageous properties for the development of high-performance nanocomposite membranes for liquid separation.- Published
- 2023
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7. Nanocrystalline cellulose incorporated biopolymer tailored polyethersulfone mixed matrix membranes for efficient treatment of produced water.
- Author
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Yogarathinam LT, Goh PS, Ismail AF, Gangasalam A, Ahmad NA, Samavati A, Mamah SC, Zainol Abidin MN, Ng BC, and Gopal B
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- Biopolymers, Cellulose, Cross-Sectional Studies, Polymers, Sulfones, Membranes, Artificial, Water chemistry
- Abstract
Membrane technology is a sustainable method to remove pollutants from petroleum wastewater. However, the presence of hydrophobic oil molecules and inorganic constituents can cause membrane fouling. Biomass derived biopolymers are promising renewable materials for membrane modification. In this study, fouling resistant biopolymer N-phthaloylchitosan (CS)- based polythersulfone (PES) mixed matrix membranes (MMMs) incorporated with nanocrystalline cellulose (NCC) was fabricated via phase inversion method and applied for produced water (PW) treatment. The morphological and Fourier-transform infrared spectroscopy (FTIR) analyses of the as-prepared NCC evidenced the formation of fibrous sheet-like structure and the presence of hydrophilic group. The membrane morphology and AFM analysis showed that the NCC altered the surface and cross-sectional morphology of the CS-PES MMMs. The tensile strength of NCC-CS-PES MMMs was also enhanced. 0.5 wt% NCC-CS-PES MMMs displayed a water permeability of 1.11 × 10
-7 m/s.kPa with the lowest contact angle value of 61°. It affirmed that its hydrophilicity increased through the synergetic interaction between CS biopolymer and NCC. The effect of process variables such as transmembrane pressure (TMP) and synthetic produced water (PW) concentration were evaluated for both neat PES and NCC-CS-PES MMMs membranes. 0.5 wt% NCC-CS-PES MMMs exhibited the highest PW rejection of 98% when treating 50 mgL-1 of synthetic PW at a transmembrane pressure (TMP) of 200 kPa. The effect of nano silica and sodium chloride on the long-term PW filtration of NCC-CS-PES MMMs was also investigated., (Copyright © 2022 Elsevier Ltd. All rights reserved.)- Published
- 2022
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8. Indocyanine Green-Assisted Endoscopic Transorbital Excision of Lateral Orbital Apex Cavernous Hemangioma.
- Author
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Fong Ng BC, Kwan Mak CH, Chan NL, Lam CW, Yuen HK, and Poon TL
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- Endoscopy methods, Female, Humans, Indocyanine Green, Middle Aged, Hemangioma, Cavernous diagnostic imaging, Hemangioma, Cavernous pathology, Hemangioma, Cavernous surgery, Orbital Neoplasms diagnostic imaging, Orbital Neoplasms pathology, Orbital Neoplasms surgery, Pupil Disorders
- Abstract
Orbital apex lesions posed operative difficulties to neurosurgeons and ophthalmologists due to limited surgical corridor and close vicinity to cranial nerves and arteries. Lateral orbital apex lesions were traditionally operated via the transcranial route by neurosurgeons. Recently, only a handful of reports have described the use of endoscope alone for excision of lateral orbital apex lesion. Our group, with both endoscopic skull base neurosurgeons and oculoplastic surgeons, has adopted the endoscopic transorbital approach for orbital apex lesions. We also used an indocyanine green (ICG) endoscope to aid identification and dissection of orbital apex cavernous hemangioma, which otherwise can be difficult to differentiate from surrounding intraconal recti muscles. Video 1 captured the first reported case of excision of lateral orbital apex cavernous hemangioma via endoscopic transorbital approach, using a zero-degree ICG endoscope. This was a 64-year-old Chinese woman who presented with right eye painless blurring of vision with visual acuity of 0.6 and right relative afferent pupillary defect. Fundoscopic examination showed absence of right optic disc swelling, and automated visual field testing confirmed a superior and infratemporal visual field defect in the right eye. On magnetic resonance imaging, there was a 1-cm oval mass that was hypointense on T1-weighted and hyperintense on T2-weighted images, with slow enhancement, suggestive of cavernous hemangioma. Optical coherence tomography of the retinal nerve fiber layer showed evidence of subtle right nerve fiber layer thinning. Right endoscopic transorbital excision of the tumor was performed with an ICG-assisted endoscope. Lateral skin crease incision was followed by crescent-shaped superolateral orbital rim removal. Superior and inferior orbital fissures were identified after stripping off the periorbita. The meningoorbital band was divided to release the orbital apex from the middle fossa dura. The greater wing of sphenoid bone was drilled with a 3-mm high-speed diamond burr under irrigation to create space for dissection. Injection of ICG resulted in delayed enhancement of the lesion at around 1 minute and 30 seconds, in contrast to rapid enhancement of surrounding recti muscles at around 30 seconds. Incision of periorbita was guided by ICG enhancement of lesion. The tumor was dissected from the lateral rectus and superior division of oculomotor nerve and was excised en bloc. The supraorbital rim was reconstructed with 2 miniplates. Pathology confirmed the diagnosis of cavernous hemangioma. Postoperatively, the patient had good recovery, with right eye visual acuity of 0.8 and resolution of the relative afferent pupillary defect., (Copyright © 2021 Elsevier Inc. All rights reserved.)
- Published
- 2022
- Full Text
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9. A systematic review of morbidities suggestive of the multiple sclerosis prodrome.
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Yusuf FLA, Ng BC, Wijnands JMA, Kingwell E, Marrie RA, and Tremlett H
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- Humans, Anxiety epidemiology, Cognitive Dysfunction epidemiology, Depression epidemiology, Migraine Disorders epidemiology, Morbidity, Multiple Sclerosis epidemiology, Prodromal Symptoms
- Abstract
Introduction: The identification of a prodromal phase in multiple sclerosis (MS) could have major implications for earlier recognition and management of MS. The authors conducted a systematic review assessing studies of morbidities before, or at, MS onset or diagnosis. Areas covered : Two independent reviewers searched Medline, Embase, Psycinfo and CINAHL from inception to February 8
th , 2019. To be eligible, studies had to be published in English and report the relative occurrence of at least one morbidity or symptom before, or at, MS onset or diagnosis among MS cases in comparison to a control group not known to have MS. Findings were narratively synthesized. Study quality was assessed using the Newcastle-Ottawa scale (NOS, maximum score 9). Expert opinion : Twenty-nine studies were included, which comprised 83,590 MS cases and 396,343 controls. Most were case-control studies (25/29), 8/29 were of high quality (NOS≥8) and 19/29 examined the period before MS symptom onset. Most studies assessing anxiety, depression, migraine and lower cognitive performance found these conditions to be more prevalent before MS onset or diagnosis relative to controls. There was limited evidence to implicate other conditions. Thus, there is evidence that anxiety, depression, migraine and lower cognitive performance form part of the MS prodrome.- Published
- 2020
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10. Co-Adsorptive Removal of Creatinine and Urea by a Three-Component Dual-Layer Hollow Fiber Membrane.
- Author
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Zainol Abidin MN, Goh PS, Said N, Ismail AF, Othman MHD, Hasbullah H, Abdullah MS, Ng BC, Sheikh Abdul Kadir SH, Kamal F, and Mansur S
- Subjects
- Adsorption, Particle Size, Porosity, Surface Properties, Carbon chemistry, Creatinine chemistry, Polymers chemistry, Polymethyl Methacrylate chemistry, Sulfones chemistry, Urea chemistry
- Abstract
The development of wearable artificial kidney demands an efficient dialysate recovery, which relies upon the adsorption process. This study proposes a solution to solve the problem of competitive adsorption between the uremic toxins by employing two adsorptive components in a membrane separation process. Dual-layer hollow fiber (DLHF) membranes, which are composed of a polysulfone (PSf)/activated carbon (AC) inner layer and a PSf/poly(methyl methacrylate) (PMMA) outer layer, were prepared for co-adsorptive removal of creatinine and urea from aqueous solution. The DLHF membranes were characterized in terms of morphological, physicochemical, water transport, and creatinine adsorption properties. The membrane was then subjected to an ultrafiltration adsorption study for performance evaluation. The incorporation of AC in membrane, as confirmed by microscopic and surface analyses, has improved the pure water flux up to 25.2 L/(m
2 h). A membrane with optimum AC loading (9 wt %) demonstrated the highest maximum creatinine adsorption capacity (86.2 mg/g) based on the Langmuir adsorption isotherm model. In the ultrafiltration adsorption experiment, the membrane removed creatinine and urea with a combined average percent removal of 29.3%. Moreover, the membrane exhibited creatinine and urea uptake recoveries of 98.8 and 81.2%, respectively. The combined action of PMMA and AC in the PSf DLHF membrane has made the adsorption of multiple uremic toxins possible during dialysate recovery.- Published
- 2020
- Full Text
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11. ZrO 2 -TiO 2 Incorporated PVDF Dual-Layer Hollow Fiber Membrane for Oily Wastewater Treatment: Effect of Air Gap.
- Author
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Yaacob N, Goh PS, Ismail AF, Nazri NAM, Ng BC, Abidin MNZ, and Yogarathinam LT
- Abstract
Dual-layer hollow fiber (DLHF) nanocomposite membrane prepared by co-extrusion technique allows a uniform distribution of nanoparticles within the membrane outer layer to enhance the membrane performance. The effects of spinning parameters especially the air gap on the physico-chemical properties of ZrO
2 -TiO2 nanoparticles incorporated PVDF DLHF membranes for oily wastewater treatment have been investigated in this study. The zeta potential of the nanoparticles was measured to be around -16.5 mV. FESEM-EDX verified the uniform distribution of Ti, Zr, and O elements throughout the nanoparticle sample and the TEM images showed an average nanoparticles grain size of ~12 nm. Meanwhile, the size distribution intensity was around 716 nm. A lower air gap was found to suppress the macrovoid growth which resulted in the formation of thin outer layer incorporated with nanoparticles. The improvement in the separation performance of PVDF DLHF membranes embedded with ZrO2 -TiO2 nanoparticles by about 5.7% in comparison to the neat membrane disclosed that the incorporation of ZrO2 -TiO2 nanoparticles make them potentially useful for oily wastewater treatment., Competing Interests: The authors declare no conflict of interest.- Published
- 2020
- Full Text
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12. Effects of long-term inhaled corticosteroid treatment on fragility fractures in older women: the Manitoba BMD registry study.
- Author
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Ng BC, Leslie WD, Johnson KM, FitzGerald JM, Sadatsafavi M, and Chen W
- Subjects
- Administration, Inhalation, Adrenal Cortex Hormones administration & dosage, Aged, Bone Density, Female, Humans, Manitoba epidemiology, Registries, Adrenal Cortex Hormones adverse effects, Asthma drug therapy, Asthma epidemiology, Fractures, Bone chemically induced, Fractures, Bone epidemiology, Pulmonary Disease, Chronic Obstructive drug therapy, Pulmonary Disease, Chronic Obstructive epidemiology
- Abstract
The effects of inhaled corticosteroids (ICS) on fracture risk in older women with chronic respiratory diseases are not well established. Our results indicate long-term ICS use in this population does not increase the risk of major osteoporotic fracture. This finding further elucidates the long-term safety of ICS in older women., Introduction: Inhaled corticosteroids (ICS) are frequently used in older women with chronic respiratory diseases. There is insufficient evidence regarding the association between long-term ICS use and the risk of fragility fractures in this population., Methods: We used linked Manitoba health administrative databases and the provincial bone mineral density (BMD) registry (1996-2013) to identify women ≥ 40 years of age with asthma and/or chronic obstructive pulmonary disease (COPD) within 3 years preceding the baseline BMD test. We followed them until the first major osteoporotic fracture or end of study, whichever came first. ICS use, stratified by exposure tertiles, was measured within the 12-month period following the baseline BMD test (by total days and quantity, primary outcome), and over the entire follow-up period (by medication possession ratio (MPR) and average annual dose, secondary outcome). The hazard ratio of fracture with ICS use was estimated using a Cox proportional hazards model, controlling for baseline determinants of fracture., Results: Of 6880 older women with asthma (38%) or COPD (62%), 810 (12%) experienced a major osteoporotic fracture over a mean follow-up of 7.7 years (SD = 3.9). ICS use at any tertile was not associated with an increased risk of fracture (dispensed days, p = 0.90; dispensed quantity, p = 0.67). Similarly, ICS use at any tertile during the entire follow-up period was not associated with an increased risk of fracture (MPR, p = 0.62; average annual dose, p = 0.58)., Conclusion: Our findings do not support an increased risk of major osteoporotic fracture in older women with chronic respiratory diseases due to long-term ICS use.
- Published
- 2020
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13. Adsorptive nanocomposite membranes for heavy metal remediation: Recent progresses and challenges.
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Nasir AM, Goh PS, Abdullah MS, Ng BC, and Ismail AF
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- Adsorption, Carbon, Filtration, Ions, Kinetics, Metal-Organic Frameworks, Metals, Heavy analysis, Nanocomposites chemistry, Oxides, Water Pollutants, Chemical analysis, Water Purification methods, Zeolites chemistry, Environmental Restoration and Remediation, Metals, Heavy chemistry
- Abstract
Heavy metal contamination in aqueous system has attracted global attention due to the toxicity and carcinogenicity effects towards living bodies. Among available removal techniques, adsorptive removal by nanosized materials such as metal oxide, metal organic frameworks, zeolite and carbon-based materials has attracted much attention due to the large active surface area, large number of functional groups, high chemical and thermal stability which led to outstanding adsorption performance. However, the usage of nanosized materials is restricted by the difficulty in separating the spent adsorbent from aqueous solution. The shift towards the use of adsorptive composite membrane for heavy metal ions removal has attracted much attention due to the synergistic properties of adsorption and filtration approaches in a same chamber. Thus, this review critically discusses the development of nanoadsorbents and adsorptive nanocomposite membranes for heavy metal removal over the last decade. The adsorption mechanism of heavy metal ions by the advanced nanoadsorbents is also discussed using kinetic and isotherm models. The challenges and future prospect of adsorptive membrane technology for heavy metal removal is presented at the end of this review., (Copyright © 2019 Elsevier Ltd. All rights reserved.)
- Published
- 2019
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14. Correction: Effects of affective priming through music on the use of emotion words.
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Tay RYL and Ng BC
- Abstract
[This corrects the article DOI: 10.1371/journal.pone.0214482.].
- Published
- 2019
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15. Synthesis and characterisation of composite sulphonated polyurethane/polyethersulphone membrane for blood purification application.
- Author
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Mansur S, Othman MHD, Ismail AF, Kadir SHSA, Goh PS, Hasbullah H, Ng BC, Abdullah MS, Kamal F, Abidin MNZ, and Lusiana RA
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- Blood Coagulation, Complement Activation, Complement C3a metabolism, Humans, Hydrogen-Ion Concentration, Hydrophobic and Hydrophilic Interactions, Microscopy, Atomic Force, Platelet Adhesiveness, Polymers chemistry, Polyurethanes chemistry, Proton Magnetic Resonance Spectroscopy, Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization, Spectroscopy, Fourier Transform Infrared, Sulfones chemistry, Surface Properties, Temperature, Thrombosis pathology, Blood Cells cytology, Cell Separation methods, Membranes, Artificial, Polymers chemical synthesis, Polyurethanes chemical synthesis, Sulfones chemical synthesis
- Abstract
Polyurethane (PU) with three different functional groups: carboxyl, hydroxyl and sulphonyl group on its molecular structure were synthesised in this work. The synthesised material suppresses blood clotting and exhibits anticoagulant characteristics due to the presence of the important anionic groups. The synthesised PU was blended with polyethersulphone (PES) and fabricated into flat-sheet membrane to study the physico-chemical and biocompatibility properties of the PES membrane for blood purification application. PES-PU flat-sheet membranes were fabricated via the dry-wet phase separation technique. Different loading of PU (0, 1, 2, 3, 4, and 5%) blended with PES was studied and compared. Based on the in-vitro biocompatibility analysis of the membrane, it can be suggested that the membrane incorporated with PU has better anticoagulant properties compared to the pristine PES membrane. PU incorporation prolonged the clotting time, decreased the formation of thrombin, decreased soluble complement component 3a (C3a) generation and suppressed platelet adhesion and aggregation. The anionic groups on the membrane surface might bind to coagulation factors (antithrombin) and the calcium ions, Ca
2+ and thus improve anticoagulant ability. Based on both physico-chemical and in-vitro studied, 4% loading of PU is the optimum loading for incorporation with PES membrane. These results suggested that the blended PES-PU membranes with good haemocompatibility allowed practical application in the field of blood purification., (Copyright © 2019 Elsevier B.V. All rights reserved.)- Published
- 2019
- Full Text
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16. Effects of affective priming through music on the use of emotion words.
- Author
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Tay RYL and Ng BC
- Subjects
- Acoustic Stimulation, Adult, Arousal, Female, Humans, Male, Reaction Time, Singapore, Young Adult, Affect physiology, Emotions, Language, Music
- Abstract
Understanding how music can evoke emotions and in turn affect language use has significant implications not only in clinical settings but also in the emotional development of children. The relationship between music and emotion is an intricate one that has been closely studied. However, how the use of emotion words can be influenced by auditory priming is a question which is still not known. The main interest in this study was to examine how manipulation of mode and tempo in music affects the emotions induced and the subsequent effects on the use of emotion words. Fifty university students in Singapore were asked to select emotion words after exposure to various music excerpts. The results showed that major modes and faster tempos elicited greater responses for positive words and high arousal words respectively, while minor modes elicited more high arousal words and original tempos resulted in more positive words being selected. In the Major-Fast, Major-Slow and Minor-Slow conditions, positive correlations were found between the number of high arousal words and their rated intensities. Upon further analysis, categorization of emotion words differed from the circumplex model. Taken together, the findings highlight the prominence of affective auditory priming and allow us to better understand our emotive responses to music., Competing Interests: The authors have declared that no competing interests exist.
- Published
- 2019
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17. Highly adsorptive oxidized starch nanoparticles for efficient urea removal.
- Author
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Abidin MNZ, Goh PS, Ismail AF, Said N, Othman MHD, Hasbullah H, Abdullah MS, Ng BC, Kadir SHSA, and Kamal F
- Abstract
Portable dialysis is a need to implement daily and nocturnal hemodialysis. To realize portable dialysis, a dialysate regeneration system comprising superior adsorbents is required to regenerate the used dialysate. This study aims to develop a nano-adsorbent, derived from corn starch for urea removal. Oxidized starch nanoparticles (oxy-SNPs) were prepared via liquid phase oxidation, followed by chemical dissolution and non-solvent precipitation. The oxy-SNPs possessed Z-average size of 177.7 nm with carbonyl and carboxyl contents of 0.068 and 0.048 per 100 glucose units, respectively. The urea adsorption achieved the equilibrium after 4 h with 95% removal. The adsorption mechanism fitted Langmuir isotherm while the adsorption kinetics obeyed pseudo-second-order model. This new material has a maximum adsorption capacity of 185.2 mg/g with a rate constant of 0.04 g/mg.h. Moreover, the oxy-SNPs exhibited the urea uptake recovery of 91.6%. Oxy-SNPs can become a promising adsorbent for dialysate regeneration system to remove urea., (Copyright © 2018 Elsevier Ltd. All rights reserved.)
- Published
- 2018
- Full Text
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18. Moral Judgement in Early Bilinguals: Language Dominance Influences Responses to Moral Dilemmas.
- Author
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Wong G and Ng BC
- Abstract
The Foreign-Language effect (FLe) on morality describes how late bilinguals make different decisions on moral judgements, when presented in either their native or foreign language. However the relevance of this phenomenon to early bilinguals, where a language's "nativeness" is less distinct, is unknown. This study aims to verify the effect of early bilinguals' languages on their moral decisions and examine how language experience may influence these decisions. Eighty-six early English-Chinese bilinguals were asked to perform a moral dilemmas task consisting of personal and impersonal dilemmas, in either English or Mandarin Chinese. Information on language experience factors were also collected from the participants. Findings suggest that early bilinguals do show evidence of a language effect on their moral decisions, which is dependent on how dominant they are in the language. Particularly, the more dominant participants were in their tested language, the larger the difference between their personal and impersonal dilemma response choice. In light of these findings, the study discusses the need to re-examine how we conceptualize the FLe phenomenon and its implications on bilinguals' moral judgement. It also addresses the importance of treating bilingualism as multidimensional, rather than a unitary variable.
- Published
- 2018
- Full Text
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19. Pulsatile operation of a continuous-flow right ventricular assist device (RVAD) to improve vascular pulsatility.
- Author
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Ng BC, Kleinheyer M, Smith PA, Timms D, Cohn WE, and Lim E
- Subjects
- Blood Pressure, Equipment Design, Feasibility Studies, Heart-Assist Devices, Hemodynamics, Humans, Models, Cardiovascular, Pulsatile Flow, Heart Ventricles physiopathology, Pulmonary Artery physiology
- Abstract
Despite the widespread acceptance of rotary blood pump (RBP) in clinical use over the past decades, the diminished flow pulsatility generated by a fixed speed RBP has been regarded as a potential factor that may lead to adverse events such as vasculature stiffening and hemorrhagic strokes. In this study, we investigate the feasibility of generating physiological pulse pressure in the pulmonary circulation by modulating the speed of a right ventricular assist device (RVAD) in a mock circulation loop. A rectangular pulse profile with predetermined pulse width has been implemented as the pump speed pattern with two different phase shifts (0% and 50%) with respect to the ventricular contraction. In addition, the performance of the speed modulation strategy has been assessed under different cardiovascular states, including variation in ventricular contractility and pulmonary arterial compliance. Our results indicated that the proposed pulse profile with optimised parameters (Apulse = 10000 rpm and ωmin = 3000 rpm) was able to generate pulmonary arterial pulse pressure within the physiological range (9-15 mmHg) while avoiding undesirable pump backflow under both co- and counter-pulsation modes. As compared to co-pulsation, stroke work was reduced by over 44% under counter-pulsation, suggesting that mechanical workload of the right ventricle can be efficiently mitigated through counter-pulsing the pump speed. Furthermore, our results showed that improved ventricular contractility could potentially lead to higher risk of ventricular suction and pump backflow, while stiffening of the pulmonary artery resulted in increased pulse pressure. In conclusion, the proposed speed modulation strategy produces pulsatile hemodynamics, which is more physiologic than continuous blood flow. The findings also provide valuable insight into the interaction between RVAD speed modulation and the pulmonary circulation under various cardiovascular states.
- Published
- 2018
- Full Text
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20. Development of biocompatible and safe polyethersulfone hemodialysis membrane incorporated with functionalized multi-walled carbon nanotubes.
- Author
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Abidin MNZ, Goh PS, Ismail AF, Othman MHD, Hasbullah H, Said N, Kadir SHSA, Kamal F, Abdullah MS, and Ng BC
- Subjects
- Polymers, Renal Dialysis, Sulfones, Nanotubes, Carbon
- Abstract
A novel approach in the design of a safe, high performance hemodialysis membrane is of great demand. Despite many advantages, the employment of prodigious nanomaterials in hemodialysis membrane is often restricted by their potential threat to health. Hence, this work focusses on designing a biocompatible polyethersulfone (PES) hemodialysis membrane embedded with poly (citric acid)-grafted-multi walled carbon nanotubes (PCA-g-MWCNTs). Two important elements which could assure the safety of the nanocomposite membrane, i.e. (i) dispersion stability and (ii) leaching of MWCNTs were observed. The results showed the improved dispersion stability of MWCNTs in water and organic solvent due to the enriched ratio of oxygen-rich groups which subsequently enhanced membrane separation features. It was revealed that only 0.17% of MWCNTs was leached out during the membrane fabrication process (phase inversion) while no leaching was detected during permeation. In terms of biocompatibility, PES/PCA-g-MWCNT nanocomposite membrane exhibited lesser C3 and C5 activation (189.13 and 5.29ng/mL) and proteins adsorption (bovine serum albumin=4.5μg/cm
2 , fibrinogen=15.95μg/cm2 ) as compared to the neat PES membrane, while keeping a normal blood coagulation time. Hence, the PES/PCA-g-MWCNT nanocomposite membrane is proven to have the prospect of becoming a safe and high performance hemodialysis membrane., (Copyright © 2017 Elsevier B.V. All rights reserved.)- Published
- 2017
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21. Longitudinal study of Middle East Respiratory Syndrome coronavirus infection in dromedary camel herds in Saudi Arabia, 2014-2015.
- Author
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Hemida MG, Alnaeem A, Chu DK, Perera RA, Chan SM, Almathen F, Yau E, Ng BC, Webby RJ, Poon LL, and Peiris M
- Subjects
- Animals, Antibodies, Viral blood, Coronavirus Infections epidemiology, Coronavirus Infections transmission, Coronavirus Infections virology, Disease Transmission, Infectious prevention & control, Longitudinal Studies, Middle East Respiratory Syndrome Coronavirus classification, Middle East Respiratory Syndrome Coronavirus genetics, Middle East Respiratory Syndrome Coronavirus immunology, Nose virology, Phylogeny, Polymerase Chain Reaction, RNA, Viral blood, Rectum virology, Saudi Arabia epidemiology, Viral Load, Zoonoses, Camelus virology, Coronavirus Infections veterinary, Middle East Respiratory Syndrome Coronavirus isolation & purification
- Abstract
Two herds of dromedary camels were longitudinally sampled with nasal and rectal swabs and serum, between September 2014 and May 2015, and the samples were tested for Middle East Respiratory Syndrome (MERS) coronavirus RNA and antibodies. Evidence of MERS-CoV infection was confirmed in one herd on the basis of detection of virus RNA in nasal swabs from three camels and significant increases in the antibody titers from three others. The three viruses were genetically identical, thus indicating introduction of a single virus into this herd. There was evidence of reinfection of camels that were previously seropositive, thus suggesting that prior infection does not provide complete immunity from reinfection, a finding that is relevant to camel vaccination strategies as a means to prevent zoonotic transmission.
- Published
- 2017
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22. Hemocompatibility evaluation of poly(1,8-octanediol citrate) blend polyethersulfone membranes.
- Author
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Zailani MZ, Ismail AF, Sheikh Abdul Kadir SH, Othman MH, Goh PS, Hasbullah H, Abdullah MS, Ng BC, and Kamal F
- Subjects
- Adult, Blood Proteins chemistry, Blood Proteins metabolism, Humans, Male, Renal Dialysis instrumentation, Renal Dialysis methods, Blood Platelets metabolism, Citrates chemistry, Citrates pharmacology, Materials Testing, Membranes, Artificial, Platelet Adhesiveness drug effects, Polymers chemistry, Polymers pharmacology, Sulfones chemistry, Sulfones pharmacology
- Abstract
In this study, poly (1,8-octanediol citrate) (POC) was used to modify polyethersulfone (PES)-based membrane to enhance its hemocompatibility. Different compositions of POC (0-3%) were added into the polyethersulfone (PES) dope solutions and polyvinylpyrrolidone (PVP) was used as pore forming agent. The hemocompatible POC modified PES membranes were fabricated through phase-inversion technique. The prepared membranes were characterized using attenuated total reflectance-Fourier transform infrared (ATR-FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Atomic-force microscopy (AFM), contact angle, Zeta-potential, membrane porosity and pore size and pure water flux (PWF) and BSA rejection. The hemocompatibility of the modified PES membranes was evaluated by human serum fibrinogen (FBG) protein adsorption, platelet adhesion, activated partial thromboplastin time (APTT) and prothrombin time (PT), and thrombin-antithrombin III (TAT), complement (C3a and C5a) activation and Ca
2+ absorption on membrane. Results showed that by increasing POC concentration, FBG adsorption was reduced, less platelets adhesion, prolonged APTT and PT, lower TAT, C5a and C3a activation and absorb more Ca2+ ion. These results indicated that modification of PES with POC has rendered improved hemocompatibility properties for potential application in the field of blood purification, especially in hemodialysis. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1510-1520, 2017., (© 2017 Wiley Periodicals, Inc.)- Published
- 2017
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23. Risk factors for MERS coronavirus infection in dromedary camels in Burkina Faso, Ethiopia, and Morocco, 2015.
- Author
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Miguel E, Chevalier V, Ayelet G, Ben Bencheikh MN, Boussini H, Chu DK, El Berbri I, Fassi-Fihri O, Faye B, Fekadu G, Grosbois V, Ng BC, Perera RA, So TY, Traore A, Roger F, and Peiris M
- Subjects
- Animals, Burkina Faso, Coronavirus Infections blood, Coronavirus Infections diagnosis, Coronavirus Infections epidemiology, Coronavirus Infections virology, Ethiopia, Humans, Molecular Sequence Data, Morocco, RNA, Viral analysis, Risk Factors, Sequence Analysis, RNA, Zoonoses epidemiology, Zoonoses virology, Camelus virology, Coronavirus Infections veterinary, Disease Outbreaks veterinary, Disease Reservoirs virology, Middle East Respiratory Syndrome Coronavirus genetics, Zoonoses diagnosis
- Abstract
Understanding Middle East respiratory syndrome coronavirus (MERS-CoV) transmission in dromedary camels is important, as they consitute a source of zoonotic infection to humans. To identify risk factors for MERS-CoV infection in camels bred in diverse conditions in Burkina Faso, Ethiopia and Morocco, blood samples and nasal swabs were sampled in February-March 2015. A relatively high MERS-CoV RNA rate was detected in Ethiopia (up to 15.7%; 95% confidence interval (CI): 8.2-28.0), followed by Burkina Faso (up to 12.2%; 95% CI: 7-20.4) and Morocco (up to 7.6%; 95% CI: 1.9-26.1). The RNA detection rate was higher in camels bred for milk or meat than in camels for transport (p = 0.01) as well as in younger camels (p = 0.06). High seropositivity rates (up to 100%; 95% CI: 100-100 and 99.4%; 95% CI: 95.4-99.9) were found in Morocco and Ethiopia, followed by Burkina Faso (up to 84.6%; 95% CI: 77.2-89.9). Seropositivity rates were higher in large/medium herds (≥51 camels) than small herds (p = 0.061), in camels raised for meat or milk than for transport (p = 0.01), and in nomadic or sedentary herds than in herds with a mix of these lifestyles (p < 0.005)., (This article is copyright of The Authors, 2017.)
- Published
- 2017
- Full Text
- View/download PDF
24. Application of Adaptive Starling-Like Controller to Total Artificial Heart Using Dual Rotary Blood Pumps.
- Author
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Ng BC, Smith PA, Nestler F, Timms D, Cohn WE, and Lim E
- Subjects
- Humans, Heart, Artificial, Heart-Assist Devices
- Abstract
The successful clinical applicability of rotary left ventricular assist devices (LVADs) has led to research interest in devising a total artificial heart (TAH) using two rotary blood pumps (RBPs). The major challenge when using two separately controlled LVADs for TAH support is the difficulty in maintaining the balance between pulmonary and systemic blood flows. In this study, a starling-like controller (SLC) hybridized with an adaptive mechanism was developed for a dual rotary LVAD TAH. The incorporation of the adaptive mechanism was intended not only to minimize the risk of pulmonary congestion and atrial suction but also to match cardiac demand. A comparative assessment was performed between the proposed adaptive starling-like controller (A-SLC) and a conventional SLC as well as a constant speed controller. The performance of all controllers was evaluated by subjecting them to three simulated scenarios [rest, exercise, head up tilt (HUT)] using a mock circulation loop. The overall results showed that A-SLC was superior in matching pump flow to cardiac demand without causing hemodynamic instabilities. In contrast, improper flow regulation by the SLC resulted in pulmonary congestion during exercise. From resting supine to HUT, overpumping of the RBPs at fixed speed (FS) caused atrial suction, whereas implementation of SLC resulted in insufficient flow. The comparative study signified the potential of the proposed A-SLC for future TAH implementation particularly among outpatients, who are susceptible to variety of clinical scenarios.
- Published
- 2017
- Full Text
- View/download PDF
25. Antifouling polyethersulfone hemodialysis membranes incorporated with poly (citric acid) polymerized multi-walled carbon nanotubes.
- Author
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Abidin MNZ, Goh PS, Ismail AF, Othman MHD, Hasbullah H, Said N, Kadir SHSA, Kamal F, Abdullah MS, and Ng BC
- Subjects
- Animals, Cattle, Humans, Serum Albumin, Bovine chemistry, Membranes, Artificial, Nanotubes, Carbon chemistry, Polymers chemistry, Renal Dialysis, Sulfones chemistry
- Abstract
Poly (citric acid)-grafted-MWCNT (PCA-g-MWCNT) was incorporated as nanofiller in polyethersulfone (PES) to produce hemodialysis mixed matrix membrane (MMM). Citric acid monohydrate was polymerized onto the surface of MWCNTs by polycondensation. Neat PES membrane and PES/MWCNTs MMMs were fabricated by dry-wet spinning technique. The membranes were characterized in terms of morphology, pure water flux (PWF) and bovine serum albumin (BSA) protein rejection. The grafting yield of PCA onto MWCNTs was calculated as 149.2%. The decrease of contact angle from 77.56° to 56.06° for PES/PCA-g-MWCNTs membrane indicated the increase in surface hydrophilicity, which rendered positive impacts on the PWF and BSA rejection of the membrane. The PWF increased from 15.8Lm(-2)h(-1) to 95.36Lm(-2)h(-1) upon the incorporation of PCA-g-MWCNTs due to the attachment of abundant hydrophilic groups that present on the MWCNTs, which have improved the affinity of membrane towards the water molecules. For protein rejection, the PES/PCA-g-MWCNTs MMM rejected 95.2% of BSA whereas neat PES membrane demonstrated protein rejection of 90.2%. Compared to commercial PES hemodialysis membrane, the PES/PCA-g-MWCNTs MMMs showed less flux decline behavior and better PWF recovery ratio, suggesting that the membrane antifouling performance was improved. The incorporation of PCA-g-MWCNTs enhanced the separation features and antifouling capabilities of the PES membrane for hemodialysis application., (Copyright © 2016 Elsevier B.V. All rights reserved.)
- Published
- 2016
- Full Text
- View/download PDF
26. Numerical Simulation of a Biventricular Assist Device with Fixed Right Outflow Cannula Banding During Pulmonary Hypertension.
- Author
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Nadeem K, Ng BC, Lim E, Gregory SD, Salamonsen RF, Stevens MC, Mubin M, and Lovell NH
- Subjects
- Blood Volume, Cannula, Computer Simulation, Heart Ventricles physiopathology, Humans, Vascular Resistance, Heart-Assist Devices, Hypertension, Pulmonary physiopathology, Models, Cardiovascular
- Abstract
As a left ventricular assist device is designed to pump against the systemic vascular resistance (SVR), pulmonary congestion may occur when using such device for right ventricular support. The present study evaluates the efficacy of using a fixed right outflow banding in patients receiving biventricular assist device support under various circulatory conditions, including variations in the SVR, pulmonary vascular resistance (PVR), total blood volume (BV), as well as ventricular contractility. Effect of speed variation on the hemodynamics was also evaluated at varying degrees of PVR. Pulmonary congestion was observed at high SVR and BV. A reduction in right ventricular assist device (RVAD) speed was required to restore pulmonary pressures. Meanwhile, at a high PVR, the risk of ventricular suction was prevalent during systemic hypotension due to low SVR and BV. This could be compensated by increasing RVAD speed. Isolated right heart recovery may aggravate pulmonary congestion, as the failing left ventricle cannot accommodate the resultant increase in the right-sided flow. Compared to partial assistance, the sensitivity of the hemodynamics to changes in VAD speed increased during full assistance. In conclusion, our results demonstrated that the introduction of a banding graft with a 5 mm diameter guaranteed sufficient reserve of the pump speed spectrum for the regulation of acceptable hemodynamics over different clinical scenarios, except under critical conditions where drug administration or volume management is required.
- Published
- 2016
- Full Text
- View/download PDF
27. Assessment of the new nodal classification for cutaneous squamous cell carcinoma and its effect on patient stratification.
- Author
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Brunner M, Ng BC, Veness MJ, and Clark JR
- Subjects
- Aged, Australia, Carcinoma, Squamous Cell mortality, Carcinoma, Squamous Cell therapy, Cohort Studies, Databases, Factual, Female, Head and Neck Neoplasms mortality, Head and Neck Neoplasms therapy, Humans, Kaplan-Meier Estimate, Male, Middle Aged, Multivariate Analysis, Neoplasm Invasiveness pathology, Proportional Hazards Models, Prospective Studies, Sensitivity and Specificity, Skin Neoplasms mortality, Skin Neoplasms therapy, Societies, Medical, Survival Analysis, Carcinoma, Squamous Cell parasitology, Head and Neck Neoplasms pathology, Lymph Nodes pathology, Neoplasm Staging classification, Skin Neoplasms pathology
- Abstract
Background: The American Joint Committee on Cancer (AJCC) substantially changed the staging of cutaneous squamous cell carcinoma (SCC) in the seventh edition of its staging manual. Although the system is well established in mucosal SCC, very little data are available on its prognostic value in cutaneous SCC., Methods: We conducted a multivariable analysis of 672 patients with metastatic cutaneous SCC from 2 prospective cancer center databases., Results: The differentiation between N1 and N2 subgroups demonstrate little prognostic importance in cutaneous SCC, whereas survival is significantly worse for N3., Conclusion: Although the introduction of a unified N system for mucosal SCC and cutaneous SCC has added complexity, it does not translate into optimal distribution and stratification for metastatic cutaneous SCC., (© 2014 Wiley Periodicals, Inc.)
- Published
- 2015
- Full Text
- View/download PDF
28. Impedance and structural studies on plasticized PCL-LiSO3CF3-SiO2 polymer electrolytes.
- Author
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Ng BC, Wong HY, and You AH
- Abstract
Plasticized polymer electrolytes in this study are consist of biodegradable polycaprolactone (PCL) as a host, ethylene carbonate (EC) as a plasticizer, lithium triflate (LiSO3CF3) as salt and nanocomposite silicon dioxide (SiO2) as filler. Solution cast technique is used in the preparation of the plasticized polymer electrolytes. The electrical properties of the plasticized polymer electrolytes with different composition of lithium salt, plasticizer and nano-sized filler are reported in this paper. Conductivity as high as 4.30 x 10(-3) S cm(-1) is obtained in ambient temperature. Ionic conductivity of the plasticized polymer electrolytes are measured using electrochemistry impedance spectroscopy (EIS). The structural and complex formations are studied by X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. The ionic conductivity result can be further verified and supported by XRD and FTIR reading in which the ionic conductivity is directly proportional to the amorphous phase behaviour of the sample.
- Published
- 2014
- Full Text
- View/download PDF
29. Comparison of the AJCC N staging system in mucosal and cutaneous squamous head and neck cancer.
- Author
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Brunner M, Ng BC, Veness MJ, and Clark JR
- Subjects
- Aged, Carcinoma, Squamous Cell diagnosis, Diagnosis, Differential, Follow-Up Studies, Head and Neck Neoplasms diagnosis, Humans, Male, Middle Aged, Mouth Neoplasms diagnosis, Prognosis, Reproducibility of Results, Retrospective Studies, Risk Factors, Squamous Cell Carcinoma of Head and Neck, Carcinoma, Squamous Cell secondary, Head and Neck Neoplasms secondary, Mouth Mucosa pathology, Mouth Neoplasms secondary, Neoplasm Staging methods, Skin pathology, Skin Neoplasms pathology
- Abstract
Objectives/hypothesis: The American Joint Committee on Cancer (AJCC) substantially changed the staging of cutaneous squamous cell carcinoma (cSCC) in the seventh edition of its staging manual. Given that oral mucosal squamous cell carcinoma (mSCC) and cSCC behave differently and affect different patient populations, the aim of this study was to provide a side-by-side comparison and to evaluate the current nodal (N) grouping for cSCC alongside oral mSCC to determine whether the same system is justified., Study Design: Retrospective analysis of prospectively collected data., Methods: Multivariable analysis of 672 patients with metastatic cSCC and of 225 patients with metastatic mSCC from two prospective cancer-center databases., Results: While, as expected, the N grouping functioned well in mSCC in terms of distribution and stratification of patients, it performed much less favorably in cSCC. In contrast to mSCC, the different N groups demonstrate much less prognostic importance in cSCC., Conclusion: Although the introduction of a unified N system for mSCC and cSCC has definite advantages, it does not translate into optimal distribution and stratification for metastatic cSCC., Level of Evidence: 4., (© 2013 The American Laryngological, Rhinological and Otological Society, Inc.)
- Published
- 2014
- Full Text
- View/download PDF
30. Multidisciplinary vascular malformations clinic in Hong Kong.
- Author
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Ng BC, San CY, Lau EY, Yu SC, and Burd A
- Subjects
- Adolescent, Adult, Child, Child, Preschool, Female, Hong Kong, Hospitals, Teaching, Humans, Interdisciplinary Communication, Magnetic Resonance Angiography methods, Male, Prognosis, Referral and Consultation, Retrospective Studies, Risk Assessment, Sclerotherapy methods, Severity of Illness Index, Survival Rate, Treatment Outcome, Ultrasonography, Doppler methods, Vascular Malformations mortality, Vascular Surgical Procedures methods, Young Adult, Ambulatory Care Facilities organization & administration, Diagnostic Imaging methods, Vascular Malformations diagnosis, Vascular Malformations therapy
- Abstract
Objective: To review clinical characteristics, imaging modalities, and treatment outcomes of patients referred to a multidisciplinary clinic for management of vascular malformations., Design: Retrospective case series., Setting: Multidisciplinary vascular malformation out-patient referral clinic in a teaching hospital in Hong Kong., Patients: The 141 attendees of the clinic from August 2005 to November 2011., Main Outcome Measures: Management and treatments offered, and responses to treatment., Results: Of the 141 patients, 46% were diagnosed to have low-flow vascular malformations, 16% were diagnosed to have high-flow vascular malformations, and 15% were diagnosed to have a haemangioma. Prior to attending the clinic, approximately one third (32%) of the patients had a clinical diagnosis that was consistent with the final diagnosis. Overall, the radiological and clinical diagnoses were consistent in 43% of the patients. Magnetic resonance imaging and ultrasonography were the most commonly used imaging modalities. Of the 73 patients who received active treatment, 70% had a good response, 12% had minimal improvement, 8% had no change, and 7% had a recurrence or a major complication; in 3% of the patients the outcome was unknown., Conclusion: From this retrospective case series, it is evident that confusion still exists over vascular malformations and haemangiomas. Multidisciplinary clinics have a role in providing an accurate diagnosis and facilitating appropriate management and treatment plans. Magnetic resonance imaging and ultrasonography had demonstrable utility in determining the extent of the lesions and flow type.
- Published
- 2013
31. Self-assembling semiconducting polymers--rods and gels from electronic materials.
- Author
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Clark AP, Shi C, Ng BC, Wilking JN, Ayzner AL, Stieg AZ, Schwartz BJ, Mason TG, Rubin Y, and Tolbert SH
- Subjects
- Gels, Hydrophobic and Hydrophilic Interactions, Micelles, Models, Molecular, Molecular Conformation, Optical Phenomena, Solutions, Electric Conductivity, Fluorenes chemistry, Polymers chemistry, Semiconductors, Thiophenes chemistry
- Abstract
In an effort to favor the formation of straight polymer chains without crystalline grain boundaries, we have synthesized an amphiphilic conjugated polyelectrolyte, poly(fluorene-alt-thiophene) (PFT), which self-assembles in aqueous solutions to form cylindrical micelles. In contrast to many diblock copolymer assemblies, the semiconducting backbone runs parallel, not perpendicular, to the long axis of the cylindrical micelle. Solution-phase micelle formation is observed by X-ray and visible light scattering. The micelles can be cast as thin films, and the cylindrical morphology is preserved in the solid state. The effects of self-assembly are also observed through spectral shifts in optical absorption and photoluminescence. Solutions of higher-molecular-weight PFT micelles form gel networks at sufficiently high aqueous concentrations. Rheological characterization of the PFT gels reveals solid-like behavior and strain hardening below the yield point, properties similar to those found in entangled gels formed from surfactant-based micelles. Finally, electrical measurements on diode test structures indicate that, despite a complete lack of crystallinity in these self-assembled polymers, they effectively conduct electricity.
- Published
- 2013
- Full Text
- View/download PDF
32. BMP-binding protein twisted gastrulation is required in mammary gland epithelium for normal ductal elongation and myoepithelial compartmentalization.
- Author
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Forsman CL, Ng BC, Heinze RK, Kuo C, Sergi C, Gopalakrishnan R, Yee D, Graf D, Schwertfeger KL, and Petryk A
- Subjects
- Animals, Apoptosis physiology, Blotting, Western, Bromodeoxyuridine, Cell Line, Cell Proliferation, Epithelium metabolism, Female, Galactosides, Gene Expression Regulation, Developmental genetics, Gene Knock-In Techniques, Hematoxylin, Immunohistochemistry, Indoles, Mammary Glands, Animal metabolism, Mammary Glands, Animal transplantation, Mice, Mice, Knockout, Proteins genetics, Real-Time Polymerase Chain Reaction, Reverse Transcriptase Polymerase Chain Reaction, Bone Morphogenetic Proteins metabolism, Gene Expression Regulation, Developmental physiology, Mammary Glands, Animal growth & development, Proteins metabolism, Signal Transduction physiology
- Abstract
Bone morphogenetic proteins (BMPs) are involved in embryonic mammary gland (MG) development and can be dysregulated in breast cancer. However, the role BMPs play in the postnatal MG remains virtually unknown. BMPs are potent morphogens that are involved in cell fate determination, proliferation, apoptosis and adult tissue homeostasis. Twisted gastrulation (TWSG1) is a secreted BMP binding protein that modulates BMP ligand availability in the extracellular space. Here we investigate the consequences of TWSG1 deletion on development of the postnatal MG. At puberty, Twsg1 is expressed in the myoepithelium and in a subset of body cells of the terminal end buds. In the mature duct, Twsg1 expression is primarily restricted to the myoepithelial layer. Global deletion of Twsg1 leads to a delay in ductal elongation, reduced secondary branching, enlarged terminal end buds, and occluded lumens. This is associated with an increase in luminal epithelial cell number and a decrease in apoptosis. In the MG, pSMAD1/5/8 level and the expression of BMP target genes are reduced, consistent with a decrease in BMP signaling. GATA-3, which is required for luminal identity, is reduced in Twsg1(-/-) MGs, which may explain why K14 positive cells, which are normally restricted to the myoepithelial layer, are found within the luminal compartment and shed into the lumen. In summary, regulation of BMP signaling by TWSG1 is required for normal ductal elongation, branching of the ductal tree, lumen formation, and myoepithelial compartmentalization in the postnatal MG., (Copyright © 2012 Elsevier Inc. All rights reserved.)
- Published
- 2013
- Full Text
- View/download PDF
33. Pre-treatment of multi-walled carbon nanotubes for polyetherimide mixed matrix hollow fiber membranes.
- Author
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Goh PS, Ng BC, Ismail AF, Aziz M, and Hayashi Y
- Abstract
Mixed matrix hollow fibers composed of multi-walled carbon nanotubes (MWCNTs) and polyetherimide (PEI) were fabricated. Pre-treatment of MWCNTs was carried out prior to the incorporation into the polymer matrix using a simple and feasible two stages approach that involved dry air oxidation and surfactant dispersion. The characterizations of the surface treated MWCNTs using TEM and Raman spectroscopy have evidenced the effectiveness of dry air oxidation in eliminating undesired amorphous carbon and metal catalyst while surfactant dispersion using Triton X100 has suppressed the agglomeration of MWCNTs. The resultant mixed matrix hollow fibers were applied for O(2)/N(2) pure gas separation. Interestingly, it was found that removal of disordered amorphous carbons and metal particles has allowed the hollow structures to be more accessible for the fast and smooth transport of gas molecules, hence resulted in noticeable improvement in the gas separation properties. The composite hollow fibers embedded with the surface modified MWCNTs showed increase in permeability as much as 60% while maintaining the selectivity of the O(2)/N(2) gas pair. This study highlights the necessity to establish an appropriate pre-treatment approach for MWCNTs in order to fully utilize the beneficial transport properties of this material in mixed matrix polymer nanocomposite for gas separation., (Copyright © 2012 Elsevier Inc. All rights reserved.)
- Published
- 2012
- Full Text
- View/download PDF
34. Using polymer conformation to control architecture in semiconducting polymer/viral capsid assemblies.
- Author
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Ng BC, Chan ST, Lin J, and Tolbert SH
- Subjects
- Fluorescence Polarization, Microscopy, Electron, Transmission, Solvents chemistry, Bromovirus chemistry, Capsid chemistry, Molecular Conformation, Polyvinyls chemistry, Semiconductors virology
- Abstract
Cowpea chlorotic mottle virus is a single-stranded RNA plant virus with a diameter of 28 nm. The proteins comprising the capsid of this virus can be purified and reassembled either by themselves to form hollow structures or with polyanions such as double-stranded DNA or single-stranded RNA. Depending on pH and ionic strength, a diverse range of structures and shapes can form. The work presented here focuses on using these proteins to encapsulate a fluorescent polyanionic semiconducting polymer, MPS-PPV (poly-2-methoxy-5-propyloxy sulfonate phenylene vinlyene), in order to obtain optically active virus-like particles. After encapsulation, fluorescence from MPS-PPV shows two distinct peaks, which suggests the polymer may be in two conformations. A combination of TEM, fluorescence anisotropy, and sucrose gradient separation indicate that the blue peak arises from polymer encapsulated into spherical particles, while the redder peak corresponds to polymers contained in rod-like cages. Ionic strength during assembly can be used to tune the propensity to form rods or spheres. The results illustrate the synergy of hybrid synthetic/biological systems: polymer conformation drives the structure of this composite material, which in turn modifies the polymer optical properties. This synergy could be useful for the future development of synthetic/biological hybrid materials with designated functionality.
- Published
- 2011
- Full Text
- View/download PDF
35. Vaults are dynamically unconstrained cytoplasmic nanoparticles capable of half vault exchange.
- Author
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Yang J, Kickhoefer VA, Ng BC, Gopal A, Bentolila LA, John S, Tolbert SH, and Rome LH
- Subjects
- Animals, Cell Line, Tumor, Diffusion, Fluorescence Resonance Energy Transfer, Humans, Microscopy, Electron, Transmission, Models, Molecular, Polyethylene Glycols chemistry, Protein Conformation, Protein Transport, Scattering, Small Angle, X-Ray Diffraction, Cytoplasm metabolism, Nanoparticles, Vault Ribonucleoprotein Particles chemistry, Vault Ribonucleoprotein Particles metabolism
- Abstract
Vaults are naturally occurring ribonucleoprotein particles with an enormous interior volume, large enough to encapsulate hundreds of proteins. They are highly conserved and are present in nearly all eukaryotic cells ranging from 10(4) to 10(7) particles per cell. Recombinant vaults can be produced in vitro and engineered to allow cell targeting and protein packaging. These nanometer-sized particles have many desirable characteristics that may give them advantages for use as drug delivery vehicles. Using photoactivatable green fluorescent protein (PAGFP) labeled vaults, we demonstrate that the particles rapidly diffuse throughout the cytoplasm following single pixel photoactivation in live cells. Their in vivo movement remained relatively unchanged despite exposure to a variety of cellular stresses, suggesting that vaults are largely unconstrained in the cytoplasm. Fluorescence resonance energy transfer (FRET) was observed from polyethylene glycol (PEG) fused hybrid cells that expressed either CFP or YFP labeled vaults, indicating that vaults can exchange major vault protein (MVP) subunits in vivo. Investigation into the mechanism of this exchange in vitro using recombinant vaults demonstrated that they were capable of rapidly separating at the particle waist and reassembling back into whole vaults, supporting a half vault exchange mechanism. This data suggests a means whereby vaults can functionally interact with their cellular environment and deliver materials packaged within their interior.
- Published
- 2010
- Full Text
- View/download PDF
36. Reversible pH lability of cross-linked vault nanocapsules.
- Author
-
Yu M, Ng BC, Rome LH, Tolbert SH, and Monbouquette HG
- Subjects
- Amines chemistry, Animals, Biotechnology methods, Chemistry, Pharmaceutical methods, Cross-Linking Reagents chemistry, Drug Delivery Systems, Electrons, Humans, Hydrogen-Ion Concentration, Models, Chemical, Molecular Conformation, Nanocapsules chemistry, Nanoparticles chemistry, Nanotechnology methods
- Abstract
Vaults are ubiquitous, self-assembled protein nanocapsules with dimension in the sub-100 nm range that are conserved across diverse phyla from worms to humans. Their normal presence in humans at a copy number of over 10,000/cell makes them attractive as potential drug delivery vehicles. Toward this goal, bifunctional amine-reactive reagents are shown to be useful for the reversible cross-linking of recombinant vaults such that they may be closed and opened in a controllable manner.
- Published
- 2008
- Full Text
- View/download PDF
37. Encapsulation of semiconducting polymers in vault protein cages.
- Author
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Ng BC, Yu M, Gopal A, Rome LH, Monbouquette HG, and Tolbert SH
- Subjects
- DNA chemistry, Drug Carriers, Drug Delivery Systems, Genetic Therapy methods, Humans, Microscopy, Electron, Transmission, Models, Statistical, Nanocomposites chemistry, Polymers chemistry, Proteins chemistry, Spectrometry, Fluorescence methods, X-Rays, Nanocapsules chemistry, Semiconductors
- Abstract
We demonstrate that a semiconducting polymer [poly(2-methoxy-5-propyloxy sulfonate phenylene vinylene), MPS-PPV] can be encapsulated inside recombinant, self-assembling protein nanocapsules called "vaults". Polymer incorporation into these nanosized protein cages, found naturally at approximately 10,000 copies per human cell, was confirmed by fluorescence spectroscopy and small-angle X-ray scattering. Although vault cellular functions and gating mechanisms remain unknown, their large internal volume and natural prevalence within the human body suggests they could be used as carriers for therapeutics and medical imaging reagents. This study provides the groundwork for the use of vaults in encapsulation and delivery applications.
- Published
- 2008
- Full Text
- View/download PDF
38. The cerebro-costo-mandibular syndrome: 9-year follow-up of a case.
- Author
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Hosalkar HS, Shaw BA, Ceppi CL, and Ng BC
- Subjects
- Child, Cleft Palate, Follow-Up Studies, Hearing Loss, Conductive, Humans, Kyphosis, Male, Patient Care Team, Scoliosis, Syndrome, Abnormalities, Multiple, Micrognathism, Ribs abnormalities
- Abstract
Cerebro-costo-mandibular syndrome (CCMS) is a rare multiple congenital anomaly with a low survival rate. There are few reports of long-term survival in this condition. We describe the findings and management of a 9-year-old survivor of CCMS, outline the importance of early intervention and multidisciplinary team approach. The child presented in the neonatal period in respiratory distress with classical features of the syndrome. Aggressive initial respiratory management was later followed up with an integrated multidisciplinary team approach. He has been carefully followed up for nine years now, illustrating well, the course of the syndrome.
- Published
- 2000
39. A radioimmunoassay of 15 (S) 15 methyl prostaglandin F-2alpha.
- Author
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Salmon JA, Ng BC, and Karim SM
- Subjects
- Amniotic Fluid analysis, Animals, Female, Immune Sera, Prostaglandins F blood, Rabbits, Radioimmunoassay methods, Prostaglandins F analysis
- Abstract
A sensitive and relatively specific radioimmunoassay for 15 (S) 15 methyl prostaglandin F-2alpha has been developed to enable the measurements of the concentrations of the drug in biological fluids after its administration for therapeutic abortion. The precision, accuracy and specificity of the assay are described.
- Published
- 1975
- Full Text
- View/download PDF
40. Heroin abuse in Singapore--a profile and characteristics study.
- Author
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Teo SH, Chee KT, Tan CT, and Ng BC
- Subjects
- Adolescent, Adult, Child, Female, Humans, Male, Singapore, Socioeconomic Factors, Substance Withdrawal Syndrome epidemiology, Substance-Related Disorders, Time Factors, Heroin Dependence epidemiology
- Published
- 1978
41. Treatment and rehabilitation of drug addicts in Singapore 1977-1982.
- Author
-
Ng BC
- Subjects
- Adolescent, Adult, Combined Modality Therapy, Female, Humans, Male, Middle Aged, Prognosis, Rehabilitation, Vocational methods, Singapore, Heroin Dependence rehabilitation
- Abstract
In Singapore, the treatment and rehabilitation of drug addicts consist of detoxification, recuperation and orientation, indoctrination, physical training and work programme. This is followed by a Day Release Scheme to bridge the gap between the strict disciplinary regime and the free environment of the outside world. The addicts are given the opportunities to pursue academic studies. Two review committees monitor their progress. There has been a significant decrease in the total number of admission from 7084 in 1977 to 2043 in 1982. Over this period, there appears to be a drop in the number of youths recruited into drug abuse. At the same time, more and more of those who have been previously treated are coming into the drug scene.
- Published
- 1984
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