Publications

We give NC algorithms for determining the number and degrees of the absolute factors (factors irreducible over the complex numbers C) of a multivariate polynomial with rational coefficients. NC is the class of functions computable by logspace-uniform boolean circuits of polynomial size and polylogarithmic depth. The measures of size of the input polyne mial are its degree d, coefficient length c, number of variables ra, and for sparse polynomials, the number of non-zero coefficients s. For the general case, we give a random (Monte-Carlo) NC algorithm in these input measures. If n is fixed, or if the polynomial is dense, we give a deterministic NC algorithm. The algorithm also works in random NC for polynomials represented by straight-line programs, provided the polynomial can be evaluated at integer points in NC. Finally, we discuss a method for obtaining an approximation to the coefficients of each factor whose running time is polynomial in the size of the original (dense) polynomial. These methods rely on the fact that the connected components of a complex hypersurface P(zl,..., zn) = 0 minus its singular points correspond to the absolute factors of P.

The interactions of H/sub 2/ and CO with Pd/SiO/sub 2/ promoted with La/sub 2/O/sub 3/, CeO/sub 2/, Pr/sub 6/O/sub 11/, Nd/sub 2/O/sub 3/, and Sm/sub 2/O/sub 3/ have been investigated using temperature-programmed desorption and temperature-programmed surface reaction. Introduction of the promoter following the preparation of the Pd/SiO/sub 2/ catalyst results in a partial coverage of the Pd particles by the oxide promoter. Upon reduction of the promoted catalysts, portions of the promoter in contact with Pd undergo reduction. The partially reduced rare earth oxide species covering the Pd particles reduce the amounts of H/sub 2/ and CO that can be adsorbed on the metal. The rare earth oxide moieties have a slight influence on the distribution of H/sub 2/ adstates but cause a significant change in the distribution of CO adstates. Decoration of Pd by rare earth oxide moieties also aids the dissociation of CO, and raises thereby the activity for CH/sub 4/ synthesis relative to that for Pd/SiO/sub 2/. The promoter also serves to increase the activity for CH/sub 3/OH synthesis and the formation of CO/sub 2/ via the water-gas shift reaction. 42 references.

Although nanocrystals and nanowires have proliferated new scientific avenues in the study of their physics and chemistries, the bottom-up assembly of these small-scale building blocks remains a formidable challenge for device fabrication and processing. An attractive nanoscale assembly strategy should be cheap, fast, defect tolerant, compatible with a variety of materials, and parallel in nature, ideally utilizing the self-assembly to generate the core of a device, such as a memory chip or optical display. Langmuir-Blodgett (LB) assembly is a good candidate for arranging vast numbers of nanostructures on solid surfaces. In the LB technique, uniaxial compression of a nanocrystal or nanowire monolayer floating on an aqueous subphase causes the nanostructures to assemble and pack over a large area. The ordered monolayer can then be transferred to a solid surface en masse and with fidelity. In this Account, we present the Langmuir-Blodgett technique as a low-cost method for the massively parallel, controlled organization of nanostructures. The isothermal compression of fluid-supported nanoparticles or nanowires is unique in its ability to achieve control over nanoscale assembly by tuning a macroscopic property such as surface pressure. Under optimized conditions (e.g., surface pressure, substrate hydrophobicity, and pulling speed), it allows continuous variation of particle density, spacing, and even arrangement. For practical application and device fabrication, LB compression is ideal for forming highly dense assemblies of nanowires and nanocrystals over unprecedented surface areas. In addition, the dewetting properties of LB monolayers can be used to further achieve patterning within the range of micrometers to tens of nanometers without a predefined template. The LB method should allow for easy integration of nanomaterials into current manufacturing schemes, in addition to fast device prototyping and multiplexing capability.

The ability of first-principles computational methods to reproduce ground-state crystal structure selection is key to their application in the discovery of new materials, and yet presents a formidable challenge due to the low-energy scale of the problem and lack of systematic error cancellation. The recently developed Strongly Constrained and Appropriately Normed (SCAN) functional is notable for accurately calculating physical properties such as formation energies and in particular, correctly predicting ground-state structures. Here in this paper, we attempt to rationalize the improved structure prediction accuracy in SCAN by investigating the relationship between preferred coordination environments, the description of attractive van der Waals (vdW) interactions, and the overall ground-state prediction in bulk main-group solids. We observe a systematic undercoordination error in the traditional Perdew, Burke, and Ernzerhof (PBE) functional which is not present in SCAN results and find that semiempirical dispersion corrections in the form of PBE + D 3 fail to correct this error in a consistent or physical manner. We conclude that the medium-range vdW interaction is correctly parametrized in SCAN and yields meaningful relative energies between coordination environments.

This paper considers the support of real-time applications in an Integrated Services Packet Network (ISPN). We first review the characteristics of real-time applications. We observe that, contrary to the popular view that real-time applications necessarily require a fixed delay bound, some real-time applications are more flexible and can adapt to current network conditions. We then propose an ISPN architecture that supports two distinct kinds of real-time service: guaranteed service, which is the traditional form of real-time service discussed in most of the literature and involves pre-computed worst-case delay bounds, and predicted service which uses the measure performance of the network in computing delay bounds. We then propose a packet scheduling mechanism that can support both of these real-time services as well as accommodate datagram traffic. We also discuss two other aspects of an overall ISPN architecture: the service interface and the admission control criteria.

Certain disclosed embodiments generally relate to oxide materials having relatively high energy and/or power densities. Various aspects of the embodiments are directed to oxide materials having a structure B.sub.i(M.sub.jY.sub.k)O.sub.2, for example, a structure Li.sub.j(Ni.sub.jY.sub.k)O.sub.2 such as Li(Ni.sub.0.5Mn.sub.0.5)O.sub.2. In this structure, Y represents one or more atoms, each independently selected from the group consisting of alkaline earth metals, transition metals, Group 14 elements, Group 15, or Group 16 elements. In some embodiments, such an oxide material may have an O3 crystal structure, and/or a layered structure such that the oxide comprises a plurality of first, repeating atomic planes comprising Li, and a plurality of second, repeating atomic planes comprising Ni and/or Y.