On the notion of control signals in digital designs

The concept of control signals is fundamental to digital design. It evokes the notion of one or more signals that influence computation on other signals in a system, and regulate the behavior of the system. A formal definition of control signals is presented. It is argued that knowledge of the control signals in a complex design such as a microprocessor or a computer is crucial to the comprehension and specification of the design and that knowledge of the control signals of a design leads to a more efficient hardware implementation. The identification of control signals in two microprocessors are presented as examples     

Copper extraction into emulsion liquid membranes using LIX 984N-C®

The extraction of copper from aqueous sulfate media into ELMs using the extractant LIX 984N-C was studied. Appropriately characterized emulsions on the basis of viscosity and internal drop sizes were used to study the effect of different parameters on extraction. The effects of stirring speed, surfactant concentration, pH of the external continuous phase, carrier concentration, internal phase stripping acid concentration and initial copper concentration are reported. These results show that LIX 984N-C efficiently extracts copper at low pH values typical of leach solutions. It was found that LIX 984N-C could extract up to 80% copper from aqueous solutions at pH value of 1. Performance of LIX 984N-C was also compared with LIX 84 and LIX 84-I at different pH values. Results indicate that LIX 984N-C could open up new avenues for extraction of copper into ELMs, not only from dilute solutions, but also from sulfuric acid leach solutions.     

Nanostructured, molecularly imprinted, and template-patterned polythiophenes for chiral sensing and differentiation

An innovation to thin-film molecular imprinting is presented for the sensitive detection and effective discrimination of chiral compounds using a portable quartz crystal microbalance transduction technique. The facile approach involves i) colloidal sphere layering of latex particles onto the surface via a Langmuir-Blodgett-like technique followed by ii) template molecular imprinting using electrodeposition of a single functional and cross-linking monomer.     

Negation as Failure as Resolution

Providing a clean procedural semantics of the Negation As Failure rule in Logic Programming has been an open problem for some time now. This rule has been treated as a technique in nonmonotonic reasoning, not as a rule in classical logic. This paper contains a demonstration of the negation as failure rule as a resolution procedure in first-order logic. We present a sound and complete resolution scheme for negation as failure rule for the larger class of constraint logic programs. The approach is to consider a canonical partition of the completion of a definite (constraint) program into the IF and the FI programs. We show that a negated goal, provable from the completed definite program is provable from just the FI part. The clauses in this program have a structure dual to that of definite Horn clauses. We describe a sound and complete linear resolution rule for this fragment, and show that a resolution proof of the negated goal from the FI part corresponds to a finite failure tree resulting from classical linear resolution applied to the goal on the If part of the original definite program. Our work shows that negation as failure rule can be computationally efficient in the sense that the SLD-resolution on the If part of a definite program along with the negation as failure rule is more efficient than a direct resolution procedure on the completion of that program.     

Chimie douce hydrogen production from Hg contaminated water,with desirable throughput,and simultaneous Hg-removal

Hydrogen's widespread use is fraught with many difficulties. The challenges currently are to do with safety concerns in gas storage and transportation, and low rate of production leading to non-viability of technologies at the point-of-use. Another global concern of immediate relevance involves heavy-metal ion pollution. Viable processes which can simultaneously remove and result in beneficiation of the contaminants are hitherto rarely reported. In this context we report a single-step, in situ co-reduction approach which has the dual advantage of (i) Hg contaminant removal, and (ii) room temperature hydrogen production. Hydrogen is produced via galvanic corrosion of in situ synthesized nanoaluminium amalgam. The production rate (720 mL/min for 0.5 g-Al salt) is far superior to what would be expected from the use of pure hydrides, and/or using bulk amalgams at room temperature. The method is simple, chimie douce (i.e soft chemical), hence potentially affordable, and capable of providing a means of beneficiating Hg contaminated water present in effluents from certain industries (for example, industries which uses chlor-alkali process). The in situ co-reduction approach helps in bypassing the usual rate limiting step which involves formation of an alumina passivation layer on hydrolytic material surface. Given the potential that exists in scale down and up, this approach offers a method to address the long standing challenge of point-of-use hydrogen availability.     

Estimation of sharma constant and thermoacoustic properties of fatty acids

From the volume expansivity α, a number of thermoacoustic parameters, including the Sharma constant,S ₀, are estimated for four fatty acids as a function of temperature. The Sharma constant, which was established to be a constant with the characteristic value 1.11 ± 0.01 over a number of systems investigated by earlier investigators, is also found to be a constant with the same value for all fatty acids under investigation. Further, the Sharma constant,S ₀, is independent of temperature and dependent only on α. All other parameters estimated are discussed and compared with the values reported in the literature by earlier workers for different systems.     

Application of natural receptors in sensors and assays

Biosensors are analytical devices that use a biological or biologically derived material immobilized at a physicochemical transducer to measure one or more analytes. Although there are a large number of reviews on biosensors in general, there has been little systematic information presented on the application of natural receptors in sensor technology. This perspective discusses broadly the fundamental properties of natural receptors, which make them an attractive option for use as biorecognition elements in sensor technology. It analyses the current situation by reference to typical examples, such as the application of nicotinic acetylcholine receptor and G protein-linked receptors in affinity sensors and analyses the problems that need to be resolved prior to any commercialization of such devices.     

A Technique for Optimal Sequential Maintenance Scheduling

This paper presents the mathematical development of, and a simple solution technique for, an optimal sequential maintenance scheduling problem. The model is shown to satisfy the Kuhn-Tucker conditions, the necessary and sufficient conditions for the existence of an optimal solution. Real-world systems consisting of mixtures of constant and increasing failure rate devices are considered in the model. Sequential preventive maintenance schedules are developed for groups of identical items with increasing failure rates. Provision is made for the corrective maintenance of these groups if failures occur in between the preventive maintenance schedules. Also, constant failure rate devices are accorded corrective maintenance when failures occur. Optimality is achieved by minimizing the total annual maintenance cost, subject to constraints on the system availability, number of maintenance personnel and intervals of preventive maintenance. The model is applied to a coal mine power system example.     

Structure and function of animal fatty acid synthase

Fatty acid synthase (FAS; EC 2.3.1.85) of animal tissues is a complex multifunctional enzyme consisting of two identical monomers. The FAS monomer (approximately 270 kDa) contains six catalytic activities and from the N-terminus the order is beta-ketoacyl synthase (KS), acetyl/malonyl transacylase (AT/MT), beta-hydroxyacyl dehydratase (DH), enoyl reductase (ER), beta-ketoacyl reductase (KR), acyl carrier protein (ACP), and thioesterase (TE). Although the FAS monomer contains all the activities needed for palmitate synthesis, only the dimer form of the synthase is functional. Both the biochemical analyses and the small-angle neutron-scattering analysis determined that in the dimer form of the enzyme the monomers are arranged in a head-to-tail manner generating two centers for palmitate synthesis. Further, these analyses also suggested that the component activities of the monomer are organized in three domains. Domain I contains KS, AT/MT, and DH, domain II contains ER, KR, and ACP, and domain III contains TE. Approximately one fourth of the monomer protein located between domains I and II contains no catalytic activities and is called the interdomain/core region. This region plays an important role in the dimer formation. Electron cryomicrographic analyses of FAS revealed a quaternary structure at approximately 19 A resolution, containing two monomers (180 x 130 x 75 A) that are separated by about 19 A, and arranged in an antiparallel fashion, which is consistent with biochemical and neutron-scattering data. The monomers are connected at the middle by a hinge generating two clefts that may be the two active centers of fatty acid synthesis. Normal mode analysis predicted that the intersubunit hinge region and the intrasubunit hinge located between domains II and III are highly flexible. Analysis of FAS particle images by using a simultaneous multiple model single particle refinement method confirmed that FAS structure exists in various conformational states. Attempts to get higher resolution of the structure are under way.     

Indium doped silver oxide thin films prepared by reactive electron beam evaporation technique: electrical properties

The indium doped silver oxide thin films have been prepared at 275 °C on soda lime glass and silicon substrates by reactive electron beam evaporation technique; the deposition rate has been varied (by varying the electron beam current) in the range 0.94–16.88 nm/s keeping the oxygen flow rate constant. These films are polycrystalline. The electrical resistivity for these films decreases with increasing deposition rate. The AIO films prepared with a deposition rate of 5.7 nm/s show near p-type conductivity. The work function has been measured on these films by contact potential method using Kelvin Probe. The surface morphology of the films has been evaluated using atomic force microscopy (AFM). The roles of indium doping and oxygen vacancies in the electrical properties of these films have been analyzed; the ionized impurity scattering is the dominant mechanism controlling the electrical conduction in these films.