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Computing the external geodesic diameter of a simple polygon (1990)

Samuel, D. ; Toussaint, G. T.

Springer

Computing 44 (1990), S. 1-19

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ISSN: 1436-5057

Keywords: 68U05 ; 68C25 ; Polygon ; geodesics ; diameter ; furthest neighbour ; algorithm ; complexity ; computational geometry

Source: Springer Online Journal Archives 1860-2000

Topics: Computer Science

Description / Table of Contents: Zusammenfassung Gegeben sei ein einfaches PolygonP mitn Ecken. Wir geben einen Algorithmus an, der ein Punktepaar auf der Begrenzung vonP liefert, welches die Länge des kürzesten Weges maximiert, der im Äußeren des Polygons verläuft. Den Weg bezeichnen wir als den äußeren geodätischen Durchmesser vonP. Unser Algorithmus benötigt 0(n 2) Zeit und erfordert 0(n) Speicherplatz. Zu unserer Überraschung ist das Problem von dem, der Berechnung des inneren geodätischen Durchmessers vonP völlig verschieden. Während der innere Durchmesser immer in Ecken vonP endet, muß dies für den äußeren Durchmesser nicht der Fall sein. Schließlich zeigen wir noch, daß der Algorithmus so erweitert werden kann, daß er das Problem der entferntesten äußeren geodätischen Nachbarn löst.

Notes: Abstract Given a simple polygonP ofn vertices, we present an algorithm that finds the pair of points on the boundary ofP that maximizes theexternal shortest path between them. This path is defined as theexternal geodesic diameter ofP. The algorithm takes0(n 2) time and requires0(n) space. Surprisingly, this problem is quite different from that of computing theinternal geodesic diameter ofP. While the internal diameter is determined by a pair of vertices ofP, this is not the case for the external diameter. Finally, we show how this algorithm can be extended to solve theall external geodesic furthest neighbours problem.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02247961

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A method for isolating and culturing vascular smooth muscle cells from porcine cerebral arteries (1996)

Tao, Hong ; Zhang, Li-Ming ; Castresana, Manuel R. ; [et al.]

Springer

Methods in cell science 18 (1996), S. 41-46

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ISSN: 1573-0603

Keywords: Brain ; Artery ; Cultured smooth muscle cells ; cGMP ; cAMP

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Cerebral blood vessels have unique properties when compared to most peripheral vascular beds. One such property is that large cerebral vessels are involved in the regulation of cerebral vascular resistance. Studying smooth muscle cells isolated from these vessels will determine how phenotypic properties of these cells contribute to unique cerebrovascular function. Therefore we developed a method of culturing smooth muscle cells from explants of cerebral arteries of porcine brains obtained, gratis, from a local slaughter house. Cells isolated and cultured by the methods described herein were of smooth muscle origin as indicated by histochemical staining for smooth muscle α-actin. Further, we examined the response of the cultured cells to agonists which activate the cGMP dependent vasodilator system by stimulating soluble guanylyl cyclase (nitroglycerin and sodium nitroprusside) or particulate guanylyl cyclase (C-type natriuretic peptide). Also, forskolin activation of adenylyl cyclase was examined. These agents stimulated an increase in intracellular cGMP and cAMP in a manner that was reproducible in every cell isolation (20 brains) and which remained unchanged through nine passages. Additionally, the cells could be frozen, thawed and replated without loss of responsiveness to these agents. The protocol reported here provides a method for culturing cerebral artery smooth muscle cells that is inexpensive, relatively simple, and which yields cells that can be utilized through multiple passages.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00123522

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Detecting and adjusting for non-linearities in calibration of near-infrared data using principal components (1993)

Oman, Samuel D. ; Naes, Tormod ; Zube, Anan

New York, NY : Wiley-Blackwell

Journal of Chemometrics 7 (1993), S. 195-212

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ISSN: 0886-9383

Keywords: Calibration ; Non-linearity ; Principal components ; Stein estimate ; Chemistry ; Analytical Chemistry and Spectroscopy

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: A new regression method for non-linear near-infrared spectroscopic data is proposed. The technique is based on a model which is linear in the principal components and simple functions (squares and products) of them. Added variable plots are used to determine which squares and products to incorporate into the model. The regression coefficients are estimated by a Stein estimate which shrinks towards the estimate determined by the first several principal components and the selected non-linear terms. The technique is not computationally intensive and is appropriate for routine predictions of chemical concentrations. The method is tested on three data sets and in all cases gives more accurate predictions than does linear principal components regression.

Additional Material: 8 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/cem.1180070306

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Cyclic ions in the mass spectra of trimethylsilyl derivatives of substituted o-dihydroxybenzenesMention of a company or product name does not imply its approval or recommendation by the USDA to the exclusion of others that may be suitable. (1983)

Horvat, Robert J. ; Senter, Samuel D.

Chichester : Wiley-Blackwell

Biological Mass Spectrometry 18 (1983), S. 413-417

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ISSN: 0030-493X

Keywords: Chemistry ; Analytical Chemistry and Spectroscopy

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The mass spectra of trimethylsilyl (TMS) ethers/methyl esters of phenolic acids containing o-dihydroxybenzene groups have base peaks at [M-119]+ instead of the usual [M-15]+ and [M-31]+ that are characteristic of TMS/methyl esters of monohydroxyphenolic acids. These ions, formed by the loss of 31+88 u from the parent ion, possess a cyclic moiety as proven by substitution of deuterium atoms for hydrogen atoms in the TMS groups of the methyl esters of 3,4,5-trihydroxybenzoic (gallic), 3,4-dihydroxybenzoic (protocatechuic) and β-(3,4-dihydroxyphenyl)propenoic (caffeic) acids. Although these cyclic ions are the base peaks in TMS-derivatized o-dihydroxyphenolic acid esters, similar ions represent intense peaks but not necessarily the base peak in other derivatized compounds such as 1,2-dihydroxybenzene, 1,2-dihydroxy-3-methyl- and 1,2-dihydroxy-4-methyl-benzenes and flavan-3-ols that possess o-dihydroxybenzene groups. Compounds possession m- or p-dihydroxybenzene groups do not form these cyclic ions; therefore, this procedure for derivatization and interpretation of mass spectra is valuable for the identification of compounds containing o-dihydroxybenzene groups in complex mixtures of isomeric compounds.

Additional Material: 3 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/oms.1210181002

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