A model for conceptual processing of naturalistic scenes.

Reports on 3 experiments, with 251 undergraduates, that examine serial position effects for rapidly-presented naturalistic scenes. The experiments provide a basis for comparison with the U-shaped serial position curve and list-length effect that typically result from verbal learning experiments. In contrast to the U-shaped verbal serial position function, results show a flat function at the beginning serial positions and a recency effect that is small and limited to the last serial position. There is also a set-size effect. Results suggest that the processing leading to a memory representation for visual stimuli such as pictures and linguistic stimuli such as words is qualitatively dissimilar. The findings can be accounted for by a serial processing model whose main parameter is the probability that the subject will switch attention from one picture to the next. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The origin of the hydroxyl radical oxygen in the Fenton reaction

There is an ongoing discussion in the chemical literature regarding the nature of the highly reactive hydroxyl radical formed from the reaction between ferrous iron and hydrogen peroxide (the Fenton reaction). However, the fundamental experiment of directly determining the source of the hydroxyl radicals formed in the reaction has not yet been carried out. In this study, we have used both hydrogen peroxide and water labeled with 17O, together with ESR spin trapping, to detect the hydroxyl radicals formed in the reaction. ESR experiments were run in phosphate buffer with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin trap, and either H2O2 or H2O labeled with 17O. The hydroxyl radical was generated by addition of Fe2+ ion to H2O2, or as a control, by photolysis of H2O2 in the ESR cavity. Observed ESR spectra were the sum of DMPO/.16OH and DMPO/.17OH radical adduct spectra. Within experimental accuracy, the percentage of 17O-labeled hydroxyl radical trapped by the DMPO was the same as in the original hydrogen peroxide, for either method of hydroxyl radical generation, indicating that the trapped hydroxyl radical was derived exclusively from hydrogen peroxide and that there was no exchange of oxygen atoms between H2O2 and solvent water. Likewise, the complementary reaction with ordinary H2O2 and 17O-labeled water also showed that none of the hydroxyl radical was derived from water. Our results do not preclude the ferryl intermediate, [Fe = O]2+ reacting with DMPO to form DMPO/.OH if the ferryl oxygen is derived from H2O2 rather than from a water ligand.     

Vinyl chloride-ethylene copolymers: The effect of modest ethylene concentrations on the physical properties of compounds

Vinyl chloride-ethylene copolymers containing from 1.0 to 5.5 wt.% ethylene were synthesized and compounded with DOP plasticizer at levels of 0, 5, 10, 20, 30, and 40 parts per hundred parts of resin. Physical property tests indicated that, as an internal plasticizer, ethylene was 2 to 3 times more efficient than DOP in the range studied. An examination of room temperature modulus as well as brittleness also indicated that crystallinity was still apparent in all copolymers.     

Velocity filters for multiple interference attenuation ingeophysical array data

The problem of velocity filtering a record of seismic data with the objective of extracting a desired signal by attenuating the coherent interferences traveling at different velocities is considered. A two-dimensional (N-input (N-M+1)-output) processing scheme is used where the (N-M+1) output traces are generated from the N-input traces by multichannel processing of overlapping subsets of M-input races. Each output is generated by using a vector of multichannel arrays filters designed to attenuate multiple coherent interference and random noise. The two-dimensional frequency-wavenumber expression corresponding to the proposed multiple-input-multiple-output processing scheme is derived so that it can be implemented using the two-dimensional fast Fourier transform. Two illustrative examples are included     

Nuclear Magnetic Resonance Analysis of Phenytoin and Sodium Phenytoin in Solid Dosage Forms

A rapid and specific nuclear magnetic resonance (NMR) spectroscopic method was developed for determining phenytoin and its sodium salt in capsules and tablets. Acetamide was used as the internal standard and 0.5% sodium deuteroxide in deuterium oxide served as the NMR solvent. The concentration of drug per unit dose was calculated from the integration values for the resonance signals of phenytoin at about 7.40 ppm and of the internal standard at about 1.97 ppm. The average recovery value of phenytoin added to synthetic samples, in concentrations ranging from 84 to 122 mg, was 99.9 ± 0.2% (SD) with a coefficient of variation of 0.2%. The method using commercial products gave results comparable to those obtained by the titrimetric and gravimetric methods of USP XX. Excipients of tablets and capsules such as sucrose and lactose did not interfere with the determinations. The proposed method was found suitable for measuring the content uniformity of capsules and tablets, and offered a positive means of identification on phenytoin in these dosage forms.     

Cervical orthoses effect on cervical spine motion: roentgenographic and goniometric method of study

Movement of the cervical spine in the sagittal plane was studied in ten normal subjects from 20 to 30 years of age without and with four different cervical orthoses: (1) polyethylene Camp plastic collar with chin and occiput piece, (2) plastizote Philadelphia collar, (3) four-poster and (4) SOMI (sternal occipital mandibular immobilization). The effect of the orthoses on restricting sagittal motion was measured simultaneously using roentgenographic and bubble goniometric methods. The subject was immobilized in a straight back chair to eliminate trunk motion, and lateral cervical spine films were taken of each subject in neutral, flexion and extension without and with each orthotic device. Distortion forces exerted on the orthotic devices were standardized by measurement of pressures at the chin and occiput. Roentgenographic measurements of flexion and extension and anteroposterior displacement of the cervical spine were compared to the measurements obtained by bubble goniometry. The four-poster and SOMI were found to be most effective in restricting extension and flexion respectively. The polyethylene and plastizote orthoses were significantly less effective in restricting motion. The bubble goniometer is an adequate clinical tool in assessing overall flexion-extension of the cervical spine but is not so precise and does not give information on the degree of motion at an individual vertebral level.     

Hydration of dibarium silicate II. rate of hydration

The rate of hydration of dibarium silicate (Ba²SiO₄) in paste form at room temperature was investigated. The uncombined barium hydroxide produced in the reaction, determined by a modified Franke method, was used as a measure of the extent of hydration. The linear relationship obtained between the uncombined barium hydroxide and the chemically combined water confirms that similar hydration products are formed at all stages of hydration, and either may be used as a measure of the degree of hydration. The rate of hydration of dibarium silicate was found to be lower than that of tricalcium aluminate, but higher than those of alite, tricalcium silicate and β-dicalcium silicate. The effect of water/solid ratio on the rate of hydration was also investigated. Dibarium silicate was completely hydrated after 30 days when it was mixed with a water/solid weight ratio > 0.7:1.