The Boolean power sequence of graphs

The adjacency matrix A of a graph G is a 0-1 matrix. The Boolean power sequence of A is convergent or periodic of period p = 2: The index y­ of A is the least integer m such that Am = Am+1 if A converges and the least integer m such that Am = Am+2 if A is periodic. In this paper we determine the index ­y of A if the graph G is bipartite. In the case of non-bipartite connected graphs, we give new lower and upper bounds for y , which are sharp.peer-reviewe

Phase-field modeling and simulation of fracture in brittle materials with strongly anisotropic surface energy

Crack propagation in brittle materials with anisotropic surface energy is important in applications involving single crystals, extruded polymers, or geological and organic materials. Furthermore, when this anisotropy is strong, the phenomenology of crack propagation becomes very rich, with forbidden crack propagation directions or complex sawtooth crack patterns. This problem interrogates fundamental issues in fracture mechanics, including the principles behind the selection of crack direction. Here, we propose a variational phase-field model for strongly anisotropic fracture, which resorts to the extended Cahn-Hilliard framework proposed in the context of crystal growth. Previous phase-field models for anisotropic fracture were formulated in a framework only allowing for weak anisotropy. We implement numerically our higher-order phase-field model with smooth local maximum entropy approximants in a direct Galerkin method. The numerical results exhibit all the features of strongly anisotropic fracture and reproduce strikingly well recent experimental observations.Peer ReviewedPostprint (author’s final draft

Verbal abuse and internalizing problems in early adolescence: negative attributional style as mediator

This study examined the contributions of verbal abuse to internalizing problems among 324 early adolescent students (aged 11-13 years) in Selangor, and the mediating role negative attributional style plays in this relationship. Students were selected using a cluster sampling method and responded to a self-administered questionnaire. Children.s Perception of Parental Verbal Aggression (CPPVA; Solomon & Serres, 1999), The Children.s Attributional Style Questionnaire (CASQ; Seligman et al., 1984) and Internalizing Symptoms Scale for Children (ISSC; Merrell & Walters, 1998) were used to measure the variables in this study. Data were analyzed using Baron and Kenny.s (1986) statistical framework for assessing the mediational effects. Findings suggest that negative attributional style partially mediates verbal abuse and internalizing problems. This study sheds light on how verbal abuse contributes to internalizing problems in Asian context. Implications for intervention and prevention work related to internalizing problems among early adolescent students are also discussed

The effect of alcohol use on neuroimaging correlates of cognitive and emotional processing in human adolescence.

ObjectiveThis article provides an overview of the scientific literature pertaining to the effects of alcohol on neural correlates of cognitive and emotional functioning, including reward processing and cue-reactivity, in adolescence and young adulthood.MethodPeer-reviewed, original research articles that included a neuroimaging assessment of alcohol effects on subsequent cognitive or emotional processing in adolescent or young adult samples were searched (through November 2018) and summarized in the review.ResultsCross-sectional studies provided early evidence of alcohol-related differences in neural processing across a number of cognitive domains. Longitudinal studies have identified neural abnormalities that predate drinking within most domains of cognitive functioning, while a few neural alterations have been observed within the domains of visual working memory, inhibitory control, reward processing, and cue-reactivity that appear to be related to the neurotoxic effect of alcohol use during adolescence. In contrast, neural correlates of emotion functioning appear to be relatively stable to the effects of alcohol.ConclusionsLarger prospective studies are greatly needed to disentangle premorbid factors from neural consequences associated with drinking, and to detect subsets of youth who may be particularly vulnerable to alcohol's effects on cognitive and emotional functioning. (PsycINFO Database Record (c) 2019 APA, all rights reserved)

Mechanical properties of La-based bulk amorphous alloy and composites

Influence of different microstructure of La-based fully amorphous samples and its composites on the impact fracture energy were investigated and discussed. Results showed improvement in fracture energy of glassy metals with the presence intermetallic phases, but deteriorated in the presence of dendrite phases and high volume % of crystalline phases.Singapore-MIT Alliance (SMA

Impact of the dicyanomethylene substitution position on the cyclophane macrocycle formation in carbazole-based biradicals

π-Conjugated biradical compounds, featuring unique unsaturated valences and radical centers in the ground state, are fundamentally important for understanding the nature of chemical bonds and have potential applications in material science. [1] Recently, it has been demonstrated that several -conjugated mono- and biradicals systems form long strain -bonds between two unpaired electrons resulting in macrocyclic or staircase oligomers or polymers by self-assembly processes. [2] Therefore, these materials are potential building blocks for dynamic covalent chemistry (DCC) since the aggregates can be formed or broken upon soft external stimuli. For instance, 2,7-dicyanomethylene-9-(2-ethylhexyl)carbazole biradical (p-Cz-alkyl in Figure 1) reversibly converts upon soft stimuli (temperature, pressure, light) to a cyclophane tetramer as a result from the formation (or bond cleavage) of long C-C single bonds.[3] Here, we present an experimental and theoretical study in order to investigate how the N-substitution and the change from para- to meta-dicyanomethylene substitution on carbazole-based biradicals affects their biradical character and thus, their tendency to act as useful motifs for DCC (see Figure 1).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

cDNA-RNA subtractive hybridization reveals increased expression of mycocerosic acid synthase in intracellular Mycobacterium bovis BCG.

Identifying genes that are differentially expressed by Mycobacterium bovis BCG after phagocytosis by macrophages will facilitate the understanding of the molecular mechanisms of host cell-intracellular pathogen interactions. To identify such genes a cDNA-total RNA subtractive hybridization strategy has been used that circumvents the problems both of limited availability of bacterial RNA from models of infection and the high rRNA backgrounds in total bacterial RNA. The subtraction products were used to screen a high-density gridded Mycobacterium tuberculosis genomic library. Sequence data were obtained from 19 differential clones, five of which contained overlapping sequences for the gene encoding mycocerosic acid synthase (mas). Mas is an enzyme involved in the synthesis of multi-methylated long-chain fatty acids that are part of phthiocerol dimycocerosate, a major component of the complex mycobacterial cell wall. Northern blotting and primer extension data confirmed up-regulation of mas in intracellular mycobacteria and also revealed a putative extended -10 promoter structure and a long untranslated upstream region 5' of the mas transcripts, containing predicted double-stranded structures. Furthermore, clones containing overlapping sequences for furB, groEL-2, rplE and fadD28 were identified and the up-regulation of these genes was confirmed by Northern blot analysis. The cDNA-RNA subtractive hybridization enrichment and high density gridded library screening, combined with selective extraction of bacterial mRNA represents a valuable approach to the identification of genes expressed during intra-macrophage residence for bacteria such as M. bovis BCG and the pathogenic mycobacterium, M. tuberculosis

Formation of stimuli-responsive cyclophanes by self-assembly: the case of carbazole-based biradicals

Dynamic covalent bonds has recently received lot of attention because of their unique feature to become reversible under mild conditions.[1] In this context, π-conjugated biradical compounds has emerged as essential building blocks.[2] For instance, we have demonstrated that 2,7-dicyanomethylene-9-(2-ethylhexyl)carbazole biradical reversibly converts to a macrocycle cyclophane upon soft stimuli (temperature, pressure, light), showing strong chromic effects.[3] We now extent this study towards longer conjugated carbazole backbone (i.e., indolocarbazole shown in Figure 1), aiming at investigating how the elongation of the conjugated backbone impacts on the formation of stimuli-responsive cyclophanes. The self-assembly process is investigated both in solution and solid state by linking theory and experiments.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech