Catalytic Molecular Logic Devices by DNAzyme Displacement

Chemical reactions catalyzed by DNAzymes offer a route to programmable modification of biomolecules for therapeutic purposes. To this end, we have developed a new type of catalytic DNA‐based logic gates in which DNAzyme catalysis is controlled via toehold‐mediated strand displacement reactions. We refer to these as DNAzyme displacement gates. The use of toeholds to guide input binding provides a favorable pathway for input recognition, and the innate catalytic activity of DNAzymes allows amplification of nanomolar input concentrations. We demonstrate detection of arbitrary input sequences by rational introduction of mismatched bases into inhibitor strands. Furthermore, we illustrate the applicability of DNAzyme displacement to compute logic functions involving multiple logic gates. This work will enable sophisticated logical control of a range of biochemical modifications, with applications in pathogen detection and autonomous theranostics.     

A characterisation of thick film resistors for strain gauge applications

Some commercial thick film resistors with sheet resistivities from 1 kohm/sq. up to 1 Mohm/sq. were evaluated for strain gauge applications. Temperature coefficients of resistivity, noise indices and gauge factors (GFs) were measured. For the same resistor series GFs and noise indices increase with increasing sheet resistivity. However, both GFs and noise indices are different for resistors with the same nominal sheet resistivity but from different resistor series. The results indicated that the microstructure rather than the different chemical composition of the conductive phase in thick film resistors is the primary reason for the different gauge factors.     

Synthesis and characterization of maghemite nanosheets

Magnetic maghemite nanoparticles in the form of nanosheets were prepared by a topotactic transformation during the dehydroxylation of a γ-FeO(OH) precursor. The precursor was synthesized from tetrapyridin Fe(II) chloride (Fe(py)₄Cl₂). The nanosheets are several hundreds of nanometers wide, and less than 5 nm thick; they frequently bend and curl at the edges; they are nanocrystalline; and they are composed of smaller maghemite nanostructured domains, from a few nanometers up to several tens of nanometers wide.     

Microstructural, XRD and electrical characterization of some thick film resistors

The microstructural and electrical characteristics (sheet resistivities, TCRs, and noise indices) of some 1 k/sq. and 10 k/sq. thick films were evaluated. The conductive phase was determined by X-ray diffraction (XRD) analysis. The microstructures of fired resistors were investigated by scanning electron microscopy (SEM) and analyzed by energy dispersive spectrometry (EDS). Some resistors were fired for a relatively long time at the highest temperature, i.e., 6 h at 850 °C, to allow the reactions in the material to reach equilibria. Sheet resistivities, temperature coefficients of resistivity, and noise indices of these resistors were compared with normally (10 min at 850 °C) fired resistors. After 6 h firing absolute temperature coefficient of resistivity (TCR) values of most resistors increased significantly, while sheet resistivities decreased. Complex impedance analysis showed that in most cases resistors with low noise indices showed nearly ideal resistor response while those with higher noise had a larger imaginary part.     

On minimum cost isolated failure immune networks

A telecommunications network is isolated failure immune (IFI) if and only if communication between operative sites can be completed as long as network failures are isolated. It is known that the class of minimal IFI networks is equivalent to the class of spanning 2-trees. To the best of our knowledge, this work is the first computational study dealing with the construction of a minimum cost IFI network. The problem is known to be NP-complete. We develop a tabu search based heuristic for solving the minimum cost spanning 2-tree (MCS2T) problem. The complex structure of 2-trees makes the tabu search heuristic highly dependent on the starting solution. We develop four heuristic algorithms to obtain diversified good starting solutions. They are: completion of a 2-tree from a spanning tree, two greedy approaches, and a method based on the recursive definition of a 2-tree. We also formulate an integer programming problem (IP) whose objective function value is a lower bound to the MCS2T problem. We solve the IP by developing a constraint generation scheme. The algorithms were tested on complete random graphs with Euclidean distances and on two real data sets (Civil Aeronautics Board) with instances of 10, 15, 20 and 25 nodes. As a result of this research for small problems (10 and 15 nodes), the heuristic solutions are on average within 0.8% from the optimal solution and for large problems (20 and 25 nodes), the average error is less than 2.8%.     

Incidence of Helicobacter pylori infection in Ghanaian patients with dyspeptic symptoms referred for upper gastrointestinal endoscopy

There is a lack of information in the United Kingdom on the prevalence of third molars in older patients. The aim of this study was therefore to define the pattern of lower third molar retention in UK dental practice attenders aged 35 years and over. A random sample of 599 eligible patients from a rural dental practice were included in the study. Information was obtained from clinical notes and panoramic radiographs. Data collected included age, gender, presence or absence of lower third molars, number of teeth present in the lower arch and eruption status. Two hundred and sixty-four (44.1 per cent) had at least one lower third molar present (mean age = 57.1 years) while 335 (55.9 per cent) had no lower third molars (mean age = 50.2 years). The data suggest that a greater proportion of men than women retain at least one lower third molar although this finding was not statistically significant. Seventy per cent of retained lower third molars reported in the study were fully erupted. Sixty per cent were vertically placed. There was an association between age and number of teeth present (chi 2 = 38.85, 4DF, P < 0.05), older patients having fewer lower teeth. These data suggest that a large number of patients can expect to keep their lower third molars beyond the age of 35 years and that in many cases a conservative "wait and see' policy for lower third molars in the early twenties is appropriate.     

The optimization of material flow in production

Market demands are different: they tend to require individual, customized products of high reliability and high quality and also produced in right time. Material flow optimization is an indispensable step to be taken. The proposed optimization method is material flow analysis, which is giving an insight of the production organization of a company and its evaluation at different organizational levels. The analysis is based on a technological database and on the organization of individual departments of a company. It enables a material and information flow analysis as well as an analysis of the department and machines layout respectively. The result of the analysis is material flow rationalization, thus minimizing production costs.     

Fabrication of porous mullite-based ceramic bricks from Al-rich water treatment sludge and kaolinitic-based clay

A large quantity of water treatment sludge (WTS) is generated yearly from Ghana's Weija water treatment plant. The sludge contains some heavy metals and other toxic chemicals, which must be managed to minimize environmental impact. In the current work, WTS was mixed with varying quantities of kaolinitic-based clays (kaolin and lithomargic clays) to produce porous mullite-based bricks. The bricks were fired at 1200°C for 1 h, and their properties were determined. Lithomargic clay-based mixtures had less dimensional variation and were suitable to produce near-net shape bricks compared to WTS-based bricks. The addition of WTS increased the linear firing shrinkage and apparent porosity whilst decreasing bulk density and compressive strength. Porous mullite-based bricks fabricated from lithomargic clay exhibited high compressive strength (6.3 MPa) at 10 wt.% WTS addition. The highest apparent porosity of 27% was attained at 40 wt.% WTS addition with compressive strength of 5.1 MPa and thermal conductivity of .5 W/m K.     

Application Areas of Ionic Hydraulic Fluids

Ionic liquids, as high-tech technical fluids, have been in practical application in various fields of technology for several years. The search for ionic liquids suitable for use within hydraulic systems, as another new very important field of technology, has taken more than a decade. The development included the identification of material properties important for usage as a hydraulic fluid, an extensive preselection process and laboratory testing of suitable ionic liquids, as well as long-term testing using real hydraulic components under real operating conditions. Based on the findings, potential areas of industrial application of ionic liquids as hydraulic fluids are presented, which arise from their extraordinary physicochemical properties.