Palladacycles with Palladium-Bonded Stereogenic Carbons: Tools for Exploring Reaction Pathways in Organometallic Chemistry

While reactions with organopalladium intermediates often give useful organic products, little is known about how the ligand sphere impacts the reactivity of these intermediates. To explore the interactions between the auxiliary ligand and the other substitutents on the metal center, we performed synthetic and structural studies on both polymer-bound palladacycles and a new organometallic scaffold, the palladapyrrolidinone. In the case of palladacycles on solid-phase, we observed that the precise characteristics of the polymer-bound ligand had a large impact on the reactivity of the complex. In the case of the palladapyrrolidinones, we observed that the shape and size of the ligand sphere had a large impact on the diastereoselective formation of a sp3-C stereocenter bound to a palladium center. We found that a chiral non-racemic ligand had little impact on the stereoselectivity. In conclusion, the ligand sphere has a distinct impact on both the reactivity and stereoselectivity of reactions involving palladacycles

Practical methods for approximating shortest paths on a convex polytope in R3

AbstractWe propose an extremely simple approximation scheme for computing shortest paths on the surface of a convex polytope in three dimensions. Given a convex polytope P with n vertices and two points p, q on its surface, let dP(p, q) denote the shortest path distance between p and q on the surface of P. Our algorithm produces a path of length at most 2dP(p, q) in time O(n). Extending this result, we can also compute an approximation of the shortest path tree rooted at an arbitrary point x ∈ P in time O(n log n). In the approximate tree, the distance between a vertex v ∈ P and x is at most cdP(x, v), where c = 2.38(1 + ε) for any fixed ε > 0. The best algorithms for computing an exact shortest path on a convex polytope take Ω(n2) time in the worst case; in addition, they are too complicated to be suitable in practice. We can also get a weak approximation result in the general case of k disjoint convex polyhedra: in O(n) time our algorithm gives a path of length at most 2k times the optimal

Morphing Binary Trees

We investigate the problem of transforming one binary tree into another by rotatoins, subject to certain weight ocnstraints on the nodes of the trees. These constraints arise in the problem of morphing one simple polygon to another simple polygon by continuous deformatinos (translations and scalings) that preserve the turn angles and the simplicity of the polygon; the two polygons must have the same sequence of turn angles. Our main theorem is that two arbitrary n-leaf binary trees satisfying our weight constraint can be morphed into each other with O(n log n) rotations. Furthermore, we also present an O(n log n) time algorithm to determine these rotations. The previous best algorithm for this problem used O(n4/3 + ε) rotations

Trucks involved in fatal accidents codebook 2009 (preliminary version October 18, 2011)

Special Report Task AThis report provides documentation for UMTRI’s file of Trucks Involved in Fatal Accidents (TIFA), 2009, including distributions of the code values for each variable in the file. The 2009 TIFA file is a census of all medium and heavy trucks involved in a fatal accident in the United States. The TIFA database provides coverage of all medium and heavy trucks recorded in the Fatality Analysis Reporting System (FARS) file. TIFA combines vehicle, accident, and occupant records from FARS with information about the physical configuration and operating authority of the truck from the TIFA survey.Federal Motor Carrier Safety Adminstration, Washington, D.C.http://deepblue.lib.umich.edu/bitstream/2027.42/89937/1/48532_A55.pd

Shortest Paths in the Plane with Obstacle Violations

We study the problem of finding shortest paths in the plane among h convex obstacles, where the path is allowed to pass through (violate) up to k obstacles, for k <= h. Equivalently, the problem is to find shortest paths that become obstacle-free if k obstacles are removed from the input. Given a fixed source point s, we show how to construct a map, called a shortest k-path map, so that all destinations in the same region of the map have the same combinatorial shortest path passing through at most k obstacles. We prove a tight bound of Theta(kn) on the size of this map, and show that it can be computed in O(k^2 n log n) time, where n is the total number of obstacle vertices

Largest Empty Circle Centered on a Query Line

The Largest Empty Circle problem seeks the largest circle centered within the convex hull of a set $P$ of $n$ points in $\mathbb{R}^2$ and devoid of points from $P$. In this paper, we introduce a query version of this well-studied problem. In our query version, we are required to preprocess $P$ so that when given a query line $Q$, we can quickly compute the largest empty circle centered at some point on $Q$ and within the convex hull of $P$. We present solutions for two special cases and the general case; all our queries run in $O(\log n)$ time. We restrict the query line to be horizontal in the first special case, which we preprocess in $O(n \alpha(n) \log n)$ time and space, where $\alpha(n)$ is the slow growing inverse of the Ackermann's function. When the query line is restricted to pass through a fixed point, the second special case, our preprocessing takes $O(n \alpha(n)^{O(\alpha(n))} \log n)$ time and space. We use insights from the two special cases to solve the general version of the problem with preprocessing time and space in $O(n^3 \log n)$ and $O(n^3)$ respectively.Comment: 18 pages, 13 figure

The Union of Probabilistic Boxes: Maintaining the Volume

Suppose we have a set of n axis-aligned rectangular boxes in d-space, {B-1, B-2,..., B-n}, where each box B-i is active (or present) with an independent probability pi. We wish to compute the expected volume occupied by the union of all the active boxes. Our main result is a data structure for maintaining the expected volume over a dynamic family of such probabilistic boxes at an amortized cost of O(n((d-1)/2) log n) time per insert or delete. The core problem turns out to be one-dimensional: we present a new data structure called an anonymous segment tree, which allows us to compute the expected length covered by a set of probabilistic segments in logarithmic time per update. Building on this foundation, we then generalize the problem to d dimensions by combining it with the ideas of Overmars and Yap [13]. Surprisingly, while the expected value of the volume can be efficiently maintained, we show that the tail bounds, or the probability distribution, of the volume are intractable-specifically, it is NP-hard to compute the probability that the volume of the union exceeds a given value V even when the dimension is d = 1

La Banque asiatique de développement et les jeux d’influences chinois et japonais

Le théâtre de la Banque asiatique de développement présente un aperçu de la nouvelle évolution de la Chine par rapport à son « multilatéralisme intéressé ». Il permet aussi de vérifier, ou d’avancer, un certain nombre d’hypothèses sur l’avenir des relations sino-japonaises, très souvent réduites au présupposé d’un inévitable conflit d’intérêts qui ne peut déboucher que dans une lutte entre les deux puissances asiatiques pour l’hégémonie régionale. Depuis son entrée à la BAD en 1986 la Chine a fait du chemin à l’intérieur de cette institution : jusqu’où ira-t-elle ? Les visions chinoises et japonaises, qui différent dans le cas du développement de la Région du Grand Mékong, programme phare de la Banque, vont-elles se contredire ou se rejoindre ? Enfin, les « styles diplomatiques » de la Chine et du Japon, très éloignés, ne se rapprocheront-ils pas à terme dans une approche partagée pour une diplomatie plus constructive, plus consensuelle, et plus « douce », une soft diplomacy ?The Asian Development Bank provides an overview of the new developments on China’s “self-interested multilateralism”. It also allows us to verify certain assumptions about the future of Sino-Japanese relations, often reduced to a presupposed inevitable conflict of interests that would lead to a struggle between two Asian powers for regional hegemony. Since joining ADB in 1986, China has come a long way within this institution. In the case of the Greater Mekong Subregion development, a flagship programme of the bank, Chinese and Japanese visions differ. Will they contradict each other or converge? Finally, the diplomatic “styles” of China and Japan are poles apart. Will they come together in a common approach to a more efficient and more consensual “soft diplomacy”

Can You be Vaccinated from Teasing? A Retrospective Study of Teasing History and Current Self Esteem Levels

Teasing is prevalent throughout the lives of most individuals beginning in childhood. Teasing can be a positive "pro-social" interaction, or a negative "anti-social" experience. Childhood teasing on the "anti-social" level has been show to have detrimental effects on an individual's self-esteem and has been linked to increased psychological distress in adulthood. The purpose of this study was to investigate the effects of an individual's environment, as defined by his or her teasing history with their peers and families, at different stages during their development on their level of self-esteem. Two hundred and three adult participants completed a questionnaire packet designed to measure teasing history, self-esteem, and perceived social support from family and peers. Results indicated that negative teasing interactions were related to lower reported levels of self-esteem. Negative teasing from one's family during elementary school and negative teasing from one's peers during middle school were found to have the greatest influence on current self-esteem levels. Results also showed that early and concurrent exposure to teasing at the pro-social level during elementary school could negate the later influence future anti-social teasing might have on one's self esteem levels. Implications for practice and recommendations for future research are presented

Kinetic collision detection between two simple polygons

AbstractWe design a kinetic data structure for detecting collisions between two simple polygons in motion. In order to do so, we create a planar subdivision of the free space between the two polygons, called the external relative geodesic triangulation, which certifies their disjointness. We show how this subdivision can be maintained as a kinetic data structure when the polygons are moving, and analyze its performance in the kinetic setting