Silent research vessels are not quiet

Behavior of herring (Clupea harengus) is stimulated by two ocean-going research vessels; respectively designed with and without regard to radiated-noise-standards. Both vessels generate a reaction pattern, but, contrary to expectations, the reaction initiated by the silent vessel is stronger and more prolonged than the one initiated by the conventional vessel. The recommendations from the scientific community on noise-reduced designs were motivated by the expectation of minimizing bias on survey results caused by vessel-induced fish behavior. In conclusion, the candidate stimuli for vessel avoidance remain obscure. Noise reduction might be necessary but is insufficient to obtain stealth vessel assets during surveys.     

Stereoselective preparation of (RP)-8-hetaryladenosine-3',5'-cyclic phosphorothioic acids

Cyclic adenosine monophosphate (cAMP) has been converted into its 8-bromo derivative and 2'O-TBDMS protected before activation of the phosphoric acid moiety with a reagent generated in situ from oxalyl chloride and DMF. Further reactions with primary amines furnished corresponding phosphoramidates with high stereoselectivity at the phosphorus atom. Cross-coupling reactions with the 8-bromopurine yielded 8-hetaryl derivatives. X-Ray analyses showed the amidates to possess the (S(P))-configuration. Carbon disulfide effected thiylation under strongly basic conditions stereospecifically provided the (R(P))-phosphorothioic acids.     

Quantitative comparison of IMAC and TiO<Subscript>2</Subscript> surfaces used in the study of regulated,dynamic protein phosphorylation

Protein phosphorylation regulates many aspects of cellular function, including cell proliferation, migration, and signal transduction. An efficient strategy to isolate phosphopeptides from a pool of unphosphorylated peptides is essential to global characterization using mass spectrometry. We describe an approach employing isotope tagging reagents for relative and absolute quantification (iTRAQ) labeling to compare quantitatively commercial and prototypal immobilized metal affinity chelate (IMAC) and metal oxide resins. Results indicate a prototype iron chelate resin coupled to magnetic beads outperforms either the Ga(3+)-coupled analog, Fe(3+), or Ga(3+)-loaded, iminodiacetic acid (IDA)-coated magnetic particles, Ga(3+)-loaded Captivate beads, Fe(3+)-loaded Poros 20MC, or zirconium-coated ProteoExtract magnetic beads. For example, compared with Poros 20MC, the magnetic metal chelate (MMC) studied here improved phosphopeptide recovery by 20% and exhibited 60% less contamination from unphosphorylated peptides. With respect to efficiency and contamination, MMC performed as well as prototypal magnetic metal oxide-coated (TiO(2)) beads (MMO) or TiO(2) chromatographic spheres, even if the latter were used with 2,5-dihydroxybenzoic acid (DHB) procedures. Thus far, the sensitivity of the new prototypes reaches 50 fmol, which is comparable to TiO(2) spheres. In an exploration of natural proteomes, tryptic (phospho)peptides captured from stable isotopic labeling with amino acids in cell culture (SILAC)-labeled immunocomplexes following EGF-treatment of 5 x 10(7) HeLa cells were sufficient to quantify stimulated response of over 60 proteins and identify 20 specific phosphorylation sites.     

Eindeutige Hahn-Banach-Erweiterungen

Ohne ZusammenfassungHerrnGottfried Köthe zum 60. Geburtstag am 25. Dezember 1965 gewidmet     

Halley and Newton are one step apart

One of the central problems of scientific computation is the efficient numerical solution of the system of n equations in n unknowns F (x) = 0 where F: Rⁿ → Rⁿ is sufficiently smooth. While Newton's method is usually used for solving such systems, third order methods will in general use fewer iterations than a second order method to reach the same accuracy. However, the number of arithmetic operations per iteration is higher for third order methods than second order methods. In this note we will consider the case where F = ∇f, where f is three times continuously differentiable. We will show that for a large class of sparse problems the ratio of the number of arithmetic operations of a third order method and Newton's method is constant per iteration. It is shown that when the structure of the tensor is induced by a general sparse structured Hessian matrix which gives no fill-ins when we use a direct method to solve a system of linear equations. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Column generation approaches to ship scheduling with flexible cargo sizes

We present a Dantzig–Wolfe procedure for the ship scheduling problem with flexible cargo sizes. This problem is similar to the well-known pickup and delivery problem with time windows, but the cargo sizes are defined by intervals instead of by fixed values. The flexible cargo sizes have consequences for the times used in the ports because both the loading and unloading times depend on the cargo sizes. We found it computationally hard to find exact solutions to the subproblems, so our method does not guarantee to find the optimum over all solutions. To be able to say something about how good our solution is, we generate a bound on the difference between the true optimal objective and the objective in our solution. We have compared our method with an a priori column generation approach, and our computational experiments on real world cases show that our Dantzig–Wolfe approach is faster than the a priori generation of columns, and we are able to deal with larger or more loosely constrained instances. By using the techniques introduced in this paper, a more extensive set of real world cases can be solved either to optimality or within a small deviation from optimality.     

新型碳材料作为直接醇类燃料电池催化剂载体的评述

 电催化反应过程涉及固、液、气传输以及电子和质子传导, 为确保反应的顺利进行和提高催化剂中贵金属的利用率及延长催化剂的寿命, 理想的电催化剂载体必须同时具备高比表面积、导电性好、合适的孔结构、耐腐蚀以及合适的表面基团等. 为此, 碳载体的改性工作受到关注, 常用的方法是通过酸、碱、氧化和高分子等手段改变载体的结构和表面性质, 以期接近理想电催化剂载体的要求; 同时在开发新型碳载体方面做了更大量的工作. 本文简要评述了商品炭载体如碳黑 Vulcan XC-72R 以及其它的乙炔黑、黑珍珠-2000、Printex XE-2 和 Ketjen Black EC 等碳材料在直接醇燃料电池中的应用, 但对纳米碳纤维、碳纳米管、有序多孔碳、中间相碳小球、碳纳米角、碳纳米卷和碳气凝胶等新型碳载体则进行了较全面的评述. 与商品碳载体相比, 新型碳载体在一定程度上都表现出比 XC-72R 更优的性能, 这主要是因为新型碳材料具有特殊的结构、更高的结晶性能 (导电性) 和更好的传质能力.