Algorithms for searching massive graphs

Given a large graph, stored on disk, there is often a need to perform a search over this graph. Such a need could arise, for example, in the search component of a data-intensive expert system or to solve path problems in deductive database systems. In this paper, we present a novel data structuring technique and show how a branch-and-bound search algorithm can use this data structuring to prune the search space. Simulation results confirm that, using these techniques, a search can be expedited significantly without incurring a large storage penalty. As a side benefit, it is possible to organize the search to obtain successive approximations to the desired solution with considerable reduction in the total search     

ICP dry etching of ZnO and effects of hydrogen

Two different plasma chemistries for etching ZnO were examined. Both Cl₂/Ar and CH₄/H₂/Ar produced etch rates which increased linearly with rf power, reaching values of 1200 Å/min for Cl₂/Ar and 3000 Å/min for CH₄/H₂/Ar. The evolution of surface morphology, surface composition, and PL intensity as a function of energy during etching were monitored. The effect of H in ZnO was studied using direct implantation at doses of 10¹⁵–10¹⁶ cm⁻², followed by annealing at 500–700 °C. The hydrogen shows significant outdiffusion at 500 °C and is below the detection limits of SIMS after 700 °C anneals. SEM of the etched features showed anisotropic sidewalls, indicative of an ion-driven etch mechanism.     

A systems approach to rural housing

An attempt is made in this paper to arrive at a methodology for generating building technologies appropriate to rural housing. An evaluation of traditional/ ‘ modern ’ technologies currently in use reveals the need for alternatives. The lacunae in the presently available technologies also lead to a definition of rural housing needs. It is emphasised that contending technologies must establish a ‘ goodness of fit ’ between the house form and the pattern of needs. A systems viewpoint which looks at thedynamic process of building construction and thestatic structure of the building is then suggested as a means to match the technologies to the needs. The process viewpoint emphasises the role of building materials production and transportation in achieving desired building performances. A couple of examples of technological alternatives like the compacted soil block and the polythene-stabilised soil roof covering are then discussed. The static structural system viewpoint is then studied to arrive at methodologies of cost reduction. An illustrative analysis is carried out using the dynamic programming technique, to arrive at combinations of alternatives for the building components which lead to cost reduction. Some of the technological options are then evaluated against the need patterns. Finally, a guideline for developments in building technology is suggested.     

Synthesis of Nanocrystalline α-Alumina Powder Using Triethanolamine

Nanocrystalline α-Al₂O₃ powders have been prepared by pyrolysis of a complex compound of aluminum with triethanolamine (TEA). The soluble metal-ion–TEA complex forms the precursor material on complete dehydration of the complex of aluminum-TEA. The single-phase α-Al₂O₃ powder has resulted after heat treatment at 1025°C. The precursors and the heat-treated final powders have been characterized by X-ray diffractometry, thermogravimetric and differential thermal analysis, and transmission electron microscopy (TEM). The average particle sizes as measured from X-ray line broadening and TEM are ∼25 nm. The powder has crystallite sizes of the same order indicates the poor agglomeration of crystallites.     

Processable aromatic polyesters based on bisphenol derived from cashew nut shell liquid: synthesis and characterization

The miscibility of chitosan/poly(ethylene oxide) (CS/PEO) blends was investigated by a combination of experiment and molecular simulation. Results from X-ray diffraction (WAXD) and thermal analysis (DSC) suggest that the maximum miscibility was seen at the PEO weight fraction (w _PEO) =0.2; the optimum stoichiometric ratio for CS and PEO functional groups. The change in vibrational frequencies from infrared spectra was attributed to the specific interaction between PEO ether oxygen with the amino and hydroxyl groups of CS. Radial distribution functions (RDF) from MD simulation suggest that all CS functional groups (NH₂, C3-OH, and C6-OH) can interact with PEO ether groups for which NH₂ has the highest activity. For CS hydroxyl groups, a more significant contribution of C6-OH rather than C3-OH groups that interact with PEO ether oxygen was observed. The interaction parameter (χ) determined from MD simulation was in good agreement with that of the DSC experiment (χ_CS-PEO?=?-0.21). Based on a comparison between χ and χ _critical , CS/PEO blend was predicted to be miscible for w _PEO <0.58 with a maximum at w _PEO =0.2. In addition, the order parameter from the mesoscale simulation was employed to monitor the phase separation in these blends. From MesoDyn simulation, the miscibility was decreased with increasing PEO content, and miscible CS/PEO blends were obtained only with w _PEO <0.58, in good agreement with MD simulation and experiment.     

Antimony Induced {112}A Faceted Triangular GaAs1−xSbx/InP Core/Shell Nanowires and Their Enhanced Optical Quality

Mid‐infrared GaAs_1?xSb_x/InP core/shell nanowires are grown coherently with perfectly twin‐free zinc blende crystal structure. An unusual triangular InP shell with predominantly {112}A facets instead of {112}B facets is reported. It is found that this polarity preference is due to the surfactant role of Sb, which inhibits InP shell growth rate in the 〈112〉A directions. This behavior reveals a new degree of control and tunability allowed in manipulating nanowire facet geometry and polarity in radial heterostructures by a simple means. Tuning the Sb composition in the core yields controllable intense photoluminescence emission in both the 1.3 and 1.5 μm optical telecommunication windows, up to room temperature for single nanowires. The internal quantum efficiency of the core/shell nanowires is experimentally determined to be as high as 56% at room temperature. Transient Rayleigh scattering analysis brings complementary information, revealing the photoexcited carrier lifetime in the core/shell nanowire to be ≈100 ps at 300 K and ≈800 ps at 10 K. In comparison, the carrier lifetime of core‐only nanowire is below the detection limit of the system (25 ps). The demonstrated superior optical quality of the core/shell nanowires and their ideal emission wavelength range makes them highly relevant candidates for near‐infrared optoelectronic applications.     

Effective Gene Delivery into Human Stem Cells with a Cell‐Targeting Peptide‐Modified Bioreducible Polymer

Stem cells are poorly permissive to non‐viral gene transfection reagents. In this study, we explored the possibility of improving gene delivery into human embryonic (hESC) and mesenchymal (hMSC) stem cells by synergizing the activity of a cell‐binding ligand with a polymer that releases nucleic acids in a cytoplasm‐responsive manner. A 29 amino acid long peptide, RVG, targeting the nicotinic acetylcholine receptor (nAchR) was identified to bind both hMSC and H9‐derived hESC. Conjugating RVG to a redox‐sensitive biodegradable dendrimer‐type arginine‐grafted polymer (PAM‐ABP) enabled nanoparticle formation with plasmid DNA without altering the environment‐sensitive DNA release property and favorable toxicity profile of the parent polymer. Importantly, RVG‐PAM‐ABP quantitatively enhanced transfection into both hMSC and hESC compared to commercial transfection reagents like Lipofectamine 2000 and Fugene. ～60% and 50% of hMSC and hESC were respectively transfected, and at increased levels on a per cell basis, without affecting pluripotency marker expression. RVG‐PAM‐ABP is thus a novel bioreducible, biocompatible, non‐toxic, synthetic gene delivery system for nAchR‐expressing stem cells. Our data also demonstrates that a cell‐binding ligand like RVG can cooperate with a gene delivery system like PAM‐ABP to enable transfection of poorly‐permissive cells.     

Estimation of the social costs of home injury: a comparison with estimates for road injury

Home injury is thought to constitute a major health burden in most developed countries. However, efforts to address this burden have been hampered by reluctance from outside agencies to interfere with the home environment of individuals, even if it benefits the occupant's safety. This paper outlines cost–benefit evaluation methods established in the transport safety domain applied to home safety to estimate the social cost of unintentional home injury in New Zealand. Estimates of costs imposed on society by home injury can provide an important motivator for initiating research and programmes to reduce home injury risk. Data sources used included mortality data, hospitalisation data and data on minor injuries that required medical treatment, but not hospital admission. We estimated that unintentional home injuries in New Zealand impose an annual social cost of about $NZ 13 billion (about $US 9 billion), which is about 3.5 times the annual social cost of road injury. These estimates provide a rational evidence base for decisions on housing-focused safety regulation or interventions that always carry some cost, and therefore need to be weighed against the benefits of injuries potentially prevented.     

Self-healing of fractured GaAs nanowires

In-situ deformation experiments were carried out in a transmission electron microscope to investigate the structural response of single crystal GaAs nanowires (NWs) under compression. A repeatable self-healing process was discovered in which a partially fractured GaAs NW restored its original single crystal structure immediately after an external compressive force was removed. Possible mechanisms of the self-healing process are discussed.