Niementowski-type synthesis of pyrido[3,2-e][1,2,4]triazines: potent aza-analogs of pyrido[2,3-b]pyrazine fungicides

Novel trisubstituted pyrido[3,2-e][1,2,4]triazines have been found to possess similar biological activity to the corresponding pyridopyrazine fungicides against important phytopathogens such as Mycosphaerella graminicola (wheat leaf blotch), Magnaporthe grisea (rice blast), and Rhizoctonia solani (rice sheath blight). They have been prepared for the first time from a monocyclic triazine by Niementowski-type ring condensation.     

Synthesis,Crystal Structure,and Characterization of a New Metal Borophosphate: PbII4{Co2[B(OH)2P2O8](PO4)2}Cl

A new metal borophosphate Pb^II₄{Co₂[B(OH)₂P₂O₈](PO₄)₂}Cl ( 1 ), containing both Pb²⁺ cations and Cl^– anions, was hydrothermally synthesized and characterized by powder X‐ray diffraction, ICP, TG/DTA, and FTIR spectroscopic analyses. The crystal structure determination from single‐crystal X‐ray diffraction reveals that compound 1 crystallizes in the trigonal space group R c (No. 167), a = 9.7513(7) Å, c = 91.060(13) Å, V = 7498.7(13) Å³ and Z = 18. Its structure features a new cobalt borophosphate layer {Co₂[B(OH)₂P₂O₈](PO₄)₂}^7– built up from CoO₅ square pyramids, [B(OH)₂P₂O₈]^5– borophosphate trimers and PO₄ tetrahedra. Extra‐framework Pb²⁺ and Cl^– ions are located at the vacancy of layers to achieve the charge neutrality of the framework. Magnetic measurements indicate that antiferromagnetic interactions exist between Co²⁺ ions with a negative Weiss constant of –20.3 K.     

PotLLL: a polynomial time version of LLL with deep insertions

Lattice reduction algorithms have numerous applications in number theory, algebra, as well as in cryptanalysis. The most famous algorithm for lattice reduction is the LLL algorithm. In polynomial time it computes a reduced basis with provable output quality. One early improvement of the LLL algorithm was LLL with deep insertions (DeepLLL). The output of this version of LLL has higher quality in practice but the running time seems to explode. Weaker variants of DeepLLL, where the insertions are restricted to blocks, behave nicely in practice concerning the running time. However no proof of polynomial running time is known. In this paper PotLLL, a new variant of DeepLLL with provably polynomial running time, is presented. We compare the practical behavior of the new algorithm to classical LLL, BKZ as well as blockwise variants of DeepLLL regarding both the output quality and running time.     

The Hydrogen-Bonded Coordination Polymer Tetracesium Bis(5-nitroisophthalate) Heptahydrate

Abstract  

The coordination polymer complex tetracesium bis(5-nitroisophthalate) heptahydrate [Cs₄(C₈H₃NO₆)₂ (H₂O)₇] _n has been synthesized and characterized using single-crystal X-ray diffraction. Crystals are monoclinic, space group P2₁/c, with Z = 4 in a cell with dimensions a = 12.3213(3), b = 6.7557(2), c = 36.2020(9) ?, β = 90.548(2)^o. The complex is based on a repeating unit comprising four independent and different Cs coordination centres, two 6-coordinate, and two 8-coordinate [Cs–O, range 2.959(5)–3.386(5) ?], and seven water molecules, two of which are monodentate and the other five bridging, while all other oxygen atoms in the structure, including those of the nitro groups form inter-Cs bridges. Extensive water O–H···O hydrogen-bonding interactions give a three-dimensional framework. This structure represents the first of an alkali metal compound of 5-nitroisophthalic acid that has been reported.     

The asymptotic Plateau problem in Gromov hyperbolic manifolds

We solve the asymptotic Plateau problem in every Gromov hyperbolic Hadamard manifold (X,g) with bounded geometry. That is, we prove existence of complete (possibly singular) k-dimensional area minimizing surfaces in X with prescribed boundary data at infinity, for a large class of admissible limit sets and for all . The result also holds with respect to any riemannian metric on X which is lipschitz equivalent to g. Received: 23 January 2001 / Accepted: 25 October 2001 Published online: 28 February 2002     

A New Convergent Synthesis of Thiamine Hydrochloride

Thiamine hydrochloride ( 1a ; 3-[(4-amino-2-methylpyrimidin-5-yl)methyl]-5-(2-hydroxyethyl)-4-methylthia-zolium chloride hydrochloride; vitamin B¹) has been synthesized in excellent yield by condensation of 3-mercapto-4-oxopentyl acetate (5a) with 3, 4-dihydro-7-methylpyrimido[4, 5-d]pyrimidine (4) in formic acid. The two intermediates 5a and 4 are prepared from 3-chloro-4-oxopentyl acetate (3) and 4-amino-2-methyl-5-(aminomethyl)-pyrimidine (Grewe diamine; 2a ), respectively.     

Näherungsweise Darstellung des Geschwindigkeitsfeldes um einen Zylinder bei Schleichströmung

Zusammenfassung Die Kenntnis des Geschwindigkeitsfeldes um Zylinder bei schleichender Strömung ist u.a. für Glasschmelzaggregate von Interesse, in denen die Schmelze um zylindrische Elektroden strömt [1] oder wo Messungen mit Stabsonden durchgeführt werden sollen [2]. Während für die langsame Umströmung der Kugel schon von Stokes [3] eine Lösung angegeben wurde, bereitet die mathematische Behandlung des als unendlich lang angenommenen Zylinders größere Schwierigkeiten. Hier soll gezeigt werden, wie sie durch Auffinden einer Näherungslösung umgangen werden können.

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Approximate calculation of velocity fields past a cylinder in the case of creeping motion

The knowledge of the velocity distribution past a cylinder in the case of creeping motion is of interest e.g. for glass melting tanks containing rod electrodes [1] or for measurements using cylindrical probes [2]. Stokes [3] already published a solution concerning the slow flow past a sphere but the mathematical calculation of an infinite long cylinder leads to some difficulties. In this paper is shown to avoid them using an approximate solution.

     

Simultaneous determination of perfluoroalkyl phosphonates, carboxylates, and sulfonates in drinking water

A trace analytical method based on high performance liquid chromatography coupled to quadrupole time-of-flight high resolution mass spectrometry was developed for simultaneous determination of perfluoroalkyl phosphonates (PFPAs, carbon chain lengths C6,8,10), perfluoroalkyl carboxylates (PFCAs, C5-12), and perfluoroalkyl sulfonates (PFSAs, C4,6,8,10) in drinking water (tap water). Analytes were enriched on a mixed mode co-polymeric sorbent (C8+quaternary amine) using solid phase extraction. Chromatographic separation was achieved on a Zorbax Extend C18 reversed phase column using a mobile phase gradient consisting of water, methanol, and acetonitrile containing 2mM ammonium acetate and 5 mM 1-methyl piperidine. The mass spectrometer was operated in electrospray negative ion mode. Use of 1-methyl piperidine in the mobile phase resulted in a significant increase in instrument sensitivity for PFPAs through improved chromatographic resolution, background suppression, and increased ionization efficiency. Method detection limits for extraction of 500 mL tap water were in the ranges of 0.095-0.17 ng/L, 0.027-0.17 ng/L, and 0.014-0.052 ng/L for PFPAs, PFCAs, and PFSAs, respectively. Whole method recoveries at a spiking level of 0.5 ng/L to 500 mL HPLC grade water were 40-56%, 56-97%, and 55-77% for PFPAs, PFCAs, and PFSAs, respectively. A matrix effect (signal enhancement) was observed in the detection of PFPAs in tap water extracts, leading to calculated recoveries of 249-297% at a 0.5 ng/L spiking level. This effect resulted in an additional improvement of method sensitivity for PFPAs. To compensate for the matrix effect, PFPAs in tap water were quantified using matrix-matched and extracted calibration standards. The method was successfully applied to the analysis of drinking water collected from six European countries. PFPAs were not detected except for perfluorooctyl phosphonate (PFOPA) at close to the detection limit of 0.095 ng/L in two water samples from Amsterdam, the Netherlands. Highest levels were found for perfluorobutane sulfonate (PFBS, 18.8 ng/L) and perfluorooctanoate (PFOA, 8.6 ng/L) in samples from Amsterdam as well as for perfluorooctane sulfonate (PFOS, 8.8 ng/L) in tap water from Stockholm, Sweden.