The symplectic Deligne-Mumford stack associated to a stacky polytope

We discuss a symplectic counterpart of the theory of stacky fans. First, we define a stacky polytope and construct the symplectic Deligne-Mumford stack associated to the stacky polytope. Then we establish a relation between stacky polytopes and stacky fans: the stack associated to a stacky polytope is equivalent to the stack associated to a stacky fan if the stacky fan corresponds to the stacky polytope.Comment: 20 pages; v2: To appear in Results in Mathematic

On Non-Abelian Symplectic Cutting

We discuss symplectic cutting for Hamiltonian actions of non-Abelian compact groups. By using a degeneration based on the Vinberg monoid we give, in good cases, a global quotient description of a surgery construction introduced by Woodward and Meinrenken, and show it can be interpreted in algebro-geometric terms. A key ingredient is the `universal cut' of the cotangent bundle of the group itself, which is identified with a moduli space of framed bundles on chains of projective lines recently introduced by the authors.Comment: Various edits made, to appear in Transformation Groups. 28 pages, 8 figure

976-14 Immediate Heart Rate Response to Orthostatic Stress During β-blocker Therapy for Vasodepressor Syncope

Although β-blockers are preferred agents for therapy of vasodepressor syncope (VDS), they are not uniformly effective and their mechanism of action is incompletely understood. Since we have previously shown a differential therapeutic response to β-blocker therapy between pts with isoproterenol-independent [iso(-)] and isoproterenol-dependent [iso(+)] VDS during tilt table testing we sought to determine whether this was due to a differential heart rate (HR) response to orthostasis during β-blockade. We therefore examined immediate HR and blood pressure responses to upright tilt before and after initiation of therapy with atenolol (12.5–50mg daily) in 62 pts with VDS and positive tilt tests. The protocol comprised upright tilt (60°) for up to 60min followed by repeat tilt for 15min during isoproterenol (iso) infusion. Supine HR, mean arterial pressure (MAP) and pulse pressure (PP) were determined as the mean of 3 consecutive 1-min samples during supine rest; orthostatic HR, MAP, and PP were the mean of the samples recorded in the first 3min after upright tilt (before infusion of iso). Response to atenolol required completion of tilt with and without infusion of iso. There were 15 iso(-) pts and 47 iso(+) pts. The groups did not differ significantly in blood pressure response (MAP, PP) to orthostasis. Supine HR fell and the ΔHR in response to orthostasis was blunted during therapy in both groups:Baseline (Mean ± SD)Rx (Mean ± SD)Iso(+)Iso(-)pIso(+)Iso(-)pSupine HR69±1368±9NS57±958±8NSOrthostatic ΔHR8±712±9NS3±53±4NS11 iso(-) pts (73%) had a therapeutic response to β-blockade compared with 46 iso(+) pts (98%, p=0.01); the orthostatic ΔHR in the iso(-) pts who failed β-blocker therapy was no different from the response in the patients with a therapeutic response.ConclusionsThe HR response to orthostasis is comparably blunted after β-blockade in pts with iso(-) and iso(+) VDS, indicating that failure to respond is not due to inadequate β-blockade and suggests that in some pts iso-independent VDS may be independent of a cardiac β1 receptor mediated mechanism

Short Communications: First tracking of individual American Robins (Turdus migratorius) across seasons

The American Robin (Turdus migratorius) is one of the most widespread, common bird species in North America; yet, very little is known about its migratory connectivity, migration timing, and migratory routes. Using archival GPS tags, we tracked the movements of 7 individual robins from 3 breeding populations in the United States. Four robins captured in Denali National Park and Preserve, Alaska, overwintered in Texas, Nebraska, Oklahoma, and Montana, up to 4,500 km from the capture location. One robin captured in Amherst, Massachusetts, overwintered in South Carolina 1,210 km from the capture location, whereas 2 robins captured in Washington, D.C., spent the entire year within 6 km of their original capture location. Understanding the annual cycle and differences in migration strategies for a species that exhibits large regional variation in movement has the potential to provide novel insights into how conspecific populations respond to current and future heterogeneity in climate and habitat. The regionspecific patterns presented here suggest robins could serve as sentinels of environmental change at a continental scale

Adaptive Boolean Networks and Minority Games with Time--Dependent Capacities

In this paper we consider a network of boolean agents that compete for a limited resource. The agents play the so called Generalized Minority Game where the capacity level is allowed to vary externally. We study the properties of such a system for different values of the mean connectivity $K$ of the network, and show that the system with K=2 shows a high degree of coordination for relatively large variations of the capacity level.Comment: 4 pages, 4 figure

Lateral Separation of Macromolecules and Polyelectrolytes in Microlithographic Arrays

A new approach to separation of a variety of microscopic and mesoscopic objects in dilute solution is presented. The approach takes advantage of unique properties of a specially designed separation device (sieve), which can be readily built using already developed microlithographic techniques. Due to the broken reflection symmetry in its design, the direction of motion of an object in the sieve varies as a function of its self-diffusion constant, causing separation transverse to its direction of motion. This gives the device some significant and unique advantages over existing fractionation methods based on centrifugation and electrophoresis.Comment: 4 pages with 3 eps figures, needs RevTeX 3.0 and epsf, also available in postscript form http://cmtw.harvard.edu/~deniz

Contact complete integrability

Complete integrability in a symplectic setting means the existence of a Lagrangian foliation leaf-wise preserved by the dynamics. In the paper we describe complete integrability in a contact set-up as a more subtle structure: a flag of two foliations, Legendrian and co-Legendrian, and a holonomy-invariant transverse measure of the former in the latter. This turns out to be equivalent to the existence of a canonical $\R\ltimes \R^{n-1}$ structure on the leaves of the co-Legendrian foliation. Further, the above structure implies the existence of $n$ contact fields preserving a special contact 1-form, thus providing the geometric framework and establishing equivalence with previously known definitions of contact integrability. We also show that contact completely integrable systems are solvable in quadratures. We present an example of contact complete integrability: the billiard system inside an ellipsoid in pseudo-Euclidean space, restricted to the space of oriented null geodesics. We describe a surprising acceleration mechanism for closed light-like billiard trajectories

A new method for tracking of motor skill learning through practical application of Fitts’ law

This article is made available through the Brunel Open Access Publishing Fund.A novel upper limb motor skill measure, task productivity rate (TPR) was developed integrating speed and spatial error, delivered by a practical motor skill rehabilitation task (MSRT). This prototype task involved placement of 5 short pegs horizontally on a spatially configured rail array. The stability of TPR was tested on 18 healthy right-handed adults (10 women, 8 men, median age 29 years) in a prospective single-session quantitative within-subjects study design. Manipulations of movement rate 10% faster and slower relative to normative states did not significantly affect TPR, F(1.387, 25.009) = 2.465, p = .121. A significant linear association between completion time and error was highest during the normative state condition (Pearson's r = .455, p < .05). Findings provided evidence that improvements in TPR over time reflected motor learning with possible changes in coregulation behavior underlying practice under different conditions. These findings extend Fitts’ law theory to tracking of practical motor skill using a dexterity task, which could have potential clinical applications in rehabilitation

Leadership in agricultural machinery circles: experimental evidence from Tajikistan

Leadership is critical for the viability of rural groups. The way in which leadership is legitimised can mediate leader and group member behaviour in the face of social dilemmas. Yet there has been scant research on leader‐follower dynamics in naturally occurring groups. Highlighting the case of agricultural machinery circles in Tajikistan, the effect of leading by example on investments to a collective good is studied in a framed field experiment. To increase realism, and contrary to standard economic experiments, this investment is a voucher allowing the group to make a real‐world machinery purchase at reduced costs. Two treatments manipulate leaders’ legitimisation. Elected leaders achieve 30 per cent higher contributions to the collective investment against a baseline version without a leader. Contributions remain, on average, relatively stable over the course of the game. The results are discussed with reference to the debate on external intervention in agricultural producer organisations.Peer Reviewe

Dynamic light scattering study on phase separation of a protein-water mixture: Application on cold cataract development in the ocular lens

We present a detailed dynamic light scattering study on the phase separation in the ocular lens emerging during cold cataract development. Cold cataract is a phase separation effect that proceeds via spinodal decomposition of the lens cytoplasm with cooling. Intensity auto-correlation functions of the lens protein content are analyzed with the aid of two methods providing information on the populations and dynamics of the scattering elements associated with cold cataract. It is found that the temperature dependence of many measurable parameters changes appreciably at the characteristic temperature ~16+1 oC which is associated with the onset of cold cataract. Extending the temperature range of this work to previously inaccessible regimes, i.e. well below the phase separation or coexistence curve at Tcc, we have been able to accurately determine the temperature dependence of the collective and self-diffusion coefficient of proteins near the spinodal. The analysis showed that the dynamics of proteins bears some resemblance to the dynamics of structural glasses where the apparent activation energy for particle diffusion increases below Tcc indicating a highly cooperative motion. Application of ideas developed for studying the critical dynamics of binary protein/solvent mixtures, as well as the use of a modified Arrhenius equation, enabled us to estimate the spinodal temperature Tsp of the lens nucleus. The applicability of dynamic light scattering as a non-invasive, early-diagnostic tool for ocular diseases is also demonstrated in the light of the findings of the present paper