Testing Address Decoder Faults in Two-Port Memories: Fault Models, Tests, Consequences of Port Restrictions, and Test Strategy

A two-port memory contains two duplicated sets of address decoders, which operate independently. Testing such memories requires the use of single-port tests as well as special two-port tests; the test strategy determines which tests have to be used. Many two-port memories have ports which are read-only or write-only; this impacts the possible tests for single-port and two-port memories, as well as the test strategy. In this paper the effects of interference and shorts between the address decoders of the two ports on the fault modeling are investigated. Fault models and their tests are introduced. In addition, the consequences of the port restrictions (read-only or write-only ports) on the fault models and tests are discussed, together with the test strategy.     

Non‐Uniform Distribution of Two‐Phase Flows through Parallel Identical Paths

When a single‐phase fluid splits, passes through identical paths in parallel, and then recombines, the flow distributes itself uniformly among the multiple paths. However, when multi‐phase suspensions travel through identical parallel paths, the flow distribution can be significantly non‐uniform. Although the uniform distribution is a solution of the governing equations, this solution may be an unstable steady‐state solution between two or more stable solutions, or one of an array of possible steady‐state solutions. This multiplicity has arisen in practice for multiple vertical channels within fluidized beds, for cyclones in parallel, and for distributed feed suspension flows. Simple theories are employed to explain the principles involved for two cyclones and for a pair of risers in parallel.     

Contact stress distributions in a turbine disc dovetail type joint - a comparison of photoelastic and finite element results

Two dimensional photoelastic frozen stress techniques were used to investigate the stress distributions of an axially loaded dovetail joint as is found in the design of some turbine blade-disc fixings. The internal stress distributions were obtained by the shear difference method and were compared to results obtained by using the finite element method. It was found that steep principal stress gradients were present immediately below the contact surfaces in the zone adjacent to the fillet radius of the dovetail fixing, which could be an important consideration in the fatigue strength of the joint. The finite element model used gave the same trends of stress as the photoelastic model, predicted higher peak principal stresses and did not exhibit the same detailed variations of stress distribution.     

2099 Aluminum-Lithium with Key-Locked Inserts for Aerospace Applications

The purpose of this study was to determine the acceptability of nonpenetrating, key-locked inserts in 2099 aluminum-lithium. The tests conducted to make this assessment were: (1) microscopic examination for thread damage and delaminations after key installation, (2) pull-out load at 21 °C (70 °F) and −179 °C (−290 °F), and (3) mechanical cycling tests at room temperature and −179 °C (−290 °F). The test results indicated that for the three sizes evaluated, key-locked inserts in 2099-T6 and 2099-T8 were acceptable and although delaminations did occur on some T6 temper specimens, it was only as a failure mode at ultimate load and such behavior was judged to be acceptable.     

Optimal Sizing of a DBD Ozone Generator Using Response Surface Modeling

Dielectric barrier discharge (DBD) reactors used as ozone generators are well known today and widely used for water treatment and air disinfection. The purpose of this article is to propose an experimental procedure based on the response surface modeling in order to optimize the geometrical dimensions of the cylindrical shape ozone generator, i.e., the discharge gap and the electrodes length. Because an effective ozone generator is expected to give high ozone concentration with a minimum of power requirements, the applied high voltage was associated with the geometrical parameters to carry out a composite centered faces design. Obtained results indicate that for an efficient ozone generator, length of the electrodes needs to be optimized while the discharge gap should be minimized.     

The Tyrosine Gate of the Bacterial Lectin FimH: A Conformational Analysis by NMR Spectroscopy and X‐ray Crystallography

Urinary tract infections caused by uropathogenic E. coli are among the most prevalent infectious diseases. The mannose‐specific lectin FimH mediates the adhesion of the bacteria to the urothelium, thus enabling host cell invasion and recurrent infections. An attractive alternative to antibiotic treatment is the development of FimH antagonists that mimic the physiological ligand. A large variety of candidate drugs have been developed and characterized by means of in vitro studies and animal models. Here we present the X‐ray co‐crystal structures of FimH with members of four antagonist classes. In three of these cases no structural data had previously been available. We used NMR spectroscopy to characterize FimH–antagonist interactions further by chemical shift perturbation. The analysis allowed a clear determination of the conformation of the tyrosine gate motif that is crucial for the interaction with aglycone moieties and was not obvious from X‐ray structural data alone. Finally, ITC experiments provided insight into the thermodynamics of antagonist binding. In conjunction with the structural information from X‐ray and NMR experiments the results provide a mechanism for the often‐observed enthalpy–entropy compensation of FimH antagonists that plays a role in fine‐tuning of the interaction.     

Heat capacities of both PMMA stereomers: Comparison between atomistic simulation and experimental data

The domains of time and space generally covered by full atomistic simulation (AS) to represent the glass transition temperature, T_g, are very small. Physical interpretations of the phenomena occurring at this transition are inevitably limited. To specifically address such limitation, behavior of the heat capacity that accounts for the freezing of the degrees of freedom as temperature is decreased, is investigated. The selected polymer is poly(methyl methacrylate) since it offers the opportunity to exhibit a different T_g according to the tacticity of its chain. AS and experimental data are thus compared to a theoretical model that takes into account three contributions to the leap in the heat capacity occurring at T_g. The comparison discloses that an excellent agreement is obtained between simulated and experimental contributions from vibrations and free volume. However, from an AS viewpoint changes in the conformation weakly contribute to this leap. Despite this discrepancy local contributions to the glass transition as predicted by atomistic simulation, are sufficient to determine T_g.     

Membrane‐Surface Anchoring of Charged Diacylglycerol‐Lactones Correlates with Biological Activities

Synthetic diacylglycerol‐lactones (DAG‐lactones) are effective modulators of critical cellular signaling pathways, downstream of the lipophilic second messenger diacylglycerol, that activate a host of protein kinase C (PKC) isozymes and other nonkinase proteins that share similar C1 membrane‐targeting domains with PKC. A fundamental determinant of the biological activity of these amphiphilic molecules is the nature of their interactions with cellular membranes. This study examines the biological properties of charged DAG‐lactones exhibiting different alkyl groups attached to the heterocyclic nitrogen of an α‐pyridylalkylidene chain, and particularly the relationship between membrane interactions of the substituted DAG‐lactones and their respective biological activities. Our results suggest that bilayer interface localization of the N‐alkyl chain in the R² position of the DAG‐lactones inhibits translocation of PKC isoenzymes onto the cellular membrane. However, the orientation of a branched alkyl chain at the bilayer surface facilitates PKC binding and translocation. This investigation emphasizes that bilayer localization of the aromatic side residues of positively charged DAG‐lactone derivatives play a central role in determining biological activity, and that this factor contributes to the diversity of biological actions of these synthetic biomimetic ligands.     

Effect of Silicone Carbide on the Elastic Properties of Starch‐Based Composites: A Three‐Phase Model

The effect of a rigid filler on the elastic properties of starch‐based composites is investigated. Thermomolding of the targeted composite is conducted using a starch matrix with varying silicone carbide content. Mechanical testing reveals that the composite's Young modulus cannot be rationalized using two‐phase analytical models. The effect of a weak interphase region is highlighted using a finite‐element model that assumes the generation of virtual microstructures. Numerical results are discussed by describing the influence of the structural and interphase parameters on the composite's elastic modulus. Identification of optimal interphase parameters quantitatively demonstrates the weak adhesion between intrinsic phases for all studied filler fractions.