Cost analysis of a multi-component parallel redundant complex system with overloading effect and waiting under critical human error

The cost analysis of a multi-component parallel redundant complex system is considered, incorporating the concept of overloading effect and waiting time for repair under critical human error. Failure and waiting times follow an exponential time distribution, whereas repair time follows a general distribution. Using the supplementary variable technique, Laplace transforms of the probabilities of the complex system being in various states have been computed. Some graphs have been plotted to highlight the main results.     

Low-cost checkpointing and failure recovery in mobile computingsystems

A mobile computing system consists of mobile and stationary nodes, connected to each other by a communication network. The presence of mobile nodes in the system places constraints on the permissible energy consumption and available communication bandwidth. To minimize the lost computation during recovery from node failures, periodic collection of a consistent snapshot of the system (checkpoint) is required. Locating mobile nodes contributes to the checkpointing and recovery costs. Synchronous snapshot collection algorithms, designed for static networks, either force every node in the system to take a new local snapshot, or block the underlying computation during snapshot collection. Hence, they are not suitable for mobile computing systems. If nodes take their local checkpoints independently in an uncoordinated manner, each node may have to store multiple local checkpoints in stable storage. This is not suitable for mobile nodes as they have small memory. This paper presents a synchronous snapshot collection algorithm for mobile systems that neither forces every node to take a local snapshot, nor blocks the underlying computation during snapshot collection. If a node initiates snapshot collection, local snapshots of only those nodes that have directly or transitively affected the initiator since their last snapshots need to be taken. We prove that the global snapshot collection terminates within a finite time of its invocation and the collected global snapshot is consistent. We also propose a minimal rollback/recovery algorithm in which the computation at a node is rolled back only if it depends on operations that have been undone due to the failure of node(s). Both the algorithms have low communication and storage overheads and meet the low energy consumption and low bandwidth constraints of mobile computing systems     

Accuracy and speed of real and complex interpolation

Because complex arithmetic takes only a little more time than real arithmetic on modern computers it is advisable to take a closer look at some of the known mathematical tools and compare the advantages in complex computations. This paper compares real and complex interpolation from the point of view of the application for larger problems. It shows that real interpolation breaks down very early whereas complex interpolation is superior by many orders of magnitude with regard to time as well as accuracy. It is shown theoretically that complex interpolation on the unit circle is the best that can be achieved.     

ATP-Dependent human erythrocyte glutathione-conjugate transporter. I. Purification, photoaffinity labeling, and kinetic characteristics of ATPase activity

Dinitrophenyl S-glutathione (DNP-SG) ATPase is a 38 kDa membrane protein expressed in erythrocytes and other tissues. Although stimulation of ATP hydrolysis catalyzed by DNP-SG ATPase has been demonstrated in the presence of several structurally unrelated amphiphilic ions, structural and functional properties of this protein have not been well-defined. In the present study, we have developed an improved protocol for the purification of DNP-SG ATPase and investigated its kinetic and substrate-binding properties. The purification procedure was based on highly specific elution of the 38 kDa protein from DNP-SG affinity resin in the presence of ATP. The protein could not be eluted using either ADP or adenosine-5'-[beta,gamma-methylene]triphosphate (methylene-ATP), a nonhydrolyzable analogue of ATP. Doxorubicin (DOX), a weakly basic anthracycline chemotherapy agent, was found to be the preferred activator for stimulation of ATP hydrolysis by the enzyme. ATP binding to the enzyme was demonstrated using 8-azido-ATP photoaffinity labeling and binding of trinitrophenyl (TNP)-ATP, a fluorescent analogue of ATP. The photoaffinity labeling of DNP-SG ATPase (38 kDa) was saturable with respect to 8-azido ATP (Kd = 2 microM), indicating that the enzyme was capable of specific and saturable binding to ATP. DNP-SG binding was evident from the purification procedure itself and was also demonstrable by quenching of tryptophan fluorescence. Results of quenching of tryptophan fluorescence as well as radioactive isotope-binding studies indicated that DOX was bound to the purified protein as well.     

Transmission parameters of a class of coupled distributed networks

It is shown how the equations of a class of coupled distributed networks can be decoupled, and their transmission parameters expressed in terms of those of an equivalent scalar system.     

M.O.S. switched-capacitor amplifiers

Switched-capacitor voltage gain elements, in which the gain is precisely controlled by the ratio of two capacitors, are presented. The voltage gain is obtained by means of a transconductance element operating into a switched-capacitor resistor. Circuit configurations use a single operational amplifier or a unity-gain buffer. In some of these configurations, the offset voltage of the operational amplifier or the buffer is not amplified.     

Application of spherical and other polymers in capillary zone electrophoresis: separation of antiviral drugs and deoxyribonucleoside phosphates by different principles

Soluble polymers of linear chains with limited branching and spherical polymers (limit dextrins and sucrose, such as Dextran and Ficoll (Pharmacia Chemicals), yielding lower viscosities, are examined here for the separation of different nucleotides and several anti-AIDS drugs by capillary zone electrophoresis (CZE). The linear polymer forms a network but spherical polymers appear to create a second pseudo-phase. In general, they tend to enhance the solute mobility and reduce peak width; thus, they improve the column efficiency. We observe that the beads of a spherical polymer produce a pseudo-phase even in a very low polymer concentration. The proposed method involving a spherical polymer yields the best separation for twelve deoxyribonucleoside mono-, di- and triphosphates in ca. 10 min. Common anti-AIDS drugs (ddA, ddC, ddI, d4T, AZT) and an AZT metabolite (AZT-glucuronate) are resolved by using conventional micellar electrokinetic capillary chromatography (MEKC). These results not only offer fast and highly sensitive detection techniques for the pharmacokinetics of nucleotides, drugs, and their metabolites, but they also demonstrate an application of the proposed second pseudo-phase involving spherical polymer beads in CZE separations.     

Increased Uptake of Chelated Copper Ions by Lolium perenne Attributed to Amplified Membrane and Endodermal Damage

The contributions of mechanisms by which chelators influence metal translocation to plant shoot tissues are analyzed using a combination of numerical modelling and physical experiments. The model distinguishes between apoplastic and symplastic pathways of water and solute movement. It also includes the barrier effects of the endodermis and plasma membrane. Simulations are used to assess transport pathways for free and chelated metals, identifying mechanisms involved in chelate-enhanced phytoextraction. Hypothesized transport mechanisms and parameters specific to amendment treatments are estimated, with simulated results compared to experimental data. Parameter values for each amendment treatment are estimated based on literature and experimental values, and used for model calibration and simulation of amendment influences on solute transport pathways and mechanisms. Modeling indicates that chelation alters the pathways for Cu transport. For free ions, Cu transport to leaf tissue can be described using purely apoplastic or transcellular pathways. For strong chelators (ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA)), transport by the purely apoplastic pathway is insufficient to represent measured Cu transport to leaf tissue. Consistent with experimental observations, increased membrane permeability is required for simulating translocation in EDTA and DTPA treatments. Increasing the membrane permeability is key to enhancing phytoextraction efficiency.     

On the dependence of interfacial resistance on contact materials between cathode and interconnect in solid oxide fuel cells

The dependence of interfacial contact resistance (ICR) on contact materials between cathode and interconnect is systematically studied under both isothermal oxidation and thermal cycling conditions. Three kinds of cathode current-collecting layer (CCCL) are used, (La,Sr) (Co,Fe)O₃ (LSCF), LSCF+10%Ag, and Ag, and tested in a SUS430/CCCL/SUS430 sandwich structure to simulate the actual operation of the solid oxide fuel cells (SOFCs). Experimental results show that the ICR of LSCF+10%Ag exhibits the smallest value, in comparison with the specimens with LSCF and Ag paste, as well as the sample without a CCCL. For LSCF+10%Ag contact, the ICR increases from 0.0069 mΩ cm² to 3.74 mΩ cm² under an isothermal condition for 150 h, then increases from 3.74 mΩ cm² to 10.79 mΩ cm² after 15 thermal cycles. This work provides information for the understanding of possible mechanisms of performance degradation of SOFCs.