Enhanced distance-based location management of mobile communication systems using a cell coordinates approach

In managing the locations of mobile users in mobile communication systems, the distance-based strategy has been proven to have better performance than other dynamic strategies, but is difficult to implement. In this paper, a simple approach is introduced to implement the distance-based strategy by using the cell coordinates in calculating the physical distance traveled. This approach has the advantages of being independent of the size, shape, and distribution of cells, as well as catering for the direction of movement in addition to the speed of each mobile terminal. An enhanced distance-based location management strategy is proposed to dynamically adjust the size and shape of location area for each individual mobile terminal according to the current speed and direction of movement. It can reduce the location management signaling traffic of the distance-based strategy by half when mobile terminals have predictable directions of movement. Three types of location updating schemes are discussed, namely, Circular Location Area, Optimal Location Area, and Elliptic Location Area. Paging schemes using searching techniques such as expanding distance search based on the last reported location and based on the predicted location, and expanding direction search are also explored to further reduce paging signal traffic by partitioning location areas into paging areas.published_or_final_versio

MIX-crowds, an anonymity scheme for file retrieval systems

In this paper, we propose an anonymous scheme for file retrieval systems, MIX-Crowds, in which it is harder for an attacker to identify the requester of the file by making use of the idea of MIX [7] and Crowds [20] to establish a path from the requester to the file holder. Result shows that predecessor attack [26] is much more difficult to succeed compared with Crowds [20]. We are able to reduce the estimated number of rounds needed for successful predecessor attack for MIX-Crowds. We also propose a file transfer strategy according to file size. With such strategy, requests for small size files can be completed faster while the downloading time of large size files only increases slightly. © 2009 IEEE.published_or_final_versionThe 28th International Conference on Computer Communications (IEEE INFOCOM 2009), Rio de Janeiro, Brazil, 19-25 April 2009. In Proceedings of the IEEE Infocom, 2009, p. 1170-117

Initial use of knowledge forum for Chinese students: Productive discourse and knowledge building

published_or_final_versionCentre for Information Technology in Education, University of Hong Kon

Decellularization of chondrocyte-encapsulated collagen microspheres: A three-dimensional model to study the effects of acellular matrix on stem cell fate

Extracellular matrix (ECM) partially constitutes the stem cell niche. Reconstituting the ECM niche in a three-dimensional (3D) configuration will significantly enhance our understanding of how stem cells interact with and respond to the ECM niche. In this study, we aimed to reconstitute a glycosaminoglycan (GAG)-rich ECM using a microencapsulation technology, produce acellular matrix using a decellularization technique, and investigate the effect of acellular matrix on stem cell fate by repopulating the matrix with human mesenchymal stem cells (hMSCs). We demonstrated that porcine chondrocytes were able to deposit a GAG-rich ECM within the 3D collagen microsphere. All decellularization treatment groups resulted in significant removal of chondrocyte nuclei, but acellular matrix was only achieved using 2% sodium deoxycholate. Nevertheless, decellularization resulted in significant loss in GAG content in almost all treatment groups, and the 2% sodium deoxycholate group was able to preserve about 40% of the GAGs compared with the control group. We further demonstrated that hMSCs seeded onto the decellularized microspheres were able to survive and penetrate into the centre, while hMSCs seeded in the acellular matrix showed positive immunostaining against sox9, indicating that they may be differentiating toward the chondrogenic lineage without the need to supplement the chondrogenic differentiation medium. © 2009 Mary Ann Liebert, Inc.published_or_final_versio

Optimising the use and assessing the value of intraoperative shear wave elastography in neurosurgery

The clinical outcomes for epilepsy and brain tumour surgery depend on the extent of resection. Neurosurgeons frequently rely on subjective assessment of stiffness and adherence to achieve maximal resection. However, due to similarity in tactile texture and visual appearance of these lesions to normal brain, this can lead to inadequate resection. Magnetic resonance imaging (MRI) has not completely solved this problem for various reasons, including the existence of MRI-negative lesions. Shear wave elastography (SWE) is an ultrasound-based quantitative elasticity imaging technique that provides an objective assessment of stiffness, which has not previously been applied intraoperatively during neurosurgery. This thesis describes the optimisation and assessment of implementing intraoperative SWE in neurosurgery. The aims of the work described in this thesis were to validate SWE measurements; to optimise intraoperative applications by investigating the artefacts of SWE; to evaluate SWE performance in detecting epileptogenic lesions, residual tumour and slippery boundaries; and to determine the histopathological correlation with SWE measurements. Using gelatine phantoms and post-mortem mouse brains, SWE measurements were validated. Through phantom models and ex vivo porcine brains and spinal cords, the factors affecting SWE measurements were established and SWE settings optimised. In addition, novel features of slippery tumour-brain interface were demonstrated in vitro and confirmed intraoperatively. Clinical implementation of SWE in epilepsy (38 patients) and brain tumour surgery (34 patients), demonstrated SWE’s capability in differentiating epileptogenic lesions (p<0.001) and brain tumours (p=0.003) from normal brain. SWE was shown to be superior to MRI in detecting epileptogenic lesions (p=0.001), in particular MRI-negative cases where SWE managed to demonstrate lesions in 4 cases with positive histology. For detecting residual tumour, SWE was shown to be superior to surgeons’ opinion (p=0.001), and similar to MRI (p=1.000) and intraoperative B-mode ultrasound (p=0.727). Histopathologically, there was no correlation with SWE measurements, except for proliferation (p=0.007). In conclusion, this thesis demonstrated potential patient benefit of integrating intraoperative SWE into neurosurgical practice, and therefore, a compelling reason to continue development and optimisation of this technology

The effect of qigong on depressive and anxiety symptoms: a systematic review and meta-analysis of randomized controlled trials

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Bilateral macular drusen in acquired partial lipodystrophy with type 2 membranoproliferative glomerulonephritis

A 35-year-old woman with acquired partial lipodystrophy (PLD) and features of type 2 membranoproliferative glomerulonephritis (MPGN-II), presented with difficulty in her fine detailed vision over the past year. She had right amblyopia from a hypermetropic anisometropia with astigmatism, displaying a best-corrected visual acuity of 0.50 and 0.00 LogMAR, in the right and left eye, respectively. Funduscopy showed bilateral symmetrical drusenoid deposits most prominent in the temporal macula with clusters in the superior and inferior retina, outside the temporal vascular arcades. Multimodal retinal imaging was performed, which confirmed hyperautofluorescent drusen located between the retinal pigment epithelium and Bruch's membrane. Electroretinography showed bilateral mild peripheral macular dysfunction, but normal central macular function on the pattern electroretinogram. Both PLD and macular drusen, are rare as distinct disease entities, but an association does exist and may be linked to MPGN-II

Atrial fibrillation: Prevention and termination with pacing

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Exploring the mutational landscape of genes associated with inherited retinal disease using large genomic datasets: identifying loss of function intolerance and outlying propensities for missense changes

BACKGROUND: Large databases permit quantitative description of genes in terms of intolerance to loss of function (‘haploinsufficiency’) and prevalence of missense variants. We explored these parameters in inherited retinal disease (IRD) genes. METHODS: IRD genes (from the ‘RetNet’ resource) were classified by probability of loss of function intolerance (pLI) using online Genome Aggregation Database (gnomAD) and DatabasE of genomiC varIation and Phenotype in Humans using Ensembl Resources (DECIPHER) databases. Genes were identified having pLI ≥0.9 together with one or both of the following: upper bound of CI 2.99, respectively) were also identified. The genes were evaluated in the gene ontology Protein Analysis THrough Evolutionary Relationships (PANTHER) resource. RESULTS: Of 280 analysed genes, 39 (13.9%) were predicted loss of function intolerant. A greater proportion of X-linked than autosomal IRD genes fulfilled these criteria, as expected. Most autosomal genes were associated with dominant disease. PANTHER analysis showed >100 fold enrichment of spliceosome tri-snRNP complex assembly. Most encoded proteins were longer than the median length in the UniProt database. Fourteen genes (11 of which were in the ‘haploinsufficient’ group) showed under-representation of missense variants. Six genes (SAMD11, ALMS1, WFS1, RP1L1, KCNV2, ADAMTS18) showed over-representation of missense variants. CONCLUSION: A minority of IRD-associated genes appear to be ‘haploinsufficient’. Over-representation of spliceosome pathways was observed. When interpreting genetic tests, variants found in genes with over-representation of missense variants should be interpreted with caution