A divide and conquer algorithm for medial surface calculation of planar polyhedra

The Medial Axis Transform surface, (or MAT or MS) is proving to be a useful tool for several applications and geometric reasoning tasks. However, calculation of the MAT is a time-consuming task and the benefits of the mathematical-based tool are offset by the cost of the calculation. This paper presents a method for medial surface calculation which uses subdivision to simplify the problem and hence speed up the calculation, a so-called ‘divide-and-conquer’ approach. The basis for this is a modification of the dual structure of the original object. As the calculation proceeds this structure is broken up into sub-pieces each representing a simpler sub-part of the MAT. Perhaps more importantly, this method creates a correct node decomposition of the dual structure. The paper goes on to demonstrate some applications of the results for geometric tasks, specifically offsetting and model subdivision, which are normally expensive but are simpler based on the MAT calculation results.     

Bureau of Mines Method of Calibrating a Primary Radon Measuring Apparatus

One important requirement for accurate monitoring of radon in working environments, dwellings, and outdoors is to ensure that the measurement instrumentation is properly calibrated against a recognized standard. To achieve this goal, the U.S. Department of Interior Bureau of Mines (BoM) Radiation Laboratory has participated since 1983 in a program to establish international radon measurement standards. Originally sponsored by the Organization for Economic Cooperation and Development (OECD), the program is also sponsored by the International Atomic Energy Agency. While the National Institute of Standards and Technology (NIST) radium solution ampules are acceptable to all participating laboratories as a primary standard, a method of transferring radon from the NIST source into each laboratory’s primary counting apparatus is a critical problem. The Bureau’s method transfers radon from the primary solution by bubbling 3 L of air through it into a steel cylinder. After homogenizing the radon concentrations in the cylinder, eight alpha-scintillation cells are filled consecutively and measured in a standard counting system. The resulting efficiency is 81.7±1.2%.     

Monosialogangliosides of human myelogenous leukemia HL60 cells and normal human leukocytes. 2. Characterization of E-selectin binding fractions, and structural requirements for physiological binding to E-selectin

E-selectin binding gangliosides were isolated from myelogenous leukemia HL60 cells, and the E-selectin binding pattern was compared with that of human neutrophils as described in the preceding paper in this issue. The binding fractions were identified as monosialogangliosides having a series of unbranched polylactosamine cores. Structures of fractions 12-3, 13-1, 13-2, and 14, which showed clear binding to E-selectin under the conditions described in the preceding paper, were characterized by functional group analysis by application of monoclonal antibodies, 1H-NMR, FAB-MS, and electrospray mass spectrometry with collision-induced dissociation of permethylated fractions. Fractions 12-3, 13-1, and 13-2 were characterized by the presence of a major ganglioside with the following structure: NeuAc alpha 2-->3Gal beta 1-->4 GlcNAc beta 1-->3Gal beta 1-->4(Fuc alpha 1-->3) GlcNAc beta 1-->3Gal beta 1-->4(Fuc alpha 1-->3)-GlcNAc beta 1-->3Gal beta 1-->4GlcNAc beta 1-->3 Gal beta 1-->4 Glc beta Cer. Fractions 12-3 and 13-2 contained, in addition, small quantities (10-15%) of extended SLex with internally fucosylated structures: NeuAc alpha 2-->3 Gal beta 1-->4-(Fuc alpha 1-->3) GlcNAc beta 1-->3 Gal beta 1-->4(Fuc alpha 1-->3) GlcNAc beta 1-->3 Gal beta 1-->4 (+/- Fuc alpha 1-->3)GlcNA c beta 1-->3 Gal beta beta 1-->4GlcNAc beta 1-->3 Gal beta 1-->Glc Beta Cer. Fraction 13-1, showing stronger E-selectin binding activity than 12-3 and 13-2, contained only a trace quantity (< 1%) of SLex. Fraction 14, which also showed clear binding to E-selectin, was characterized by the presence of the following structures, in addition to two internally monofucosylated structures (XX and XXI, Table 2, text): NeuAc alpha 2-->3Gal beta 1-->4GlcNAc beta 1-->3Gal beta 1-->4(Fuc alpha 1-->3)GlcNAc beta 1-->3 Gal beta 1-->4(Fuc alpha 1-->3)GlcNAc beta 1-->3Gal beta 1-->4 GlcNAc beta 1-->3 Gal beta 1-->4 GlcNAc beta 1-->3 Gal beta 1-->4 Glc beta Cer; andNeuAc alpha 2-->3Gal beta 1-->4GlcNAc beta 1-->3 Gal beta 1-->4(Fuc alpha 1-->3)GlcNAc beta 1-->3Gal beta 1-->4GlcNAc beta 1-->3Gal beta 1-->4 (Fuc alpha 1--3)-GlcNAc beta 1-->3Gal beta 1-->4GlcNAc beta 1-->3Gal beta 1--4Glc beta Cer. SLex determinant was completely absent. Thus, the E-selectin binding epitope in HL60 cells is carried by unbranched terminally alpha 2-->3 sialylated polylactosamine having at least 10 monosaccharide units (4 N-acetyllactosamine units) with internal multiple fucosylation at GlcNAc. These structures are hereby collectively called "myeloglycan". Monosialogangliosides from normal human neutrophils showed an essentially identical pattern of gangliosides with selectin binding property. Myeloglycan, rather than SLex, provides a major physiological epitope in E-selectin-dependent binding of leukocytes and HL60 cells.     

Spectroscopic and microscopic characterizations of color lamellae in natural pink diamonds

Nineteen natural, untreated, type IaAB pink diamonds from various localities were studied. They display microscopic (～ 1 μm thick) pink lamellae along {111} in an otherwise colorless diamond. This coloration concentrated in lamellae is commonly referred to as “graining”. The diamonds were examined using high spatial resolution spectroscopic methods and transmission electron microscopy. TEM revealed that a pink lamella consists of a cluster of paired microtwins created under stress by plastic deformation. Raman line shift and broadening associated with the twinned pink lamellae indicate the presence of residual stress. Ultraviolet–visible absorption spectra from each of the samples showed a broad absorption band centered at ～ 550 nm, the source of the pink color. Cathodoluminescence spectra of the pink lamellae are different from those of the bulk, colorless diamond matrix. Within the lamellae only, the H3 center is observed along with a less intense N3 center. In some samples, instead of the N3 center a new center with a zero phonon line at 405.5 nm is observed. This previously unreported 405.5 nm center has phonon sidebands qualitatively identical to the N3 center, and may be an N3 center modified by a specific environment. These results suggest that lattice vacancies were created during twinning resulting from plastic deformation, and that impurity centers (such as those containing nitrogen) trap some of the diffusing vacancies. Since the pink lamellae are still under residual stress, new or modified defect centers are created, e.g. H3 and N3. The color center(s) responsible for the pink color (550 nm absorption) was not identified, but likely is only present in diamonds that experienced plastic deformation. Reported annealing of plastically deformed brown diamonds, which results in a residual pink color, suggests that the pink color is stable under these high pressure, high temperature conditions. The reported observations that annealing plastically deformed brown diamonds results in a residual pink color and that the pink color does not anneal out under similar high pressure, high temperature conditions, suggests that the deformation inducing pink color occurs inside the Earth's mantle, whereas brown coloration might be induced during a more recent event such as the ascent of the diamond to the surface in a kimberlitic/lamproitic eruption.     

Advanced process modeling at the BCL smelter: Improving economic and environmental performance

Since 1973 Bamangwato Concessions Limited (BCL) has operated a nickel-copper smelter in Selebi-Phikwe, Botswana. The smelter treats concentrates from local mines and various custom feed concentrates. The nickel throughput capacity of this smelter is constrained by a low nickel feed grade in its primary BCL concentrate. BCL contracted Xstrata Process Support (XPS) to assist in identifying key economic drivers to maximize revenue-generating opportunities. After the disclosure of essential BCL plant performance data XPS developed and utilized advanced metallurgical modeling techniques to identify production bottlenecks, calculate Ni, Cu, and Co recoveries, manage the slag volumes, increase the custom feed capacity, and perform various feasibility analyses for key unit process operations in the BCL smelter. The methodology for developing the process model and its application in contributing to the economic bottom line are outlined in this paper.     

Conference news

Fungal metabolism can be divided into two broad areas. Primary metabolism provides the organism with energy, synthetic intermediates, and key macromolecules. Secondary metabolism yields a range of species‐specific compounds which are of no obvious utility to the producing organism. The mycotoxins are fungal secondary metabolites which are toxic to mammals and which are produced on animal and human foodstuffs. It is best to see the structural relationships and biosynthesis of mycotoxins in relation to fungal metabolism in general. The paper discusses the relationship of primary and secondary metabolism, and the relative importance of the various bio‐synthetic processes in the fungi. Mycotoxins illustrate these processes.     

Influence of a patient decision aid on decisional conflict related to PSA testing: A structural equation model.

Objective: To examine the impact of a decision aid (DA) designed to promote informed decision making for screening with the prostate-specific antigen (PSA) test and to test a theoretical model of factors influencing decisional conflict. Design: Structural equation modeling examined pathways between DA exposure, knowledge, schema, prostate cancer risk perceptions, decisional anxiety, and decisional conflict. Sample participants included 200 men from the general population (exclusive of African Americans) and 200 African American men. Half of the men in each subsample were randomly assigned to receive the DA. Main Outcome Measures: Decisional conflict regarding prostate cancer screening. Results: The DA influences level of decisional conflict by increasing patient knowledge. This effect of knowledge on decisional conflict is indirect, however, through an association with greater perceived risk and lower decisional anxiety. Also, positive PSA schema was associated with lower decisional anxiety and decisional conflict. It is important that exposure to the DA had no impact on PSA schema. Conclusion: Schemas about testing must be considered in developing messages about the risks and benefits of testing. If schemas are counter to message content, mechanisms for modifying schemas must be incorporated into interventions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)