Category-based errors and the accessibility of unbiased spatial memories: A retrieval model.

Studies have consistently shown a spatial memory bias such that a target location is remembered toward the prototypical location of the region to which the target belongs, indicating a blending between the target’s specific information and the generic information of its region. The authors investigated whether people retain a veridical representation of a target location after a delay by determining the locus of the blending (during encoding, delay, or retrieval). To examine accessibility to the original target location, they used a recognition task, which is less demanding than the traditional reproduction procedure. The results showed that participants were able to recognize the original position of a target over their own biased recalled position after both a short (1,500 ms) and a longer (5,000 ms) delay. These findings reveal that spatial memories can be undistorted despite distorted recall responses. Results are discussed in terms of J. Huttenlocher, L. V. Hedges, and S. Duncan’s (1991) category adjustment model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Goblet cell number in the ileum of rats denervated during suckling and weaning.

The enteric nervous system plays a role on the stimulation of secretory cells of intestinal epithelia. We have demonstrated that ablation of ENS stimulates epithelial cell proliferation. As goblet cells are important constituents of the epithelial sheet, it is mandatory to investigate separately this cell type. The myenteric plexus of the ileum of rats in postnatal development was partially removed by the serosal application of benzalkonium chloride (BAC). Three groups of animals were used: those where BAC application was at 13 days and sacrifice was at 15 (13/28-day-old) or 23 days after treatment (13/36-day-old), and those where BAC was applied at 21 days and rats were killed 15 days after treatment (21/36-day-old) . The number of goblet cells in the ileum was estimated in sections stained by periodic acid-Schiff (PAS) histochemistry. In the 13/28 and 21/36 groups, the number of goblet cells was significantly higher after BAC treatment. These results suggest that the myenteric denervation may have an acute effect on the number of goblet cell in suckling and weanling rats, probably through submucous plexus.     

Total extractable phenolic chromatographic index: an overview of the phenolic class contents from different sources of foods

 The extractable phenolic fraction has been studied in a wide group of representative samples from the main food phenolic sources: fruits, vegetables and legumes. After quantitative extraction and quantification of each phenolic compound in the samples, the total extractable phenolic chromatographic index was defined as the sum of all extractable phenolics obtained under conventional conditions, and calculated for the main phenolic classes found in foods: hydroxybenzoic and hydroxycinnamic acids as well as flavonoids. Phenolic acids and flavonoids contents are reported for the food samples studied. The results presented in this work allow an interesting overview of the distribution of the phenolic classes in foods, as well as an approach to the knowledge of the phenolic classes composition in foods. Received: 30 May 2000     

A simplified methodology to determine the cutting stiffness and the contact stiffness in the plunge grinding process

This paper presents a simplified experimental technique to determine approximately the cutting stiffness and the contact stiffness in the plunge grinding process. The experimental methodology consists of a machine static stiffness test and several grinding processes. The cutting stiffness is obtained from the workpiece headstock static stiffness and from its displacement during the grinding processes, measured by a LVDT transducer. The contact stiffness is resolved from the expression that relates it with the grinding process time constant and other grinding parameters. The time constant is obtained from the exponential that characterises the machine deformation during the spark-out, measured as well by the LVDT transducer placed on the workpiece headstock. The variation of the obtained values of the contact stiffness with some of the grinding parameters is also shown.     

Oxidative dehydrogenation of propane to propene, 1: Kinetic study on V/MgO

The reaction kinetics of the oxidative dehydrogenation of propane to propene over a V/MgO catalyst were studied. Both propane and propene oxidation kinetics were measured independently to quantify the rates of the parallel and consecutive reactions to propene and carbon oxides. Specific experiments to evaluate reaction products effects showed that water inhibited reaction rates but co‐feeding CO₂ or propene had no measurable effect on selectivity or conversion. Kinetic data generated under integral reactor conditions and over an inert membrane reactor have also been used to estimate the kinetic parameters. Selectivity decreased as the oxygen partial pressure increased; however, propene yield was relatively insensitive to oxygen concentration. A dual site Mars‐van Krevelen model characterizes the reaction kinetics well. The role of lattice oxygen was established by alternating pulses of propane and oxygen. This redox model is able to predict the experimental tendencies observed in the three types of reactor studied.     

Melting behavior and crystallization kinetics of poly(butylene terephthalate‐co‐diethylene terephthalate) and poly(butylene terephthalate‐co‐triethylene terephthalate) copolyesters

The melting behavior of poly(butylene terephthalate‐co‐diethylene terephthalate) and poly(butylene terephthalate‐co‐triethylene terephthalate) copolymers was investigated by differential scanning calorimetry after isothermal crystallization from the melt. Multiple endotherms were found for all the samples, and attributed to the melting and recrystallization processes. By applying the Hoffman‐Weeks' method, the equilibrium melting temperatures of the copolymers under investigation were obtained. Two distinct peaks in the crystallization exothermic curve were observed for all the samples. Both of them appeared at higher times than that of PBT, indicating that the introduction of a comonomer decreased the crystallization rate. The observed dependence of this latter on composition was explained on the basis of the content of ether–oxygen atoms in diethylene and triethylene terephthalate units, and of the different sizes of these units. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3545–3551, 2001     

Processing and properties of thermoplastic starch and its blends with sodium alginate

Viscosity measurements were carried out on corn starch (CS) and CS–sodium alginate (SA) suspensions at low levels of SA [1 to 10% (w/w)], as a function of temperature. The addition of SA caused the granular CS gelatinization process to occur at a lower onset temperature. CS and CS–SA mixtures were extruded in single‐ and twin‐screw extruders, with 15% glycerol and different water contents. Processing of plasticized CS–SA mixtures required lower temperatures, which is consistent with the viscosity results. Homogeneous and flexible extrudates were obtained by processing in a twin‐screw extruder. Samples in the composition range between 0 and 10% (w/w) SA were examined using tensile tests as a function of water content. Mechanical properties were dependent on the water content and on the SA composition. A significant increase in the Young's modulus value was observed for the blend containing 1% SA. Dynamic mechanical analysis was carried out for CS and CS–SA blends. Two transitions were detected in the temperature range –80 to 150°C. Scanning electron microscopy was used to examine the morphology of the extruded samples. The surfaces of the films were homogeneous, which demonstrated that the CS granules in all samples were characteristically destructured under the conditions used in processing. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 412–420, 2001     

Microwave-Hydrothermal Synthesis of Nanocrystalline Zirconia Powders

Nanosized zirconium oxide (ZrO₂) powders were prepared by adding NaOH to a zirconyl chloride aqueous solution under microwave-hydrothermal conditions. The obtained results showed that the tetragonal polymorph increased with increasing NaOH concentration in the starting solution and reached the maximum value by using 1 M ZrOCl₂. The microwave-assisted hydrothermal synthesis is expected to be able to process continuously, and may lead to energy savings because of rapid heating to temperature and increased kinetics of crystallization. This method is very simple and can lead to powders with desirable characteristics such as very fine size, narrow size distribution, and good chemical homogeneity.     

Ni-65wt%Nb alloy by aluminothermic reduction process

Ni–Nb alloys have been used as master-alloy in the production of Ni-based superalloys containing niobium. In the case of INCONEL 718, the most used superalloy, the niobium content is in the range 5.0–5.5 wt%. The aim of this work is to present results related to the production of Ni-65wt%Nb alloy by aluminothermic reduction process. Two different reactant mixtures were used: Nb₂O₅ + Ni + Al and Nb₂O₅ + NiO + Al. For each type of mixture the Al excess was varied from 0% to 15% over the stoichiometric amount. All the alloys were produced in a bulk form with Nb and Ni composition according to specifications. The best results came from the experiments involving mixtures of Nb₂O₅ + NiO + Al, where an overall metallic yield of 86% was obtained. The alloys produced from Nb₂O₅ + Ni + Al mixtures showed low metallic yields and high oxygen contents associated to the presence of a niobium oxide-phase in the microstructure.     

In vivo assessment of the corrosion of nickel–titanium orthodontic archwires by using scanning electron microscopy and atomic force microscopy

This study was undertaken to assess in vivo the corrosion in two commercial nickel–titanium (NiTi) orthodontic archwires removed from the oral cavity of patients using fluoride mouthwashes. Five volunteers took part in this study on the corrosion behavior of two brands of NiTi archwires (3M and AO (brand of archwire)) during use of two mouthwashes with neutral sodium fluoride 1.1%, one with acidulated fluoride 1.1%, and one with placebo and a control group. Each patient used one mouthwash in three different periods of time for 1 min a day for 30 days. The archwires were assessed with scanning electron microscopy and atomic force microscopy for qualitative and quantitative analysis. The values obtained with atomic force microscopy (AFM) were submitted to normality test, two‐way analysis of variance, and Tukey's test at a significance level of 5%. The AFM images showed a gradual qualitative increase in the roughness of both types of wire between the treatments: control < placebo < neutral fluoride < acidulated fluoride. The arithmetic average of the roughness and root mean square of the roughness were similar. As for 3M archwires, only the acidulated fluoride group differed statistically from the others. As for AO archwires, the control and placebo groups did not differ from each other, but differed from the other fluoride treatments. The group using neutral fluoride also differed significantly from the acidulated fluoride group. 3M archwires were not affected by daily oral challenges. AO archwires were not affected by daily oral challenges either; their association with fluoride, either neutral or acidulated, increased their roughness.