How does the chain extension of poly (acrylic acid) scale in aqueous solution? A combined study with light scattering and computer simulation

This work adresses the question of the scaling behaviour of polyelectrolytes in solution for a realistic prototype: We show results of a combined experimental (light scattering) and theoretical (computer simulations) investigation of structural properties of poly (acrylic acid) (PAA). Experimentally, we determined the molecular weight (M_W) and the hydrodynamic radius (R_H) by static light scattering for six different PAA samples in aqueous NaCl-containing solution (0.1-1 mol/L) of polydispersity D_P between 1.5 and 1.8. On the computational side, three different variants of a newly developed mesoscopic force field for PAA were employed to determine R_H for monodisperse systems of the same M_W as in the experiments. The force field effectively incorporates atomistic information and one coarse-grained bead corresponds to one PAA monomer. We find that R_H matches with the experimental data for all investigated samples. The effective scaling exponent for R_H is found to be around 0.55, which is well below its asymptotic value for good solvents. Additionally, data for the radius of gyration (R_G) are presented.Comment: 17 pages, 3 figures, submitted to Macromolecule

Automedicação tópica ocular em Florianópolis - Santa Catarina.

Trabalho de Conclusão de Curso - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde, Departamento de Clínica Médica, Curso de Medicina, Florianópolis, 199

The absolute continuity of the integrated density of states for magnetic Schr\"odinger operators with certain unbounded random potentials

The object of the present study is the integrated density of states of a quantum particle in multi-dimensional Euclidean space which is characterized by a Schr{\"o}dinger operator with magnetic field and a random potential which may be unbounded from above and below. In case that the magnetic field is constant and the random potential is ergodic and admits a so-called one-parameter decomposition, we prove the absolute continuity of the integrated density of states and provide explicit upper bounds on its derivative, the density of states. This local Lipschitz continuity of the integrated density of states is derived by establishing a Wegner estimate for finite-volume Schr\"odinger operators which holds for rather general magnetic fields and different boundary conditions. Examples of random potentials to which the results apply are certain alloy-type and Gaussian random potentials. Besides we show a diamagnetic inequality for Schr\"odinger operators with Neumann boundary conditions.Comment: This paper will appear in "Communications in Mathematical Physics". It is a revised version of the second part of the first version of math-ph/0010013, which in its second version only contains the (revised) first par

Hidden temporalities: time and intertextuality in the medieval court diary Utatane

This paper explores intertextual expressions of temporality by way of Utatane (Fitful Slumbers, ca. 1238), a medieval memoir describing the unhappy love affair between a young lady-in-waiting and a courtier of higher standing, and her vain efforts to get over her lover. Through a close reading of the work’s beginning and end, it will be demonstrated how intertextual techniques are used in Utatane to inscribe the past into the present and to express the protagonist’s temporal sensations. Hereby it will be argued that, while allusions underline the protagonist’s dissatisfaction with the present and her longing for the past, they may also be read as encrypted expressions of nostalgia for the Heian period’s court culture. At the same time, they demonstrate the author’s sophistication, an important ‘social capital’ of court ladies at the time

"Cut holes and sink 'em": chemical weapons disposal and cold war history as a history of risk

Using the incident of the scuttling of the USS Le Baron Russell Briggs, loaded with roughly 22,000 tons of outdated chemical weapons in 1970, this contribution extrapolates how, why, and when in the United States chemical weapons that had been produced as the ultimate answer to the risk of nuclear war became reframed as a risk themselves. The analysis settles on how questions of knowing and not-knowing about potentialities of future events influenced these re-negotiation processes between the myriad actors involved such as the US military, politicians, environmentalists, Anti-Vietnam activists, and the American public. Beyond analyzing historic examples of risk assessment and management, this contribution also demonstrates how we can read the history of the Cold War as a history or risk. I argue that studying the controversy of operation CHASE 13, the sinking of the SS L. B. Briggs, from a risk perspective opens up new avenues into understanding the Cold War from a social and cultural perspective while integrating political and environmental history

The transatlantic telegraphs and the Class of 1866: the formative years of transnational networks in telegraphic space, 1858-1884/89

'Im Sommer 1866 war es gelungen, ein Seetelegraphenkabel durch den Atlantik zu verlegen und so die Alte und die Neue Welt unmittelbar zu verbinden. Dieses Ingenieurs-technische Großprojekt steht nicht nur am Beginn der Entwicklung eines globalen Seetelegraphennetzwerks, sondern ist auch das Sinnbild einer einzigartigen Gemeinschaft von Kabelakteuren, der hiernach genannten Class of 1866. Aus dieser Kabelgemeinschaft institutionalisierten sich verschiedenste Netzwerke, wie z.B. die Society of Telegraph Engineers, welche fortan den internationalen Seetelegraphenmarkt wirtschaftlich, politisch wie auch kulturell dominieren sollten. Die Verkabelung des Atlantiks von 1866 stellt innerhalb der Geschichte der Seetelegraphie den zentralen Reflexionspunkt dar und die Pioniere des Atlantikkabels nutzten ihre Teilhabe daran, den eigenen Status als exklusive Kabel-Elite zu legitimieren. Durch die festliche Überhöhung des Ereignisses sowie die Veröffentlichung persönlicher Memoiren beeinflussten die Akteure bewusst die historische Wahrnehmung ihrer Zeitgenossen, wie auch der Geschichtsschreibung von heute.' (Autorenreferat)'In 1866 the first lasting submarine cable was laid across the Atlantic. This project not only initiated the development of world-wide submarine telegraph networks, but also the formation of a cable community, the Class of 1866, and their subsequent networks, as for example the Society of Telegraph Engineers, that came to dominate the global cable market economically, politically and culturally. The Atlantic cable project of 1866 represented the central reflection point within the history of submarine telegraphy and the Atlantic cable pioneers used it to legitimate their status as exclusive cable elite. With banquets, soirées and other festivities as well as in their diaries, memoirs and official histories of the cabling of the Atlantic, the Class of 1866 greatly influenced the historic perception of its contemporaries and until today.' (author's abstract

Characterization of MRIP2 as a NO-sensitive guanylyl cyclase-associated protein

Poster presentation: NO-sensitive guanylyl cyclases (sGCs) are cytosolic receptors for nitric oxide (NO) catalyzing the conversion of GTP to cGMP. sGCs are obligate heterodimers composed of one alpha and beta subunit each. The allosteric mechanism of sGC activation via NO is well understood, however, our knowledge about alternative mechanisms such as protein-protein interactions regulating activity, availability, translocation and expression of sGC is rather limited. In a search by the yeast two-hybrid system using the catalytic domain of the alpha1 subunit as the bait, we have identified two structurally related proteins AGAP1 [1] and MRIP2 as novel sGC interacting proteins. MRIP2 is a multi-domain protein of 75 kDa comprising a single PH and ArfGAP domain each and two ankyrin repeats. Co-immunoprecipitation experiments using COS1 cells overexpressing both proteins demonstrated the interaction of MRIP2 with both subunits of the sGC alpha1beta1. Confocal microscopical analysis showed a prominent plasma membrane staining of MRIP2. This membrane association is mediated through an N-terminal myristoylation site and through binding of its PH domain to phospholipids such as phosphatidylinositol-3,5-bisphosphate (PI(3,5)P2). We hypothesize that MRIP2 may represent an acceptor protein for sGC that mediates recruitment of cytosolic sGC to the plasma membrane or other subcellular compartments

Dressing the chopped-random-basis optimization: a bandwidth-limited access to the trap-free landscape

In quantum optimal control theory the success of an optimization algorithm is highly influenced by how the figure of merit to be optimized behaves as a function of the control field, i.e. by the control landscape. Constraints on the control field introduce local minima in the landscape --false traps-- which might prevent an efficient solution of the optimal control problem. Rabitz et al. [Science 303, 1998 (2004)] showed that local minima occur only rarely for unconstrained optimization. Here, we extend this result to the case of bandwidth-limited control pulses showing that in this case one can eliminate the false traps arising from the constraint. Based on this theoretical understanding, we modify the Chopped Random Basis (CRAB) optimal control algorithm and show that this development exploits the advantages of both (unconstrained) gradient algorithms and of truncated basis methods, allowing to always follow the gradient of the unconstrained landscape by bandwidth-limited control functions. We study the effects of additional constraints and show that for reasonable constraints the convergence properties are still maintained. Finally, we numerically show that this approach saturates the theoretical bound on the minimal bandwidth of the control needed to optimally drive the system.Comment: 8 pages, 6 figure

Quantum optimal control within the rotating wave approximation

We study the interplay between rotating wave approximation and optimal control. In particular, we show that for a wide class of optimal control problems one can choose the control field such that the Hamiltonian becomes time-independent under the rotating wave approximation. Thus, we show how to recast the functional minimization defined by the optimal control problem into a simpler multi-variable function minimization. We provide the analytic solution to the state-to-state transfer of the paradigmatic two-level system and to the more general star configuration of an $N$-level system. We demonstrate numerically the usefulness of this approach in the more general class of connected acyclic $N$-level systems with random spectra. Finally, we use it to design a protocol to entangle Rydberg via constant laser pulses atoms in an experimentally relevant range of parameters.Comment: 8 pages, 5 figure