On the conditions for success of sklansky''s convex hull algorithm

The convex hull algorithm for simple polygons, due to Sklansky, fails in some cases, but its extreme simplicity, compared to the later algorithms, revived an interest in this algorithm. A sufficient condition for its success was given recently by Toussaint and Avis. They have proved that the algorithm works for polygons known as weakly externally visible polygons.

In this paper a new notion called external left visibility is introduced and it is shown that this is a necessary and sufficient condition for the success of Sklansky's algorithm. Moreover, algorithms testing simple polygons for external left visibility and weak external visibility are given.     

Modification of polyvinylchloride in solution or suspension by nucleophilic substitution

Nucleophilic displacement of chlorine from polyvinylchloride (PVC) suspended either in water or in solution can be achieved using a nucleophile such as a sodium thiolate (R? S^?, Na⁺). The nucleophilicity of the salt increases if an ether linkage exists in a β position to the thiol group [R? O? (CH₂)₂? S^?, Na⁺]. Addition of a solvent such as cyclohexanone (which is a good solvent for PVC) to the slurry increases substantially the degree of substitution. Elemental analysis shows that every chlorine displaced from the polymer is replaced by a thiolate group; thus almost no dehydrochlorination occurs. It is possible to obtain by this method a grafted polymer in which 33% of the chlorine atoms are replaced by the β-ether thiolate group. The resulting polymer behaves like an internally plasticized PVC. The higher the degree of substitution of chlorine, the greater the flexibility of the grafted polymer is. Other compounds, such as lauryl thiolate and diethyl dithiocarbamate, also were used as nucleophiles, the latter one resulting in a brittle crosslinked polymer whenever sulfur was above 2%. Grafting of polytetrahydrofuran from PVC also was achieved using tetrahydrofuran as solvent and silver-perchlorate as catalyst. The resulting flexible grafted polymer is believed to consist of longer chains of polytetrahydrofuran grafted from few displaced chlorine atoms along the PVC chain.     

An observational study of maternal models.

Observed 35 mothers in interaction with their 19-mo old infants in seminaturalistic settings. Mothers' modeling techniques, their reinforcements for imitation, and children's imitations were recorded. Imitation and reinforcement for imitation were complexly related; for some children maternal reinforcement appeared to control the amount of imitation, but equally prominent were patterns in which reciprocal or interactive mother-child influences were in evidence. Characteristics of the mother, other than reinforcement of imitation, were positively associated with the child's imitation, particularly the amount of variation and the enthusiasm in the mother's modeling. Interpretations of findings in a seminaturalistic setting and findings from the laboratory are discussed with regard to methodological issues and theories relating to imitative learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An investigation of late closure: The role of syntax, thematic structure, and pragmatics in initial interpretation.

Four reading-time experiments investigated the application of the late closure principle in Italian. The experiments tested the principle governing the initial attachment of different types of modifiers (relative clause, adjectival phrase, and prepositional phrase) to a complex noun phrase. By manipulating the type of preposition within the complex noun phrase, the authors investigated the role of the thematic structure in initial and final parsing. The results show that the late closure principle applies to initial parsing in Italian without being affected by the thematic structure of the complex noun phrase. Final interpretation, however, shows an effect of pragmatic preference and an effect of thematic structure on syntactic revisions. The results are discussed in terms of a parsing model that adopts syntactic parsing strategies and makes modular use of linguistic information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Obese people who seek treatment have different characteristics than those who do not seek treatment.

A group of obese people who had not sought treatment; an obese group who had sought treatment in a professional, hospital-based program; and normal-weight controls (N?=?547) were compared in regard to level of psychopathology, binge eating, and negative emotional eating. Because the groups differed significantly on several demographic variables, 3 demographically matched groups were created and compared (n?=?177, 59 per group). In the matched subgroups, obese people who had sought treatment reported greater psychopathology and more binge eating than did normal-weight controls or those who had not sought treatment. Both obese groups (including those who had not sought treatment) endorsed more symptoms of distress, negative emotional eating, overeating, difficulty resisting temptation, and less exercise than did normal-weight controls. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A psychometric study of the Adult Attachment Interview: Reliability and discriminant validity.

The Adult Attachment Interview (AAI) stimulates Ss to retrieve and evaluate attachment-related autobiographical memories and has increasingly been used to predict the quality of parent–child interactions and infant–parent attachment relationships. Its reliability and discriminate validity, however, have not yet been examined. In this study, 83 mothers were interviewed twice, 2 mo apart, by different interviewers so that the instrument's test–retest reliability and potential interviewer effects can be evaluated. To examine the AAI's discriminate validity, tests were administered for autobiographical memory, intelligence, and social desirability. The reliability of the AAI classifications was quite high over time (78% on the level of the 3 main categories κ?=?.63) and across interviewers. The unresolved category was less stable. The AAI classifications turned out to be independent on non-attachement-related memory, verbal and performance intelligence, and social desirability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Integral estimates for the displacement and strain energy in nonlinear elasticity in terms of the body force

The boundary value problem of place in nonlinear hyperelastostatics is considered. Integral estimates for the displacement and the strain energy are obtained for the weak (or classical) solution in terms of the given body force. These estimates then imply continuous dependence of the solution on the given data in the appropriate norm.     

Effects of differential experience on dendritic spine counts in rat cerebral cortex.

Measured the effects of 30 days experience in enriched conditions (EC) or impoverished conditions (IC) on pyramids in the occipital cortex of 40 male Berkeley S1 strain littermate pairs in 4 replication experiments. Using the rapid Golgi method, counts were made of dendritic spines, and the lateral width of basal dendrites was measured. The density of spines was greater in EC than in IC Ss on basal dendrites (9.7%, p     

Who is for children?

Discusses some of the unmet needs of children in the areas of mental health care, day care, and foster and institutional care. It is argued that children with serious emotional problems do not get the treatment they need because adequate funds have not been set aside for children's mental health and because few incentives exist to serve children in community settings or in the most familylike settings possible. Specific functions that can be served by psychologists are presented, and strategies for creating public and private sector policies more responsive to the needs of children and their families are outlined. (2 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)