Two Novel Lyso-Ornithine Lipids Isolated from an Arctic Marine Lacinutrix sp. Bacterium

The Lacinutrix genus was discovered in 2005 and includes 12 Gram-negative bacterial species. To the best of our knowledge, the secondary metabolite production potential of this genus has not been explored before, and examination of Lacinutrix species may reveal novel chemistry. As part of a screening project of Arctic marine bacteria, the Lacinutrix sp. strain M09B143 was cultivated, extracted, fractionated and tested for antibacterial and cytotoxic activities. One fraction had antibacterial activity and was subjected to mass spectrometry analysis, which revealed two compounds with elemental composition that did not match any known compounds in databases. This resulted in the identification and isolation of two novel isobranched lyso-ornithine lipids, whose structures were elucidated by mass spectrometry and NMR spectroscopy. Lyso-ornithine lipids consist of a 3-hydroxy fatty acid linked to the alpha amino group of an ornithine amino acid through an amide bond. The fatty acid chains were determined to be iso-C15:0 (1) and iso-C16:0 (2). Compound 1 was active against the Gram-positive S. agalactiae, while 2 showed cytotoxic activity against A2058 human melanoma cells.     

Free expansion of a Bose–Einstein condensate from an Ioffe–Pritchard magnetic trap

5 rubidium-87 atoms released from an Ioffe–Pritchard magnetic trap is investigated experimentally. The expansion dynamics depend only on the trap frequencies, which are determined independently. The data are in good agreement with the expected expansion of a condensate, and are clearly distinct from the behaviour of a classical gas in the hydrodynamic regime. Received: 3 June 1998/Final version: 25 September 1998     

Multi-horizon stochastic programming

Infrastructure-planning models are challenging because of their combination of different time scales: while planning and building the infrastructure involves strategic decisions with time horizons of many years, one needs an operational time scale to get a proper picture of the infrastructure’s performance and profitability. In addition, both the strategic and operational levels are typically subject to significant uncertainty, which has to be taken into account. This combination of uncertainties on two different time scales creates problems for the traditional multistage stochastic-programming formulation of the problem due to the exponential growth in model size. In this paper, we present an alternative formulation of the problem that combines the two time scales, using what we call a multi-horizon approach, and illustrate it on a stylized optimization model. We show that the new approach drastically reduces the model size compared to the traditional formulation and present two real-life applications from energy planning.     

Effects of chemical and biological warfare remediation agents on the materials of museum objects

In the fall of 2001, anthrax-contaminated letters were sent to public figures in the United States. Chemical and radiation treatments were employed to decontaminate exposed buildings, objects, and materials. These treatments are effective, but potentially damaging to exposed objects and materials. The recommended surface chemical treatments include solutions, gels, and foams of oxidizing agents such as peroxides or chlorine bleaching agents. Such oxidizing agents are effective against a wide range of hazardous chemical and biological agents. Knowing how these reagents affect various substrates would help to anticipate and to minimize any potential damage. We are examining the effects on typical museum materials of reagents likely to be used, including hydrogen peroxide, sodium hypochlorite, and potassium peroxymonosulfate. Results so far show significant changes in a number of materials. Surface corrosion was observed on metals such as copper, silver, iron, and brass. Color changes occurred with at least one reagent in about one-fourth of the dyed fabric swatches tested, and about half of the inks. Samples of aged yellowed paper are bleached. Effects varied with both the substrate and the tested reagent. The observed changes were generally less drastic than might have been expected. Enough materials were affected, though, to preclude the use of these reagents on museum objects unless no less drastic alternative is available. It appears that many objects of lesser intrinsic value can be treated without severe loss of properties or usefulness. For example, most documents should remain legible if the appropriate reagent is used. This work will provide a basis for determining which treatment is most appropriate for a specific situation and what consequences are to be expected from other treatments. PACS 81.65.Mq; 81.70.Jb; 82.30.Lp     

Die Optimierung linearer Modelle überlasteter Straßennetze mit öffentlichem Verkehr

Zusammenfassung In der vorliegenden Arbeit wird gezeigt, daß die Theorie überlasteter Straßennetze sehr einfach wird, wenn man die Wartezeitfunktionen linearisiert. Die Straßennetze dürfen außer den überlasteten Straßenabschnitten auch schwach belastete Abschnitte enthalten, deren Abflüsse nicht durch die Grünzeiten bestimmt sind. Mit Hilfe der Theorie linearer überlasteter Straßen netze kann man z.B. zeigen, daß in überlasteten Straßenzügen mit öffentlichem Verkehr die Dosierung des zufließenden Individualverkehrs günstiger sein kann als die Einrichtung von Sonderspuren für den öffentlichen Verkehr.

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Summary The presented paper shows, that the theory of oversaturated road networks is greatly simplified by linearization of the waiting time functions. The road networks may contain not only oversaturated links but also less loaded links, whose output is not determined by the green times. By the theory of linear oversaturated road networks one may show e.g., that in oversaturated main roads with public transport the metering of the entering cars may be favourable to the installation of segregated lanes for the public transport.

     

What spatial light modulators can do for optical microscopy

With the availability of high‐resolution miniature spatial light modulators (SLMs) new methods in optical microscopy have become feasible. The SLMs discussed in this review consist of miniature liquid crystal displays with micron‐sized pixels that can modulate the phase and/or amplitude of an optical wavefront. In microscopy they can be used to control and shape the sample illumination, or they can act as spatial Fourier filters in the imaging path. Some of these applications are reviewed in this article. One of them, called spiral phase contrast, generates isotropic edge enhancement of thin phase samples or spiral‐shaped interference fringes for thicker phase samples, which can be used to reconstruct the phase topography from a single on‐axis interferogram. If SLMs are used for both illumination control and spatial Fourier filtering, this combination for instance allows for the generalization of the Zernike phase contrast principle. The new SLM‐based approach improves the effective resolution and avoids some shortcomings and artifacts of the traditional method. The main advantage of SLMs in microscopy is their flexibility, as one can realize various operation modes in the same setup, without the need for changing any hardware components, simply by electronically switching the phase pattern displayed on the SLMs.     

Decarboxylation of 6-nitrobenzisoxazole-3-carboxylate in aqueous cationic micelles: kinetic evidence of microinterface property changes

We studied decarboxylation of 6-nitrobenzisoxazole-3-carboxylate, 1, as a kinetic probe to investigate microinterface properties of aqueous micelles formed by cationic surfactants of increasing head group bulk, i.e., cetyltrialkylammonium bromide, with alkyl=Me (CTABr), Et (CTEABr), n-Pr (CTPABr), n-Bu (CTBABr) and p-octyloxybenzyltrialkylammonium bromide surfactants with alkyl=Me (pOOTABr), n-Pr (pOOTPABr), and n-Bu (pOOTBABr), and the longer p-dodecyloxybenzyltrimethylammonium bromide (pDoTABr) at concentrations higher than 0.05 M. The pseudophase kinetic treatment fails to fit the data that show anomalies with abrupt increases in k(obs) for CTPABr and CTBABr (but not for CTEABr) and with smooth and continuos increase of k(obs) for all p-alkyloxybenzyltrilakylammonium bromides. Abrupt and successive modifications of the micellar interface properties, undergoing only when the polar head or the alkyl chain have some covalent structure, account for the observed kinetic behavior.