Des coloriages de pavages super et superbes

II existe une vaste littérature sur le sujet des groupes de couleurs et des coloriages des motifs dans le plan [2, chapitre 8], [6], [8]. II est toutefois étrange qu’aucun de ces travaux ne semble porter directement sur les problèmes du coloriage des pavages comme tel. Plus particulièrernent, bien que les groupes de couleurs soient souvent présentés comme des groupes de symétrie de couleurs des pavages, un examen approfondi révélera que ce ne sont que les motifs des pavés du pavage qui sont considérés; d’autres propriétés essentielles d’un pavage tel que son type topologique et I’adjacence de certaines paires de pavés sont ignorées. Si, par contre, on en tient compte, plusieurs problèmes intéressants (et complexes) se présentent. Le but de cet article est d’aborder quelques-uns de ces problèmes. On s’intéressera plus particulièrement à ce qu’on appelle les super coloriages de pavages isoédriques. (On expliquera ci-dessous les termes essentiels.) Au-delà de I’intérêt mathématique, les super coloriages sont très attrayants d’un point devue esthétique et, à ce titre, ils ont été utilisés par des artistes comme M.C. Escher. En fait dans I’ensemble des collections publiées d’oeuvres d’Escher, tous les coloriages de pavages isoédriques sont super. (On peut consulter, par exemple, [ 1 , Planches E2-E23, E32-E31, E36-E51, E55, E62-E66, E70, E73-E79, E86, E88-E92, E94-E98, E l 02-E109, E116-E119, E124, E127, E128].) Ce fait fut à I’origine du présent article, il est la suite d’une présentation de I’auteur au Escher Symposium de Rome en mars 1985 (un rapport en a été donné dans les Comptes-rendus de cette rencontre [7]). Toutefois, dans I’intérêt du lecteur, on répétera ici la terminologie jugée essentielle et cette présentation sera auto-suffisante. L’auteurtient à exprimer sa reconnaissance à Marjorie Senechal et à Tom Wieting pour hi avoir suggéré les corrections à [6], et, plus particulièrement a Branko Grünbaum pour nos discussions utiles et les commentaires qu’il porta sur les versions préliminaires de cet article, commentaires qui menèrent à plusieurs améliorations.There exists an extensive literature concerning colour groups and the related colourings of the motifs of a plane pattern [2, Chapter 81, [6], [8]. It is strange that none of this work seems to refer directly to the problems of colouring tilings as such. To be more specific, though colour groups are often displayed as the colour symmetry groups of tilings, careful examination will show that it is only the patterns of the tiles in the tilings which are under consideration; other essential properties of a tiling such as its topological type, and the adjacencies of certain pairs of tiles, are ignored. If the latter are taken into account, several interesting (and difficult) problems emerge. It is the purpose of the present paper to consider some of these. In particular, we shall be concerned with what are called super colourings of isohedral tilings. (These words and other essential terminology, will be explained shortly.) Besides being mathematically interesting, super colourings are very attractive from an aesthetic point of view, and have been used by artists such as M.C. Escher. In fact, in the published collections of Escher’s works, all his colourings of isohedral tilings are super. (See, for example, [ l , Plates E2-E23, E32-E31, E36-E51, E55, E62-E66, E70, E73-E79, E86, E88-E92, E94-E98, E102-E109, E l 16-El 19, E 124, E 127, E 1281.) This fact motivated the present paper, which isasequel to the talkgiven bythe authoratthe ExherSymposium in Rome in March 1985, and reported in the Proceedings of that meeting [7]. However, for the convenience of the reader, essential terminology will be repeated here and the presentation will be self-contained. The author wishes to express his gratitude to Marjorie Senechal and Tom Wieting for supplying him with corrections to [6], and, more especially to Branko Grunbaum for helpful discussions and for his comments on preliminary versions of this paper which led to many improvements.Peer Reviewe

Transcriptional profiling of colicin-induced cell death of Escherichia coli MG1655 identifies potential mechanisms by which bacteriocins promote bacterial diversity

We report the transcriptional response of Escherichia coli MG1655 to damage induced by colicins E3 and E9, bacteriocins that kill cells through inactivation of the ribosome and degradation of chromosomal DNA, respectively. Colicin E9 strongly induced the LexA-regulated SOS response, while colicin E3 elicited a broad response that included the induction of cold shock genes, symptomatic of translational arrest. Colicin E3 also increased the transcription of cryptic prophage genes and other laterally acquired mobile elements. The transcriptional responses to both these toxins suggest mechanisms that may promote genetic diversity in E. coli populations, pointing to a more general role for colicins in adaptive bacterial physiology than has hitherto been realized

Structural Congruency of Ligand Binding to the Insulin and Insulin/Type 1 Insulin-like Growth Factor Hybrid Receptors

SummaryThe homodimeric insulin and type 1 insulin-like growth factor receptors (IR and IGF-1R) share a common architecture and each can bind all three ligands within the family: insulin and insulin-like growth factors I and II (IGF-I and IFG-II). The receptor monomers also assemble as heterodimers, the primary ligand-binding sites of which each comprise the first leucine-rich repeat domain (L1) of one receptor type and an α-chain C-terminal segment (αCT) of the second receptor type. We present here crystal structures of IGF-I bound to such a hybrid primary binding site and of a ligand-free version of an IR αCT peptide bound to an IR L1 plus cysteine-rich domain construct (IR310.T). These structures, refined at 3.0-Å resolution, prove congruent to respective existing structures of insulin-complexed IR310.T and the intact apo-IR ectodomain. As such, they provide key missing links in the emerging, but sparse, repertoire of structures defining the receptor family

The salience of children increases adult prosocial values

Organizations often put children front and center in campaigns to elicit interest and support for prosocial causes. Such initiatives raise a key theoretical and applied question that has yet to be addressed directly: Does the salience of children increase prosocial motivation and behavior in adults? We present findings aggregated across eight experiments involving 2,054 adult participants: Prosocial values became more important after completing tasks that made children salient compared to tasks that made adults (or a mundane event) salient or compared to a no-task baseline. An additional field study showed that adults were more likely to donate money to a child-unrelated cause when children were more salient on a shopping street. The findings suggest broad, reliable interconnections between human mental representations of children and prosocial motives, as the child salience effect was not moderated by participants’ gender, age, attitudes, or contact with children

Mutations in FRMD7, a newly identified member of the FERM family, cause X-linked idiopathic congenital nystagmus.

Idiopathic congenital nystagmus is characterized by involuntary, periodic, predominantly horizontal oscillations of both eyes. We identified 22 mutations in FRMD7 in 26 families with X-linked idiopathic congenital nystagmus. Screening of 42 singleton cases of idiopathic congenital nystagmus (28 male, 14 females) yielded three mutations (7%). We found restricted expression of FRMD7 in human embryonic brain and developing neural retina, suggesting a specific role in the control of eye movement and gaze stability

Effects of alteplase for acute stroke according to criteria defining the European Union and United States marketing authorizations : Individual-patient-data meta-analysis of randomized trials

Background The recommended maximum age and time window for intravenous alteplase treatment of acute ischemic stroke differs between the Europe Union and United States. Aims We compared the effects of alteplase in cohorts defined by the current Europe Union or United States marketing approval labels, and by hypothetical revisions of the labels that would remove the Europe Union upper age limit or extend the United States treatment time window to 4.5h. Methods We assessed outcomes in an individual-patient-data meta-analysis of eight randomized trials of intravenous alteplase (0.9mg/kg) versus control for acute ischemic stroke. Outcomes included: excellent outcome (modified Rankin score 0-1) at 3-6 months, the distribution of modified Rankin score, symptomatic intracerebral hemorrhage, and 90-day mortality. Results Alteplase increased the odds of modified Rankin score 0-1 among 2449/6136 (40%) patients who met the current European Union label and 3491 (57%) patients who met the age-revised label (odds ratio 1.42, 95% CI 1.21-1.68 and 1.43, 1.23-1.65, respectively), but not in those outside the age-revised label (1.06, 0.90-1.26). By 90 days, there was no increased mortality in the current and age-revised cohorts (hazard ratios 0.98, 95% CI 0.76-1.25 and 1.01, 0.86-1.19, respectively) but mortality remained higher outside the age-revised label (1.19, 0.99-1.42). Similarly, alteplase increased the odds of modified Rankin score 0-1 among 1174/6136 (19%) patients who met the current US approval and 3326 (54%) who met a 4.5-h revised approval (odds ratio 1.55, 1.19-2.01 and 1.37, 1.17-1.59, respectively), but not for those outside the 4.5-h revised approval (1.14, 0.97-1.34). By 90 days, no increased mortality remained for the current and 4.5-h revised label cohorts (hazard ratios 0.99, 0.77-1.26 and 1.02, 0.87-1.20, respectively) but mortality remained higher outside the 4.5-h revised approval (1.17, 0.98-1.41). Conclusions An age-revised European Union label or 4.5-h-revised United States label would each increase the number of patients deriving net benefit from alteplase by 90 days after acute ischemic stroke, without excess mortality.Peer reviewe

Demystifying academics to enhance university-business collaborations in environmental science

In countries globally there is intense political interest in fostering effective university-business collaborations, but there has been scant attention devoted to exactly how an individual scientist's workload (i.e. specified tasks) and incentive structures (i.e. assessment criteria) may act as a key barrier to this. To investigate this an original, empirical dataset is derived from UK job specifications and promotion criteria, which distil universities' varied drivers into requirements upon academics. This work reveals the nature of the severe challenge posed by a heavily time-constrained culture; specifically, tension exists between opportunities presented by working with business and non-optional duties (e.g. administration and teaching). Thus, to justify the time to work with business, such work must inspire curiosity and facilitate future novel science in order to mitigate its conflict with the overriding imperative for academics to publish. It must also provide evidence of real-world changes (i.e. impact), and ideally other reportable outcomes (e.g. official status as a business' advisor), to feed back into the scientist's performance appraisals. Indicatively, amid 20-50 key duties, typical full-time scientists may be able to free up to 0.5 day per week for work with business. Thus specific, pragmatic actions, including short-term and time-efficient steps, are proposed in a "user guide"to help initiate and nurture a long-term collaboration between an early- to mid-career environmental scientist and a practitioner in the insurance sector. These actions are mapped back to a tailored typology of impact and a newly created representative set of appraisal criteria to explain how they may be effective, mutually beneficial and overcome barriers. Throughout, the focus is on environmental science, with illustrative detail provided through the example of natural hazard risk modelling in the insurance sector. However, a new conceptual model of academics' behaviour is developed, fusing perspectives from literature on academics' motivations and performance assessment, which we propose is internationally applicable and transferable between sectors. Sector-specific details (e.g. list of relevant impacts and user guide) may serve as templates for how people may act differently to work more effectively together