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Search Results: 1 - 10 of 10082 matches for " Wai-Ting Lam "
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Interaction Energy between an Atomic Force Microscope Tip and a Charged Particle in Electrolyte  [PDF]
Wai-Ting Lam, Fredy R. Zypman
Journal of Applied Mathematics and Physics (JAMP) , 2016, DOI: 10.4236/jamp.2016.411199
Abstract: A variational principle to the nonlinear Poisson-Boltzmann equation (PB) in three dimensions is used to first obtain solutions to the electrostatic potential surrounding a pair of spherical colloidal particles, one of them modeling the tip of an Atomic Force Microscope. Specifically, we consider the PB action integral for the electrostatic potential produced by charged colloidal particles and propose an analytical ansatz solution. This solution introduces the density and its corresponding electrostatic potential parametrically. The PB action is then minimized with respect to the parameter. Polynomial-exponential approximations for the parameters as functions of tip-particle separation and boundary electrostatic potential are obtained. With that information, tip-particle energy-separation curves are computed as well. Finally, based on the shape of the energy-separation curves, we study the stability properties predicted by this theory.
A Shortened Barnes Maze Protocol Reveals Memory Deficits at 4-Months of Age in the Triple-Transgenic Mouse Model of Alzheimer's Disease
Aida Attar, Tingyu Liu, Wai-Ting Coco Chan, Jane Hayes, Mona Nejad, KaiChyuan Lei, Gal Bitan
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0080355
Abstract: Alzheimer's disease is a progressive neurodegenerative disease that manifests as memory loss, cognitive dysfunction, and dementia. Animal models of Alzheimer's disease have been instrumental in understanding the underlying pathological mechanism and in evaluation of potential therapies. The triple transgenic (3×Tg) mouse model of AD is unique because it recapitulates both pathologic hallmarks of Alzheimer's disease - amyloid plaques and neurofibrillary tangles. The earliest cognitive deficits in this model have been shown at 6-m of age by most groups, necessitating aging of the mice to this age before initiating evaluation of the cognitive effects of therapies. To assess cognitive deficits in the 3×Tg mice, originally we employed a typical Barnes maze protocol of 15 training trials, but found no significant deficits in aged mice. Therefore, we shortened the protocol to include only 5 training trials to increase difficulty. We found cognitive deficits using this protocol using mainly measures from the probe day, rather than the training trials. This also decreased the effort involved with data analysis. We compared 3×Tg and wild-type mice at 4-m- and 15-m of age using both the original, long training, and the short training paradigms. We found that differences in learning between 3×Tg and wild-type mice disappeared after the 4th training trial. Measures of learning and memory on the probe day showed significant differences between 3×Tg and wild-type mice following the short, 5-training trial protocol but not the long, 15-training trial protocol. Importantly, we detected cognitive dysfunction already at 4-m of age in 3×Tg mice using the short Barnes-maze protocol. The ability to test learning and memory in 4-m old 3×Tg mice using a shortened Barnes maze protocol offers considerable time and cost savings and provides support for the utilization of this model at pre-pathology stages for therapeutic studies.
Structural studies of the mechanism for biosensing antibiotics in a fluorescein-labeled β-lactamase
Wai-Ting Wong, Ho-Wah Au, Hong-Kin Yap, Yun-Chung Leung, Kwok-Yin Wong, Yanxiang Zhao
BMC Structural Biology , 2011, DOI: 10.1186/1472-6807-11-15
Abstract: Here we report the crystal structure of a Class A β-lactamase PenP from Bacillus licheniformis 749/C with fluorescein conjugated at residue 166 after E166C mutation, both in apo form (PenP-E166Cf) and in covalent complex form with cefotaxime (PenP-E166Cf-cefotaxime), to illustrate its biosensing mechanism. In the apo structure the fluorescein molecule partially occupies the antibiotic binding site and is highly dynamic. In the PenP-E166Cf-cefatoxime complex structure the binding and subsequent acylation of cefotaxime to PenP displaces fluorescein from its original location to avoid steric clash. Such displacement causes the well-folded Ω-loop to become fully flexible and the conjugated fluorescein molecule to relocate to a more solvent exposed environment, hence enhancing its fluorescence emission. Furthermore, the fully flexible Ω-loop enables the narrow-spectrum PenP enzyme to bind cefotaxime in a mode that resembles the extended-spectrum β-lactamase.Our structural studies indicate the biosensing mechanism of a fluorescein-labelled β-lactamase. Such findings confirm our previous proposal based on molecular modelling and provide useful information for the rational design of β-lactamase-based biosensor to detect the wide spectrum of β-lactam antibiotics. The observation of increased Ω-loop flexibility upon conjugation of fluorophore may have the potential to serve as a screening tool for novel β-lactamase inhibitors that target the Ω-loop and not the active site.β-Lactamase is one of the major mechanisms of antibiotic resistance in bacteria. Enzymes of this family deactivate β-lactam antibiotics by hydrolyzing the conserved β-lactam moiety in the antibiotics and rendering them ineffective to bind to their target proteins, the penicillin-binding proteins (PBPs), which are essential for bacterial cell wall synthesis and survival [1,2]. Detailed mechanistic studies of these enzymes over the past decades have revealed a conserved mechanism of β-lactam hydrolysis that co
In Vivo Study on the Pharmacological Interactions between a Chinese Herbal Formula ELP and Antiresorptive Drugs to Counteract Osteoporosis
Chun-Hay Ko,Wing-Sum Siu,Hing-Lok Wong,Si Gao,Wai-Ting Shum,Ching-Po Lau,Sau-Wan Cheng,Jacqueline Chor-Wing Tam,Leung-Kim Hung,Kwok-Pui Fung,Clara Bik-San Lau,Quan-Bin Han,Ping-Chung Leung
Evidence-Based Complementary and Alternative Medicine , 2012, DOI: 10.1155/2012/203732
Abstract: Antiresorptive drugs, alendronate and raloxifene, are effective in lowering bone mineral density (BMD) loss in postmenopausal women. However, long-term treatment may be associated with serious side effects. Our research group has recently discovered that a Chinese herbal formula, ELP, could significantly reduce BMD loss in animal and human studies. Therefore, the present study aimed to investigate the potential synergistic bone-protective effects of different herb-drug combinations using ovariectomized rats. To assess the efficacy of different combinations, the total BMD was monitored biweekly in the 8-week course of daily oral treatment. Bone microarchitecture, bone strength, and deoxypyridinoline level were also determined after 8 weeks. From our results, coadministration of ELP and raloxifene increased the total tibial BMD by 5.26% (2.5 mg/kg/day of raloxifene; ) and 5.94% (0.25 mg/kg/day of raloxifene; ) when compared with the respective dosage groups with raloxifene alone. Similar synergistic effects were also observed in BMD increase at distal femur (0.25 mg/kg/day; ) and reduction in urinary deoxypyridinoline crosslink excretion (2.5 and 0.25 mg/kg/day; both ). However, such interactions could not be observed in all alendronate-treated groups. Our data provide first evidence that ELP could synergistically enhance the therapeutic effects of raloxifene, so that the clinical dosage of raloxifene could be reduced.
The Study of Teacher Efficacy in Hong Kong Subdegree Sector
Wai-Hung Lam
Education Research International , 2012, DOI: 10.1155/2012/265293
The Study of Teacher Efficacy in Hong Kong Sub-Degree Sector
Wai-Hung Lam
Education Research International , 2012, DOI: 10.1155/2012/265293
Abstract: Introduction. Sub-degree sector is rising in Hong Kong. The number of enrolled students was over 50000 in 2011. Students’ characteristics and teachers’ roles in the sub-degree sector are different from other sectors. It was important to investigate the factors related with teacher efficacy of sub-degree teachers. Method. Sixty sub-degree teachers were surveyed, and 58 of them were valid (33 males and 25 females). The questionnaire contained three teacher efficacy scales: Teacher Efficacy Scale (TES) (short form), Bandura’s Instrument Teacher Self-Efficacy Scale (TSES), and Teachers’ Sense of Efficacy Scale (TSoES) and an instrument of self-rating’s levels of concerns. Results. The teacher efficacy scales were found to be reliable in the sub-degree sector. The levels of education and educational trainings were not found to be related with any teacher efficacy scales. Level of concerns of teacher efficacy was found to be significant related with TSES’ efficacy to influence parental involvement and ToSES’s instruction strategies. Conclusion. This study found that educational trainings and levels of educations were not related with teacher efficacy and could persuade institutes not to view educational backgrounds as the most influencing factor in employment selections and design better staff developments instead of only sponsoring teachers to pursue further studies. 1. Introduction In 1999, Hong Kong Education Bureau (HKEB) published the “Review of education system: Framework for education reform” to review the academic system and urged to engage full-time post-secondary colleges (i.e., institutes providing postsecondary courses and compensatory courses into lifelong learning academic structure) into the system. It meant that students who graduated from secondary education can choose to continue their studies in either full-time postsecondary colleges or universities. Those post-secondary colleges are different from vocational training bodies and universities as they provide more academic-oriented and less vocational-oriented programs (e.g., diplomas, higher diplomas, Project Yin Jin, and associate degrees) which are qualified as lower level than bachelor degree level. Those programs prepare students to purse degree programs after graduation. Those institutes formed a new sector called subdegree sector which is different from “Technical Vocational Education and Training” (TVET) comprised of vocational training bodies and “Higher Education” comprised of universities. “Sub-degree” was defined as the comprising of both “the Higher Diploma of a vocational
Discrete minimal surfaces: critical points of the area functional from integrable systems
Wai Yeung Lam
Mathematics , 2015,
Abstract: We define two types of discrete minimal surfaces whose cell decompositions are arbitrary. These two types of discrete minimal surfaces are conjugate to each other and generalize earlier notions of discrete minimal surfaces: circular minimal, s-isothermic minimal and conical minimal surfaces. We show that each discrete minimal surface corresponds to a harmonic function on a planar mesh. Furthermore we show that all minimal surfaces in certain associated family, including those from discrete isothermic nets and Schramm's orthogonal circle patterns, are critical points of the area functional.
Using Causal Information and Local Measures to Learn Bayesian Networks
Wai Lam,Fahiem Bacchus
Computer Science , 2013,
Abstract: In previous work we developed a method of learning Bayesian Network models from raw data. This method relies on the well known minimal description length (MDL) principle. The MDL principle is particularly well suited to this task as it allows us to tradeoff, in a principled way, the accuracy of the learned network against its practical usefulness. In this paper we present some new results that have arisen from our work. In particular, we present a new local way of computing the description length. This allows us to make significant improvements in our search algorithm. In addition, we modify our algorithm so that it can take into account partial domain information that might be provided by a domain expert. The local computation of description length also opens the door for local refinement of an existent network. The feasibility of our approach is demonstrated by experiments involving networks of a practical size.
Using New Data to Refine a Bayesian Network
Wai Lam,Fahiem Bacchus
Computer Science , 2013,
Abstract: We explore the issue of refining an existent Bayesian network structure using new data which might mention only a subset of the variables. Most previous works have only considered the refinement of the network's conditional probability parameters, and have not addressed the issue of refining the network's structure. We develop a new approach for refining the network's structure. Our approach is based on the Minimal Description Length (MDL) principle, and it employs an adapted version of a Bayesian network learning algorithm developed in our previous work. One of the adaptations required is to modify the previous algorithm to account for the structure of the existent network. The learning algorithm generates a partial network structure which can then be used to improve the existent network. We also present experimental evidence demonstrating the effectiveness of our approach.
A Traditional Chinese Medicine Approach in Treating Depression by Promoting Liver Qi Circulation: A Western Medicine Perspective  [PDF]
Raphaella Wai Lam So, Hoi Shan Wong, Kam Ming Ko
Chinese Medicine (CM) , 2015, DOI: 10.4236/cm.2015.64021
Abstract: Depression is a prevalent mental illness in developed countries. In Western medicine, experimental and clinical investigations have demonstrated that depression is associated with the dysregulation of neurotransmitter signaling, and symptoms of depression can be alleviated by therapeutic intervention. However, patients taking antidepressant drugs often experience serious side effects and high relapse rates. On the other hand, traditional Chinese medicine (TCM) views depression as a manifestation of liver qi stagnation. Practitioners of TCM have long been treating depression with herbs that promote qi circulation in the liver. In this article, we offer a hypothesis stating the biochemical basis of the linkage between liver qi stagnation and depression. Liver qi is involved in the processing of macronutrients into molecules to fuel energy metabolism in brain neurons, as well as the synthesis of plasma proteins that maintain blood circulation to the brain, thereby enabling these fuel molecules to be delivered to the brain. In cases of liver qi stagnation, the failure in delivering sufficient fuel molecules to the brain disrupts mitochondrial ATP production in neurons. Because neurotransmitter release and neurotropin transport are driven by ATP, the deficiency in release and transport processes resulting from insufficient ATP production could lead to depression. Therefore, if liver qi stagnation is causally related to the pathogenesis of depression, the promotion of liver qi circulation by Chinese herbs might offer a promising prospect for the effective treatment of depression.
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