Directed nonabelian sandpile models on trees

We define two general classes of nonabelian sandpile models on directed trees (or arborescences) as models of nonequilibrium statistical phenomena. These models have the property that sand grains can enter only through specified reservoirs, unlike the well-known abelian sandpile model. In the Trickle-down sandpile model, sand grains are allowed to move one at a time. For this model, we show that the stationary distribution is of product form. In the Landslide sandpile model, all the grains at a vertex topple at once, and here we prove formulas for all eigenvalues, their multiplicities, and the rate of convergence to stationarity. The proofs use wreath products and the representation theory of monoids.Comment: 43 pages, 5 figures; introduction improve

Markov chains, R\mathscr R-trivial monoids and representation theory

We develop a general theory of Markov chains realizable as random walks on $\mathscr R$-trivial monoids. It provides explicit and simple formulas for the eigenvalues of the transition matrix, for multiplicities of the eigenvalues via M\"obius inversion along a lattice, a condition for diagonalizability of the transition matrix and some techniques for bounding the mixing time. In addition, we discuss several examples, such as Toom-Tsetlin models, an exchange walk for finite Coxeter groups, as well as examples previously studied by the authors, such as nonabelian sandpile models and the promotion Markov chain on posets. Many of these examples can be viewed as random walks on quotients of free tree monoids, a new class of monoids whose combinatorics we develop.Comment: Dedicated to Stuart Margolis on the occasion of his sixtieth birthday; 71 pages; final version to appear in IJA

Listening to Their Voices: Middle Schoolers’ Perspectives of Life in Middle School

This article examines middle schoolers’ perspectives on their lives in middle school. Fifteen middle school students from three middle schools in the Southeast region of the United States participated in a basic qualitative study using focus groups at their schools where they were asked the central question, “If you could change one thing at your middle school, what would it be?” Findings show that students’ desire caring teachers, students want active classrooms, and students’ technology use impacts attitudes towards learning. Implications are that middle-school learning can increase relevance by teachers demonstrating care for students as individuals; structuring opportunities for students to interact with them and each other around real-world problems; and incorporating technology into learning in ways adolescents already use it

Kaliedescope of Opinions: Varying Perceptions of Public School Experience

Grounded theory and Phenomenological data analyses of information collected through interviews with administrators, teachers and students are used to understand how leadership responsibilities were distributed among school staff, how services to students with identified disabilities were delivered through response to intervention and inclusive practices, and how middle school students perceived themselves as consumers of education

Le conte au 18e siecle: pour une nouvelle esthetique

L'amour et le conte sont intrinsèquement liés depuis la naissance de ce genre à la définition impossible. Si les critiques ont tenté d'établir des catégories auxquelles le conte se plie (libertin, merveilleux, moral, réaliste, etc...), il est encore difficile de comprendre la place qu'il possède dans l'histoire littéraire du 18ème siècle et la façon dont l'amour participe à lui conférer une nouvelle esthétique. Trois auteurs en marge du clan philosophique, Crébillon fils, Marmontel et Rétif de la Bretonne se sont servis du conte pour véhiculer à la fois des idéaux en phase et en marge des Lumières, révélant la potentialité expérimentale d'un format encore considéré comme frivole et irrationnel. Au carrefour du théâtre, du roman et de son ancêtre le conte de fées, ce genre « mineur » redessine non seulement les contours du champ littéraire mais aussi ceux de la parole efficace. Cette étude entend montrer comment chez ces trois auteurs, la rhétorique de l'amour au sein du conte engage pour Crébillon fils un discours sur la connaissance, dont le clair-obscur régit l'esthétique. Pour Marmontel, le conte est un moyen de s'ancrer dans le champ littéraire de la mi siècle, en y inscrivant les valeurs bourgeoises émergentes et lui donnant une définition qui le détache du roman. Rétif, lui, fait du conte une véritable économie narrative qui au crépuscule de l'Ancien Régime promeut une valeur essentielle: le travail.Doctor of Philosoph

Children’s Mental Health: Recommendations for Research, Practice and Policy

A recent study documented a large increase in prescriptions of stimulants and antidepressants among preschoolers, and has prompted public and professional concern about the effects of mood-altering drugs on young children. In response, the White House announced a broad initiative on children’s mental health, including more government money for research, new labels on drugs for pediatric use, educational materials for parents, and a fall White House conference. To place these events in their larger context, this Issue Brief summarizes the findings of the Children’s Mental Health Alliance Project, which conducted a multidisciplinary consensus conference in November 1998 followed by a year-long dialogue with clinicians, researchers, and families

Studying the “New” Civil Judges

We know very little about the people and institutions that make up the bulk of the United States civil justice system: state judges and state courts. Our understanding of civil justice is based primarily on federal litigation and the decisions of appellate judges. Staggeringly little legal scholarship focuses on state courts and judges. We simply do not know what most judges are doing in their day-to-day courtroom roles or in their roles as institutional actors and managers of civil justice infrastructure. We know little about the factors that shape and influence judicial practices, let alone the consequences of those practices for courts, litigants, and the public. From top to bottom, we can describe and theorize about our existing civil justice system in only piecemeal ways. Given legal scholarship\u27s near-complete focus on federal civil courts, the stories we tell about the civil justice system may be based on assumptions and models that only apply in the rarefied world of federal court. Meanwhile, state judges and courts--which handle ninety-nine percent of all civil cases--are ripe for theoretical and empirical exploration.In response, we call for more research aimed at increasing our understanding of state civil courts and judges and offer a theoretical framework to support this work, one that reflects how state courts differ from federal courts. This framework is grounded in a core fact of American civil justice, one both easily observed and largely overlooked: the majority of parties in state civil courts are unrepresented. Given this new pro se reality, our theoretical framework identifies four novel assumptions to guide future research: (1) the adversary process is disappearing; (2) most state court business is still conducted through in-person interactions between judges and parties; (3) the judicial role is ethically ambiguous in pro se cases; and (4) a largely static body of written law has not kept pace with the evolving and dynamic issues facing state courts. Building on the growth of empiricism and empirically grounded theory in traditional legal scholarship and access to justice research, we call on scholars to develop theory and gather data to map the new reality of civil justice and judging in America, and suggest questions to guide future research

Latitudinal distribution of the solar wind properties in the low- and high-pressure regimes: Wind observations

International audienceThe solar wind properties depend on ?, the heliomagnetic latitude with respect to the heliospheric current sheet (HCS), more than on the heliographic latitude. We analyse the wind properties observed by Wind at 1 AU during about 2.5 solar rotations in 1995, a period close to the last minimum of solar activity. To determine ?, we use a model of the HCS which we fit to the magnetic sector boundary crossings observed by Wind. We find that the solar wind properties mainly depend on the modulus |?|. But they also depend on a local parameter, the total pressure (magnetic pressure plus electron and proton thermal pressure). Furthermore, whatever the total pressure, we observe that the plasma properties also depend on the time: the latitudinal gradients of the wind speed and of the proton temperature are not the same before and after the closest HCS crossing. This is a consequence of the dynamical stream interactions. In the low pressure wind, at low |?|, we find a clear maximum of the density, a clear minimum of the wind speed and of the proton temperature, a weak minimum of the average magnetic field strength, a weak maximum of the average thermal pressure, and a weak maximum of the average ß factor. This overdense sheet is embedded in a density halo. The latitudinal thickness is about 5° for the overdense sheet, and 20° for the density halo. The HCS is thus wrapped in an overdense sheet surrounded by a halo, even in the non-compressed solar wind. In the high-pressure wind, the plasma properties are less well ordered as functions of the latitude than in the low-pressure wind; the minimum of the average speed is seen before the HCS crossing. The latitudinal thickness of the high-pressure region is about 20°. Our observations are qualitatively consistent with the numerical model of Pizzo for the deformation of the heliospheric current sheet and plasma sheet

Egg on Hegranes: Geophysical Prospection, Coring, & Test Excavations—Report 2016

This report describes the 2016 archaeological work at the farm of Egg is in the southernmost part of Hegranes, North Iceland