Secure secret sharing in the cloud

In this paper, we show how a dealer with limited resources is possible to share the secrets to players via an untrusted cloud server without compromising the privacy of the secrets. This scheme permits a batch of two secret messages to be shared to two players in such a way that the secrets are reconstructable if and only if two of them collaborate. An individual share reveals absolutely no information about the secrets to the player. The secret messages are obfuscated by encryption and thus give no information to the cloud server. Furthermore, the scheme is compatible with the Paillier cryptosystem and other cryptosystems of the same type. In light of the recent developments in privacy-preserving watermarking technology, we further model the proposed scheme as a variant of reversible watermarking in the encrypted domain

Reversible data hiding in JPEG images based on adjustable padding

In this paper, we propose a reversible data hiding scheme that enables an adjustable amount of information to be embedded in JPEG images based on padding strategy. The proposed embedding algorithm only modifies, in a subtle manner, an adjustable number of zero-valued quantised DCT coefficients to embed the message. Hence, compared with a state-of-the-art based on histogram shifting, the proposed scheme has a relatively low distortion to the host images. In addition to this, we found that by representing the message in ternary instead of in binary, we can embed a greater amount of information while the level of distortion remains unchanged. Experimental results support that the proposed scheme can achieve better visual quality of the marked JPEG image than the histogram shifting based scheme. The proposed scheme also outperforms this state-of-the-art in terms of the ease of implementation

Failure matters: Reassembling eco-urbanism in a globalizing China

This paper is an attempt to reassess the role of failure in policy mobilities. Empirically, this paper examines the various aftermaths of, and the continuing trans-local connections originating from, the prominent but un-materialized Sino-British Shanghai-Dongtan eco-city—with a particular consideration on its relation with a subsequently realized project—the Sino-Singapore Tianjin eco-city. The findings reveal that despite its apparent failure, Dongtan eco-city established a set of urban planning procedures adopted by many, including those who designed and delivered the Tianjin eco-city. Meanwhile, Dongtan’s failure to materialize motivated the Chinese government to pursue collaboration with the Singaporean government over the increased involvement of private Western partners. The intent to avoid association with Dongtan’s failure also fostered a new eco-urbanism model based on rebranding the planning practices of Singapore’s public housing. Parts of Dongtan eco-city have also lived on through the international circulation of a piece of planning software that was first developed for the failed project. This paper contributes to the policy mobilities literature by challenging its dominant focus on successful exemplars and exploring how a project fails in implementation yet parts of it remain mobile, influential and present in other developments. This paper also advances the understanding of contemporary urban sustainability by revealing how eco-urbanism models are co-produced in this globalizing era between the global North and South, as well as within the global South. </jats:p

The Role of Hedgehog Acyltransferase & Heparan Sulphate Proteoglycans in Human Sonic Hedgehog Signalling

Hedgehog proteins (Hh) are morphogens and major mediators in many developmental processes. Hh signalling is significant for many aspects of embryonic development, whereas dysregulation of this pathway is associated with several types of cancers. Hh proteins require dual lipidation and Heparan Sulfate Proteoglycans (HSPGs) for their proper distribution and signalling activity. My first aim was to study the role of HSPGs in human (h) Sonic Hedgehog (Shh) signalling and clarify the biological function of hShh/HSPGs complexes in hShh signalling, by investigating the interaction between human hShh and HSPGs. I used DNA mutagenesis and heparin affinity chromatography to determine key residues in hShh involved in heparin binding (K37/38 and K178). The activity of these mutants was tested by detecting induced Alkaline Phosphatase activity in C3H10T1/2 cells and hShh-inducible gene expression in PANC1 human pancreatic carcinoma cells. I examined the biological function of mutated hShhs (K37/38S, K178S and K37/38/178S) that cannot interact with heparin efficiently and showed that they had reduced signalling activity compared to wild type hShh and a control mutation (K74S). Also, I showed that mutant hShh proteins mediate reduced proliferation and invasion of PANC1 cells following hShh RNAi knockdown (KD), and this correlated with reduced Shh multimeric complex formation. Structurally, Shh proteins are unusual in being dually lipid-modified to be fully active. During the post-translational modifications of Shh, N-terminal palmitoylation is facilitated by the product (Hhat) of the hedgehog acyltransferase gene. I have carried out a thorough analysis of Hhat in PANC1 cells. First, I characterised an antibody prepared in the lab to hHhat. I confirmed the specificity of the antibody by immunoblotting using a self-constructed hHhat-EGFP clone, and a control mGup1-EGFP clone. By subcellular fractionation and Western blotting I found Hhat to be a membrane protein. In addition, I used the hHhat antibody to determine the intracellular localisation of hHhat in PANC1 cells by confocal microscopy and showed that hHhat localised in ER mainly but not in Golgi apparatus. I confirmed this using the hHhat-EGFP clone for fluorescence microscopy in transfected cells. To illuminate the biological function of palmitoylation of hShh in production of active hShh and in the formation of hShh multimeric complex I optimised hHhat RNAi knockdown (KD) in PANC1 cells and confirmed this by a cell-based palmitoylation assay. Using semi-quantitative RT-PCR and immunoblot analyses, I showed that hHhat KD caused decreased signalling through the Shh pathway due to reduced production of active hShh. In addition, I investigated the effect of the addition of palmitate to hShh on its association with cells by comparing hHhat KD cells with control cells. Immunoblotting suggests that palmitoylation of Shh improves its ability to associate to cell membranes. Using hHhat KD, gel filtration of high molecular weight complexes of hShh and immunoblotting of hShh I characterised the role of palmitoylation of hShh in multimeric complex formation. Lastly, I investigated the effect of hHhat KD on PANC1 proliferation and invasion, showing that it represses PANC1 proliferation and invasion. These studies provide a firm basis for understanding the functional roles of hShh palmitoylation and its interactions with HSPGs, and provide proof-of-principle for targeting these aspects of hShh biology in tumour cell therapeutics, specifically in the pancreatic carcinoma context

Potential Vorticity Mixing in a Tangled Magnetic Field

A theory of potential vorticity (PV) mixing in a disordered (tangled) magnetic field is presented. The analysis is in the context of $\beta$-plane MHD, with a special focus on the physics of momentum transport in the stably stratified, quasi-2D solar tachocline. A physical picture of mean PV evolution by vorticity advection and tilting of magnetic fields is proposed. In the case of weak-field perturbations, quasi-linear theory predicts that the Reynolds and magnetic stresses balance as turbulence Alfv\'enizes for a larger mean magnetic field. Jet formation is explored quantitatively in the mean field-resistivity parameter space. However, since even a modest mean magnetic field leads to large magnetic perturbations for large magnetic Reynolds number, the physically relevant case is that of a strong but disordered field. We show that numerical calculations indicate that the Reynolds stress is modified well before Alfv\'enization -- i.e. before fluid and magnetic energies balance. To understand these trends, a double-average model of PV mixing in a stochastic magnetic field is developed. Calculations indicate that mean-square fields strongly modify Reynolds stress phase coherence and also induce a magnetic drag on zonal flows. The physics of transport reduction by tangled fields is elucidated and linked to the related quench of turbulent resistivity. We propose a physical picture of the system as a resisto-elastic medium threaded by a tangled magnetic network. Applications of the theory to momentum transport in the tachocline and other systems are discussed in detail.Comment: 17 pages, 10 figures, 2 table