A practical solution to a newspaper distribution problem

In this paper the problem of distributing newspapers is treated. After a general introduction on this topic, a mathematical model for a hierarchical distribution system is given explicitly and a heuristic consisting of several solution techniques is described. Furthermore, some results of the application of this heuristic in a study performed for a Dutch regional newspaper are presented and discussed. There is also an indication as to how the approach could be improved

Matching times of leading and following suggest cooperation through direct reciprocity during V-formation flight in ibis

One conspicuous feature of several larger bird species is their annual migration in V-shaped or echelon formation. When birds are flying in these formations, energy savings can be achieved by using the aerodynamic up-wash produced by the preceding bird. As the leading bird in a formation cannot profit from this up-wash, a social dilemma arises around the question of who is going to fly in front? To investigate how this dilemma is solved, we studied the flight behavior of a flock of juvenile Northern bald ibis (Geronticus eremita) during a human-guided autumn migration. We could show that the amount of time a bird is leading a formation is strongly correlated with the time it can itself profit from flying in the wake of another bird. On the dyadic level, birds match the time they spend in the wake of each other by frequent pairwise switches of the leading position. Taken together, these results suggest that bald ibis cooperate by directly taking turns in leading a formation. On the proximate level, we propose that it is mainly the high number of iterations and the immediacy of reciprocation opportunities that favor direct reciprocation. Finally, we found evidence that the animals' propensity to reciprocate in leading has a substantial influence on the size and cohesion of the flight formations

Electric-field control of domain wall nucleation and pinning in a metallic ferromagnet

The electric (E) field control of magnetic properties opens the prospects of an alternative to magnetic field or electric current activation to control magnetization. Multilayers with perpendicular magnetic anisotropy (PMA) have proven to be particularly sensitive to the influence of an E-field due to the interfacial origin of their anisotropy. In these systems, E-field effects have been recently applied to assist magnetization switching and control domain wall (DW) velocity. Here we report on two new applications of the E-field in a similar material : controlling DW nucleation and stopping DW propagation at the edge of the electrode

Spin injection in a single metallic nanoparticle: a step towards nanospintronics

We have fabricated nanometer sized magnetic tunnel junctions using a new nanoindentation technique in order to study the transport properties of a single metallic nanoparticle. Coulomb blockade effects show clear evidence for single electron tunneling through a single 2.5 nm Au cluster. The observed magnetoresistance is the signature of spin conservation during the transport process through a non magnetic cluster.Comment: 3 page

A quantitative description of skyrmions in ultrathin ferromagnetic films and rigidity of degree ±1\pm1 harmonic maps from R2\mathbb{R}^2 to S2\mathbb{S}^2

We characterize skyrmions in ultrathin ferromagnetic films as local minimizers of a reduced micromagnetic energy appropriate for quasi two-dimensional materials with perpendicular magnetic anisotropy and interfacial Dzyaloshinskii-Moriya interaction. The minimization is carried out in a suitable class of two-dimensional magnetization configurations that prevents the energy from going to negative infinity, while not imposing any restrictions on the spatial scale of the configuration. We first demonstrate existence of minimizers for an explicit range of the model parameters when the energy is dominated by the exchange energy. We then investigate the conformal limit, in which only the exchange energy survives and identify the asymptotic profiles of the skyrmions as degree 1 harmonic maps from the plane to the sphere, together with their radii, angles and energies. A byproduct of our analysis is a quantitative rigidity result for degree $\pm 1$ harmonic maps from the two-dimensional sphere to itself

A study investigating the effects of modified goggle optical designs on swimmer performance

Background: Use of prisms to improve comfort and posture is a common practice in optometry. This concept can be expanded into the competitive sports world by incorporating prisms into swim goggles. Prisms can theoretically allow the competitive swimmer to maintain a more efficient posture throughout their event. The current study assesses the potential benefits of base-up prism in goggles for free-style swimming. Method: Twenty-four collegiate swimmers were surveyed and tested. Each participant filled out an initial survey detailing their preferences and concerns pertaining to competition goggles. All swimmers performed two 1500-meter practices with the prototype, 35 prism diopter (p.d.), goggles prior to testing. Testing consisted of swimming a 200-meter timed trial with each of the experimental goggles and filling out a corresponding survey immediately after each trial. 35 p.d. base-up prism prototype goggles, 1 p.d. base-up prism goggles, and plano control goggles were evaluated by each participant. Results: Fit was the most important concern for these swimmers. Fit also had the lowest standard deviation, denoting a common level of concern among most of the participants. The second most important concern for these swimmers was fogging. The least important concern for the participants was drag, which had the second lowest number of responders. Swimmers also thought that clarity of the goggles was important. Swimmers thought that restriction of peripheral vision was one of the least important problems. The 1 p.d. goggle produced the fastest mean time, and yet was ranked the worst by participants. In the surveys following the time trials, participants specified that their posture and field of view were greatly improved with the 35 p.d. goggles. They were also willing to pay more for the 35 p.d. goggles than the plano goggles. Conclusion: Although the swimmers swam faster with the 35 p.d. goggles and ranked them higher than the plano goggles, these differences were not statistically significant. However, significantly more subjects did perceive the 35 p.d. goggles to be more beneficial than plano or 1 p.d. goggles

Two-year outcome of an observe-and-plan regimen for neovascular age-related macular degeneration treated with Aflibercept.

The purpose of our study was to investigate the two-year outcome of Aflibercept treatment for neovascular age-related macular degeneration (nAMD), using the Observe-and-Plan regimen, an individually planned treatment regimen, based on the predictability of an individual's need for retreatment, aiming to reduce the clinical burden. Our prospective study used the Observe-and-Plan regimen with Aflibercept to treat nAMD: Three loading doses, followed by monthly observation visits until the disease-recurrence interval was determined, which then was shortened by 2 weeks in a treatment plan for the next three injections without intermediate monitoring visits. The subsequent treatment plans were adjusted according to periodically assessed disease activity. The primary outcome measures were visual acuity changes, number of injections, and number of monitoring visits. The study included 112 eyes of 102 patients with a mean age of 80.7 years (SD 7.6). Mean visual acuity (VA) improved from 61.8 ETDRS letters (20/60(+2)) at baseline, by 8.5, 8.0, and 6.2 letters at months 3, 12 and 24, respectively. Mean central retinal thickness was 438um at baseline, and reduced by 152um, 155um, and 150um at months 3, 12 and 24, respectively. The mean number of injections was 8.7 and 6.5 in the first and second year, respectively. The mean number of monitoring visits after baseline was 3.8 and 2.8 during the first and second year, respectively. The Observe-and-Plan regimen significantly improved VA, while fewer monitoring visits were needed as compared to other variable dosing regimens, thus reducing the workload for chronic care management of nAMD

Testing Conditional Independence of Discrete Distributions

We study the problem of testing \emph{conditional independence} for discrete distributions. Specifically, given samples from a discrete random variable $(X, Y, Z)$ on domain $[\ell_1]\times[\ell_2] \times [n]$, we want to distinguish, with probability at least $2/3$, between the case that $X$ and $Y$ are conditionally independent given $Z$ from the case that $(X, Y, Z)$ is $\epsilon$-far, in $\ell_1$-distance, from every distribution that has this property. Conditional independence is a concept of central importance in probability and statistics with a range of applications in various scientific domains. As such, the statistical task of testing conditional independence has been extensively studied in various forms within the statistics and econometrics communities for nearly a century. Perhaps surprisingly, this problem has not been previously considered in the framework of distribution property testing and in particular no tester with sublinear sample complexity is known, even for the important special case that the domains of $X$ and $Y$ are binary. The main algorithmic result of this work is the first conditional independence tester with {\em sublinear} sample complexity for discrete distributions over $[\ell_1]\times[\ell_2] \times [n]$. To complement our upper bounds, we prove information-theoretic lower bounds establishing that the sample complexity of our algorithm is optimal, up to constant factors, for a number of settings. Specifically, for the prototypical setting when $\ell_1, \ell_2 = O(1)$, we show that the sample complexity of testing conditional independence (upper bound and matching lower bound) is \[ \Theta\left({\max\left(n^{1/2}/\epsilon^2,\min\left(n^{7/8}/\epsilon,n^{6/7}/\epsilon^{8/7}\right)\right)}\right)\,. \