Influence of molecular weight distribution on the structure and properties of melt-spun polypropylene filaments

The role of molecular weight distribution on the spinnability, structure, and properties of melt-spun isotactic polypropylene filaments was studied with the aim of clearly distinguishing the effect of the breadth of the distribution from the effect of the average molecular weight and resin melt flow rate (MFR). Nine resins were chosen for this purpose, ranging in MFR from 16 to 78 and in polydispersity from 2.6 to 5.4. It was observed that the spinnability, structure, and properties of the spun filaments were all strong functions of the breadth of the distribution. Spinnability decreased with increasing breadth. At given spinning conditions and polydispersity, an increase in the weight-average molecular weight (decrease in MFR) produces an increase in crystallinity, birefringence, tensile strength, and tensile modulus. But at given spinning conditions and resin MFR, broadening the molecular weight distribution (increasing the polydispersity) produces an increase in crystallinity, tensile modulus, and elongation-to-break while birefringence and tensile strength decrease. The major influence of the polydispersity on the structure and properties developed was attributed to its effect on both the elongational viscosity of the resin and the ability of high molecular weight tails in the distribution to influence the stress-induced crystallization that occurs in the spinline. © 1995 John Wiley & Sons, Inc.     

Perspective taking combats automatic expressions of racial bias.

Five experiments investigated the hypothesis that perspective taking—actively contemplating others' psychological experiences—attenuates automatic expressions of racial bias. Across the first 3 experiments, participants who adopted the perspective of a Black target in an initial context subsequently exhibited more positive automatic interracial evaluations, with changes in automatic evaluations mediating the effect of perspective taking on more deliberate interracial evaluations. Furthermore, unlike other bias-reduction strategies, the interracial positivity resulting from perspective taking was accompanied by increased salience of racial inequalities (Experiment 3). Perspective taking also produced stronger approach-oriented action tendencies toward Blacks (but not Whites; Experiment 4). A final experiment revealed that face-to-face interactions with perspective takers were rated more positively by Black interaction partners than were interactions with nonperspective takers—a relationship that was mediated by perspective takers' increased approach-oriented nonverbal behaviors (as rated by objective, third-party observers). These findings indicate that perspective taking can combat automatic expressions of racial biases without simultaneously decreasing sensitivity to ongoing racial disparities. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Itineraries of rigid rotations and diffeomorphisms of the circle

We examine the itinerary of 0∈S¹=R/Z under the rotation by α∈R?Q. The motivating question is: if we are given only the itinerary of 0 relative to I⊂S¹, a finite union of closed intervals, can we recover α and I? We prove that the itineraries do determine α and I up to certain equivalences. Then we present elementary methods for finding α and I. Moreover, if g:S¹→S¹ is a C², orientation preserving diffeomorphism with an irrational rotation number, then we can use the orbit itinerary to recover the rotation number up to certain equivalences.     

Stereotype performance boosts: The impact of self-relevance and the manner of stereotype activation.

The activation of positive stereotypes has been shown to produce academic performance boosts. Evidence regarding the role of self-relevance in producing such effects has been mixed. The authors propose that the subtlety of stereotype activation plays a key role in creating performance boosts among targets and nontargets of stereotypes. Study 1 found that subtle stereotype activation boosted performance in targets, but blatant activation did not. Study 2 was conducted on both targets and nontargets using different methods of stereotype activation. Again, targets showed performance boosts when stereotypes were subtly activated but not when they were blatantly activated. Nontargets, however, showed boosts in performance only when stereotypes were blatantly activated. The role of self-relevance in mediating sensitivity to stimuli is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the Categorization of Admired and Disliked Exemplars of Admired and Disliked Racial Groups.

The present work examined the influence of affective fit in the racial categorization process. Study 1 tested whether famous exemplars of stigmatized and nonstigmatized racial groups are categorized by race at differential rates, depending on whether they are admired or disliked. Using an inverted-face paradigm, Study 2 examined whether racial categorization accuracy differs for admired and disliked exemplars of these groups. Study 3 examined the influence of collective self-esteem on Whites' tendency to differentially categorize admired and disliked Black and White exemplars. Last, Study 4 replicated the pattern of results found in the previous studies for White participants, making use of unknown exemplars about whom participants learned either positive or negative information prior to categorizing them. Taken together, the results suggested that phenotypically irrelevant affective information regarding exemplars and their social group memberships influences the racial categorization process. Implications for prejudice and stereotyping are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

To be liked versus respected: Divergent goals in interracial interactions.

Pervasive representations of Blacks and Latinos as unintelligent and of Whites as racist may give rise to divergent impression management goals in interracial interactions. We present studies showing that in interracial interactions racial minorities seek to be respected and seen as competent more than Whites do, whereas Whites seek to be liked and seen as moral more than racial minorities do. These divergent impression management goals are reflected in Whites' and racial minorities' self-report responses (Studies 1a, 1b, 2, and 4) and behaviors (Studies 3a and 3b). Divergent goals are observed in pre-existing relationships (Study 2), as well as in live interactions (Studies 3a, 3b, and 4), and are associated with higher levels of negative other-directed affect (Study 4). Implications of these goals for interracial communication and misunderstandings are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Why Do Interracial Interactions Impair Executive Function? A Resource Depletion Account.

Three studies investigated the veracity of a resource depletion account of the impairment of inhibitory task performance after interracial contact. White individuals engaged in either an interracial or same-race interaction, then completed an ostensibly unrelated Stroop color-naming test. In each study, the self-regulatory demands of the interaction were either increased (Study 1) or decreased (Studies 2 and 3). Results revealed that increasing the self-regulatory demands of an interracial interaction led to greater Stroop interference compared with control, whereas reducing self-regulatory demands led to less Stroop interference. Manipulating self-regulatory demands did not affect Stroop performance after same-race interactions. Taken together, the present studies point to resource depletion as the likely mechanism underlying the impairment of cognitive functioning after interracial dyadic interactions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)