Histone Tail Sequences Balance Their Role in Genetic Regulation and the Need To Protect DNA against Destruction in Nucleosome Core Particles Containing Abasic Sites

Abasic sites (AP) are produced 10 000 times per day in a single cell. Strand cleavage at AP is accelerated ≈100-fold within a nucleosome core particle (NCP) compared to free DNA. The lysine-rich N-terminal tails of histone proteins catalyze single-strand breaks through a mechanism used by base-excision-repair enzymes, despite the general dearth of glutamic acid, aspartic acid, and histidine—the amino acids that are typically responsible for deprotonation of Schiff base intermediates. Incorporating glutamic acid, aspartic acid, or histidine proximal to lysine residues in histone N-terminal tails increases AP reactivity as much as sixfold. The rate acceleration is due to more facile DNA cleavage of Schiff-base intermediates. These observations raise the possibility that histone proteins could have evolved to minimize the presence of histidine, glutamic acid, and aspartic acid in their lysine-rich N-terminal tails to guard against enhancing the toxic effects of DNA damage.     

Is it possible for dislocations to self-lock after high-pressure torsion?

The evolution of the dislocation structure of the intermetallic compound Ni₃Ge upon high-pressure torsion has been investigated. It has been determined that, under certain conditions, subsequent heating without loading leads to the self-locking of dislocations, while in other cases, this does not take place. The role played by the lattice distortions that arise under torsion is emphasized.     

Structure of the transition zone and its influence on the strength of copper-tantalum joint (Explosion welding)

The joint of copper and tantalum, metals without mutual solubility, formed by explosion welding is studied. The mechanism of the influence of mutual solubility on the structure of the transition zone is established. It is demonstrated that the interface contains heterogeneities, and their role in the strength of the materials joint is revealed. A microheterogeneous structure of the joint zones is detected.     

Not all faces are processed equally: Evidence for featural rather than holistic processing of one's own face in a face-imaging task.

The present work considers the mental imaging of faces, with a focus in own-face imaging. Experiments 1 and 3 demonstrated an own-face disadvantage, with slower generation of mental images of one's own face than of other familiar faces. In contrast, Experiment 2 demonstrated that mental images of facial parts are generated more quickly for one's own face. Finally, Experiment 4 established that a bias toward local processing is advantageous for one's own face, whereas a global-processing bias produces an enhanced own-face disadvantage. The results suggest that own-face imaging is more synchronized with retrieval of face features and less attuned to a face's holistic pattern than is imaging of other people's faces. The authors propose that the salient information for own and other face identification reflects, in part, differences in the purpose and experiences (expertise) generally associated with processing of own and other faces. Consistent with work examining the range of face processing, including other-race faces, our results suggest that not all faces receive the same holistic emphasis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Wave formation during explosive welding: the relaxation of a nonequilibrium structure

The sequence of the transition states of the interface in the process of explosion welding has been studied. The self-organization of splash-shaped cusps first into a quasi-wave surface and, then into a perfect wavy surface has been revealed. A similarity between a quasi-wave surface and the periodic surface relief, which has been observed in the well-known experiments of G. R. Abrahamson, of a steel bullet after collision with a target has been found. Simulation tests have been performed in order to find possible methods of the relaxation of a nonequilibrium structure that possess excess area.     

Influence of free volume fraction,inter/intramolecular energy ratio,and chain segment density on the Gibbs-DiMarzio theory of the glass transition

Based upon computer analysis, the Gibbs-DiMarzio (G-DM) theory is evaluated for the case of (a) constant V₀ and (b) constant r where V₀ is the fractional free volume at T_g and r is the ratio of the hole (E₀) to the flex (ε) energy. For each respective case, results are presented in a reduced variables format that indicate the extent to which r and V₀ vary at the transition temperature as a function of the reciprocal degree of polymerization (P^?1). To further account for chemical differences that exist among polymers, an index (n) is introduced that ultimately incorporates the effective number average of chain atom segments (x?) per P?. Using these reduced variables plots, the effects of V₀, r, and n are compared with the T_g data for four well-documented polymers. Although the theory adequately describes the PMMA, PS, and PVC data, for PαMS the fit is doubtful. The analysis demonstrates that, in order to maintain V₀ within the range of 0.015–0.045, r must remain within approximately 1.0–1.1. Moreover, under conditions of either constant V₀ or r, other more flexible polymers require that $\text{n?10}$.     

Is a sense of inequity an ancestral primate trait? Testing social inequity in cotton top tamarins (Saguinus oedipus).

To address a controversy in the literature concerning whether monkeys show an aversion to inequity, individuals of a New World monkey species, cotton top tamarins (Saguinus oedipus) were tested in an offering task and in a bartering task. At issue was whether the monkeys rejected rewards because of a violation of expectancy of the preferred reward, or whether they rejected rewards because of a sensitivity to socially mediated inequity. The data from both tasks indicated that the subjects were more likely to reject when preferred rewards were presented, either because of another animal eating the reward (the social condition) or because of rewards being presented but inaccessible. The bartering task led to the only behavioral indication of aversion due specifically to social inequity, which was demonstrated when tamarins' sensitivity to the difference in rewards increased with exposure to other tamarins working to receive the preferred rewards. The results suggest that social inequity aversion will be assessed by tamarins, and possibly by other primates, only under conditions of limited resources and a requirement of work, which may make the situation a bit more competitive and thus drives attention toward both social and reward evaluation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optimal levels of emotional arousal in experiential therapy of depression.

Objective: To determine the relationship between length of time spent expressing highly aroused emotion and therapeutic outcome. Method: Thirty-eight clients (14 male, 24 female) between the ages of 22 and 60 years (M = 39.5, SD = 9.71), treated for depression with experiential therapy, were rated on working alliance and expressed emotional arousal (with the Client Expressed Emotional Arousal Scale) in their three highest arousal sessions. Among the clients, 34 were of European ethnicity, 2 were of Asian ethnicity, 1 was of Latino ethnicity, and 1 was of Caribbean–Canadian ethnicity. Clients were administered the short form of the Working Alliance Inventory following their 4th therapy session and also completed, pre- and posttherapy, the Beck Depression Inventory (BDI), the Global Severity Index (GSI) of the Symptom Checklist–90–Revised (SCL-90-R), the Inventory of Interpersonal Problems, and the Rosenberg Self-Esteem Scale. Results: Hierarchical regressions showed that a nonlinear pattern of expressed emotional arousal predicted outcome significantly above the alliance. This combination predicted 30% of outcome variance on the BDI and 24% on the GSI (p     

Self-blocking of dislocations in intermetallic compound Ni<Subscript>3</Subscript>Ge: Cubic slip

Self-blocking of dislocations belonging to the cube plane has been detected in the intermetallic compound Ni₃Ge. The nature of cubic slip has been clarified. The experiments included deformation at a temperature above T _max (the temperature of the yield-stress peak) and subsequent heating without stress. In addition, changes in the dislocation structure upon slow cooling from the temperature of the preliminary deformation have been investigated; in doing so, self-blocking of dislocations has been revealed for the first time. Based on the totality of experimental data, a conclusion has been made on the two-valley potential relief for a dislocation motion in the cube plane. It is the difference in the depths between the Peierls valley (a diffuse core in the cube plane) and the deepest valley (a superpartial dislocation split in the octahedron plane) that provides for the driving force of self-blocking in the absence of an external stress. Different aspects of cubic slip have been considered: the disappearance of cubic slip at T < T _max and, correspondingly, the nonobservation of an anomalous behavior of the yield stress, as well as the disappearance of octahedral slip at T > T _max.