3-D vertical ray shooting and 2-D point enclosure, range searching, and arc shooting amidst convex fat objects

We present a new data structure for a set of n convex simply-shaped fat objects in the plane, and use it to obtain efficient and rather simple solutions to several problems including (i) vertical ray shooting—preprocess a set of n non-intersecting convex simply-shaped flat objects in 3-space, whose xy-projections are fat, for efficient vertical ray shooting queries, (ii) point enclosure—preprocess a set C of n convex simply-shaped fat objects in the plane, so that the k objects containing a query point p can be reported efficiently, (iii) bounded-size range searching— preprocess a set C of n convex fat polygons, so that the k objects intersecting a “not-too-large” query polygon can be reported efficiently, and (iv) bounded-size segment shooting—preprocess a set C as in (iii), so that the first object (if exists) hit by a “not-too-long” oriented query segment can be found efficiently. For the first three problems we construct data structures of size O(λ_s(n)log³n), where s is the maximum number of intersections between the boundaries of the (xy-projections) of any pair of objects, and λ_s(n) is the maximum length of (n, s) Davenport-Schinzel sequences. The data structure for the fourth problem is of size O(λ_s(n)log²n). The query time in the first problem is O(log⁴n), the query time in the second and third problems is O(log³n + klog²n), and the query time in the fourth problem is O(log³n).

We also present a simple algorithm for computing a depth order for a set as in (i), that is based on the solution to the vertical ray shooting problem. (A depth order for , if exists, is a linear order of , such that, if K₁, K₂ and K₁ lies vertically above K₂, then K₁ precedes K₂.) Unlike the algorithm of Agarwal et al. (1995) that might output a false order when a depth order does not exist, the new algorithm is able to determine whether such an order exists, and it is often more efficient in practical situations than the former algorithm.     

Extended Rees algebras and mixed multiplicities

Partially supported by the general research fund at the University of Kansas     

Quantitative analysis of imazamox herbicide in environmental water samples by capillary electrophoresis electrospray ionization mass spectrometry

Capillary electrophoresis-mass spectrometry (CE-MS) with an electrospray ionization interface was applied for the quantitative analysis of imazamox pesticide in well water, potable water, and pond water. The detector response for imazamox was determined to be linear over the concentration range of 50-1 ng/ml. The limits of quantitation and detection of the method were determined to be 200 and 20 ng/l for imazamox compound in each type of water sample, respectively. The total sample preparation and CE-MS analysis time was under 2 h.     

A single crystal study of eight-layer barium managanese oxide,BaMnO3

A single crystal study of hydrothermally prepared eight-layer BaMnO₃ has been carried out which confirms the (Zhdanov notation) 121121 layer stacking scheme for the BaO₃ layers. The MnO₆ octahedra share faces in strings of four, and these strings are connected to each other by corner sharing. The compound has an hexagonal unit cell of dimensions a = 5.667 ± 0.003 and c = 18.738 ± 0.009 Å, probable space group $\text{P6}{}_3\text{mmc}\text{, Z = 8}$. Its structure has been determined from 352 independent reflections, of which 242 were considered observed, collected manually by a counter technique and refined to a conventional R value of 0.079.     

Inorganic oxide core, polymer shell nanocomposite as a high K gate dielectric for flexible electronics applications

Organic/inorganic core shell nanoparticles have been synthesized using high K TiO(2) as the core nanoparticle, and polystyrene as the shell. This material is easy to process and forms transparent continuous thin films, which exhibit a dielectric constant enhancement of over 3 times that of bulk polystyrene. This new dielectric material has been incorporated into capacitors and thin film transistors (TFTs). Mobilities approaching 0.2 cm(2)/V.s have been measured for pentacene TFTs incorporating the new TiO(2) polystyrene nanostructured gate dielectric, indicating good surface properties for pentacene film growth. This novel strategy for generating high K flexible gate dielectrics will be of value in improving organic and flexible electronic device performance.     

Thermal lens spectrometric determination of hexavalent chromium

The applicability of thermal lens spectrometry (TLS) for quantification and routine determination of hexavalent chromium was investigated by using a collinear dual beam thermal lens spectrometer. In aqueous solutions the LOD of 0.1 μg l⁻¹ was obtained for Cr(VI) by using 160 mW laser power. The performance of the technique was verified by the determination of hexavalent chromium in standard reference water samples (NIST SRM 1643a and NIST SRM 1643c) and comparing the results for Cr(VI) in CCA (Cr, Cu, As)-treated timber extracts to concentrations obtained by atomic absorption spectrometry (AAS). Good agreement between the TLS results and reported values for Cr(VI) in SRMs as well as AAS results for Cr(VI) in CCA-treated timbers confirmed that TLS is a reliable and accurate analytical technique applicable for the determination of Cr(VI) in aqueous solutions at concentration levels 0.5–100 μg l⁻¹.     

Magnetic field effects on cytochrome c-mediated bioelectrocatalytic transformations

Constant magnetic fields affect many biological transformations, but we lack mechanistic understanding of the processes. The magnetohydrodynamic effect may account for the enhancement of bioelectrocatalytic transformations at interfaces. This is exemplified by the bioelectrocatalyzed cytochrome c-mediated reduction of oxygen and oxidation of lactate in the presence of cytochrome oxidase and lactate dehydrogenase, respectively. We observe significant magnetic field effects on the rates of bioelectrochemical transformations (ca. 3-fold increase) at the functionalized interfaces at field strengths, B, up to 1 T. We show that the limiting current is proportional to the B(1/3)C*(4/3), where C is the concentration of electroactive species. The results may have important implications on the understanding of the magnetic field effects on natural biocatalytic processes at membranes and on the enhancement of biotransformations in biotechnology.     

Role of vibrationally excited NO in promoting electron emission when colliding with a metal surface: a nonadiabatic dynamic model

A nonadiabatic quantum dynamic model has been developed to study the process of electron emission from a low-work-function metal surface. The process is initiated by scattering a highly vibrationally excited NO molecule from a surface composed of a Cs layer covering a Ru crystal. The model addresses the increasing quantum yield of the electron emission as a function of the molecular vibrational excitation and incident kinetic energy. The reaction mechanism is identified as a long-range harpooning electron transfer to a molecular ion which is then accelerated toward the surface. Upon impact, the molecular ion emits its excess electron.     

An attempt to prepare and characterize a soil reference material for Cr(VI) and Cr(III)

Reference materials for the speciation and quantification of chromium in contaminated soils were prepared by impregnating diatomaceous earth with BaCrO₄ and Cr₂O₃. The chronium concentrations of these materials were confirmed to be 200 mg/kg both by atomic absorption spectrometry and by instrumental neutron activation analysis, but monthly assays over two calendar quarters of the reference material impregnated with BaCrO₄ revealed the hexavalent chromium was not stable in this matrix.