Mechanism of the Enzymic Reduction of N_2: The Binding of Adenosine 5'-Triphosphate and Cyanide to the N_2-reducing System

The in vitro reduction of N_2 is a complex process involving at least six different reactants: two proteins [1,2] for which the names azoferredoxin (AzoFd) and molybdoferredoxin (MoFd) have been proposed[3], an electron source, the electron acceptor, ATP[4], and Mg2+[5-7]. One of the goals of research in this area is to define the orderly and quantitative participation of these reactants leading to the reduction of the electron acceptor with concomitant breakdown of ATP to ADP and inorganic phosphate[7]. The work described in this paper shows that (1) AzoFd reversibly binds both ATP, a reactant in N2 reduction, and ADP, a specific inhibitor of N2 reduction, and (2) MoFd reversibly binds cyanide, which is also reduced by the N_2-reducing system. It is suggested that the binding of ATP and of cyanide are partial reactions of the N_2-reducing system

Demonstration of wide band RF photonic transversal phase-shifter

A transversal phase-shifter using multiple MZMs is demonstrated. The device exhibits continuously variable phase-shift exceeding 360° at 2 GHz and amplitude uniformity within 3 dB over 0.2-2 GHz. The device stability and practicality are discussed

Entrainment and thrust augmentation in pulsatile ejector flows

This study comprised direct thrust measurements, flow visualization by use of a spark shadowgraph technique, and mean and fluctuating velocity measurements with a pitot tube and linearized constant temperature hot-wire anemometry respectively. A gain in thrust of as much as 10 to 15% was observed for the pulsatile ejector flow as compared to the steady flow configuration. From the velocity profile measurements, it is concluded that this enhanced augmentation for pulsatile flow as compared to a nonpulsatile one was accomplished by a corresponding increased entrainment by the primary jet flow. It is also concluded that the augmentation and total entrainment by a constant area ejector critically depends upon the inlet geometry of the ejector. Experiments were performed to evaluate the influence of primary jet to ejector area ratio, ejector length, and presence of a diffuser on pulsatile ejector performance

Wide-band variable transversal phase-shifter

We present a novel broadband phase-shifter based on a transversal filter configuration. This approach allows flexible control of the amplitude response while providing continuous variation of a linear phase slope. Numerical examples, both ideal and using practical RF components are presented and practical challenges in realising the phase-shifter are identified

Wideband RF photonic vector sum phase-shifter

A novel broadband linear phase phase-shifter based on the vector summation method is proposed. A photonic implementation of the phase-shifter with a continuously variable linear phase-shift up to 120° over the frequency range of DC-4 GHz is demonstrated. Good agreement between the measured responses and theoretical predictions is obtained

Synergistic and Antagonistic Effects of Aromatics on the Agglomeration of Gas Hydrates

Surfactants are often used to stabilize aqueous dispersions. For example, surfactants can be used to prevent hydrate particles from forming large plugs that can clog, and sometimes rupture pipelines. Changes in oil composition, however dramatically affect the performance of said surfactants. In this work we demonstrate that aromatic compounds, dissolved in the hydrocarbon phase, can have both synergistic and antagonistic effects, depending on their molecular structure, with respect to surfactants developed to prevent hydrate agglomerations. While monocyclic aromatics such as benzene were found to disrupt the structure of surfactant films at low surfactant density, they are expelled from the interfacial film at high surfactant density. On the other hand, polycyclic aromatics, in particular pyrene, are found to induce order and stabilize the surfactant films both at low and high surfactant density. Based on our simulation results, polycyclic aromatics could behave as natural anti-agglomerants and enhance the performance of the specific surfactants considered here, while monocyclic aromatics could, in some cases, negatively affect performance. Although limited to the conditions chosen for the present simulations, the results, explained in terms of molecular features, could be valuable for better understanding synergistic and antagonistic effects relevant for stabilizing aqueous dispersions used in diverse applications, ranging from foodstuff to processing of nanomaterials and advanced manufacturing

Wafer scale texturing of LiNbO3

We report a novel technique for micro texturing of LiNbO<sub>3</sub>. Well-defined raised ridges and etched trenches are demonstrated. This technique is suitable for the realization of surface relief gratings and photonic crystals

Comprehensive design and whole-cavity simulation of a multi-beam inductive output tube using a 3rd harmonic drive on the grid

In this paper, we discuss the design and whole-cavity simulation of a Multi-Beam Inductive Output Tube (MBIOT) that uses a 3rd harmonic component to the drive voltage on the grid. High-efficiency inductive output tubes (IOTs) are typically characterized by efficiencies up to 70 - 75%. However, the achievement of efficiencies greater than 80% would substantially reduce the operating costs of next-generation accelerators. To achieve this goal, we consider the addition of a 3rd harmonic component to the drive signal on the grid. We anticipate that the MBIOT will be used to provide the rf power to drive RF linacs. We discuss and model an 8-beam MBIOT with a 700 MHz resonant cavity using beams with a voltage of 35 kV and an average current of 7.25 A yielding a perveance of about 1.1 microP. We simulate this MBIOT using the NEMESIS simulation code which has been extended using a three-dimensional Poisson solver based upon the Petsc package from Argonne National Laboratory. The effect of the 3rd harmonic on the efficiency is greatest when the phase of the 3rd harmonic is shifted by pi radians with respect to the fundamental drive signal and with 3rd harmonic powers greater than about 50% of the fundamental drive power. For the present example, we show that efficiencies approaching 82% are possible. Designs for the MBIOT input coupler, grids and output cavity have been developed based on these simulations and will be discussed.Comment: 12 pages, 30 figure