Reaction of a Ni-coated Al nanoparticle to form B2-NiAl: A molecular dynamics study

The kinetic reaction in a Ni-coated Al nanoparticle with equi-atomic fractions and diameter of approximately 4.5 nm is studied by means of molecular dynamics simulation, using a potential of the embedded atom type to model the interatomic interactions. First, the large driving force for the alloying of Ni and Al initiates solid state amorphization of the nanoparticle with the formation of Ni₅₀Al₅₀ amorphous alloy. Amorphization makes intermixing of the components much easier compared to the crystalline state. The average rate of penetration of Ni atoms can be estimated to be about two times higher than Al atoms, whilst the total rate of inter-penetration can be estimated to be of the order of 10^?2 m/s. The heat of the intermixing with the formation of Ni₅₀Al₅₀ amorphous alloy can be estimated at approximately ?0.34 eV/at. Next, the crystallization of the Ni₅₀Al₅₀ amorphous alloy into B2-NiAl ordered crystal structure is observed. The heat of the crystallization can be estimated as approximately ?0.08 eV/at. Then, the B2-NiAl ordered nanoparticle melts at a temperature of approximately 1500 K. It is shown that, for the alloying reaction in the initial Ni-coated Al nanoparticle, the ignition temperature can be as low as approximately 200 K, while the adiabatic temperature for the reaction is below the melting temperature of the nanoparticle with the B2-NiAl ordered structure.     

Nostalgia and lost identity

Nostalgia for the Soviet Union is a major social phenomenon in Russia today due to the irrevocable losses of the recent past in which Soviet citizens involuntarily became immigrants in their own country. With reference to discussions of nostalgia in philosophical and psychoanalytic literature, I suggest that nostalgia may represent either a defensive regression to the past or a progressive striving for wholeness through re‐connecting with what has been lost in the service of a greater integration. I compare this with the processes of adaptation seen in immigrants and provide a clinical illustration of a young man coming to terms with loss and change in the post‐Soviet era. When nostalgia is recognized as a legitimate emotional experience it may facilitate mourning and enable the integration of the past with the present and the development of a new identity.     

Peer Difficulties in Children with Epilepsy: Association with Seizure,Neuropsychological, Academic,and Behavioral Variables

Purpose/Objective: A developmental psychopathology framework was used to examine variables associated with peer problems in children with epilepsy (CWE). Variables commonly associated with peer difficulties in typically developing children, such as inattentive behavior, anxious behavior, and academic achievement were investigated. Neuropsychological functioning, age at epilepsy onset, and seizure status were also examined.

Research Method/Design: Participants were 173 CWE, ages 8–15. Structural equation modeling (SEM) was used to determine which variables predicted peer problems in CWE and to test hypothesized interrelations among variables.

Results: The SEM revealed that anxious behavior mediated relations between neuropsychological functioning and peer difficulties and seizure status and peer difficulties. Inattentive behavior mediated the association between neuropsychological functioning and peer difficulties. Neuropsychological functioning mediated the relation between age at epilepsy onset and inattentive behavior, anxious behavior, and academic achievement.

Conclusions/Implications: As seen with typically developing children, inattentive and anxious behaviors are related to peer difficulties in CWE. Neuropsychological functioning, age at epilepsy onset, and seizure status are indirectly associated with peer difficulties; therefore, these variables are important to examine in CWE who are experiencing peer problems.     

Memory coding in individuals with Down syndrome

Previous research has identified a deficit in phonological short-term memory in individuals with Down syndrome.

The present work aimed to analyze how a group of 30 individuals with Down syndrome performed in a picture span task compared with 30 typically developing children of the same mental age. The task involved four conditions (i.e., dissimilar, phonologically similar, visually similar, and long-name items) chosen to analyze the strategy used by individuals with Down syndrome to code visually presented nameable items.

Individuals with Down syndrome performed less well than typically developing children. Both groups showed the visual similarity effect.

Taken together, our results confirm that individuals with Down syndrome have a verbal working memory deficit, even when nameable items are presented visually. Mental age appears to be an important determinant of memory coding stage in individuals with Down syndrome.     

Abstract Rule Learning in 11- and 14-Month-Old Infants

This study tests the hypothesis that distributional information can guide infants in the generalization of word order movement rules at the initial stage of language acquisition. Participants were 11- and 14-month-old infants. Stimuli were sentences in Russian, a language that was unknown to our infants. During training the word order of each sentence was transformed following a consistent pattern (e.g., ABC–BAC). During the test phase infants heard novel sentences that respected the trained rule and ones that violated the trained rule (i.e., a different transformation such as ABC–ACB). Stimuli words had highly variable phonological and morphological shapes. The cue available was the positional information of words and their non-adjacent relations across sentences. We found that 14-month-olds, but not 11-month-olds, showed evidence of abstract rule generalization to novel instances. The implications of this finding to early syntactic acquisition are discussed.     

Dialectic and Dialetheism

In this article, I consider the possibility of interpreting Hegel's dialectic as dialetheism. After a first basic recapitulation about the meaning of the words ‘dialetheism’ and ‘dialectic’ and a consideration of Priest's own account of the relation between dialectical and dialetheic logic in 1989, I discuss some controversial issues, not directly considered by Priest. As a matter of fact, the reflection on paraconsistent logics and dialetheism has enormously grown in recent years. In addition, the reception of Hegel's logic and metaphysics has also impressively improved. So I suggest that the discussion about the binomial dialectic/dialetheism should be reopened, on these new bases.     

Perceived racial/ethnic discrimination, posttraumatic stress symptoms, and health risk behaviors among Mexican American adolescents

Utilizing the concept of race-based traumatic stress, this study tested whether posttraumatic stress symptoms explain the process by which perceived discrimination is related to health risk behaviors among Mexican American adolescents. One hundred ten participants were recruited from a large health maintenance organization in Northern California. Mediational analyses indicated that adolescents who perceived more discrimination reported worse posttraumatic stress symptoms, controlling for covariates. In turn, adolescents who experienced heightened posttraumatic stress symptoms reported more alcohol use, more other drug use, involvement in more fights, and more sexual partners. Perceived discrimination was also directly related to involvement in more fights. Results provide support for the notion of race-based traumatic stress, specifically, that perceived discrimination may be traumatizing for Mexican American adolescents. Counseling psychologists and counselors in schools and community settings should assess Mexican American adolescents for the effects of discrimination and provide appropriate interventions to reduce its negative emotional impact.     

Aggressive behavior,related conduct problems,and variation in genes affecting dopamine turnover

A number of dopamine‐related genes have been implicated in the etiology of violent behavior and conduct problems. Of these genes, the ones that code for the enzymes that influence the turnover of dopamine (DA) have received the most attention. In this study, we investigated 12 genetic polymorphisms in four genes involved with DA functioning (COMT, MAOA and MAOB, and DβH) in 179 incarcerated male Russian adolescents and two groups of matched controls: boys without criminal records referred to by their teachers as (a) “troubled‐behavior‐free” boys, n=182; and (b) “troubled‐behavior” boys, n=60. The participants were classified as (1) being incarcerated or not, (2) having the DSM‐IV diagnosis of conduct disorder (CD) or not, and (3) having committed violent or nonviolent crimes (for the incarcerated individuals only). The findings indicate that, although no single genetic variant in any of the four genes differentiated individuals in the investigated groups, various linear combinations (i.e., haplotypes) and nonlinear combinations (i.e., interactions between variants within and across genes) of genetic variants resulted in informative and robust classifications for two of the three groupings. These combinations of genetic variants differentiated individuals in incarceration vs. nonincarcerated and CD vs. no‐CD groups; no informative combinations were established consistently for the grouping by crime within the incarcerated individuals. This study underscores the importance of considering multiple rather than single markers within candidate genes and their additive and interactive combinations, both with themselves and with nongenetic indicators, while attempting to understand the genetic background of such complex behaviors as serious conduct problems. Aggr. Behav. 36:158–176, 2010. © 2010 Wiley‐Liss, Inc.     

Motivational systems in adolescence: Possible implications for age differences in substance abuse and other risk-taking behaviors

Adolescence is an evolutionarily conserved developmental phase characterized by hormonal, physiological, neural and behavioral alterations evident widely across mammalian species. For instance, adolescent rats, like their human counterparts, exhibit elevations in peer-directed social interactions, risk-taking/novelty seeking and drug and alcohol use relative to adults, along with notable changes in motivational and reward-related brain regions. After reviewing these topics, the present paper discusses conditioned preference and aversion data showing adolescents to be more sensitive than adults to positive rewarding properties of various drugs and natural stimuli, while less sensitive to the aversive properties of these stimuli. Additional experiments designed to parse specific components of reward-related processing using natural rewards have yielded more mixed findings, with reports of accentuated positive hedonic sensitivity during adolescence contrasting with studies showing less positive hedonic affect and reduced incentive salience at this age. Implications of these findings for adolescent substance abuse will be discussed.