The round plume due to a falling point source of heat

Summary The natural convection due to a point source of heat, which falls with constant velocity, is given in the form of an asymptotic series.

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Zusammenfassung Die natürliche Konvektion einer Wärmequelle (die mit konstanter Geschwindigkeit fällt) wird in einer asymptotischen Reihe dargestellt.

     

Observation of muon neutrino disappearance with the MINOS detectors in the NuMI neutrino beam

This Letter reports results from the MINOS experiment based on its initial exposure to neutrinos from the Fermilab NuMI beam. The rates and energy spectra of charged current nu(mu) interactions are compared in two detectors located along the beam axis at distances of 1 and 735 km. With 1.27 x 10(20) 120 GeV protons incident on the NuMI target, 215 events with energies below 30 GeV are observed at the Far Detector, compared to an expectation of 336+/-14 events. The data are consistent with nu(mu) disappearance via oscillations with |Delta(m)2/32|=2.74 +0.44/-0.26 x10(-3)eV(2) and sin(2)(2theta(23))>0.87 (68% C.L.).     

Iron(III) amine-bis(phenolate) complexes as catalysts for the coupling of alkyl halides with aryl Grignard reagents

Catalytic cross-coupling of aryl Grignard reagents with primary and secondary alkyl halides bearing beta-hydrogens is achieved using Fe(III) amine-bis(phenolate) halide complexes.     

Synthesis and structure of iron(iii) diamine-bis(phenolate) complexes

The structures and properties of six new iron(iii) diamine-bis(phenolate) complexes are reported. Reaction of anhydrous FeX(3) salts (where X = Cl or Br) with the diprotonated tripodal tetradentate ligands 2-pyridylamino-N,N-bis(2-methylene-4-methyl-6-tert-butylphenol), H(2)[L(1)], and N,N-dimethyl-N',N'-bis(2-methylene-4-methyl-6-tert-butylphenol)ethylenediamine, H(2)[L(2)], produces the trigonal bipyramidal iron(iii) complexes, [L(1)]FeCl , [L(1)]FeBr , [L(2)]FeCl and [L(2)]FeBr . Reaction of FeX(3) with the related linear tetradentate ligand N,N'-bis(4,6-tert-butyl-2-methylphenol)-N,N'-bismethyl-1,2-diaminoethane, H(2)[L(3)], generates square pyramidal iron(iii) complexes, [L(3)]FeCl and [L(3)]FeBr . Complexes have been characterized using electronic absorption spectroscopy and magnetometry. Single crystal X-ray molecular structures have been determined for complexes 1, 3, 5 and 6.     

Hamiltonian Type Properties in Claw-Free $$P_5$$-Free Graphs

A graph G on n vertices is said to be (k, m)-pancyclic if every set of k vertices in G is contained in a cycle of length r for each integer r in the set \(\{ m, m + 1, \ldots , n \}\). This property, which generalizes the notion of a vertex pancyclic graph, was defined by Faudree et al. in (Graphs Combin 20:291–310, 2004). The notion of (k, m)-pancyclicity provides one way to measure the prevalence of cycles in a graph. Broersma and Veldman showed in (Contemporary methods in graph theory, BI-Wiss.-Verlag, Mannheim, Wien, Zürich, pp 181–194, 1990) that any 2-connected claw-free \(P_5\)-free graph must be hamiltonian. In fact, every non-hamiltonian cycle in such a graph is either extendable or very dense. We show that any 2-connected claw-free \(P_5\)-free graph is (k, 3k)-pancyclic for each integer \(k \ge 2\). We also show that such a graph is (1, 5)-pancyclic. Examples are provided which show that these results are best possible. Each example we provide represents an infinite family of graphs.     

Dependence of DNA sequence selectivity and cell cytotoxicity on azinomycin A and B epoxyamide stereochemistry

Evaluation of the importance of C18/C19 stereochemistry of azinomycin A/B epoxyamide partial structures with respect to DNA alkylation sequence selectivity is reported using a unique assay with a DNA oligomer containing imbedded normal (5'-GGC-3'/3'-CCG-5') and inverted (5'-CGG-3'/3'-GCC-5') azinomycin consensus cross-linking sequences. Both species were found to have unique selectivity profiles and alkylate DNA in a manner distinct from azinomycin B. Computational docking experiments support altered binding modes for the enantiomers.     

Copper and iron interactions with angiotensin-converting enzyme inhibitors. A study by fast-atom bombardment tandem mass spectrometry

Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd.     

Tuning magnetic properties of magnetoelectric BiFeO3-NiFe2O4 nanostructures

Multifunctional thin film nanostructures containing soft magnetic materials such as nickel ferrite are interesting for potential applications in microwave signal processing because of the possibility to shrink the size of device architecture and limit device power consumption. An essential prerequisite to future applications of such a system is a firm understanding of its magnetic properties. We show that nanostructures composed of ferrimagnetic NiFe₂O₄ pillars in a multiferroic BiFeO₃ matrix can be tuned magnetically by altering the aspect ratio of the pillars by depositing films of varying thickness. Magnetic anisotropy is studied using ferromagnetic resonance, which shows that the uniaxial magnetic anisotropy in the growth direction changes sign upon increasing the film thickness. The magnitude of this anisotropy contribution can be explained via a combination of shape and magnetostatic effects, using the object-oriented micromagnetic framework (OOMMF). The key factors determining the magnetic properties of the films are shown to be the aspect ratio of individual pillars and magnetostatic interactions between neighboring pillars.     

Solvent isotope effects on interfacial protein electron transfer in crystals and electrode films

D(2)O-grown crystals of yeast zinc porphyrin substituted cytochrome c peroxidase (ZnCcP) in complex with yeast iso-1-cytochrome c (yCc) diffract to higher resolution (1.7 A) and pack differently than H(2)O-grown crystals (2.4-3.0 A). Two ZnCcP's bind the same yCc (porphyrin-to-porphyrin separations of 19 and 29 A), with one ZnCcP interacting through the same interface found in the H(2)O crystals. The triplet excited-state of at least one of the two unique ZnCcP's is quenched by electron transfer (ET) to Fe(III)yCc (k(e) = 220 s(-1)). Measurement of thermal recombination ET between Fe(II)yCc and ZnCcP+ in the D(2)O-treated crystals has both slow and fast components that differ by 2 orders of magnitude (k(eb)(1) = 2200 s(-1), k(eb)(2) = 30 s(-1)). Back ET in H(2)O-grown crystals is too fast for observation, but soaking H(2)O-grown crystals in D(2)O for hours generates slower back ET, with kinetics similar to those of the D(2)O-grown crystals (k(eb)(1) = 7000 s(-1), k(eb)(2) = 100 s(-1)). Protein-film voltammetry of yCc adsorbed to mixed alkanethiol monolayers on gold electrodes shows slower ET for D(2)O-grown yCc films than for H(2)O-grown films (k(H) = 800 s(-1); k(D) = 540 s(-1) at 20 degrees C). Soaking H(2)O- or D(2)O-grown films in the counter solvent produces an immediate inverse isotope effect that diminishes over hours until the ET rate reaches that found in the counter solvent. Thus, D(2)O substitution perturbs interactions and ET between yCc and either CcP or electrode films. The effects derive from slow exchanging protons or solvent molecules that in the crystal produce only small structural changes.     

NO-releasing zeolites and their antithrombotic properties

Transition metal-exchanged zeolite-A adsorbs and stores nitric oxide in relatively high capacity (up to 1 mmol of NO/g of zeolite). The stored NO is released on contact with an aqueous environment under biologically relevant conditions of temperature and pH. The release of the NO can be tuned by altering the chemical composition of the zeolite, by controlling the amount of water contacting the zeolite, and by blending the zeolite with different polymers. The high capacity of zeolite for NO makes it extremely attractive for use in biological and medical applications, and our experiments indicate that the NO released from Co-exchanged zeolite-A inhibits platelet aggregation and adhesion of human platelets in vitro.