A comparison of specular reflection and PA-FTIR techniques in the analysis of annealed injection-molded polyamide 6,6

A comparative study between the specular reflectance and photoacoustic FTIR techniques is presented in this work. The potential and limitations of these two methods are investigated by following and analyzing structural variations that take place at the surface in annealed injection-molded polyamide 6,6. Both spectroscopic techniques appear to be quite sensitive in detecting small structural changes that occur in polyamide 6,6 when submitted to different annealing temperatures. However, the presence of distorted bands in the specular reflection spectra makes the photoacoustic FTIR method more attractive for the IR vibrational analysis of difficult materials (e.g., composites, black-filled polymers, paints, etc.) that cannot be easily characterized by conventional transmission FTIR. © 1994 John Wiley & Sons, Inc.     

Heme and the endothelium. Effects of nitric oxide on catalytic iron and heme degradation by heme oxygenase

We studied the effects of nitric oxide (NO) on the control of excess cellular heme and release of catalytically active iron. Endothelial cells (ECs) exposed to hemin followed by a NO donor have a ferritin content that is 16% that of cells exposed to hemin alone. Hemin-treated ECs experience a 3.5-fold rise in non-heme, catalytic iron 2 h later, but a hemin rechallenge 20 h later results in only a 24% increase. The addition of a NO donor after the first hemin exposure prevents this adaptive response, presumably due to effects on ferritin synthesis. NO donors were found to reduce iron release from hemin, while hemin accumulated in cells. A NO donor, in a dose-dependent fashion, inhibited heme oxygenase activity, measured by bilirubin production. Using low temperature EPR spectroscopy, heme oxygenase inhibition correlated with nitrosylation of free heme in microsomes. Nitrosylation of cellular heme prevented iron release, for while there was heme oxygenase-dependent release of iron in cells incubated with hemin for 24 h, the addition of a NO donor blocked iron release. This indicates that NO readily nitrosylates intracellular free heme and prevents its degradation by heme oxygenase. Nitrosylation of heme was found to reduce sensitization of cells to oxidative injury.     

Finite element method and limit analysis theory for soil mechanics problems

This paper deals with a finite element formulation of problems of limit loads in soil mechanics via limit analysis theory. After recalling the principal results of this theory, the authors describe a numerical formulation for both the static and kinematic approaches of the ultimate load. Thanks to linearization of the yield criterion, the finite element model leads to a linear programming problem. The efficiency of the two proposed computing procedures is demonstrated by their application to the problem of pulling out of foundations and slope stability.     

Crystal growth of alkaline earth fluorides in a reactive atmosphere. Part II

Crystal growth of MF₂ (M = Ca, Sr, and Ba) is carried out under two different reactive atmospheres, HF and HF + CF₄, with the same carrier gas (He). The effect of processing is seen in a comparison of the optical transparency in the near infrared of the single-crystal specimens.     

Congruently melting compounds of CaF2 · rcRF3: Part II

Crystals of congruently melting CaF₂ · r_cRF₃, where R = Gd, Tb, Dy, Ho, Y and Er, were shown to have the tysonite (LaF₃-type) structure. From the lattice constants, crystal composition (r_c) and density (p), these compounds are seen to be an extended form of the hexagonal (tysonite) structure of the corresponding RF₃. In these compounds, Ca²⁺ enters substitutionally compensated by a fluoride ion vacancy. The partial molar volume of RF₃ in the compound is a constant of the class of R and equals 37.6 cm³.     

The quality of mother–infant attachment and its relationship to toddlers' initial sociability with peers.

37 age- and sex-matched toddler dyads were observed between ages 20 and 23 mo in a 30-min play session with mothers present. Assignment to dyad was determined by attachment classification, assessed at 18 mo in the M. D. Ainsworth et al (1978) Strange Situation procedure. Ss classified as securely attached (SAs), anxiously avoidant (AAs), or anxiously resistant (ARs) were paired with SAs. In the play situation, SAs were more sociable and more positively oriented toward both mother and peer. Mothers of SAs were more supportive and appropriately directive and played an important role in successful outcomes for their children. AAs participated actively in the play session but were rated as more negative in their orientation toward both mother and peer. ARs appeared highly stressed by this situation; they ignored most peer offers and were most negative toward their mothers. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Condiciones suficientes para la existencia de solucion optima en un programa semi-infinito

The boundness of the feasible set of a Semi-infinite Programming Problem guarantees, in many cases, the existence of an optimum point. Therefore we study such property in connection with the solution-set of a system of infinitely many constraints. Later on we give existence-theorems for an optimum point, involving the objective function in different ways such as: the generalized Lagrange-function; a specific cone of directions; a special dual problem; and, certain infinite systems associated to the problem.

     

Infrared-transparent glasses derived from the fluorides of zirconium,thorium, and barium

Glasses consisting solely of high-purity ZrF₄, ThF₄, and BaF₂ have been synthesized using reactive atmosphere processing (RAP) techniques. RAP of the individual components and the molten material with anhydrous HF and CCl₄ is described. The glass molds easily at 312°C and 1920 psi with a high-fidelity replication of the die surface. The glass is water insoluble, unusually hard and strong, and continuously transparent from 0.3 to 7 μm.     

Crystal growth of alkaline earth fluorides in a reactive atmosphere

Crystal growth of MF₂ (M = Ca, Sr, or Ba) is carried out in a reactive atmosphere consisting of HF and a carrier gas (He). Single-crystal Bridgman ingots, with the axis oriented at 〈111〉, are grown up to 5.2 cm in diameter. The mechanical strength of these specimens is found to be higher than what has been reported.     

An examination of exposure control and content balancing restrictions on item selection in CATs using the partial credit model

The purpose of the present investigation was to systematically examine the effectiveness of the Sympson-Hetter technique and rotated content balancing relative to no exposure control and no content rotation conditions in a computerized adaptive testing system (CAT) based on the partial credit model. A series of simulated fixed and variable length CATs were run using two data sets generated to multiple content areas for three sizes of item pools. The 2 (exposure control) X 2 (content rotation) X 2 (test length) X 3 (item pool size) X 2 (data sets) yielded a total of 48 conditions. Results show that while both procedures can be used with no deleterious effect on measurement precision, the gains in exposure control, pool utilization, and item overlap appear quite modest. Difficulties involved with setting the exposure control parameters in small item pools make questionable the utility of the Sympson-Hetter technique with similar item pools.