Most dangerous slip direction in face-centered cubic silver crystals under (111)〈$$ \bar 2 $$〉 shear deformation

Using computer simulation, the failure mechanism of an fcc silver crystal under (111)〈$ \bar 2 $ \bar 2 〉 shear deformation is studied and the direction of unstable atomic displacement under the conditions of dynamic stability violation is determined. It is shown that the most dangerous direction of atomic motion, which makes the crystal structurally unstable, does not completely coincide with the 〈$ \bar 2 $ \bar 2 〉 direction lying in the (111) plane and has a component normal to the [111] direction.     

Solving the ordered one-median problem in the plane

In this paper, we propose a general approach solution method for the single facility ordered median problem in the plane. All types of weights (non-negative, non-positive, and mixed) are considered. The big triangle small triangle approach is used for the solution. Rigorous and heuristic algorithms are proposed and extensively tested on eight different problems with excellent results.     

The first example of isomeric solid amide and its enol

[Structure: see text] The first example of a crystalline amide and its tautomeric enol was obtained for the amide MeNHCSCH(CN)CONHMe (8) and its enol MeNHCSC(CN)=C(OH)NHMe (9). Their X-ray structures were determined, and their structural features resemble those of other related amides and enols. No other example of a similar pair was obtained. In solution, both 8 and 9 and a small percentage of the isomeric enol of thioamide MeNHCOC(CN)=C(SH)NHMe (10) were obtained in solvent-dependent compositions, which are rapidly established.     

A distribution map for the one-median location problem on a network

In this paper we consider the Weber (one-median) location problem on a network. The weights at the nodes are drawn from a multivariate normal distribution. We find the probability that the optimal location is at each of the nodes. This set of probabilities is the distribution map. The methodology is illustrated on two networks of 20 nodes each.     

Development of an oligoamide coating as a surface mimetic for aromatic polyamide films used in reverse osmosis membranes

We developed a method for the in situ synthesis of an oligoamide coating on gold. The resultant surface chemical composition, wettability, and chemical nature were comparable to aromatic polyamide films used as reverse osmosis membranes. Hence, the oligoamide wafer may be used in adsorption/fouling studies as a surface mimetic of reverse osmosis membranes.     

Connectivity guarantees for wireless networks with directional antennas

We study a combinatorial geometric problem related to the design of wireless networks with directional antennas. Specifically, we are interested in necessary and sufficient conditions on such antennas that enable one to build a connected communication network, and in efficient algorithms for building such networks when possible.We formulate the problem by a set P of n points in the plane, indicating the positions of n transceivers. Each point is equipped with an α-degree directional antenna, and one needs to adjust the antennas (represented as wedges), by specifying their directions, so that the resulting (undirected) communication graph G is connected. (Two points p,q∈P are connected by an edge in G, if and only if q lies in p?s wedge and p lies in q?s wedge.) We prove that if α=60°, then it is always possible to adjust the wedges so that G is connected, and that α?60° is sometimes necessary to achieve this. Our proof is constructive and yields an time algorithm for adjusting the wedges, where k is the size of the convex hull of P.Sometimes it is desirable that the communication graph G contain a Hamiltonian path. By a result of Fekete and Woeginger (1997) [8], if α=90°, then it is always possible to adjust the wedges so that G contains a Hamiltonian path. We give an alternative proof to this, which is interesting, since it produces paths of a different nature than those produced by the construction of Fekete and Woeginger. We also show that for any n and ε>0, there exist sets of points such that G cannot contain a Hamiltonian path if α=90°−ε.     

Injectors of finite solvable groups

It is well known that in a free group the simple commutator [Y, X](alternatively called the first Engel word) can be expressed as a product of squares. Likewise the second Engel word [Y, X, X] can be expressed as a product of cubes. Results on groups of exponent four imply that the fifth Engel word [Y, X, X, X, X, X] can be expressed as a product of fourth powers, and explicit expressions have now been obtained with the assistance of a computer. The results and the computeraided technique are described.     

11th Annual BNL Accelerator Test Facility Program Committee and Users' Meeting

The Seventh Annual Users' Meeting of the Canadian Light Source was a great success, as the world's newest synchrotron welcomed close to 400 researchers and students from across Canada, the U.S., Europe and Australia to the University of Saskatchewan on November 17–21, 2004. The plenary session of the Users' Meeting, held November 20, was preceded by five workshops: “XAFS Analysis Using Ifeffit, Athena and Artemis,” “SR Applications in Environmental Science,” “Medical Imaging,” “Protein Crystallography,” and “Applications of Elliptically Polarized Synchrotron Radiation.” Meetings of the Beamline Advisory Committee and beamline teams were held on November 21.

After welcoming remarks by Dr. Alan Anderson, Chair of the CLS User Advisory Committee, the meeting opened with a briefing by CLS Executive Director William Thomlinson regarding the accomplishments made by the CLS over the preceding year.