HKBU Institute of Research and Continuing Education

Shenzhen, China

HKBU Institute of Research and Continuing Education

Shenzhen, China
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Bi Z.,CAS Institute of Theoretical Physics | Bi Z.,Hong Kong Baptist University | Zhou C.,Hong Kong Baptist University | Zhou C.,Beijing Computational Science Research Center | Zhou C.,HKBU Institute of Research and Continuing Education
Frontiers in Computational Neuroscience | Year: 2016

In neural systems, synaptic plasticity is usually driven by spike trains. Due to the inherent noises of neurons and synapses as well as the randomness of connection details, spike trains typically exhibit variability such as spatial randomness and temporal stochasticity, resulting in variability of synaptic changes under plasticity, which we call efficacy variability. How the variability of spike trains influences the efficacy variability of synapses remains unclear. In this paper, we try to understand this influence under pair-wise additive spike-timing dependent plasticity (STDP) when the mean strength of plastic synapses into a neuron is bounded (synaptic homeostasis). Specifically, we systematically study, analytically and numerically, how four aspects of statistical features, i.e., synchronous firing, burstiness/regularity, heterogeneity of rates and heterogeneity of cross-correlations, as well as their interactions influence the efficacy variability in converging motifs (simple networks in which one neuron receives from many other neurons). Neurons (including the post-synaptic neuron) in a converging motif generate spikes according to statistical models with tunable parameters. In this way, we can explicitly control the statistics of the spike patterns, and investigate their influence onto the efficacy variability, without worrying about the feedback from synaptic changes onto the dynamics of the post-synaptic neuron. We separate efficacy variability into two parts: the drift part (DriftV) induced by the heterogeneity of change rates of different synapses, and the diffusion part (DiffV) induced by weight diffusion caused by stochasticity of spike trains. Our main findings are: (1) synchronous firing and burstiness tend to increase DiffV (2) heterogeneity of rates induces DriftV when potentiation and depression in STDP are not balanced, and (3) heterogeneity of cross-correlations induces DriftV together with heterogeneity of rates. We anticipate our work important for understanding functional processes of neuronal networks (such as memory) and neural development. © 2016 Bi and Zhou.

Sun H.,Hong Kong Baptist University | Li W.,Hong Kong Baptist University | Dong Z.-Z.,Hong Kong Baptist University | Hu C.,Hong Kong Baptist University | And 5 more authors.
Biosensors and Bioelectronics | Year: 2018

A paper-based microfluidic device based on unconventional principle was developed and used to detect lead ions through a two-step process including heated incubation and subsequent mixing. The device was made by generating a superhydrophobic pattern, which defines channel and reservoir barriers, on a water-impermeable paper substrate, followed by loading and drying the reagents in the defined reservoirs. Different from the conventional paper-based devices that are made of water-permeable paper, the as-prepared device holds water drops in discrete reservoirs, and the water drops will not move unless the device is titled along the direction of the predefined channels. In this way, the liquid samples applied onto the device are handled as individual drops and could be stored, transported, and mixed on demand. Different from the conventional paper-based devices that use capillary force to drive liquid, our new device uses wetting and gravity as driving force. We name this operation principle suspending-droplet mode paper-based device (SD-μPAD). The use of a Teflon contact-printing stamp makes the production of such devices rapid, cost efficient, and mass productive. Utilizing a G-quadruplex-based luminescence switch-on assay, we demonstrated rapid, convenient, highly sensitive, and low cost detection of lead(II) ions in water samples, using a custom made battery-powered portable device, and a smart phone as the detector. © 2017 Elsevier B.V.

Wang Q.,Hong Kong Baptist University | Xu P.,Hong Kong Baptist University | Zhang Y.,Hong Kong Baptist University | Chu X.,Hong Kong Baptist University | Chu X.,HKBU Institute of Research and Continuing Education
e-Energy 2017 - Proceedings of the 8th International Conference on Future Energy Systems | Year: 2017

To address the ever-increasing demand for computing capacities, more and more heterogeneous systems have been designed to use both general-purpose and special-purpose processors. On the other hand, the huge energy consumption of these heterogeneous systems raises new environmental concerns and challenges. Besides performance, energy efficiency is now another key factor to be considered by system designers and also consumers. In this paper, we present a benchmark suite EPPMiner for evaluating the performance, power, and energy of different heterogeneous systems. EPPMiner consists of 16 benchmark programs that cover a broad range of application domains, and it shows a great variety in the intensity of utilizing the processors. We have implemented a prototype of EPPMiner that supports OpenMP, CUDA, and OpenCL, and demonstrated its usage by three showcases. Firstly, we use EPPMiner to compare the power efficiency of a set of processors, including two Intel x86 CPUs, two Nvidia GPUs, and one AMD GPU. Secondly, we investigate the impact of multi-threading on the power efficiency of multi-core CPUs. At last, we use EPPMiner to illustrate the effectiveness of GPU Dynamic Voltage and Frequency Scaling (DVFS) on the power efficiency of GPGPU applications. We show that DVFS can improve the energy efficiency by 86% over the default setting on an AMD GPU. © 2017 Association for Computing Machinery.

Cao G.,Hong Kong Baptist University | Ruan D.,Hong Kong Baptist University | Ruan D.,HKBU Institute of Research and Continuing Education | Chen Z.,University of Sichuan | And 3 more authors.
TrAC - Trends in Analytical Chemistry | Year: 2017

Cooking oil, composed of great variety of chemical constitutes, has been increasingly prevailing in public diet due to its functional and nutritional benefits to consumers. The long-term storage, deep frying process and repeated use of cooking oil will release numerous deterioration products, such as aldehydes, ketones, epoxides, polymerides and cyclic aromatic hydrogen compounds, which influences the quality of cooking oil and has emerged safety concerns on used cooking oil. Analyzing these components with complex molecular structures and dynamic concentration ranges in oil samples poses a big challenge to researchers. In this article, we review the recent developments of mass spectrometry as a powerful tool for quality assessment of cooking oil and highlight its increasing applications in authentication, aging and marker-detection of used cooking oil. Additionally, the current technical challenges and future prospects associated with these methodologies are provided. © 2017 Elsevier B.V.

Hu C.,Hong Kong Baptist University | Lin S.,Hong Kong Baptist University | Li W.,Hong Kong Baptist University | Sun H.,Hong Kong Baptist University | And 8 more authors.
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2016

An ultra-fast, extremely cost-effective, and environmentally friendly method was developed for fabricating flexible microfluidic chips with plastic membranes. With this method, we could fabricate plastic microfluidic chips rapidly (within 12 seconds per piece) at an extremely low cost (less than $0.02 per piece). We used a heated perfluoropolymer perfluoroalkoxy (often called Teflon PFA) solid stamp to press a pile of two pieces of plastic membranes, low density polyethylene (LDPE) and polyethylene terephthalate (PET) coated with an ethylene-vinyl acetate copolymer (EVA). During the short period of contact with the heated PFA stamp, the pressed area of the membranes permanently bonded, while the LDPE membrane spontaneously rose up at the area not pressed, forming microchannels automatically. These two regions were clearly distinguishable even at the micrometer scale so we were able to fabricate microchannels with widths down to 50 microns. This method combines the two steps in the conventional strategy for microchannel fabrication, generating microchannels and sealing channels, into a single step. The production is a green process without using any solvent or generating any waste. Also, the chips showed good resistance against the absorption of Rhodamine 6G, oligonucleotides, and green fluorescent protein (GFP). We demonstrated some typical microfluidic manipulations with the flexible plastic membrane chips, including droplet formation, on-chip capillary electrophoresis, and peristaltic pumping for quantitative injection of samples and reagents. In addition, we demonstrated convenient on-chip detection of lead ions in water samples by a peristaltic-pumping design, as an example of the application of the plastic membrane chips in a resource-limited environment. Due to the high speed and low cost of the fabrication process, this single-step method will facilitate the mass production of microfluidic chips and commercialization of microfluidic technologies. © 2016 The Royal Society of Chemistry.

Lu Y.,Hong Kong Baptist University | Cheung Y.-M.,Hong Kong Baptist University | Cheung Y.-M.,HKBU Institute of Research and Continuing Education | Tang Y.Y.,Macau University of Science and Technology
Proceedings of the World Congress on Intelligent Control and Automation (WCICA) | Year: 2016

Boosting-based methods are effective for class imbalance problem, where the numbers of samples in two or more classes are severely unequal. However, the classifier weights of existing boosting-based methods are calculated by minimizing the error rate, which is inconsistent with the objective of class imbalance learning. As a result, the classifier weights cannot represent the performance of individual classifiers properly when the data is imbalanced. In this paper, we therefore propose a G-mean Optimized Boosting (GOBoost) framework to assign classifier weights optimized on G-mean. Subsequently, high weights are assigned to the classifier with high accuracy on both the majority class and the minority class. The GOBoost framework can be applied to any AdaBoost-based method for class imbalance learning by simply replacing the calculation of classifier weights. Accordingly, we extend six AdaBoost-based methods to GOBoost-based methods for comparative studies in class imbalance learning. The experiments conducted on 12 real class imbalance data sets show that GOBoost-based methods significantly outperform the corresponding AdaBoost-based methods in terms of F1 and G-mean metrics. © 2016 IEEE.

Cheung Y.-M.,Hong Kong Baptist University | Cheung Y.-M.,United International College | Cheung Y.-M.,HKBU Institute of Research and Continuing Education | Peng Q.,Hong Kong Baptist University
IEEE Transactions on Human-Machine Systems | Year: 2015

This paper addresses the eye gaze tracking problem using a low cost and more convenient web camera in a desktop environment, as opposed to gaze tracking techniques requiring specific hardware, e.g., infrared high-resolution camera and infrared light sources, as well as a cumbersome calibration process. In the proposed method, we first track the human face in a real-time video sequence to extract the eye regions. Then, we combine intensity energy and edge strength to obtain the iris center and utilize the piecewise eye corner detector to detect the eye corner. We adopt a sinusoidal head model to simulate the 3-D head shape, and propose an adaptive weighted facial features embedded in the pose from the orthography and scaling with iterations algorithm, whereby the head pose can be estimated. Finally, the eye gaze tracking is accomplished by integration of the eye vector and the head movement information. Experiments are performed to estimate the eye movement and head pose on the BioID dataset and pose dataset, respectively. In addition, experiments for gaze tracking are performed in real-time video sequences under a desktop environment. The proposed method is not sensitive to the light conditions. Experimental results show that our method achieves an average accuracy of around 1.28° without head movement and 2.27° with minor movement of the head. © 2013 IEEE.

Hu C.,Hong Kong Baptist University | Sun H.,Hong Kong Baptist University | Liu Z.,Hong Kong Baptist University | Chen Y.,Hong Kong University of Science and Technology | And 3 more authors.
Biomicrofluidics | Year: 2016

The diffusion of molecules such as nutrients and oxygen through densely packed cells is impeded by blockage and consumption by cells, resulting in a limited depth of penetration. This has been a major hurdle to a bulk (3-D) culture. Great efforts have been made to develop methods for generating branched microchannels inside hydrogels to support mass exchange inside a bulk culture. These previous attempts faced a common obstacle: Researchers tried to fabricate microchannels with gels already loaded with cells, but the fabrication procedures are often harmful to the embedded cells. Herein, we present a universal strategy to create microchannels in different types of hydrogels, which effectively avoids cell damage. This strategy is based on a freestanding alginate 3-D microvascular network prepared by in-situ generation of copper ions from a sacrificial copper template. This alginate network could be used as implants to create microchannels inside different types of hydrogels. This approach effectively addresses the issue of cell damage during microfabrication and made it possible to create microchannels inside different types of gels. The microvascular network produced with this method is (1) strong enough to allow handling, (2) biocompatible to allow cell culturing, and (3) appropriately permeable to allow diffusion of small molecules, while sufficiently dense to prevent blocking of channels when embedded in different types of gels. In addition, composite microtubules could be prepared by simply pre-loading other materials, e.g., particles and large biomolecules, in the hydrogel. Compared with other potential strategies to fabricate freestanding gel channel networks, our method is more rapid, low-cost and scalable due to parallel processing using an industrially massproducible template. We demonstrated the use of such vascular networks in creating microchannels in different hydrogels and composite gels, as well as with a cell culture in a nutrition gradient based on microfluidic diffusion. In this way, the freestanding hydrogel vascular network we produced is a universal functional unit that can be embedded in different types of hydrogel; users will be able to adopt this strategy to achieve vascular mass exchange in the bulk culture without changing their current protocol. The method is readily implementable to applications in vascular tissue regeneration, drug discovery, 3-D culture, etc.

Ouyang G.,Hong Kong Baptist University | Sommer W.,Humboldt University of Berlin | Zhou C.,Hong Kong Baptist University | Zhou C.,HKBU Institute of Research and Continuing Education | Zhou C.,Beijing Computational Science Research Center
Psychophysiology | Year: 2015

Trial-to-trial latency variability pervades cognitive EEG responses and may mix and smear ERP components but is usually ignored in conventional ERP averaging. Existing attempts to decompose temporally overlapping and latency-variable ERP components show major limitations. Here, we propose a theoretical framework and model of ERPs consisting of temporally overlapping components locked to different external events or varying in latency from trial to trial. Based on this model, a new ERP decomposition and reconstruction method was developed: residue iteration decomposition (RIDE). Here, we describe an update of the method and compare it to other decomposition methods in simulated and real datasets. The updated RIDE method solves the divergence problem inherent to previous latency-based decomposition methods. By implementing the model of ERPs as consisting of time-variable and invariable single-trial component clusters, RIDE obtains latency-corrected ERP waveforms and topographies of the components, and yields dynamic information about single trials. © 2015 Society for Psychophysiological Research.

Tang Y.-C.,Hong Kong Baptist University | Tian H.-X.,Guangdong General Hospital and Guangdong Academy of Medical science | Yi T.,Hong Kong Baptist University | Yi T.,HKBU Institute of Research and Continuing Education | Chen H.-B.,Hong Kong Baptist University
Protein and Cell | Year: 2016

ABSTRACT: Mitochondria play a key role in various cell processes including ATP production, Ca2 + homeostasis, reactive oxygen species (ROS) generation, and apoptosis. The selective removal of impaired mitochondria by autophagosome is known as mitophagy. Cerebral ischemia is a common form of stroke caused by insufficient blood supply to the brain. Emerging evidence suggests that mitophagy plays important roles in the pathophysiological process of cerebral ischemia. This review focuses on the relationship between ischemic brain injury and mitophagy. Based on the latest research, it describes how the signaling pathways of mitophagy appear to be involved in cerebral ischemia. © 2016 The Author(s)

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