Ending on a high note: Adding a better end to effortful study.

Remembered utility is the retrospective evaluation about the pleasure and pain associated with a past experience. It has been shown to influence prospective choices about whether to repeat or to avoid similar situations in the future (D. Kahneman 2000; D. Kahneman, D. L. Fredrickson, C. A. Schreiber, & D. A. Redelmeier, 1993). Evaluations about our hedonic past often disregard the duration of the experience and are influenced more by the peak and the final levels of discomfort (B. L. Fredrickson & D. Kahneman, 1993). Two experiments explored the remembered discomfort of an effortful learning experience and the influence of this evaluation on prospective study choices. The design of the studies mimicked D. Kahneman et al.'s (1993) cold-pressor study, but used an exceptionally challenging learning experience in place of the painful experience of submerging one's hand in ice water. An extremely effortful study episode extended by a more moderate interval was preferred to a shorter, unextended interval, despite better test performance following the shorter interval. Future study choices reflected this preference. These findings suggest that the act of acquiring knowledge has value in the learning process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Familiarity and retrieval processes in delayed judgments of learning.

Two processes are postulated to underlie delayed judgments of learning (JOLs)--cue familiarity and target retrievability. The two processes are distinguishable because the familiarity-based judgments are thought to be faster than the retrieval-based processes, because only retrieval-based JOLs should enhance the relative accuracy of the correlations between the JOLs and criterion test performance, and because only retrieval-based judgments should enhance memory. To test these predictions, in three experiments, the authors either speeded people's JOLs or allowed them to be unspeeded. The relative accuracy of the JOLs in predicting performance on the criterion test was higher for the unspeeded JOLs than for the speeded JOLs, as predicted. The unspeeded JOL conditions showed enhanced memory as compared with the speeded JOL conditions, as predicted. Finally, the unspeeded JOLs were sensitive to manipulations that modified recallability of the target, whereas the speeded JOLs were selectively sensitive to experimental variations in the familiarity of the cues. Thus, all three of the predictions about the consequences of the two processes potentially underlying delayed JOLs were borne out. A model of the processes underlying delayed JOLs based on these and earlier results is presented. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Novel silicon-containing analogues of the retinoid agonist bexarotene: syntheses and biological effects on human pluripotent stem cells

Twofold sila‐substitution (C/Si exchange) of the clinically used RXR‐selective retinoid agonist bexarotene leads to disila‐bexarotene, which displays pharmacological potency similar to that of the parent carbon compound, as shown in a HeLa‐cell‐based RXR assay. Formal exchange of the SiCH₂CH₂Si group in disila‐bexarotene with a SiCH₂Si or SiOSi moiety leads to the disila‐bexarotene analogues 8 and 9 . The silicon compounds 8 and 9 were synthesized in multistep syntheses, starting from HC?C(CH₃)₂SiCH₂Si(CH₃)₂C?CH and HC?C(CH₃)₂SiOSi(CH₃)₂C?CH, respectively. The key step in the syntheses of 8 and 9 is a cobalt‐catalyzed [2+2+2] cycloaddition reaction that affords the 1,3‐disilaindane and 2‐oxa‐1,3‐disilaindane skeletons. Disila‐bexarotene and its analogues 8 and 9 were studied for their biological effects relative to all‐trans retinoic acid in cultured human pluripotent stem cells. The parent carbon compound bexarotene was included in some of these biological studies. Although the silicon‐containing bexarotene analogues disila‐bexarotene, 8 , and 9 appear not to regulate the differentiation of TERA2.cl.SP12 stem cells, preliminary evidence indicates that these compounds may possess enhanced functions over the parent compound bexarotene, such as induction and regulation of cell death and cell numbers. The biological data obtained indicate that bexarotene, contrary to the silicon‐containing analogues disila‐bexarotene, 8 , and 9 , may partially act to induce cell differentiation.     

Electrocatalytic performance of Pt-based trimetallic alloy nanoparticle catalysts in proton exchange membrane fuel cells

The electrocatalytic performance of nanoengineered PtNiFe catalysts in proton exchange membrane fuel cells (PEMFC) is described in this report. The membrane electrode assembly was prepared using carbon-supported PtNiFe nanoparticles treated at two different temperatures as the cathode electrocatalysts in PEMFC. The PtNiFe/C catalysts were found to exhibit excellent fuel cell performance, much better than that of commercial Pt/C catalyst. In addition to assessing the mass activities in the kinetic current region, the fuel cell performance was also determined in the ohmic and mass transport regions. The electrocatalytic and fuel cell performance are shown to depend on the thermal treatment temperature of the trimetallic catalysts. The higher-temperature treated catalysts showed a higher power density than the lower-temperature treated catalysts. The results are also discussed in terms of the effect of lattice shrinking in the trimetallic alloy nanoparticles on the electrocatalytic activity.     

People's hypercorrection of high-confidence errors: Did they know it all along?

This study investigated the “knew it all along” explanation of the hypercorrection effect. The hypercorrection effect refers to the finding that when people are given corrective feedback, errors that are committed with high confidence are easier to correct than low-confidence errors. Experiment 1 showed that people were more likely to claim that they knew it all along when they were given the answers to high-confidence errors as compared with low-confidence errors. Experiments 2 and 3 investigated whether people really did know the correct answers before being told or whether the claim in Experiment 1 was mere hindsight bias. Experiment 2 showed that (a) participants were more likely to choose the correct answer in a 2nd guess multiple-choice test when they had expressed an error with high rather than low confidence and (b) that they were more likely to generate the correct answers to high-confidence as compared with low-confidence errors after being told they were wrong and to try again. Experiment 3 showed that (c) people were more likely to produce the correct answer when given a 2-letter cue to high- rather than low-confidence errors and that (d) when feedback was scaffolded by presenting the target letters 1 by 1, people needed fewer such letter prompts to reach the correct answers when they had committed high- rather than low-confidence errors. These results converge on the conclusion that when people said that they knew it all along, they were right. This knowledge, no doubt, contributes to why they are able to correct those high-confidence errors so easily. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The role of memory for past test in the underconfidence with practice effect.

According to the Memory for Past Test (MPT) heuristic, judgments of learning (JOLs) may be based, in part, on memory for the correctness of answers on a previous test. The authors explored MPT as the source of the underconfidence with practice effect (UWP; A. Koriat, L. Sheffer, & H. Ma'ayan, 2002), whereby Trial 1 overconfidence switches to underconfidence by Trial 2. Immediate and delayed JOLs were contrasted because only immediate JOLs demonstrate UWP. Consistent with MPT for immediate JOLs, Trial 1 test performance better predicted Trial 2 JOLs than did Trial 2 test performance. Delayed JOLs showed the reverse. Furthermore, items forgotten on Trial 1 but remembered on Trial 2 contributed disproportionately to UWP, but only with immediate JOLs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparative studies on the pyrolysis of cellulose,hemicellulose, and lignin based on combined kinetics

The thermal degradation behavior and pyrolytic mechanism of cellulose, hemicellulose, and lignin are investigated at different heating rates from 10 Kmin^?1 to 100 Kmin^?1 with a step-size of 10 Kmin^?1 using thermogravimetric analysis (TGA) equipment. It is observed that there are one, two, and three stages of pyrolytic reactions takes place in cellulose, hemicellulose, and lignin respectively. Isoconversional method is not suitable to analyse pyrolysis of hemicellulose and lignin as it involves multi-step reactions. The activation energies of the main decomposition stage for cellulose, hemicellulose, and lignin are 199.66, 95.39, and 174.40 kJ mol^?1 respectively. It is deduced that the pyrolysis reaction of cellulose corresponds to random scission mechanism while the pyrolysis reaction of hemicellulose and lignin follows the order based reaction mechanisms.