Pulmonary embolism: comparison of cut-film and digital pulmonary angiography

Sedoheptulose-1,7-bisphosphatase (SBPase) is an enzyme unique to photosynthetic organisms and has a key role in regulating the photosynthetic Calvin cycle through which nearly all carbon enters the biosphere. This makes SBPase an appropriate target for intensive study. We have expressed wheat SBPase in Escherichia coli either with or without an N-terminal polyhistidine tag. The identity of the recombinant SBPases was confirmed by SDS-PAGE analysis and immunological detection with a specific antibody. Recombinant SBPase with a polyhistidine tag (His-SBPase) was obtained in soluble, active form and purified by one-step metal-chelate chromatography. Like the native enzyme, recombinant His-SBPase was specific for the substrate sedoheptulose-1,7-bisphosphate and required the presence of a reducing agent for activity. Polyclonal antibodies were raised against recombinant SBPase and were then used to determine relative levels of the enzyme in plant extracts. The availability of large amounts of active recombinant SBPase will also allow detailed structural studies by site-directed mutagenesis and X-ray crystallography.     

On the optimal checkpointing of critical tasks andtransaction-oriented systems

The probability distribution of the overhead caused by the use of the checkpointing rollback recovery technique is evaluated in both cases of a single critical task and of an overall transaction-oriented system. This distribution is obtained in Laplace-Stieltjes transform form, from which all the moments can be easily calculated. Alternatively, inversion methods can be used to evaluate the distribution. The authors propose checkpointing strategies based on the above distribution in order to optimize performance criteria motivated, in the case of critical tasks, by real time constraints, and in the case of transaction-oriented systems, by the need of guaranteeing the users about the maximum system unavailability     

Scaling of the energy gap in pattern-hydrogenated graphene

Recent experiments show that a substantial energy gap in graphene can be induced via patterned hydrogenation on an iridium substrate. Here, we show that the energy gap is roughly proportional to N(H)(1/2)/N(C) when disorder is accounted for, where N(H) and N(C) denote concentrations of hydrogen and carbon atoms, respectively. The dispersion relation, obtained through calculation of the momentum-energy resolved density of states, is shown to agree with previous angle-resolved photoemission spectroscopy results. Simulations of electronic transport in finite size samples also reveal a similar transport gap, up to 1 eV within experimentally achievable N(H)(1/2)/N(C) values.     

Prediction of stiffness and stresses in z-fibre reinforced composite laminates

The mechanical properties of z-pinned composite laminates were examined numerically. Finite element calculations have been performed to understand how the through-thickness reinforcement modifies the engineering elastic constants and local stress distributions. Solutions were found for four basic laminate stacking sequences, all having two percent volume fraction of z-fibres. For the stiffness analysis, a micro-mechanical finite element model was employed that was based on the actual geometric configuration of a z-pinned composite unit cell. The numerical results agreed very well with some published solutions. It showed that by adding 2% volume fraction of z-fibres, the through-thickness Young's modulus was increased by 22–35%. The reductions in the in-plane moduli were contained within 7–10%. The stress analysis showed that interlaminar stress distributions near a laminate free edge were significantly affected when z-fibres were placed within a characteristic distance of one z-fibre diameter from the free edge. Local z-fibres carried significant amount of interlaminar normal and shear stresses.     

Management of Congenital Diaphragmatic Hernia (CDH): Role of Molecular Genetics

Congenital diaphragmatic hernia (CDH) is a relatively common major life-threatening birth defect that results in significant mortality and morbidity depending primarily on lung hypoplasia, persistent pulmonary hypertension, and cardiac dysfunction. Despite its clinical relevance, CDH multifactorial etiology is still not completely understood. We reviewed current knowledge on normal diaphragm development and summarized genetic mutations and related pathways as well as cellular mechanisms involved in CDH. Our literature analysis showed that the discovery of harmful de novo variants in the fetus could constitute an important tool for the medical team during pregnancy, counselling, and childbirth. A better insight into the mechanisms regulating diaphragm development and genetic causes leading to CDH appeared essential to the development of new therapeutic strategies and evidence-based genetic counselling to parents. Integrated sequencing, development, and bioinformatics strategies could direct future functional studies on CDH; could be applied to cohorts and consortia for CDH and other birth defects; and could pave the way for potential therapies by providing molecular targets for drug discovery.     

Phonon-scattering effects in CNT-FETs with different dimensions and dielectric materials

The impact of acoustic and optical phonon scattering on the performance of CNT-FETs is investigated using a full-quantum transport model within the NEGF formalism. Different gate lengths, dielectric materials and chiralities are considered. It is shown that the use of a high-κ dielectric lowers the off-current dominated by phonon-assisted band-to-band tunneling. The device scalability is demonstrated: with the oxide thickness fixed to 1.5 nm, good performance is obtained with 15 nm and 10 nm gate lengths with SiO₂ and HfO₂ gate dielectrics, respectively. The role of phonon scattering in CNT-FETs of different chiralities is investigated for the HfO₂ devices. A similar analysis has also been carried out for source/drain underlap geometries. The results confirm that the calculation of the off-currents and delay times is strongly influenced by phonon scattering.     

Markov analysis of the PRMA protocol for local wireless networks

PRMA (packet reservation multiple access) is a reservation-ALOHA access protocol specifically designed for wireless microcellular networks that handle both real-time and non-real-time traffic. We present a thorough analysis of this protocol, considering real-time traffic only, based on a suitable Markov model. The size of the model is such that it can be directly used for an exact quantitative analysis of the system. In particular, we are able to analyze the packet dropping process, by evaluating both average and distribution measures. The latter are particularly useful to characterize the degradation caused to real-time traffic (e.g., voice) by the loss of consecutive packets. Besides, we also derive from the Markov model a qualitative analysis of the system stability, based on the equilibrium point analysis (EPA) technique. By this technique, we characterize the system stability and analyze the effect on it of several system parameters (e.g., load, permission probability). This revised version was published online in June 2006 with corrections to the Cover Date.     

Derivation of Markov models for effectiveness analysis of adaptable software architectures for mobile computing

Adaptable software architectures (SA) have been suggested as a viable solution for the design of distributed applications that operate in a mobile computing environment to cope with the high heterogeneity and variability of this environment. Mobile code techniques can be used to implement this kind of SA since they allow us to dynamically modify the load of the hosting nodes and the internode traffic to adapt to the resources available in the nodes and to the condition of the (often wireless) network link. However, moving code among nodes has a cost (e.g., in terms of network traffic and consumed energy for mobile nodes), so designing an adaptable SA based on mobile code techniques requires a careful analysis to determine its effectiveness from the early design stages. In this respect, our main contribution consists of a methodology, called ASAP (adaptable software architectures performance), to automatically derive, starting from a design model of a mobility-based SA, a Markov model whose solution provides insights about the most effective adaptation strategy based on code mobility in a given execution environment. We assume that the SA model is expressed using the Unified Modeling Language (UML) because of its widespread use in software design, also suggesting some extension to this formalism to better express the "mobility structure" of the application, i.e., which are the mobile components, and the possible targets of their movement.