Intergranular corrosion of a light aircraft aluminum alloy propeller

Examination of the wreckage of a light aircraft revealed that approximately 20 cm was missing from one tip of the aluminum alloy propeller. Fractographic and metallographic examination of the remaining portion of the propeller revealed extensive grain-boundary separation in the vicinity of the fracture, and grain edges and corners rounded by corrosion on the fracture surface. Energy dispersive X-ray analysis (EDXA) revealed fluorine on, and in the vicinity of, the fracture surface. In the ensuing litigation, it was asserted that the crash occurred because the propeller fractured in flight as the result of intergranular attack caused by the use of a fluorine-bearing cleaner.     

Poly(glycolic acid) fiber-reinforced bioabsorbable composites with improved interfacial properties

Bioabsorbable composites, designed for use as rigid tissue scaffolds, were fabricated by reinforcing free radically cured poly(D,L-lactide) fumarate matrices with absorbable poly(glycolic acid) fibers. To investigate the benefits of an improved fiber/matrix interphase, fiber pretreatments were employed including surface-etching by exposure to mild acidic conditions and incorporation of 3-methacryloxypropyltrimethoxysilane as a coupling agent. SEM of composite fracture surfaces showed that fiber pretreatment yielded improved wetting and encapsulation of the fibers by the matrix resin. The composites fabricated with poly(glycolic acid) fibers which were acid-etched and pretreated with the coupling agent showed an average 41% increase in tensile strength; a representative sample displayed an increase from 73.9 MPa to 105.5 MPa, compared to the composite made from untreated fibers.     

Application of a Compaction Simulator to the Design of a High-Dose Tablet Formulation. Part I

The compaction properties of an investigational drug are studied by the use of a compaction simulator. The effects of punch velocity over the range of 30-640 mm^-1 on the compaction properties of the pure drug and a variety of formulas incorporating a high dose of the active compound have been investigated. The data were analyzed by applying the Heckel equation. The pure drug was found to have a high yield pressure at a relatively low punch velocity of 31 mm^-1. As the punch velocity was increased there was a decrease in crushing strength, primarily as a result of increasing yield pressure. These findings indicate that the pure drug predominantly consolidated by fragmentation and elastic deformation, with a slow plastically deforming component. The information obtained on the consolidation mechanism of the pure drug and, subsequently, on model formulas were instrumental in the design and selection of a robust formula and granulation process. The advantages of conducting dosage form design and characterization studies during the early phase of tablet formulation using means such as a compaction simulator are emphasized in this investigation.     

Intermolecular interactions and formation of the hydration sphere in phosphonic acid model systems as an approach to the description of vinyl phosphonic acid based polymers

Molecular model systems based on propyl phosphonic acid (ppa) were studied by means of density functional theory calculations in order to describe the acid-acid interaction and the formation of the hydration sphere. The formation of ppa dimers is reported and the energetic difference between two dimer structures is presented. The hydration sphere of ppa was represented by model systems ppa(H₂O)_n, for which the system with n=4 formed the first hydration sphere (h¹), while n=7 can be considered a good approximation to the complete inner hydration sphere around the phosphonic acid group. The study of the ppa-H⁺ (H₂O)_n model systems showed an interesting structural behavior comparatively to the ppa(H₂O)_n systems. The protonated acids exhibited equivalent phosphorous-oxygen bonds and a general molecular structure is proposed to represent these protonated species.     

Microprocessor IDDQ testing: a case study

The author describe their incorporation of I_DDQ testing into the design of the PA-7100LC PA-RISC microprocessor. They also discuss design guidelines, measurement techniques, results after fabrication and volume production, and suggested improvement. Their 900,000-transistor custom design supports I_DDQ testing to ensure high quality without compromising 100-MHz-plus performance     

A method for rapidly assessing and refining simple solvent treatments in molecular modelling. Example studies on the antigen-combining loop H2 from FAB fragment McPC603

Different simple solvent models have been implemented in anextended simulated annealing process (ESAP), developed by Higoet al. [(1992) Biopolymers, 32, 33–43] and proven to beable to predict ab initio the conformation of the antigen-combiningloop H2 from FAB McPC603. Hie rationale used here provides auseful new method for testing solvent models in general. Thedifferent solvent models comprise a high dielectric constant,a screened coulomb potential, a dummy water model and a statisticalcontinuum treatment of the solvent effect in which the reactionfield and the solvent accessible area is accounted for. To assessthe effect of the solvent, we tested the ability of simulationsto retain the experimental conformation of loop H2. We comparedthe different structures obtained at the end of the annealingprocess in terms of root mean square deviation (r.m.s.d.), forboth the backbone and for all atoms, root mean square (r.m.s.)fluctuation, solvent accessible surface area (ASA), hydrogenbonding network and - plot distribution. The relationship betweenthe r.m.s.d. and the internal energy of a structure is alsoevaluated in terms of precision and another possible methodfor obtaining the best conformation is discussed. The accuracyof modelling the coarse effect of the solvent and the similaritiesof the resulting structures with respect to the X-ray referencestructure are examined. The possible choice of one of thesesolvent models in the structure determination of an unknownloop structure is discussed     

Hierarchical classification of data streams: a systematic literature review

The classification task usually works with flat and batch learners, assuming problems as stationary and without relations between class labels. Nevertheless, several real-world problems do not assume these premises, i.e., data have labels organized hierarchically and are made available in streaming fashion, meaning that their behavior can drift over time. Existing studies on hierarchical classification do not consider data streams as input of their process, and thus, data is assumed as stationary and handled through batch learners. The same can be said about works on streaming data, as the hierarchical classification is overlooked. Studies concerning each area individually are promising, yet, do not tackle their intersection. This study analyzes the main characteristics of the state-of-the-art works on hierarchical classification for streaming data concerning five aspects: (i) problems tackled, (ii) datasets, (iii) algorithms, (iv) evaluation metrics, and (v) research gaps in the area. We performed a systematic literature review of primary studies and retrieved 3,722 papers, of which 42 were identified as relevant and used to answer the aforementioned research questions. We found that the problems handled by hierarchical classification of data streams include mainly classification of images, human activities, texts, and audio; the datasets are mostly created or synthetic data; the algorithms and evaluation metrics are well-known techniques or based on those; and research gaps are related to dynamic context, data complexity, and computational resources constraints. We also provide implications for future research and experiments to consider common characteristics shared amongst hierarchical classification and data stream classification.