Even though artificial heart valve implants have a history of some 30 years, there is to this day no ideal valve substitute. Each of the categories of substitutes used has its own advantages as well as problems. Since my last review on the subject, that appeared in this journal, was some 13 years ago (Lim, 1977), it is perhaps appropriate to provide an update on the status of cardiac valve replacement for the general local readership.
Pursuing the current trend, the "green-polymers", polyhydroxyalkanoates (PHAs) which are degradable and made from renewable sources have been a potential substitute for synthetic plastics. Due to the increasing concern towards escalating crude oil price, depleting petroleum resource and environmental damages done by plastics, PHAs have gained more and more attractions, both from industry and research. From the view point of Escherichia coli, a microorganism that used in the biopolymer large scale production, this paper describes the backgrounds of PHA and summarizes the current advances in PHA developments. In the short-chain-length (scl) PHAs section, the study of poly[(R)-3-hydroxybutyrate] [P(3HB)] as model polymer, ultra-high-molecular-weight P(3HB) which rarely discussed, and P(3HB-co-3HV), another commercialized PHA polymer are included. Other than that, this review also shed some light on the new members of PHA family, lactate-based PHAs and P(3HP) with topics such as block copolymers and invention of novel biopolymers. Flexibility of microorganisms in utilizing different carbon sources to accumulate medium-chain-length (mcl) PHAs and lastly, the promising scl-mcl-PHAs with interesting properties are also discussed.
The central dogma of molecular biology (DNA, RNA, protein and metabolite) has engraved our understanding of genetics in all living organisms. While the concept has been embraced for many decades, the development of high-throughput technologies particularly omics (genomics, transcriptomics, proteomics and metabolomics) has revolutionised the field to incorporate big data analysis including bioinformatics and systems biology as well as synthetic biology area. These omics approaches as well as systems and synthetic biology areas are now increasingly popular as seen by the growing numbers of publication throughout the years. Several journals which have published most of these related fields are also listed in this chapter to overview their impact and target journals.
Covert channels are not new in computing systems, and have been studied since their first definition four decades ago. New platforms invoke thorough investigations to assess their security. Now is the time for Android platform to analyze its security model, in particular the two key principles: process-isolation and the permissions system. Aside from all sorts of malware, one threat proved intractable by current protection solutions, that is, collusion attacks involving two applications communicating over covert channels. Still no universal solution can countermeasure this sort of attack unless the covert channels are known. This paper is an attempt to reveal a new covert channel, not only being specific to smartphones, but also exploiting an unusual resource as a vehicle to carry covert information: sensors data. Accelerometers generate signals that reflect user motions, and malware applications can apparently only read their data. However, if the vibration motor on the device is used properly, programmatically produced vibration patterns can encode stolen data and hence an application can cause discernible effects on acceleration data to be received and decoded by another application. Our evaluations confirmed a real threat where strings of tens of characters could be transmitted errorless if the throughput is reduced to around 2.5-5 bps. The proposed covert channel is very stealthy as no unusual permissions are required and there is no explicit communication between the colluding applications.
Matched MeSH terms: Computer Communication Networks/trends*; Computer Systems/trends; Cell Phones/trends*; Accelerometry/trends*; Mobile Applications/trends*