Computing low-capacity 0–1 knapsack polytopes

A procedure is proposed that, given a linear inequalityL having positive integral coefficients in 0–1 variables, finds all the facets of the convex hull of the solutions ofL. This is done for allL by doing once and for all the computations for a particular sequenceM ₁,M ₂,... of such linear inequalities, called master knapsack problems. To find the facets for a givenL, it is enough to know the facets for the master knapsack problemM _b, whereb is the free term inL (no matter how many variablesL might have). ThisM _b has no more than order ofb logb variables. The procedure is based on polarity. All the facets forM ₁,...,M ₇ are tabulated.

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Zusammenfassung Es wird ein Verfahren vorgestellt, das für eine lineare UngleichungL in binären Variablen mit positiven ganzzahligen Koeffizienten alle Facetten der konvexen Hülle der Lösungen vonL bestimmt. Um diese Facetten für irgendeine UngleichungL mit rechter Seiteb zu erhalten, braucht man nur die Facetten des sogenannten Master-Knapsack-ProblemsM _b zu kennen, dasO (b log b) Variablen besitzt. Fürb=1,..., 7 werden alle Facetten vonM _b angegeben.

     

Aza- and oxa-eburnamonine : Reactions with indole derivatives,part XLVII

Ring opening reactions of cyclopropane intermediates give rise to pentacyclic eburnamonines with a nitrogen or oxygen atom at position 15.     

Cut-threshold graphs

We study the structure of the networks in which connectedness and disconnectedness can be expressed by a threshold system. This means that the elements of the network have a certain “destruction cost” and that the enemy can disconnect the network if and only if they pay a large enough price. We give polynomial algorithms for the recognition of such networks, and for the determination of the appropriate costs and threshold value.     

An automated fluorescence assay for dissolved total amino acids from marine waters in the presence of interfering material

Summary For the determination of dissolved total amino acids from seawater a method is recommended that was based on the fluorimetric detection of primary amines with o-phthaldialdehyde (OPA). Automatic measurements are performed and calibrated with an amino acid mixture standard. Proteins which interfere with the procedure are separated by gel filtration. Ammonia which is also detected by OPA has to be determined additionally and corrected. The fluorescent response is linear over a wide range. The detection limit is in femtomol concentrations.

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Automatische fluorimetrische Bestimmung von gelösten Gesamt-Aminosäuren in Meerwasser in Gegenwart von störenden Substanzen

Zusammenfassung Für die Bestimmung von im Meerwasser gelösten Gesamt-Aminosäuren wird eine Methode empfohlen, die auf einem fluorimetrischen Nachweis primärer Amine mit o-Phthaldialdehyd (OPA) basiert. Die Messungen erfolgen automatisch und werden gegen ein Aminosäurengemisch als Standard geeicht. Proteine, die den Nachweis stören, werden durch Gelfiltration abgetrennt. Ammonium, das ebenfalls durch OPA angezeigt wird, muß separat gemessen und korrigiert werden. Das Fluoreszenz-Signal ist über einen weiten Bereich linear. Die untere Nachweisgrenze liegt im Femtomolbereich.

     

Stellar reaction rate of 20Ne(α, γ)24Mg

The reaction ²⁰Ne(α, γ)²⁴Mg has been investigated at E_α(lab) = 0.55–3.20 MeV. Neon gas enriched to 99.95% in ²⁰Ne was recirculated in differentially pumped gas target systems of the extended and quasipoint jet types. New resonances were found at E_α(lab) = 958, 1226, 1260, 1704 and 2277 keV, which correspond to known states in ²⁴Mg. Excitation energies, γ-ray decay schemes, γ-ray angular distributions, resonance widths and strengths as well as J^π and T-assignments are reported for all the resonances. Information on low-lying states in ²⁴Mg is also obtained. The nuclear and astrophysical aspects of the results are discussed.     

Protease‐Triggered,Integrin‐Targeted Cellular Uptake of Recombinant Protein Micelles

Targeting nanoparticles for drug delivery has great potential for improving efficacy and reducing side effects from systemic toxicity. New developments in the assembly of materials afford the opportunity to expose cryptic targeting domains in tissue‐specific microenvironments in which certain proteases are expressed. Here, recombinant proteins are designed to combine the responsiveness to environmental proteases with specific targeting. Materials made recombinantly allow complete control over amino acid sequence, in which each molecule is identically functionalized. Previously, oleosin, a naturally occurring plant protein that acts as a surfactant, has been engineered to self‐assemble into spherical micelles—a useful structure for drug delivery. To make oleosins that are locally activated to bind receptors, oleosin is genetically modified to incorporate the integrin‐binding motif RGDS just behind a domain cleavable by thrombin. The resulting modified oleosin self‐assembles into spherical micelles in aqueous environments, with the RGDS motif protected by the thrombin‐cleavable domain. Upon the addition of thrombin, the RGDS is exposed and the binding of the spherical micelles to breast cancer cells is increased fourfold.

     

Application of in situ silylation for improved, convenient preparation of fluorenylmethoxycarbonyl (Fmoc)-protected phosphinate amino acids

A convenient and efficient method has been developed for the preparation of 9-fluorenylmethoxycarbonyl (Fmoc)-protected 1-aminoalkylphosphinic acids. Reproducible procedures for the synthesis and purification of free alpha-amino H-phosphinates are provided. Protection of free amino phosphinates as the N-Fmoc derivative was achieved by in situ trimethylsilylation of aminoalkylphosphinic acids, which then reacted with Fmoc-Cl to provide corresponding products in excellent yields and in high purity after simple extractive isolation. Mechanistic aspects of the silylation are discussed, and the application of the procedure to another class of amino phosphorus acids is presented.