Quantum fluctuations stabilize skyrmion textures

We study the quantum spin waves associated to skyrmion textures. We show that the zero-point energy associated to the quantum spin fluctuations of a noncollinear spin texture produce Casimir-like magnetic fields. We study the effect of these Casimir fields on the topologically protected noncollinear spin textures known as skyrmions. In a Heisenberg model with Dzyalonshinkii-Moriya interactions, chosen so the classical ground state displays skyrmion textures, we calculate the spin-wave spectrum, using the Holstein-Primakoff approximation, and the associated zero-point energy, to the lowest order in the spin-wave expansion. Our calculations are done both for the single-skyrmion case, for which we obtain a discrete set of skyrmion bound states, as well as for the skyrmion crystal, for which the resulting spectrum gives the spin-wave bands. In both cases, our calculations show that the Casimir magnetic field contributes up to 10% of the total Zeeman energy necessary to delete the skyrmion texture with an applied field.

The Multiple Signaling Systems Regulating Virulence in Pseudomonas aeruginosa

Cell-to-cell communication is a major process that allows bacteria to sense and coordinately react to the fluctuating conditions of the surrounding environment. In several pathogens, this process triggers the production of virulence factors and/or a switch in bacterial lifestyle that is a major determining factor in the outcome and severity of the infection. Understanding how bacteria control these signaling systems is crucial to the development of novel antimicrobial agents capable of reducing virulence while allowing the immune system of the host to clear bacterial infection, an approach likely to reduce the selective pressures for development of resistance. We provide here an up-to-date overview of the molecular basis and physiological implications of cell-to-cell signaling systems in Gram-negative bacteria, focusing on the well-studied bacterium Pseudomonas aeruginosa. All of the known cell-to-cell signaling systems in this bacterium are described, from the most-studied systems, i.e., N-acyl homoserine lactones (AHLs), the 4-quinolones, the global activator of antibiotic and cyanide synthesis (GAC), the cyclic di-GMP (c-di-GMP) and cyclic AMP (cAMP) systems, and the alarmones guanosine tetraphosphate (ppGpp) and guanosine pentaphosphate (pppGpp), to less-well-studied signaling molecules, including diketopiperazines, fatty acids (diffusible signal factor [DSF]-like factors), pyoverdine, and pyocyanin. This overview clearly illustrates that bacterial communication is far more complex than initially thought and delivers a clear distinction between signals that are quorum sensing dependent and those relying on alternative factors for their production.

The Effectiveness of Firms' Strategic Orientations: Investigating Multiple Theoretical Perspectives

The strategic orientation of firms can take on many forms. Researchers most commonly distinguish between entrepreneurial, market, and learning orientations. In combination, strategic orientations represent a firm's value proposition in terms of the markets in which it operates, where it deploys its resources, and which behavioral patterns are established. This thesis provides insights into the effectiveness of strategic orientations by adopting multiple theoretical perspectives. The strategic orientations of entrepreneurial, market, learning, and innovation orientations are investigated in an isolated as well as interrelated manner. The first research article concentrates on entrepreneurial orientation as its conceptualization and operationalization is subject to several debates in the literature. This conceptual study shows how the challenges of the entrepreneurial orientation construct can be overcome in future research to arrive at a higher level of construct clarity. Thereby, the theoretical perspectives of entrepreneurial dominant logic and the theory of planned behavior are employed. The literature has predominantly focused on investigating the effectiveness of particular strategic orientations. Recently, scholars have stressed their synergetic impact on firm performance and, as such, the relevance of considering their combined role in creating superior value for firms. However, empirical research on their interrelatedness remains scant and dispersed, making it necessary to conduct further research on strategic orientations in an integrative manner. As such, the second research article demonstrates which interrelated roles are played by entrepreneurial, market, and learning orientations in their relationship to firm performance. The rich body of existing knowledge is synthesized by means of meta-analysis under the perspective of strategic coalignment as well as the resource-based view of the firm.

Seawater carbonate chemistry and photosynthetic response of Emiliania huxleyi (CS-369) to UV radiation and elevated temperature duirng experiments, 2011

Changes in calcification of coccolithophores may affect their photosynthetic responses to both, ultraviolet radiation (UVR, 280-400 nm) and temperature. We operated semi-continuous cultures of Emiliania huxleyi (strain CS-369) at reduced (0.1 mM, LCa) and ambient (10 mM, HCa) Ca2+ concentrations and, after 148 generations, we exposed cells to six radiation treatments (>280, >295, >305, >320, >350 and >395 nm by using Schott filters) and two temperatures (20 and 25 °C) to examine photosynthesis and calcification responses. Overall, our study demonstrated that: (1) decreased calcification resulted in a down regulation of photoprotective mechanisms (i.e., as estimated via non-photochemical quenching, NPQ), pigments contents and photosynthetic carbon fixation; (2) calcification (C) and photosynthesis (P) (as well as their ratio) have different responses related to UVR with cells grown under the high Ca2+ concentration being more resistant to UVR than those grown under the low Ca2+ level; (3) elevated temperature increased photosynthesis and calcification of E. huxleyi grown at high Ca2+concentrations whereas decreased both processes in low Ca2+ grown cells. Therefore, a decrease in calcification rates in E. huxleyi is expected to decrease photosynthesis rates, resulting in a negative feedback that further reduces calcification.

Operator's manual for Multiple Integrated Laser Engagement System (MILES), simulator system, firing, laser: M82, M1 Abrams tank, NSN 1265-01-137-7697.

Includes index.

Operator's manual : Multiple Integrated Laser Engagement System (MILES) simulator system, firing laser, M73, for M901 improved TOW vehicle.

"July 1988."

Hand receipt covering contents of components of end item (COEI), basic issue items (BII), and additional authorization list (AAL) for Multiple Integrated Laser Engagement System (MILES) simulator system, firing, laser, M80, NSN 1270-01-165-6240, for AH-1S helicopter.

"October 1988."

Operator's manual : multiple integrated laser engagement system (MILES) simulator system, firing, laser: M63, NSN 1265-01-077-6082 for M113 APC.

"January 1982."

Operator's manual : multiple integrated laser engagement system (MILES) simulator system, firing, laser: M67, national stock no. 1265-01-077-6081 for M551 vehicle.

"January 1982."

Operator's manual for Multiple Integrated Laser Engagement System (MILES), simulator system, firing laser, M76, (NSN 1265-01-159-0483) for VULCAN/Product Improved VULCAN Air Defense System, Towed.

Includes index.

Operator's manual for Multiple Integrated Laser Engagement System (MILES), simulator system, firing, laser, M75 (NSN 1265-01-159-0484) for VULCAN/Product Improved VULCAN Air Defense System, self-propelled.

"August 1988."

Operator's manual for Multiple Integrated Laser Engagement System (MILES), simulator system, firing laser, M67 (NSN 1265-01-077-6081) for M551 vehicle.

"July 1988."

Operator's manual for Multiple Integrated Laser Engagement System (MILES), simulator system, firing laser, M83 (NSN 1265-01-158-4560) for M2/M3 fighting vehicles.

Includes index.

Operator's manual : Multiple Integrated Laser Engagement System (MILES) simulator system, firing, laser, M68 (NSN 1265-01-077-6079) for VIPER rocket.

"July 1988."

Operator's manual for Multiple Integrated Laser Engagement System (MILES) simulator system, firing, laser, M80, AH-1S attack helicopter weapon system, NSN 1270-01-165-6240.

Includes index.