Deterministic meeting of sniffing agents in the plane

Two mobile agents, starting at arbitrary, possibly different times from arbitrary locations in the plane, have to meet. Agents are modeled as discs of diameter 1, and meeting occurs when these discs touch. Agents have different labels which are integers from the set of 0 to L-1. Each agent knows L and knows its own label, but not the label of the other agent. Agents are equipped with compasses and have synchronized clocks. They make a series of moves. Each move specifies the direction and the duration of moving. This includes a null move which consists in staying inert for some time, or forever. In a non-null move agents travel at the same constant speed, normalized to 1. We assume that agents have sensors enabling them to estimate the distance from the other agent (defined as the distance between centers of discs), but not the direction towards it. We consider two models of estimation. In both models an agent reads its sensor at the moment of its appearance in the plane and then at the end of each move. This reading (together with the previous ones) determines the decision concerning the next move. In both models the reading of the sensor tells the agent if the other agent is already present. Moreover, in the monotone model, each agent can find out, for any two readings in moments t1 and t2, whether the distance from the other agent at time t1 was smaller, equal or larger than at time t2. In the weaker binary model, each agent can find out, at any reading, whether it is at distance less than \r{ho} or at distance at least \r{ho} from the other agent, for some real \r{ho} > 1 unknown to them. Such distance estimation mechanism can be implemented, e.g., using chemical sensors. Each agent emits some chemical substance (scent), and the sensor of the other agent detects it, i.e., sniffs. The intensity of the scent decreases with the distance.Comment: A preliminary version of this paper appeared in the Proc. 23rd International Colloquium on Structural Information and Communication Complexity (SIROCCO 2016), LNCS 998

Gathering in Dynamic Rings

The gathering problem requires a set of mobile agents, arbitrarily positioned at different nodes of a network to group within finite time at the same location, not fixed in advanced. The extensive existing literature on this problem shares the same fundamental assumption: the topological structure does not change during the rendezvous or the gathering; this is true also for those investigations that consider faulty nodes. In other words, they only consider static graphs. In this paper we start the investigation of gathering in dynamic graphs, that is networks where the topology changes continuously and at unpredictable locations. We study the feasibility of gathering mobile agents, identical and without explicit communication capabilities, in a dynamic ring of anonymous nodes; the class of dynamics we consider is the classic 1-interval-connectivity. We focus on the impact that factors such as chirality (i.e., a common sense of orientation) and cross detection (i.e., the ability to detect, when traversing an edge, whether some agent is traversing it in the other direction), have on the solvability of the problem. We provide a complete characterization of the classes of initial configurations from which the gathering problem is solvable in presence and in absence of cross detection and of chirality. The feasibility results of the characterization are all constructive: we provide distributed algorithms that allow the agents to gather. In particular, the protocols for gathering with cross detection are time optimal. We also show that cross detection is a powerful computational element. We prove that, without chirality, knowledge of the ring size is strictly more powerful than knowledge of the number of agents; on the other hand, with chirality, knowledge of n can be substituted by knowledge of k, yielding the same classes of feasible initial configurations

Differences in designations of observation care in US freestanding children's hospitals: Are they virtual or real?

OBJECTIVE: To characterize practices related to observation care and to examine the current models of pediatric observation medicine in US children's hospitals. DESIGN: We utilized 2 web‐based surveys to examine observation care in the 42 hospitals participating in the Pediatric Health Information System database. We obtained information regarding the designation of observation status, including the criteria used to admit patients into observation. From hospitals reporting the use of observation status, we requested specific details relating to the structures of observation care and the processes of care for observation patients following emergency department treatment. RESULTS: A total of 37 hospitals responded to Survey 1, and 20 hospitals responded to Survey 2. Designated observation units were present in only 12 of 31 (39%) hospitals that report observation patient data to the Pediatric Health Information System. Observation status was variably defined in terms of duration of treatment and prespecified criteria. Observation periods were limited to <48 hours in 24 of 31 (77%) hospitals. Hospitals reported that various standards were used by different payers to determine observation status reimbursement. Observation care was delivered in a variety of settings. Most hospitals indicated that there were no differences in the clinical care delivered to virtual observation status patients when compared with other inpatients. CONCLUSIONS: Observation is a variably applied patient status, defined differently by individual hospitals. Consistency in the designation of patients under observation status among hospitals and payers may be necessary to compare quality outcomes and costs, as well as optimize models of pediatric observation care. Journal of Hospital Medicine 2012;. © 2011 Society of Hospital Medicine.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91108/1/949_ftp.pd

Almost optimal asynchronous rendezvous in infinite multidimensional grids

Two anonymous mobile agents (robots) moving in an asynchronous manner have to meet in an infinite grid of dimension δ&gt; 0, starting from two arbitrary positions at distance at most d. Since the problem is clearly infeasible in such general setting, we assume that the grid is embedded in a δ-dimensional Euclidean space and that each agent knows the Cartesian coordinates of its own initial position (but not the one of the other agent). We design an algorithm permitting the agents to meet after traversing a trajectory of length O(d δ polylog d). This bound for the case of 2d-grids subsumes the main result of [12]. The algorithm is almost optimal, since the Ω(d δ) lower bound is straightforward. Further, we apply our rendezvous method to the following network design problem. The ports of the δ-dimensional grid have to be set such that two anonymous agents starting at distance at most d from each other will always meet, moving in an asynchronous manner, after traversing a O(d δ polylog d) length trajectory. We can also apply our method to a version of the geometric rendezvous problem. Two anonymous agents move asynchronously in the δ-dimensional Euclidean space. The agents have the radii of visibility of r1 and r2, respectively. Each agent knows only its own initial position and its own radius of visibility. The agents meet when one agent is visible to the other one. We propose an algorithm designing the trajectory of each agent, so that they always meet after traveling a total distance of O( ( d)), where r = min(r1, r2) and for r ≥ 1. r)δpolylog ( d r

p-wave triggered superconductivity in single-layer graphene on an electron-doped oxide superconductor

Electron pairing in the vast majority of superconductors follows the Bardeen-Cooper-Schrieffer theory of superconductivity, which describes the condensation of electrons into pairs with antiparallel spins in a singlet state with an s-wave symmetry. Unconventional superconductivity was predicted in single-layer graphene (SLG), with the electrons pairing with a $\textit{p}$-wave or chiral d-wave symmetry, depending on the position of the Fermi energy with respect to the Dirac point. By placing SLG on an electron-doped (non-chiral) d-wave superconductor and performing local scanning tunnelling microscopy and spectroscopy, here we show evidence for a $\textit{p}$-wave triggered superconducting density of states in SLG. The realization of unconventional superconductivity in SLG offers an exciting new route for the development of p-wave superconductivity using two-dimensional materials with transition temperatures above 4.2 K.The work was funded by the following agencies: Royal Society (‘Superconducting Spintronics’), Leverhulme Trust (IN-2013-033), Schiff Foundation, the EPSRC (EP/N017242/1, EP/G037221/1, EP/K01711X/1, EP/K017144/1, EP/N010345/1, EP/M507799/1, EP/L016087/1), ERC Grant Hetero2D, EU Graphene Flagship, COST Action MP-1201, MSCA-IFEF-ST No. 656485-Spin3, Outstanding Academic Fellows programme at NTNU, Research Council of Norway (205591, 216700 and 24080)

Recurrent and High‐frequency Use of the Emergency Department by Pediatric Patients

Objectives The authors sought to describe the epidemiology of and risk factors for recurrent and high‐frequency use of the emergency department (ED) by children. Methods This was a retrospective cohort study using a database of children aged 0 to 17 years, inclusive, presenting to 22 EDs of the Pediatric Emergency Care Applied Research Network (PECARN) during 2007, with 12‐month follow‐up after each index visit. ED diagnoses for each visit were categorized as trauma, acute medical, or chronic medical conditions. Recurrent visits were defined as any repeat visit; high‐frequency use was defined as four or more recurrent visits. Generalized estimating equations (GEEs) were used to measure the strength of associations between patient and visit characteristics and recurrent ED use. Results A total of 695,188 unique children had at least one ED visit each in 2007, with 455,588 recurrent ED visits in the 12 months following the index visits. Sixty‐four percent of patients had no recurrent visits, 20% had one, 8% had two, 4% had three, and 4% had four or more recurrent visits. Acute medical diagnoses accounted for most visits regardless of the number of recurrent visits. As the number of recurrent visits per patient rose, chronic diseases were increasingly represented, with asthma being the most common ED diagnosis. Trauma‐related diagnoses were more common among patients without recurrent visits than among those with high‐frequency recurrent visits (28% vs. 9%; p < 0.001). High‐frequency recurrent visits were more often within the highest severity score classifications. In multivariable analysis, recurrent visits were associated with younger age, black or Hispanic race or ethnicity, and public health insurance. Conclusions Risk factors for recurrent ED use by children include age, race and ethnicity, and insurance status. Although asthma plays an important role in recurrent ED use, acute illnesses account for the majority of recurrent ED visits. Resumen Objetivos Describir la epidemiología y los factores de riesgo de revista e hiperfrecuentación del servicio de urgencias (SU) por parte de los pacientes pediátricos. Metodología Estudio de cohorte retrospectivo mediante una base de datos de niños entre 0 y 17 años inclusive, que acudieron a 22 SU de la Pediatric Emergency Care Applied Research Network durante 2007, con un seguimiento de 12 meses tras cada visita índice. Los diagnósticos del SU de cada visita se clasificaron como traumatológico, médico agudo o enfermedades médicas crónicas. Las revisitas se definieron como cualquier visita repetida; la hiperfrecuentación se definió como cuatro o más revisitas. Se utilizaron ecuaciones de estimación generalizada para medir la fuerza de las asociaciones entre las características al paciente y la visita y la revisita del SU. Resultados Un total de 695.188 niños tuvieron al menos una visita al SU en 2007, con 455.588 revisitas al SU en los 12 meses tras las visitas índice. Un 64% de los pacientes no tuvieron revisitas, un 20% tuvo una, un 8% tuvo dos, un 4% tuvo tres y un 4% tuvo cuatro o más revisitas. Los diagnósticos médicos agudos representan la mayoría de las visitas, con independencia del número de revisitas. A medida que el número de revisitas por paciente aumentaba, las enfermedades crónicas estaban más representadas, y el asma fue el diagnóstico más común en el SU. Los diagnósticos relacionados con lo traumatológico fueron más frecuentes entre los pacientes sin revisitas que entre aquéllos con hiperfrecuentación (28% vs. 9%; p < 0,001). La alta frecuencia de revisitas fue más frecuente en las clasificaciones de gravedad más altas. En el análisis multivariable, las revisitas se asociaron con una edad más joven, raza o etnia negra o hispana, y la tenencia de un seguro de salud público. Conclusiones Los factores de riesgo para la revisita al SU por los niños incluyen la edad, la raza o etnia, y el tipo de seguro médico. Aunque el asma juega un papel importante en la revisita al SU, las enfermedades agudas representan la mayoría de la revistas al SU.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106853/1/acem12347.pd

Composing first species counterpoint with a variable neighbourhood search algorithm

In this article, a variable neighbourhood search (VNS) algorithm is developed that can generate musical fragments consisting of a melody for the cantus firmus and the first species counterpoint. The objective function of the algorithm is based on a quantification of existing rules for counterpoint. The VNS algorithm developed in this article is a local search algorithm that starts from a randomly generated melody and improves it by changing one or two notes at a time. A thorough parametric analysis of the VNS reveals the significance of the algorithm's parameters on the quality of the composed fragment, as well as their optimal settings. A comparison of the VNS algorithm with a developed genetic algorithm shows that the VNS is more efficient. The VNS algorithm has been implemented in a user-friendly software environment for composition, called Optimuse. Optimuse allows a user to specify a number of characteristics such as length, key and mode. Based on this information, Optimuse 'composes' both cantus firmus and first species counterpoint. Alternatively, the user may specify a cantus firmus, and let Optimuse compose the accompanying first species counterpoint. © 2012 Taylor & Francis

Experiences of Female Educational Leaders as Examined Through Interpretive Inquiry

This study explored the following question: How do female educational leaders experience educational leadership? The research focused on the practices of three female educational leaders and explored their perspectives over a period of single school year. I gathered data using one-on-one semistructured interviews. I then analyzed the data through the use of interpretive thematic analysis. The themes I created related to barriers women educational leaders face. Women are experiencing success within the field of educational leadership but require support and mentorship. In spite of the availability of numerous preparation programs, female educational leaders are nonetheless often feeling unprepared and overwhelmed in their positions. These women also continue to live in gendered and socialized educational environments that impact their practice, experience, and personal growth, and while these barriers exist, women are developing ideologies and ways of leading that circumvent these barriers and allow for success in their leadership roles. This study found that in spite of the gains made by women towards equality, inequality is persistent and ongoing. I discussed these themes in relation to the shared experiences of the participants. Further research is needed to understand how gendered roles affect this inequality and how to alleviate ongoing barriers to success for all women in educational leadership.

Size constancy is preserved but afterimages are prolonged in typical individuals with higher degrees of self-reported autistic traits

Deficits in perceptual constancies from early infancy have been proposed to contribute to autism and exacerbate its symptoms (Hellendoorn et al., Frontiers in Psychology 6:1–16, 2015). Here, we examined size constancy in adults from the general population (N = 106) with different levels of self-reported autistic traits using an approach based on negative afterimages. The afterimage strength, as indexed by duration and vividness, was also quantified. In opposition to the Hellendoorn and colleagues’ model, we were unable to demonstrate any kind of relationship between abilities in size constancy and autistic traits. However, our results demonstrated that individuals with higher degrees of autistic traits experienced more persistent afterimages. We discuss possible retinal and post-retinal explanations for prolonged afterimages in people with higher levels of autistic traits