Integrity protection for code-on-demand mobile agents in e-commerce

The mobile agent paradigm has been proposed as a promising solution to facilitate distributed computing over open and heterogeneous networks. Mobility, autonomy, and intelligence are identified as key features of mobile agent systems and enabling characteristics for the next-generation smart electronic commerce on the Internet. However, security-related issues, especially integrity protection in mobile agent technology, still hinder the widespread use of software agents: from the agent’s perspective, mobile agent integrity should be protected against attacks from malicious hosts and other agents. In this paper, we present Code-on-Demand(CoD) mobile agents and a corresponding agent integrity protection scheme. Compared to the traditional assumption that mobile agents consist of invariant code parts, we propose the use of dynamically upgradeable agent code, in which new agent function modules can be added and redundant ones can be deleted at runtime. This approach will reduce the weight of agent programs, equip mobile agents with more flexibility, enhance code privacy and help the recoverability of agents after attack. In order to meet the security challenges for agent integrity protection, we propose agent code change authorization protocols and a double integrity verification scheme. Finally, we discuss the Java implementation of CoD mobile agents and integrity protection

Prenatal diagnosis of common single gene disorders by DNA technology

Using the new DNA technology, it is now possible to offer prenatal diagnosis or presymptomatic testing for many genetic diseases. For prenatal diagnosis, foetal tissue is obtained y chorionic villus sampling at 9 to 11 weeks gestation or amniocentesis at 18 weeks. The programme in Hong Kong, which started in 1982, is reviewed here and now included alpha and beta thalassaemia, haemophilia A and B, Duchenne muscular dystrophy, Huntington's diseases, and spinal muscular atrophy. DNA diagnosis can now be performed using a single cell obtained from pre-implantation embryos or from rare foetal cells isolated from maternal peripheral blood. The latter is safer and more acceptable to parents. Presymptomatic testing for untreatable diseases such as Hungtington's disease poses new ethical and social problems that need to be resolved. As many more genes are being discovered, prenatal diagnosis and presymptomatic testing programmes will continue to meet new challenges in the future.published_or_final_versio

Doctors have a duty to breach patient confidentiality to protect others at risk of HIV infection

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Molecular medicine: an overview

Editorialpublished_or_final_versio

A halo model for cosmological Lyman-limit systems

We present an analytical model for cosmological Lyman-limit systems (LLSs) that successfully reproduces the observed evolution of the mean free path (L) of ionizing photons. The evolution of the co-moving mean free path is predominantly a consequence of the changing meta galactic photo-ionization rate and the increase with cosmic time of the minimum mass below which halos lose their gas due to photo-heating. In the model, Lyman-limit absorption is caused by highly ionized gas in the outskirt of dark matter halos. We exploit the association with halos to compute statistical properties of LLSs and of their bias, b. The latter increases from 1.5 to 2.6 from redshifts 2 to 6. Combined with the rapid increase with redshift of the bias of the halos that host a quasar, the model predicts a rapid drop in the value of L when measured in quasar spectra from z=5 to 6, whereas the actual value of L falls more smoothly. We derive an expression for the effective optical depth due to Lyman limit absorption as a function of wavelength and show that it depends sensitively on the poorly constrained number density of LLSs as a function of column density. The optical depth drops below unity for all wavelengths below a redshift of 2.5, which is therefore the epoch when the Universe first became transparent to ionizing photons.Comment: 18 page

Exploring the developmental changes in automatic two-digit number processing

Even when two-digit numbers are irrelevant to the task at hand, adults process them. Do children process numbers automatically, and if so, what kind of information is activated? In a novel dot-number Stroop task, children (Grades 1-5) and adults were shown two different two-digit numbers made up of dots. Participants were asked to select the number that contained the larger dots. If numbers are processed automatically, reaction time for dot size judgment should be affected by numerical characteristics. The results suggest that, like adults, children process two-digit numbers automatically. Based on the current findings, we propose a developmental trend for automatic two-digit number processing that goes from decomposed sequential (activation of decade digit followed by that of unit digit) to decomposed parallel processing (simultaneous activation of decade and unit digits). © 2011 Elsevier Inc.postprin

A measurement-based congestion alarm for self-similar traffic

Self-similar traffic is distinguished by positive correlation, which can be exploited for better traffic management. Inspired by measurement-based admission control schemes, a measurement-based congestion alarm is proposed. The aggregate traffic at an output port of a switch or router in a high-speed network is modeled by a fractional Gaussian noise process. Traffic measurements are performed in regular time intervals to determine the current traffic loading. This information is then used to predict the loading situation in the near future. If congestion is likely to occur, a congestion alarm is set off and appropriate network management functions taken to alleviate the possible congestion. The above constitutes a closed loop feedback control mechanism that maintains high resource utilization. Simulation results show that the proposed scheme, when used with dynamic bandwidth allocation, reduces bandwidth requirements by more than 20%.published_or_final_versio

A public opinion survey: is presumed consent the answer to kidney shortage in Hong Kong?

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Correlation between compositional and mechanical properties of human mesenchymal stem cell-collagen microspheres during chondrogenic differentiation

Mesenchymal stem cell (MSC)-based engineering is promising for cartilage repair. However, the compositional mechanical relationship of the engineered structures has not been extensively studied, given the importance of such relationship in native cartilage tissues. In this study, a novel human MSC-collagen microsphere system was used to study the compositional mechanical relationship during in vitro chondrogenic differentiation using histological and biochemical methods and a microplate compression assay. The mechanical property was found positively correlating with newly deposited cartilage-relevant matrices, glycosaminoglycan, and type II collagen, and with the collagen crosslinker density, in agreement with the presence of thick collagen bundles upon structural characterization. On the other hand, the mechanical property negatively correlates with type I collagen and total collagen, suggesting that the initial collagen matrix scaffold of the microsphere system was being remodeled by the differentiating human MSCs. This study also demonstrated the application of a simple, sensitive, and nondestructive tool for monitoring the progression of chondrogenic differentiation of MSCs in tissue-engineered constructs and therefore contributes to future development of novel cartilage repair strategies. © Mary Ann Liebert, Inc. 2011.published_or_final_versio

Young children's analogical reasoning across cultures: Similarities and differences

A cross-cultural comparison between U.S. and Hong Kong preschoolers examined factors responsible for young children's analogical reasoning errors. On a scene analogy task, both groups had adequate prerequisite knowledge of the key relations, were the same age, and showed similar baseline performance, yet Chinese children outperformed U.S. children on more relationally complex problems. Children from both groups were highly susceptible to choosing a perceptual or semantic distractor during reasoning when one was present. Taken together, these similarities and differences suggest that (a) cultural differences can facilitate better knowledge representations by allowing more efficient processing of relationally complex problems and (b) inhibitory control is an important factor in explaining the development of children's analogical reasoning. © 2009 Elsevier Inc. All rights reserved.postprin