Rétractions, corétractions et enveloppe injective d'une algèbre de transitions

AbstractThe notions of retraction and injectivity have been useful in the study of many categories (category of modules over a ring, category of posets, category of metric spaces over an Heyting albegra ...).In this article the category of Σ-transition algebras is considered, and in this frame, answers are given to the key questions related to these notions. For instance it is shown:—how to construct all the retraction types of a given Σ-transition algebra.—that the category of Σ-transition algebras has enough injective objects and an injective cogenerator.—that every Σ-transition algebras has an injective envelope.These allow to obtain results concerning the structure and the decomposition of a Σ-transition algebra

A one-sided Prime Ideal Principle for noncommutative rings

Completely prime right ideals are introduced as a one-sided generalization of the concept of a prime ideal in a commutative ring. Some of their basic properties are investigated, pointing out both similarities and differences between these right ideals and their commutative counterparts. We prove the Completely Prime Ideal Principle, a theorem stating that right ideals that are maximal in a specific sense must be completely prime. We offer a number of applications of the Completely Prime Ideal Principle arising from many diverse concepts in rings and modules. These applications show how completely prime right ideals control the one-sided structure of a ring, and they recover earlier theorems stating that certain noncommutative rings are domains (namely, proper right PCI rings and rings with the right restricted minimum condition that are not right artinian). In order to provide a deeper understanding of the set of completely prime right ideals in a general ring, we study the special subset of comonoform right ideals.Comment: 38 page

Perspectives from parents of autistic children on participating in early intervention and associated research

Early support should help autistic children lead flourishing lives. We sought to understand parents’ experiences of their children’s involvement in early intervention and associated research, through focus groups with 23 parents (of 22 children) enrolled in a university-affiliated service. Reflexive thematic analysis revealed four themes. Parents conveyed a strong sense of gratitude (Theme 1) arising from their perceptions of the importance of early intervention and feelings of having ‘hit the jackpot’ to secure access to the service from which they perceived their children ‘gained so much’. They valued the service and staff expertise which made them feel secure (Theme 2). University affiliation and the associated research also contributed to parents’ sense of safety, from perceived ‘accountability’ and ‘integrity’. Parents conveyed deep commitment to the service (Theme 3) but shared often-negative experiences as their child’s enrolment came to an end (Theme 4) and they expressed feelings of abandonment and disempowerment, being confronted with the reality of needing to secure next-stage support for their children and of perceived critical need for ‘conversion of research into practice’. These parents’ accounts offer insights into the benefits and ongoing challenges of achieving truly effective supports for autistic preschoolers and their families. Lay abstract: Support for autistic children early in life should help them to lead flourishing lives. However, many of the early intervention programmes for young autistic children are time-consuming and costly for families. These programmes are also often conducted in settings that are not closely matched to real life. We spoke to 23 parents (of 22 autistic children) to understand their experiences of their children’s involvement in early intervention. Parents told us they were grateful for the opportunity, that they had ‘hit the jackpot’, and their children had ‘gained so much’ from the programme. They seemed to value the service because it made them feel safe and secure during an uncertain time in their children’s lives. Parents told us they trusted staff, felt that they weren’t ‘doing it alone’, and this ‘took that pressure off’ and helped them feel empowered. They also spoke of feelings of safety from being linked to the university research programme which offered ‘accountability’ and ‘integrity’. Parents’ comments showed a strong commitment to the early intervention model and staff – but also common feelings of abandonment and disempowerment as their child’s time with the programme came to an end and they went ‘back to the real world’ and needed to find new supports for their children. These parents’ insights should help to inform the design and delivery of community supports for preschool-aged autistic children and their families, which match the reality of their lived experiences

Selection of an Efficient AAV Vector for Robust CNS Transgene Expression

Adeno-associated virus (AAV) capsid libraries have generated improved transgene delivery vectors. We designed an AAV library construct, iTransduce, that combines a peptide library on the AAV9 capsid with a Cre cassette to enable sensitive detection of transgene expression. After only two selection rounds of the library delivered intravenously in transgenic mice carrying a Cre-inducible fluorescent protein, we flow sorted fluorescent cells from brain, and DNA sequencing revealed two dominant capsids. One of the capsids, termed AAV-F, mediated transgene expression in the brain cortex more than 65-fold (astrocytes) and 171-fold (neurons) higher than the parental AAV9. High transduction efficiency was sex-independent and sustained in two mouse strains (C57BL/6 and BALB/c), making it a highly useful capsid for CNS transduction of mice. Future work in large animal models will test the translation potential of AAV-F

On the ensemble of optimal identifying codes in a twin-free graph

Let G = (V, E) be a graph. For v is an element of V and r >= 1, we denote by B-G,B- r (v) the ball of radius r and centre v. A set C subset of V is said to be an r-identifying code if the sets B-G,B- r (v) boolean AND C, v is an element of V, are all nonempty and distinct. A graph G which admits an r-identifying code is called r-twin-free, and in this case the smallest size of an r-identifying code is denoted by gamma(r)(G). We study the ensemble of all the different optimal r-identifying codes C, i.e., such that broken vertical bar C broken vertical bar = gamma(r)(G). We show that, given any collection A of k-subsets of V-1 = {1, 2, . . . , n}, there is a positive integer m, a graph G = (V, E) with V = V-1 boolean OR V-2, where V-2 = {n + 1, . . . , n + m}, and a set S subset of V-2 such that C subset of V is an optimal r-identifying code in G if, and only if, C = A boolean OR S for some A is an element of A. This result gives a direct connection with induced subgraphs of Johnson graphs, which are graphs with vertex set a collection of k-subsets of V1, with edges between any two vertices sharing k - 1 elements

The importance of the eyes: communication skills in infants of blind parents

The effects of selectively different experience of eye contact and gaze behaviour on the early development of five sighted infants of blind parents were investigated. Infants were assessed longitudinally at 6–10, 12–15 and 24–47 months. Face scanning and gaze following were assessed using eye tracking. In addition, established measures of autistic-like behaviours and standardized tests of cognitive, motor and linguistic development, as well as observations of naturalistic parent–child interaction were collected. These data were compared with those obtained from a larger group of sighted infants of sighted parents. Infants with blind parents did not show an overall decrease in eye contact or gaze following when they observed sighted adults on video or in live interactions, nor did they show any autistic-like behaviours. However, they directed their own eye gaze somewhat less frequently towards their blind mothers and also showed improved performance in visual memory and attention at younger ages. Being reared with significantly reduced experience of eye contact and gaze behaviour does not preclude sighted infants from developing typical gaze processing and other social-communication skills. Indeed, the need to switch between different types of communication strategy may actually enhance other skills during development

Brain dynamics of meal size selection in humans.

Although neuroimaging research has evidenced specific responses to visual food stimuli based on their nutritional quality (e.g., energy density, fat content), brain processes underlying portion size selection remain largely unexplored. We identified spatio-temporal brain dynamics in response to meal images varying in portion size during a task of ideal portion selection for prospective lunch intake and expected satiety. Brain responses to meal portions judged by the participants as 'too small', 'ideal' and 'too big' were measured by means of electro-encephalographic (EEG) recordings in 21 normal-weight women. During an early stage of meal viewing (105-145ms), data showed an incremental increase of the head-surface global electric field strength (quantified via global field power; GFP) as portion judgments ranged from 'too small' to 'too big'. Estimations of neural source activity revealed that brain regions underlying this effect were located in the insula, middle frontal gyrus and middle temporal gyrus, and are similar to those reported in previous studies investigating responses to changes in food nutritional content. In contrast, during a later stage (230-270ms), GFP was maximal for the 'ideal' relative to the 'non-ideal' portion sizes. Greater neural source activity to 'ideal' vs. 'non-ideal' portion sizes was observed in the inferior parietal lobule, superior temporal gyrus and mid-posterior cingulate gyrus. Collectively, our results provide evidence that several brain regions involved in attention and adaptive behavior track 'ideal' meal portion sizes as early as 230ms during visual encounter. That is, responses do not show an increase paralleling the amount of food viewed (and, in extension, the amount of reward), but are shaped by regulatory mechanisms